ISSN: 1435-8107 eISSN: 0721-7595
Subject:
botany
Published by Springer-Verlag 
No Issue Number- Changes in the Growth, Chemical Composition, and Antioxidant Activity in the Aquatic Plant Wolffia arrhiza (L.) Wimm. (Lemnaceae) Exposed to Jasmonic Acid
The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) at concentrations of 0.01–100 μM upon the growth and metabolism of the aquatic plant Wolffia arrhiza (Lemnaceae). JA acted in a concentration-dependent manner. JA at 0.1 μM stimulated plant growth and accumulation of cellular components (proteins, monosaccharides, chlorophylls, phaeophytins, and carotenoids). Treatment with JA at 0.1 μM enhanced W. arrhiza viability by the induction of biomass production and increased the level of photosynthetic pigments, monosaccharides, and soluble proteins. Moreover, JA at 0.1 μM activated the enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and nonenzymatic antioxidant (ascorbate, glutathione) system in W. arrhiza and, therefore, suppressed lipid peroxidation. In contrast, decreases in fresh weight, major photosynthetic pigments, monosaccharides, and soluble protein content were observed in W. arrhiza exposed to 100 μM JA. JA applied at 100 μM also stimulated the formation of lipid peroxides which are responsible for membrane damage. In the presence of 100 μM JA, antioxidant enzyme (catalase, ascorbate peroxidase, NADH peroxidase) activity and ascorbate as well as glutathione content were inhibited. The data support the hypothesis that JA plays an important role in W. arrhiza growth and metabolism, regulating oxidative status by direct influence on the enzymatic as well as nonenzymatic antioxidant machinery.
- Content Type Journal Article
- DOI 10.1007/s00344-009-9113-8
- Authors
- Alicja Piotrowska, University of Bialystok Department of Plant Biochemistry and Toxicology, Institute of Biology Swierkowa 20 B 15-950 Bialystok Poland
- Andrzej Bajguz, University of Bialystok Department of Plant Biochemistry and Toxicology, Institute of Biology Swierkowa 20 B 15-950 Bialystok Poland
- Romuald Czerpak, University of Bialystok Department of Plant Biochemistry and Toxicology, Institute of Biology Swierkowa 20 B 15-950 Bialystok Poland
- Katarzyna Kot, University of Bialystok Department of Plant Biochemistry and Toxicology, Institute of Biology Swierkowa 20 B 15-950 Bialystok Poland
- Contrasting Effects of GA3 Treatments on Tomato Plants Exposed to Increasing Salinity
The role of plant hormones under saline stress is critical in modulating physiological responses that will eventually lead to adaptation to an unfavorable environment. Nevertheless, the functional level of plant hormones, and their relative tissue concentration, may have a different impact on plant growth and stress tolerance at increasing salinity of the root environment. Vigorous plant growth may counteract the negative effects of salinization. In contrast, low gibberellin (GA) levels have been associated with reduced growth in response to salinity. Based on these facts and considering that the physiological basis of the cause-effect relationship between functional growth control and stress adaptation/survival is still a matter of debate, we hypothesized that exogenous applications of the plant hormone GA 3 may compensate for the salt-induced growth deficiency and consequently facilitate tomato plant adaptation to a saline environment. GA 3 application (0 or 100 mg GA 3 l −1 ) was compared under four salinity levels, obtained by adding equal increments of NaCl:CaCl 2 (2:1 molar basis) (EC = 2.5, 6.8, 11.7, 16.7 dS m −1 ) to the nutrient solution. GA 3 treatment reduced stomatal resistance and enhanced plant water use at low salinity. These responses were associated with an increased number of fruit per plant at harvest. However, moderate and high salinity nullified these differences. The fruit carotenoid level was generally lower in GA 3 -treated plants, indicating either an inhibitory effect of GA 3 treatment on carotenoid biosynthesis or a reduced perception of the stress environment by GA 3 -treated tomato plants.
- Content Type Journal Article
- DOI 10.1007/s00344-009-9114-7
- Authors
- Albino Maggio, University of Naples Federico II Department of Agricultural Engineering and Agronomy Via Università, 100 80055 Portici, Naples Italy
- Giancarlo Barbieri, University of Naples Federico II Department of Agricultural Engineering and Agronomy Via Università, 100 80055 Portici, Naples Italy
- Giampaolo Raimondi, University of Naples Federico II Department of Agricultural Engineering and Agronomy Via Università, 100 80055 Portici, Naples Italy
- Stefania De Pascale, University of Naples Federico II Department of Agricultural Engineering and Agronomy Via Università, 100 80055 Portici, Naples Italy
- Restoration of Growth of Durum Wheat (Triticum durum var. waha) Under Saline Conditions Due to Inoculation with the Rhizosphere Bacterium Azospirillum brasilense NH and Extracts of the Marine Alga Ulva lactuca
Inoculation with the rhizosphere bacterium Azospirillum brasilense NH, originally isolated from salt-affected soil in northern Algeria, greatly enhanced growth of durum wheat ( Triticum durum var. waha) under saline soil conditions. Important plant parameters like the rate of germination, stem height, spike length, dry weight of roots and shoots, chlorophyll a and b content, proline and total sugar contents, 1000-seed weight, seed number per spike, and weight of seeds per spike were measured. At salt stress conditions (160 and 200 mM NaCl) A. brasilense NH restored almost completely vegetative growth and seed production. The combination with extracts of the marine alga Ulva lactuca resulted in even more improved salt tolerance of durum wheat. Proline and total sugar accumulation, a sign of physiological plant stress under inhibitory salt conditions, was reduced in plants inoculated with A. brasilense NH with and without addition of algal extracts. Inoculation with the salt-sensitive A. brasilense strain Sp7 could not restore salt-affected plant growth at 200 mM NaCl. Furthermore, it could be demonstrated by fluorescence in situ hybridization and confocal laser scanning microscopy that A. brasilense NH is able to colonize roots of durum wheat endophytically under salt-stressed conditions. Thus, the salt-tolerant rhizobacterium A. brasilense NH could effectively provide alone or in combination with extracts of U. lactuca a promising solution to overcome salt inhibition which is a major threat hindering productive wheat cultivation in arid saline soils.
- Content Type Journal Article
- DOI 10.1007/s00344-009-9107-6
- Authors
- Elhafid Nabti, University of Bejaïa Department of Microbiology, Laboratory of Applied Microbiology, Faculty of Nature and Life Sciences Targa Ouzemmour 06000 Bejaïa Algeria
- Mohamed Sahnoune, University of Bejaïa Department of Biology of Organisms and Populations, Laboratory of Ecology and Environment, Faculty of Nature and Life Sciences Targa Ouzemmour 06000 Bejaïa Algeria
- Mostefa Ghoul, University of Setif Department of Biology, Laboratory of Bacterial Ecology, Faculty of Biology 19000 Setif Algeria
- Doreen Fischer, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München Department Microbe-Plant Interactions Ingolstädter Landstrasse 1 85764 Neuherberg Germany
- Andreas Hofmann, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München Department Microbe-Plant Interactions Ingolstädter Landstrasse 1 85764 Neuherberg Germany
- Michael Rothballer, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München Department Microbe-Plant Interactions Ingolstädter Landstrasse 1 85764 Neuherberg Germany
- Michael Schmid, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München Department Microbe-Plant Interactions Ingolstädter Landstrasse 1 85764 Neuherberg Germany
- Anton Hartmann, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München Department Microbe-Plant Interactions Ingolstädter Landstrasse 1 85764 Neuherberg Germany
No Issue Number- Effects of Plant Growth Regulators and Saccharide on In Vitro Plant and Tuberous Root Regeneration of Cassava (Manihot esculenta Crantz)
Abstract A faster system to get tuberous roots from in vitro cultured cassava plants may enhance the process of exploring the function and practical application of some root-specific expressed genes. The effects of cytokinin, auxin, sucrose, maltose, and glucose on development of shoots and tuberous roots and plantlet regeneration of in vitro cultured cassava were investigated in this study. The cytokinin N-benzyladenine (BA) (0–2.0 mg l −1 ) was effective on shoot regeneration. The auxin α-naphthalene acetic acid (NAA) (0–2.0 mg l −1 ) proved to be effective on root development. Plantlets with fibrous roots easily generated tuberous roots in vitro. The tuberous roots were induced only when both BA and NAA were used in combination. MS medium supplemented with sucrose at 175 mM (or 6% w/v) resulted in the highest frequencies of shoot induction (71.43%) and average fresh weight (0.61 g) of tuberous roots when BA (0.5 mg l −1 ) and NAA (0.5 mg l −1 ) were also added to the MS medium.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9163-y
- Authors
- Mingxia Fan, Huazhong Agricultural University National Key Laboratory of Crop Genetic Improvement, College of Plant Science Wuhan 430070 China
- Zaochang Liu, Shanghai Agrobiological Gene Center Shanghai 201106 China
- Liguo Zhou, Huazhong Agricultural University National Key Laboratory of Crop Genetic Improvement, College of Plant Science Wuhan 430070 China
- Tian Lin, Shanghai Agrobiological Gene Center Shanghai 201106 China
- Yunhua Liu, Huazhong Agricultural University National Key Laboratory of Crop Genetic Improvement, College of Plant Science Wuhan 430070 China
- Lijun Luo, Shanghai Agrobiological Gene Center Shanghai 201106 China
- Purification and Biochemical Characterization of Indole-3-acetyl-aspartic Acid Synthetase from Immature Seeds of Pea (Pisum sativum)
Abstract Indole-3-acetic acid (IAA) amidosynthetases catalyzing the ATP-dependent conjugation of IAA and amino acids play an important role in the maintenance of auxin homeostasis in plant cells. A new amidosynthetase, indole-3-acetic acid: l -aspartic acid ligase (IAA-Asp synthetase) involved in IAA-amino acid biosynthesis, was isolated via a biochemical approach from immature seeds of the pea ( Pisum sativum L). The enzyme was purified to homogeneity by a three-step procedure, involving PEG 6000 fractionation, DEAE-Sephacel anion-exchange chromatography, and preparative PAGE, and characterized as a 70-kDa monomeric protein by analytical gel filtration and SDS-PAGE. Rabbit antiserum against recombinant AtGH3.5 cross-reacted with the pea IAA-Asp synthetase, and a single immunoreactive polypeptide band was observed at 70 kDa. The purified enzyme had an apparent isoelectric point at pH 4.7, the highest activity at pH 8.2, preferred Mg 2+ as a cofactor, and was strongly activated by reducing agents. Similar to known recombinant GH3 enzymes, an IAA-Asp synthetase from pea catalyzes the conjugation of phytohormone acyl substrates to amino acids. The enzyme had the highest synthesizing activity on IAA, followed by 1-NAA, SA, 2,4-D, and IBA, whereas activities on l -Trp, IPA, PAA, (±)JA, and 2-NAA were not significant or not detected. Of 14 amino acids tested, the enzyme had the highest activity on Asp and lower activity on Ala and Lys. Glutamate was found to be a very poor substrate and no conjugating activity was observed on the rest of the amino acids. Steady-state kinetic analysis indicated that IAA and aspartate were preferred substrates for the pea IAA-Asp synthetase. The enzyme exhibited both higher affinities for IAA and Asp ( K m = 0.2 and 2.5 mM, respectively) and catalytic efficiencies ( k cat / K m = 682,608.7 and 5080 s −1 M −1 , respectively) compared with other auxins and amino acids examined. This study describes the first amidosynthetase isolated and purified from plant tissue and provides the foundation for future genetic approaches to explain the role of IAA-Asp in Pisum sativum physiology.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9164-x
- Authors
- Maciej Ostrowski, Institute of General and Molecular Biology, Nicolaus Copernicus University Department of Biochemistry ul. Gagarina 9 87-100 Toruń Poland
- Anna Jakubowska, Institute of General and Molecular Biology, Nicolaus Copernicus University Department of Biochemistry ul. Gagarina 9 87-100 Toruń Poland
- Auxins or Sugars: What Makes the Difference in the Adventitious Rooting of Stored Carnation Cuttings'
Abstract Cold storage of cuttings is frequently applied in the vegetative propagation of ornamental plants. Dianthus caryophyllus was used to study the limiting influences of auxin and sugars on adventitious root formation (ARF) in cuttings stored at 5°C. Carbohydrate levels during storage were modulated by exposing cuttings to low light or darkness. The resulting cuttings were treated (or not) with auxin and planted, and then ARF was evaluated. Carbohydrate levels in the cuttings were monitored and the influence of light treatment on indole-3-acetic acid (IAA) and zeatin (Z) in the basal stem was investigated. Dark storage for up to 4 weeks increased the percentage of early rooted cuttings and the final number and length of adventitious roots, despite decreased sugar levels in the stem base. Light during cold storage greatly enhanced sugar levels, particularly in the stem base where the Z/IAA ratio was higher and ARF was lower than observed in the corresponding dark-stored cuttings. Sugar levels in nonstored and dark-stored cuttings increased during the rooting period, and auxin application enhanced the accumulation of sugars in the stem base of nonstored cuttings. Auxin stimulated ARF most strongly in nonstored, less so in light-stored, and only marginally in dark-stored cuttings. A model of auxin-sugar interactions in ARF in carnation is proposed: cold storage brings forward root induction and sink establishment, both of which are promoted by the accumulation of auxin but not of sugars, whereas high levels of sugars and probably also of cytokinins act as inhibitors. Subsequent root differentiation and growth depend on current photosynthesis.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9174-8
- Authors
- María Ángeles Agulló-Antón, Departamento de Biología Vegetal (Fisiología Vegetal), Facultad de Biología, Universidad de Murcia, 30100 Espinardo, Murcia Spain
- José Sánchez-Bravo, Departamento de Biología Vegetal (Fisiología Vegetal), Facultad de Biología, Universidad de Murcia, 30100 Espinardo, Murcia Spain
- Manuel Acosta, Departamento de Biología Vegetal (Fisiología Vegetal), Facultad de Biología, Universidad de Murcia, 30100 Espinardo, Murcia Spain
- Uwe Druege, Department Plant Propagation, Leibniz-Institute of Vegetable and Ornamental Crops (IGZ), Kuehnhaeuser Strasse 101, 99189 Erfurt-Kuehnhausen, Germany
- Hormonal Profile in Vegetative and Floral Buds of Azalea: Levels of Polyamines, Gibberellins, and Cytokinins
Abstract The floral transition includes a complex system of factors that interact and involve various biochemical signals, including plant growth regulators. The physiological signals involved in the control of the floral transition have been sparsely studied and mainly in plant species whose genetics are poorly known. In this work, the role of polyamines, gibberellins, and cytokinins was investigated by analyzing their endogenous content in vegetative and floral buds of azalea. The results showed that there is a clear distinction between floral and vegetative buds with respect to the levels of these plant hormones, with floral buds containing higher amounts of conjugated polyamines, gibberellins (GAs) from the non-13-hydroxylation pathway (GA 9 , GA 7 , and GA 4 ), and cytokinins (particularly isopentenyl-type species), and vegetative buds containing higher amounts of free polyamines and gibberellins from the early 13-hydroxylation pathway and fewer cytokinins. In conclusion, there is a specific pattern of endogenous hormone profiles in both vegetative and floral bud development in azalea, which may be relevant for future research on the control of flowering by exogenous hormone applications.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9169-5
- Authors
- Mónica Meijón, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- María Jesús Cañal, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- Helena Fernández, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- Ana Rodríguez, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- Belén Fernández, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- Roberto Rodríguez, Laboratorio de Fisiología Vegetal, Dpto. B.O.S., Facultad de Biología, Universidad de Oviedo, C/ Cat. Rodrigo Uría s/n, 33071 Oviedo, Asturias Spain
- Isabel Feito, SERIDA, Servicio Regional de Investigación y Desarrollo Agroalimentario, Finca “La Mata”, Apdo 13, E-33820 Grado, Asturias Spain
- ABA Initiates Anthocyanin Production in Grape Cell Cultures
Abstract Abscisic acid (ABA) has a well-known positive impact on grape ripening, especially color development, but its role in the initiation of anthocyanin synthesis remains unclear. To elucidate this point, ABA treatment was applied to a simple Vitis vinifera model, consisting of Cabernet Sauvignon cell suspensions that do not spontaneously produce anthocyanins under laboratory conditions. Endogenous ABA levels, the expression of some genes in the upstream part of the anthocyanin pathway, and anthocyanin content were determined. Exogenous ABA treatment sharply increased cell ABA content and induced both structural and regulatory genes involved in anthocyanin production. These changes were promptly detected, as early as 6 h after ABA treatment, whereas anthocyanin production was observed only after 4 days in culture. These results demonstrate that ABA promotes anthocyanin synthesis in grape cell culture.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9165-9
- Authors
- Séverine Gagné, Université de Bordeaux UMR 1219 Œnologie, Faculté d’Œnologie, ISVV, 210 Chemin de Leysotte CS 50008 33882 Villenave d’Ornon Cedex France
- Stéphanie Cluzet, Université de Bordeaux, Groupe d’Etude des Substances Végétales à Activité Biologique EA 3675, UFR Sciences Pharmaceutiques, ISVV, 210 Chemin de Leysotte CS 50008 33882 Villenave d’Ornon Cedex France
- Jean-Michel Mérillon, Université de Bordeaux, Groupe d’Etude des Substances Végétales à Activité Biologique EA 3675, UFR Sciences Pharmaceutiques, ISVV, 210 Chemin de Leysotte CS 50008 33882 Villenave d’Ornon Cedex France
- Laurence Gény, Université de Bordeaux UMR 1219 Œnologie, Faculté d’Œnologie, ISVV, 210 Chemin de Leysotte CS 50008 33882 Villenave d’Ornon Cedex France
- Ustilago maydis Produces Cytokinins and Abscisic Acid for Potential Regulation of Tumor Formation in Maize
Abstract The infection of maize ( Zea mays ) by the basidiomycete fungus Ustilago maydis leads to common smut of corn characterized by the production of tumors in susceptible aboveground plant tissues. LC-(ES)MS/MS profiles of abscisic acid (ABA) and 12 different cytokinins (CKs) were determined for infected and uninfected maize tissues over a time course following fungal exposure. Samples were taken at points corresponding to the appearance of disease symptoms. Axenic cultures of haploid and dikaryon forms of U. maydis were also profiled. This study confirmed the capability of Ustilago maydis to synthesize CKs, ABA, and auxin (IAA). It also provided evidence for the involvement of CK and ABA in the U. maydis -maize infection process. Significant quantities of CKs and ABA were detected from axenic cultures of U. maydis as was IAA. CKs and ABA levels were elevated in leaves and stems of maize after infection; notable was the high level of cis- zeatin 9-riboside. Variation among hormone profiles of maize tissues was observed at different time points during infection and between infections with nonpathogenic haploid and pathogenic dikaryon strains. This suggested that CKs and ABA accumulate and are likely metabolized in maize tissue infected with U. maydis . Because U. maydis produced these phytohormones at significant levels, it is possible that the fungal pathogen is a source of these compounds in infected tissue. This is the first study to confirm the production of CKs and document the production of ABA by U. maydis . This study also established an involvement of these phytohormones and a possible functional role for ABA in U. maydis infection of maize.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9166-8
- Authors
- Stacey A. Bruce, Trent University Environmental and Life Sciences Graduate Program Peterborough ON K9J 7B8 Canada
- Barry J. Saville, Trent University Forensic Science Department Peterborough ON K9J 7B8 Canada
- R. J. Neil Emery, Trent University Biology Department Peterborough ON K9J 7B8 Canada
- Photosynthetic Potential and its Association with Lipid Peroxidation in Response to High Temperature at Different Leaf Ages in Maize
Abstract High temperature generally constrains plant growth and photosynthesis in many regions of the world; however, little is known about how photosynthesis responds to high temperature with regard to different leaf ages. The synchronous changes in gas exchange and chlorophyll fluorescence at three leaf age levels (just fully expanded, mature, and older leaves) of maize ( Zea mays L.) were determined at three temperatures (30°C as a control and 36 and 42°C as the higher temperatures). High temperature significantly decreased the net CO 2 assimilation rate ( A ), stomatal conductance ( g s ), maximal efficiency of photosystem II (PSII) photochemistry ( F v / F m ), efficiency of excitation energy capture by open PSII reaction centers ( | F ¢ \text v / F ¢ \text m | | ), photochemical quenching of variable chlorophyll fluorescence ( q P ), and the electron transport rate (ETR), whereas minimal fluorescence yield ( F 0 ) and nonphotochemical quenching of variable chlorophyll fluorescence ( q N ) were increased. The youngest fully expanded leaves had higher A , ETR, and q P compared with older leaves. Higher temperature with old leaves led to significant malondialdehyde (MDA) accumulation, a proxy for lipid peroxidation damage from active oxygen species (AOS). MDA content was significantly negatively correlated with A , F v / F m , | F ¢ \text v / F ¢ \text m | | , and q P . Thus, the results suggest that photosynthetic potentials, including stomatal regulation and PSII activity, may be restricted at high temperature, together with increasing cell peroxidation, which may be closely associated with leaf age.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9167-7
- Authors
- Zhenzhu Xu, Chinese Academy of Sciences State Key Laboratory of Vegetation and Environmental Change, Institute of Botany 20 Nanxincun, Xiangshan, Haidian Beijing 100093 China
- Guangsheng Zhou, Chinese Academy of Sciences State Key Laboratory of Vegetation and Environmental Change, Institute of Botany 20 Nanxincun, Xiangshan, Haidian Beijing 100093 China
- Guangxuan Han, Chinese Academy of Sciences State Key Laboratory of Vegetation and Environmental Change, Institute of Botany 20 Nanxincun, Xiangshan, Haidian Beijing 100093 China
- Yijun Li, Chinese Academy of Sciences State Key Laboratory of Vegetation and Environmental Change, Institute of Botany 20 Nanxincun, Xiangshan, Haidian Beijing 100093 China
- Ethylene is Involved in the Control of Male Gametophyte Development and Germination in Petunia
Abstract The time courses of 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production in developing anthers of petunia fertile and sterile lines and the effects of exogenously applied ethylene and an inhibitor of ethylene action, 2,5-norbornadiene (NBD), on male gametophyte development and germination were investigated. Fertile male gametophyte development was accompanied by two peaks of ethylene production by anther tissues. The first peak occurred during microspore development simultaneously with degeneration of both tapetal tissues and middle layers of the anther wall. The second peak coincided with maturation and dispersal of pollen grains. The mature pollen is characterized by a high ACC content (up to 300 nmol/g). Exogenously applied ethylene (1–100 ppm) induced degradation of gametophytic generation at the meiosis stage. NBD completely inhibited anther development at the early stages of its development and delayed anther dehiscence. In anther tissues of the petunia sterile line, tenfold higher ethylene production was observed at the meiosis stage compared to that in fertile male gametophytes and this correlated with degeneration of both microsporocytes and tapetal tissues. In vitro male gametophyte germination was accompanied by an increase of ethylene production, whereas NBD completely blocked male gametophyte germination. These results suggest that ethylene is an important factor in male gametophyte development and germination.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9168-6
- Authors
- Lidiya V. Kovaleva, Timirayzev Institute of Plant Physiology RAS, Botanicheskaya st. 35, Moscow, Russia 127276
- Alla Dobrovolskaya, Timirayzev Institute of Plant Physiology RAS, Botanicheskaya st. 35, Moscow, Russia 127276
- Alexander Voronkov, Timirayzev Institute of Plant Physiology RAS, Botanicheskaya st. 35, Moscow, Russia 127276
- Viktor Rakitin, Timirayzev Institute of Plant Physiology RAS, Botanicheskaya st. 35, Moscow, Russia 127276
- 2010 Reviewer Thank You
<p class="abstract">2010 Reviewer Thank You</p><ul>
<li><span class="labelName">Content Type </span><span class="labelValue">Journal Article</span></li><li>DOI 10.1007/s00344-010-9184-6</li>
</ul><ul class="parents">
<ul class="details">
<li><span class="header labelName">Journal </span><span class="labelValue"><a href="http://www.springerlink.com/content/101567/">Journal of Plant Growth Regulation</a></span></li><li><span class="labelName">Online ISSN </span><span class="labelValue">1435-8107</span></li><li><span class="labelName">Print ISSN </span><span class="labelValue">0721-7595</span></li>
</ul>
</ul>
- Direct Adventitious Shoot Formation from Apical Shoot Explants of Euphorbia tirucalli
Abstract The induction of adventitious buds from apical shoot explants of Euphorbia tirucalli was studied. On average, 10.5 adventitious buds were efficiently induced in a ring on the segment from one apical explant on MS (Murashige and Skoog) medium supplemented with 0.5 mg l −1 thidiazuron and 0.5 mg l −1 benzylaminopurine. The adventitious buds could develop into adventitious shoots during subsequent cultures on hormone-free MS medium. For rooting, shoot clumps were cultured on half-strength MS medium containing 0.2 mg l −1 α-naphthaleneacetic acid or indole-3-butyric acid. All the rooted plants survived establishment in soil within 2 months.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9170-z
- Authors
- Guohua Ma, Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650 China
- Jaime A. Teixeira da Silva, Faculty of Agriculture and Graduate School of Agriculture, Kagawa University, Miki-cho, Ikenobe 2393, Kagawa-ken, 761-0795 Japan
- Guojiang Wu, Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou, 510650 China
- Endogenous Auxin is Required but Supraoptimal for Rapid Growth of Rice (Oryza sativa L.) Seminal Roots, and Auxin Inhibition of Rice Seminal Root Growth is Not Caused by Ethylene
Abstract The dual effects of auxin and ethylene on rice seminal root growth were investigated in this study. Low concentrations of exogenous indole-3-acetic acid (IAA) had no effect on rice seminal root growth, whereas higher concentrations (≥0.003 μM) were inhibitory. In contrast, low concentrations of the auxin action inhibitor p -chlorophenoxyisobutyric acid (PCIB), ranging from 0.5 to 50 μM, promoted rice seminal root growth, whereas high concentrations of PCIB (≥500 μM) and the polar auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) inhibited rice seminal root growth. These results suggest that endogenous auxin is required but supraoptimal for rapid growth of rice seminal roots. In addition, although rice seminal root growth was inhibited by the exogenous ethylene-releasing compound ethephon or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) as well as exogenous IAA, the 50% inhibition of growth (I 50 ) caused by ethephon or ACC was weakened by certain concentrations of the ethylene action inhibitor Ag + (0.016-0.4 μM). However, the I 50 caused by exogenous IAA was strengthened by Ag + or the ethylene biosynthetic inhibitor aminoethoxyvinylglycine (AVG) and weakened by certain concentrations of PCIB (0.5-50 μM). Together, the inhibitory mechanisms of auxin and ethylene on rice seminal root growth should be different, and auxin inhibition of rice seminal root growth should not be caused by ethylene. Furthermore, our results indicated that a certain threshold level of ethylene was required to maintain rice seminal root growth, and that ethylene within the threshold may antagonize auxin inhibition of rice seminal root growth.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9162-z
- Authors
- Changxi Yin, Huazhong Agricultural University College of Plant Science and Technology Wuhan 430070 China
- Quanrong Wu, Huazhong Agricultural University College of Plant Science and Technology Wuhan 430070 China
- Hanlai Zeng, Huazhong Agricultural University College of Plant Science and Technology Wuhan 430070 China
- Kai Xia, Nanjing Agricultural University College of Life Sciences Nanjing 210095 China
- Jiuwei Xu, Huazhong Agricultural University College of Plant Science and Technology Wuhan 430070 China
- Rongwei Li, Huazhong Agricultural University College of Plant Science and Technology Wuhan 430070 China
- Isopentenyl Transferase and Cytokinin Oxidase/Dehydrogenase Gene Family Members are Differentially Expressed During Pod and Seed Development in Rapid-cycling Brassica
Abstract The plant hormone group, the cytokinins, regulates many stages of plant growth and development. Regulation includes that of cell division and enhancement of sink strength, both of which are important processes in seed development and embryonic growth. Two gene families play a key role in maintaining cytokinin homeostasis: isopentenyl transferase (IPT), which catalyzes the rate-limiting step in the formation of cytokinins, and cytokinin oxidase/dehydrogenase (CKX), which irreversibly inactivates cytokinins by cleaving the N 6 side chain. Quantitative reverse transcriptase polymerase chain reaction (PCR) was used to measure the expression of individual gene family members to investigate the source of cytokinin and its subsequent inactivation during the early stages of seed and pod development. In this study, rapid-cycling Brassica rapa (RCBr) was used because of its genetic relatedness to commercial Brassica species, its rapid life cycle, its small adult size, and its larger reproductive organs compared to Arabidopsis . Our results indicate that BrIPT1 , - 3 , and - 5 and BrCKX1 , - 2 , - 3 , and - 5 express differentially both temporally and spatially within RCBr root, stem, leaf, seed, and pod tissues. Particularly strong expression was shown by IPT3 and IPT5 and CKX2 in developing seeds.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9171-y
- Authors
- David O’Keefe, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
- Jiancheng Song, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
- Paula E. Jameson, School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
- Cadmium Accumulation in Relation to Organic Acids and Nonprotein Thiols in Leaves of the Recently Found Cd Hyperaccumulator Rorippa globosa and the Cd-accumulating Plant Rorippa islandica
Abstract It has been proposed that organic acid and nonprotein thiol are involved in the hyperaccumulation of metals. In this study, Cd accumulation, organic acid, and nonprotein thiol production and their relationships in the leaves of Cd-hyperaccumulator Rorippa globosa were examined and compared with a closely related species, Rorippa islandica . The results showed that there was no reduction in biomass of R. globosa when treated with 25 μg Cd g −1 (T 2 ), despite Cd accumulation in the leaves was up to 158.2 μg g −1 DW. On the other hand, the growth of Cd-treated R. islandica was obviously inhibited as it accumulated more than 100 μg g −1 DW in the leaves. Therefore, R. islandica behaved as a Cd-accumulating plant. The Cd treatments could significantly induce the synthesis of acetic acid in both species, suggesting that acetic acid, as the most abundant organic acid, might be related to the Cd accumulation. Significant positive correlations between Cd concentrations and both tartaric and malic acid concentrations in the leaves of R. globosa were observed. There was a significant positive correlation between Cd concentrations and acetic acid concentrations in the leaves of R. islandica . This trend of tartaric and malic acids in the leaves of R. globosa and acetic acid in the leaves of R. islandica might be related to Cd accumulation. In addition, a quadratic relationship was obviously observed for NP-SH contents and total Cd concentrations in the leaves of R. globosa , indicating that NP-SH was significantly related to Cd accumulation and tolerance.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9176-6
- Authors
- Ruilian Sun, Environment Research Institute, Shandong University, Jinan, 250100 China
- Qixing Zhou, Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071 China
- Shuhe Wei, Key Laboratory of Terrestrial Ecological Process, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016 China
- Cloning, Localization, and Expression Analysis of a New Tonoplast Monosaccharide Transporter from Vitis vinifera L
Abstract Tonoplast sugar transporters are important for sugar partitioning, immobilization, and accumulation during fruit development and ripening. Here we report the cloning, localization, and functional analysis of one of these transporters in grape berries ( Vitis vinifera L.). This clone, named VvTMT1 , encodes a 742-aa protein with a calculated molecular mass of 80.2 kDa. Predicted membrane topology and phylogenetic analysis suggest that VvTMT1 belongs to the major facilitator superfamily of membrane carriers. Semiquantitative RT-PCR suggests that VvTMT1 is a sink-specific transporter, whose expression decreases with berry development. Heterologous expression of VvTMT1 in yeast can partially restore growth of the hxt- null strain in glucose and other monosaccharide media, indicating that VvTMT1 is a functional monosaccharide transporter. Induction of VvTMT1-GFP fusion protein expression in transgenic yeast revealed its tonoplast localization. The subcellular localization of VvTMT1 in plants was shown by immunogold labeling of grape berry mesocarp cells and VvTMT1-GFP transient expression in tobacco epidermis cells. Based on the above analyses of VvTMT1, this is the first report of a functional tonoplast-localized monosaccharide transporter in grapevine.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9185-5
- Authors
- Lei Zeng, Key Lab of Functional Dairy Science of Chinese Ministry of Education and Municipal Government of Beijing, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
- Zeng Wang, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China
- Alexander Vainstein, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
- Shangwu Chen, Key Lab of Functional Dairy Science of Chinese Ministry of Education and Municipal Government of Beijing, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
- Huiqin Ma, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China
- Genetic Diversity Among Cold-Tolerant Fluorescent Pseudomonas Isolates from Indian Himalayas and Their Characterization for Biocontrol and Plant Growth-Promoting Activities
Abstract In Uttarakhand, the Organic State of India, where soils in most farming situations are deficient in nutrients and loss of crops due to soil- and seed-borne pathogens is rampant, use of native plant growth-promoting rhizobacteria (PGPRs) possessing biocontrol (BC) activities holds promise. In view of this, 600 native cold-tolerant rhizospheric bacterial isolates were collected from Uttarakhand Himalayas, of which 336 were confirmed as fluorescent Pseudomonas spp. On the basis of specific biochemical tests, these were characterized into three major groups: P. fluorescens (308 isolates), P. aeruginosa (20 isolates), and P. putida (8 isolates). Most of the isolates could grow at 8°C after 12 h of incubation, confirming their cold tolerance. In vitro biocontrol assays revealed that of 336 isolates, 74 were antagonistic to Rhizoctonia solani and 91 to Fusarium solani , the two major pathogens associated with root-rot complex in vegetables widespread in the region. Simultaneously, good HCN producers (33 isolates), siderophore producers (80 isolates), and P solubilizers (49 isolates) were also identified, which could increase the biocontrol and plant growth-promoting efficacies of the putative PGPRs. Among the different species and biovars, P. fluorescens biovar-I had the maximum number of potential isolates with BC and plant growth-promoting (PGP) activities. In French bean, under polyhouse and field conditions, five isolates (Pf-173, Pf-193, Pf-547, Pf-551, and Pf-572) showed good BC and PGP activities as up to 93% reduction in root rot was achieved. A combination of all five isolates was found to be best with respect to BC and PGP activities. In a set of 59 fluorescent Pseudomonas isolates, RAPD-PCR analysis, using three random oligodecamer primers, revealed high diversity and formed ten distinct clusters, corresponding to the host of origin (annual or perennial) or habitat (farming situations) of the isolates. The amount of diversity revealed in the set of fluorescent Pseudomonas isolates could represent enormous diversity that exists in the wild that could be exploited for improved BC and PGP activities of the PGPRs. For the first time, this study led to a large-scale characterization and repositioning of fluorescent pseudomonads from the Indian Himalayas.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9175-7
- Authors
- Yogesh Kumar Negi, G. B. Pant University of Agriculture and Technology,Pantnagar, Udham Singh Nagar, Uttarakhand India
- Deepti Prabha, G. B. Pant University of Agriculture and Technology,Pantnagar, Udham Singh Nagar, Uttarakhand India
- Satyendra K. Garg, Dr. R. M. L. Awadh University, Faizabad, Uttar Pradesh India
- J. Kumar, G. B. Pant University of Agriculture and Technology,Pantnagar, Udham Singh Nagar, Uttarakhand India
- Nitrogen Form Alters Hormonal Balance in Salt-treated Tomato (Solanum lycopersicum L.)
Abstract Mixed nitrate/ammonium fertilization can partially alleviate the negative effects of salinity on growth of some plant species compared to all-nitrate or all-ammonium fertilization. To gain insights about the mechanisms involved, tomato ( Solanum lycopersicum L. cv Moneymaker) plants were grown hydroponically for 3 weeks with two NO 3 − /NH 4 + fertilization regimes (6/0.5 and 5/1.5; N total = 6.5 mM) in the absence (control) or presence of salt stress (100 mM NaCl). Ammonium enrichment had no effect on growth and other parameters under control conditions. Under salinity, however, ammonium enrichment improved shoot and root biomass by 20% and maintained leaf PSII efficiency close to control levels. These changes were related to higher leaf K + , NO 3 − , and NH 4 + concentrations and activities of the N-assimilatory enzymes glutamate synthase (GOGAT) and glutamine synthase (GS) in the leaves. Ammonium enrichment also attenuated the salt-induced increase in leaf abscisic acid (ABA) concentration and decrease in leaf concentrations of indole 3-acetic acid (IAA) and the cytokinins trans -zeatin ( t Z) and trans -zeatin riboside ( t ZR). Enhanced cytokinin status was probably due to maintenance of root-to-shoot cytokinin transport and decreased leaf induction of the cytokinin-degrading enzyme cytokinin oxidase/dehydrogenase (CKX) under ammonium-enriched conditions. It is concluded that nitrogen form modifies salinity-induced physiological responses and that these modifications are associated with changes in plant hormone status.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9178-4
- Authors
- Michel Edmond Ghanem, Groupe de Recherche en Physiologie végétale, Earth and Life Institute, Université catholique de Louvain, 5 (Bte 13) Place Croix du Sud, 1348 Louvain-la-Neuve, Belgium
- Cristina Martínez-Andújar, Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Campus Universitario de Espinardo, 30100 Espinardo, Murcia, Spain
- Alfonso Albacete, Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Campus Universitario de Espinardo, 30100 Espinardo, Murcia, Spain
- Hana Pospíšilová, Department of Biochemistry, Palacký University, 779 00 Olomouc, Czech Republic
- Ian C. Dodd, The Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ UK
- Francisco Pérez-Alfocea, Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Campus Universitario de Espinardo, 30100 Espinardo, Murcia, Spain
- Stanley Lutts, Groupe de Recherche en Physiologie végétale, Earth and Life Institute, Université catholique de Louvain, 5 (Bte 13) Place Croix du Sud, 1348 Louvain-la-Neuve, Belgium
- Application of Digital Image Analysis System for Fine Evaluation of Varietal Differences and the Role of Ethylene in Visible Petal Senescence of Morning Glory
Abstract We detected differences in both onset and progression of visible petal senescence among morning glory cultivars by application of a digital image analysis system. The system is based on semiautomated time-lapse measurement of corolla areas. The system could also be applied to evaluate the effects of ethylene and its inhibitor on visible petal senescence. Both onset and progression of visible petal senescence were accelerated by ethylene treatment in all six cultivars tested. Treatment with aminooxyacetic acid (AOA), an ethylene biosynthesis inhibitor, prolonged time to onset of visible petal senescence in three of the six tested cultivars. In contrast, AOA treatment had no effect on duration of visible petal senescence in any tested cultivars. These data suggested differences among morning glory cultivars in the role of endogenous ethylene in controlling onset of visible petal senescence. In addition, we propose a new application of image analysis to fine quantification of time-lapse changes in the shape of plant organs.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9182-8
- Authors
- Yoshihito Shinozaki, Department of Plant Production, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
- Takanari Tanabata, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan
- Isao Ogiwara, Department of Plant Production, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
- Tetsuya Yamada, Department of Plant Production, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
- Motoki Kanekatsu, Department of Plant Production, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
- Molecular Characterization of an Aux/IAA of Catharanthus roseus
Abstract In Catharanthus roseus cells, auxins are known to negatively regulate the biosynthesis of monoterpenoid indole alkaloids (MIA), a class of valuable secondary metabolites. Despite extensive studies of this regulation, no protein of the auxin signaling pathway has been isolated to date in this plant. We therefore decided to clone and characterize a C. roseus Aux/IAA protein that belongs to a family of gene expression repressors mediating auxin effects. Using PCR, a cDNA encoding the first C. roseus Aux/IAA was cloned and named CrIAA1 . The deduced amino acid sequence has four highly conserved domains that are typical of the Aux/IAA protein family and has high homology to the Aux/IAA isoforms of Arabidopsis (>67%). The CrIAA1 gene expression, monitored by real-time PCR, was found to be dramatically induced by auxin treatment in C. roseus cells. Using GFP imagery and a bimolecular fluorescence complementation assay, we found that CrIAA1 can form oligomers in the nucleus. We also found that CrIAA1 is quickly degraded following auxin treatments, suggesting that auxin regulates CrIAA1 availability via a feedback mechanism. These results should help to elucidate the molecular nature of the processes responsible for the auxin-mediated regulation of MIA biosynthesis in C. roseus .
- Content Type Journal Article
- DOI 10.1007/s00344-010-9187-3
- Authors
- Pierre Poutrain, “Biomolécules et Biotechnologies Végétales”, Université François Rabelais de Tours, EA 2106, IFR 135 “Imagerie fonctionnelle”, 37200 Tours, France
- Grégory Guirimand, “Biomolécules et Biotechnologies Végétales”, Université François Rabelais de Tours, EA 2106, IFR 135 “Imagerie fonctionnelle”, 37200 Tours, France
- Gaëlle Glévarec, “Biomolécules et Biotechnologies Végétales”, Université François Rabelais de Tours, EA 2106, IFR 135 “Imagerie fonctionnelle”, 37200 Tours, France
- Vincent Courdavault, “Biomolécules et Biotechnologies Végétales”, Université François Rabelais de Tours, EA 2106, IFR 135 “Imagerie fonctionnelle”, 37200 Tours, France
- Olivier Pichon, “Biomolécules et Biotechnologies Végétales”, Université François Rabelais de Tours, EA 2106, IFR 135 “Imagerie fonctionnelle”, 37200 Tours, France
- Gibberellins and Abscisic Acid Promote Carbon Allocation in Roots and Berries of Grapevines
Abstract Carbon allocation within grapevines may affect berry growth and development. The plant hormones gibberellins (GAs) and abscisic acid (ABA) control various processes across the plant life and both have been involved in assimilate production and transport in different species. Hence, this work examined the distribution of sugars (sucrose, fructose, and glucose) and starch in grapevines at veraison after foliar applications of GA 3 , ABA, and an inhibitor of GA biosynthesis, paclobutrazol (PBZ). The results demonstrated that GA 3 increased total grapevine mass, with carbon allocated to the whole grapevine (as structural and soluble carbohydrates). Both GA 3 and ABA increased monosaccharide (glucose and fructose) levels in berries (up to tenfold) and roots (up to threefold). However, GA 3 increased the net carbon fixation whereas ABA did not. PBZ diminished most growth parameters except grapevine mass, and allocated more carbohydrates to roots (up to threefold more sucrose and starch). Such results indicate that GAs promote net carbon fixation and transport, whereas ABA as a stress signal only enhances sugar transport; notwithstanding the two hormones promoted carbon allocation toward roots and berries.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9186-4
- Authors
- Daniela Moreno, Instituto de Biología Agrícola de Mendoza (IBAM), Facultad de Ciencias Agrarias, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Almirante Brown 500, M5528AHB Chacras de Coria, Argentina
- Federico J. Berli, Instituto de Biología Agrícola de Mendoza (IBAM), Facultad de Ciencias Agrarias, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Almirante Brown 500, M5528AHB Chacras de Coria, Argentina
- Patricia N. Piccoli, Instituto de Biología Agrícola de Mendoza (IBAM), Facultad de Ciencias Agrarias, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Almirante Brown 500, M5528AHB Chacras de Coria, Argentina
- Rubén Bottini, Instituto de Biología Agrícola de Mendoza (IBAM), Facultad de Ciencias Agrarias, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Cuyo, Almirante Brown 500, M5528AHB Chacras de Coria, Argentina
- Comparative Analysis of Endogenous Hormones in Leaves and Roots of Two Contrasting Malus Species in Response to Hypoxia Stress
Abstract Plant hormones play important roles in regulating developmental processes and signaling networks involved in plant responses to biotic and abiotic stresses. We comparatively studied the growth and endogenous hormonal levels in leaves and roots in two Malus species ( M. sieversii and M. hupehensis ) differing in hypoxia tolerance under normoxic and hypoxia stress. The results showed that hypoxia stress inhibited growth of seedlings of both Malus species, but with significant differences in intensity . Exposure to hypoxia altered the levels of endogenous hormones in leaves and roots in both Malus seedlings. Leaf and root abscisic acid (ABA) contents increased in response to hypoxia stress in both genotypes despite different extents. Compared with M. hupehensis , M. sieversii was more responsive to hypoxia stress, resulting in larger increases in leaf and root ABA contents. The changes in leaf and root ABA contents correlating with the different tolerance levels of the genotypes confirm the involvement of this hormone in plant responses to hypoxia stress. Gibberellins (GAs; GA 1 + GA 4 ) continuously increased in leaves and roots during the whole period of stress, whereas indole-3-acetic acid (IAA) showed a sharp increase at the early stage in both Malus seedlings. In addition, zeatin riboside (ZR), dihydrozeatin riboside (DHZR), and isopentenyl adenine (IPA) differed in their pattern of changes in both Malus seedlings under hypoxia stress. Based on variations in endogenous hormonal levels in both Malus species that differ in their ability to tolerate hypoxia, we conclude that not a single hormone but multiple hormones and their interplay are responsible for hypoxia tolerance.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9173-9
- Authors
- Tuanhui Bai, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Rong Yin, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Cuiying Li, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Fengwang Ma, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Zhiyong Yue, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Huairui Shu, College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100 China
- Effects of Promoters and Inhibitors of Ethylene and ABA on Flower Senescence of Hibiscus rosa-sinensis L.
Abstract Hibiscus rosa - sinensis L. flowers (cv La France) senesce and die over a 12-h period after opening. The aim of this study was to examine the physiological mechanisms regulating the senescence process of ephemeral hibiscus flowers. Different flower stages and floral organs were used to determine whether any interaction existed during flower senescence between endogenous abscisic acid (ABA) and the predisposition of the tissue to ethylene synthesis. This was carried out on whole flowers treated with promoters and inhibitors of ethylene and ABA synthesis or a combination of them. Treatments with 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene biosynthesis, enhanced flower senescence, whereas amino-oxyacetic acid (AOA) and fluridone, an ethylene and an ABA inhibitor, respectively, extended flower longevity. These effects were more significant when applied before anthesis. Ethylene evolution was substantially reduced in all organs from open and senescent flowers treated with fluridone and AOA. Similarly, endogenous ABA accumulation was negatively affected by AOA and fluridone treatments. Application of fluridone plus ACC reduced ethylene evolution and increased ABA content in a tissue-specific manner but did not overcome the inhibitor effect on flower longevity. AOA plus fluridone treatment slightly accelerated flower longevity compared to AOA-treated flowers. Application of ABA alone promoted senescence, suppressed ethylene production, and, when applied with fluridone, countered the fluridone-induced increase in flower longevity. Taken together, these results suggest that the senescence of hibiscus flowers is an endogenously regulated ethylene- and ABA-dependent process.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9181-9
- Authors
- Alice Trivellini, Department of Crop Biology, Università di Pisa, Viale delle Piagge 23, 56124 Pisa, Italy
- Antonio Ferrante, Department of Plant Production, Università degli Studi di Milano, 20133 Milan, Italy
- Paolo Vernieri, Department of Crop Biology, Università di Pisa, Viale delle Piagge 23, 56124 Pisa, Italy
- Anna Mensuali-Sodi, Sant’Anna School of Advanced Studies, 56100 Pisa, Italy
- Giovanni Serra, Sant’Anna School of Advanced Studies, 56100 Pisa, Italy
- Feeding by Hessian Fly (Mayetiola destructor [Say]) Larvae on Wheat Increases Levels of Fatty Acids and Indole-3-Acetic Acid but not Hormones Involved in Plant-Defense Signaling
Abstract Gall-inducing insects exert a unique level of control over the physiology of their host plants. This control can extend to host–plant defenses so that some, if not most, gall-inducing species appear to avoid or modify host plant defenses to effect production of their gall. Included among gall insects is Hessian fly ( Mayetiola destructor [Say], Diptera: Cecidomyiidae), a damaging pest of wheat ( Triticum aestivum L.) and an emerging model system for studying plant–insect interactions. We studied the dynamics of some defense-related phytohormones and associated fatty acids during feeding of first instar Hessian fly larvae on a susceptible variety of wheat. We found that Hessian fly larvae significantly elevated in their host plants’ levels of linolenic and linoleic acids, fatty acids that may be nutritionally beneficial. Hessian fly larvae also elevated levels of indole-3-acetic acid (IAA), a phytohormone hypothesized to be involved in gall formation, but not the defense-related hormones jasmonic (JA) and salicylic acids. Moreover, we detected in Hessian fly-infested plants a significant negative relationship between IAA and JA that was not present in control plants. Our results suggest that Hessian fly larvae may induce nutritionally beneficial changes while concomitantly altering phytohormone levels, possibly to facilitate plant-defense avoidance.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9177-5
- Authors
- John F. Tooker, Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, PA 16802-3508, USA
- Consuelo M. De Moraes, Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, PA 16802-3508, USA
- Benzyladenine Treatment Significantly Increases the Seed Yield of the Biofuel Plant Jatropha curcas
Abstract Jatropha curcas , a monoecious perennial biofuel shrub belonging to the family Euphorbiaceae, has few female flowers, which is one of the most important reasons for its poor seed yield. This study was undertaken to determine the effects of the plant growth regulator 6-benzyladenine (BA) on floral development and floral sex determination of J. curcas . Exogenous application of BA significantly increased the total number of flowers per inflorescence, reaching a 3.6-fold increase (from 215 to 784) at 160 mg/l of BA. Furthermore, BA treatments induced bisexual flowers, which were not found in control inflorescences, and a substantial increase in the female-to-male flower ratio. Consequently, a 4.5-fold increase in fruit number and a 3.3-fold increase in final seed yield were observed in inflorescences treated with 160 mg/L of BA, which resulted from the greater number of female flowers and the newly induced bisexual flowers in BA-treated inflorescences. This study indicates that the seed yield of J. curcas can be increased by manipulation of floral development and floral sex expression.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9179-3
- Authors
- Bang-Zhen Pan, Laboratory of Molecular Breeding of Energy Plants, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 88 Xuefu Road, Kunming, 650223 Yunnan China
- Zeng-Fu Xu, Laboratory of Molecular Breeding of Energy Plants, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 88 Xuefu Road, Kunming, 650223 Yunnan China
- Micromorpho-Anatomical Examination of 2,4-D Phytotoxicity in Grapevine (Vitis vinifera L.) Leaves
Abstract The anatomical and micro-morphological alterations as induced by the auxinic herbicide, 2,4-D (2,4-dichlorophenoxy acetic acid) have not yet been elucidated for a commercially important fruit crop such as grapevine despite its super sensitivity to 2,4-D. Light and scanning electron microscopy techniques were employed to examine 2,4-D induced internal and external structural abnormalities in Merlot grapevines ( Vitis vinifera L.). Healthy leaves were dorsiventrally flattened with well developed patterns of cellular structure and composition involving adaxial palisade parenchyma and abaxial spongy mesophyll. Dorsiventral variations in epidermal features involved large epidermal cells on the adaxial surface, and trichomes and stomata with turgid elliptical guard cells on the abaxial surface. The 2,4-D injured leaves were small and enated; the veins were fasciated with rugose bands of lamina existing between fasciated veins. The epidermal cells aggregated instead of being positioned coplanar to the epidermal plane. The adaxial elongated palisade parenchyma cells were transformed into an ovoid shape with intercellular spaces. An extensive development of replacement tissues took place on the abaxial surface wherein the stomata became roundish and were either raised or sunken with collapsed and cracked guard cells that developed abnormal outer stomatal ledges. These abnormalities are expected to severely perturb the vital functions of photosynthesis and transpiration ultimately leading to vine death attributable, at least in part, to the injured leaves.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9183-7
- Authors
- B. R. Bondada, Washington State University Tri-Cities, 2710 University Drive, Richland, WA 99354, USA
- The Hormonal Regulation of Flower Development
Abstract Homeotic genes comprising the ABCE classes partly detail the genetic networks that control aspects of floral organ initiation, development, and architecture, but less is known about how these gene functions are translated into changes at the cellular level in growth and cellular differentiation that are involved in the formation of diverse floral organs with specific shapes and sizes. Hormones are the principal transducers of genetic information, and due to recent advances in understanding hormone function in floral development, it is timely to review some of these findings. Flower development is the result of a regulated balance between meristem size and coordination and organ initiation. Floral meristem size is regulated by cytokinin, gibberellin, and auxin, and auxin plays a major role in organ initiation and organogenesis. How hormones contribute to the development of each organ is partly known, with stamen development reliant on almost all hormones, petal development is affected by gibberellins, auxin, and jasmonic acid, and gynoecium development is predominantly regulated by auxin. Furthermore, the interconnections between genetic hierarchies and hormones are being elucidated, and as almost all hormone groups are implicated in floral development, points of hormone crosstalk are being revealed.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9180-x
- Authors
- J. W. Chandler, Institute of Developmental Biology, Cologne Bioresearch Centre, Zülpicher Strasse 47b, Cologne, 50674 Germany
- The Distribution and Cooperation of Antioxidant (Iso)enzymes and Antioxidants in Different Subcellular Compartments in Maize Leaves during Water Stress
Abstract The effects of mild water stress induced by polyethylene glycol (PEG) on the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR)] and their isoenzymes and the antioxidant content [ascorbate (ASC) and glutathione (GSH)] of different subcellular compartments were investigated in maize. For each subcellular compartment, the activities of almost all isoenzymes resolved on native PAGE increased after 4–12 h of exposure to water stress and declined after that, showing concomitant changes with the activities of their respective total enzymes and the antioxidant content. For each subcellular compartment, at least one isoform for the detected antioxidant enzymes was resolved, but different kinds of antioxidant isoenzymes in different subcellular compartments had different responses to water stress. The relative contribution of Fe–SOD in chloroplasts and Mn–SOD in mitochondria was higher than that in other subcellular compartments. However, in apoplasts the activities of Mn–SOD and Fe–SOD declined during the process of water stress, in contrast to those located in other subcellular compartments. The results from the activities of antioxidant (iso)enzymes demonstrated that all antioxidant enzymes in all subcellular compartments were mobilized in cooperation and responded synchronously under mild water stress, with the same trend of changes in their activity. This indicated their orchestrated effects in scavenging reactive oxygen species (ROS) in situ. Additionally, the results suggested that mitochondria and apoplasts, responding most actively, might be targets for improving plant performance under mild water stress.
- Content Type Journal Article
- DOI 10.1007/s00344-010-9189-1
- Authors
- Mingpu Tan, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
- Jun Lu, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
- Aying Zhang, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
- Bing Hu, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
- Xuewei Zhu, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
- Wenbo Li, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095 China
No Issue Number - Influence of Paclobutrazol and Application Methods on High-temperature Stress Injury in Cucumber Seedlings
Abstract Paclobutrazol (PBZ) is a member of the triazole plant growth inhibitor group that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was therefore conducted to examine whether the application of PBZ at various concentrations (0, 25, 50, and 75 mg l −1 ) by seed soaking or foliar spray would protect cucumber ( Cucumis sativus ) seedlings subjected to high-temperature stress. Thirty-five-day-old seedlings were exposed to heat stress at 40°C for 4 h per day for 5 days. PBZ improved the majority of the physiological (for example, relative chlorophyll content and chlorophyll fluorescence ratio) and morphological parameters (for example, shoot and root fresh and dry weights) measured in cucumber seedlings subjected to high-temperature stress. PBZ ameliorated the injuries caused by heat stress by increasing leaf proline content and preventing an increase in leaf electrolyte leakage. PBZ was more effective at increasing the heat tolerance of cucumber seedlings when using the seed-soaking method rather than the foliar spray method. The best protection was obtained when seeds were soaked in 50 mg l −1 PBZ.
- Content Type Journal Article
- Pages 1-7
- DOI 10.1007/s00344-010-9188-2
- Authors
- Bahram Baninasab, Department of Horticulture, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-83111 Iran
- Cyrus Ghobadi, Department of Horticulture, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-83111 Iran
- Cloning and Characterization of Three APETALA1/FRUITFULL-like Genes in Different Flower Types of Rosa × hybrida L.
Abstract To clarify the molecular mechanism of flower development in Rosa × hybrida L., three different APETALA1/FRUITFULL ( AP1/FUL )-like MADS-box genes were isolated and their expression analyzed in normally developed flowers and in malformed flowers of a stable phenotype. AP1/FUL -like genes were designated as RhAP1 - 1 , RhFUL , and RhAP1 - 2. Alignment of amino acid sequences showed 83% identity between RhAP1-1 and TrAP1 of Taihangia rupestris and 82% identity between RhFUL and TrFUL of T. rupestris. RhAP1-1 is 97% identical to RhAP1-2 and 58% identical to RhFUL. Expression of RhAP1 - 1 and RhAP1 - 2 in whorls 1 and 2 of rose flowers exclusively is in accordance with the expression pattern of class A genes in other plant species. In contrast, RhFUL showed a unique expression pattern and was expressed only in sepals. The roles of all putative A, B, and C class genes were examined in different flower organs of normally developed flowers and in malformed flowers that are similar to a classic C function mutant from Arabidopsis (with petals in whorl 3 and sepals in whorl 4). The expression pattern of the putative class B genes was similar in both normal and malformed flowers. However, the putative class A genes were upregulated and class C genes were downregulated in all flower organs of the mutant. These data suggest that suppression of the class C genes RhC1 and RhC2 leads to altered expression of RhAP1 - 1 , RhFUL , and RhAP1 - 2 in whorls 3 and 4 that leads to the mutant flower phenotype.
- Content Type Journal Article
- Pages 1-14
- DOI 10.1007/s00344-010-9190-8
- Authors
- Heiko Mibus, Faculty of Natural Sciences, Institute for Ornamental and Woody Plant Science, Leibniz University of Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
- Dirk Heckl, Faculty of Natural Sciences, Institute for Ornamental and Woody Plant Science, Leibniz University of Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
- Margrethe Serek, Faculty of Natural Sciences, Institute for Ornamental and Woody Plant Science, Leibniz University of Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
- Hydraulic and Chemical Responses of Citrus Seedlings to Drought and Osmotic Stress
Abstract In this work we investigated the function of abscisic acid (ABA) as a long-distance chemical signal communicating water shortage from the root to the shoot in citrus plants. Experiments indicated that stomatal conductance, transpiration rates, and leaf water potential decline progressively with drought. ABA content in roots, leaves, and xylem sap was also increased by the drought stress treatment three- to sevenfold. The addition of norflurazon, an inhibitor of ABA biosynthesis, significantly decreased the intensity of the responses and reduced ABA content in roots and xylem fluid, but not in leaves. Polyethylene glycol (PEG)-induced osmotic stress caused similar effects and, in general, was counteracted only by norflurazon at the lowest concentration (10%). Partial defoliation was able to diminish only leaf ABA content (22.5%) at the highest PEG concentration (30%), probably through a reduction of the active sites of biosynthesis. At least under moderate drought (3–6 days without irrigation), mechanisms other than leaf ABA concentration were required to explain stomatal closure in response to limited soil water supply. Measurements of xylem sap pH revealed a progressive alkalinization through the drought condition (6.4 vs. 7.1), that was not counteracted with the addition of norflurazon. Moreover, in vitro treatment of detached leaves with buffers iso-osmotically adjusted at pH 7.1 significantly decreased stomatal conductance (more than 30%) as much as 70% when supplemented with ABA. Taken together, our results suggest that increased pH generated in drought-stressed roots is transmitted by the xylem sap to the leaves, triggering reductions in shoot water loss. The parallel rise in ABA concentration may act synergistically with pH alkalinization in xylem sap, with an initial response generated from the roots and further promotion by the stressed leaves.
- Content Type Journal Article
- Pages 1-14
- DOI 10.1007/s00344-011-9197-9
- Authors
- M. Ángeles Forner-Giner, Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias, Oficial Box, E-46113 Moncada, Valencia, Spain
- Juan Rodríguez-Gamir, Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias, Oficial Box, E-46113 Moncada, Valencia, Spain
- Eduardo Primo-Millo, Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias, Oficial Box, E-46113 Moncada, Valencia, Spain
- Domingo J. Iglesias, Departamento de Citricultura, Instituto Valenciano de Investigaciones Agrarias, Oficial Box, E-46113 Moncada, Valencia, Spain
- Effects of Interactions Between Cadmium and Lead on Growth, Nitrogen Fixation, Phytochelatin, and Glutathione Production in Mycorrhizal Cajanus cajan (L.) Millsp.
Abstract Heavy metals (HM) are a unique class of toxicants because they cannot be broken up into nontoxic forms. Excess HM causes stunted growth, upsets mineral nutrition, and affects membrane structure and permeability. High tolerance to HM toxicity is based on reduced metal uptake or increased internal sequestration in a genotype. Arbuscular mycorrhizal (AM) fungi are important rhizospheric microorganisms that occur in metal-contaminated soils and perhaps detoxify the potential effects of metals. The aim of this work was to study the role of the AM fungus Glomus mosseae in the alleviation of cadmium (Cd) and lead (Pb) toxicities in Cajanus cajan (L.) Millsp. (pigeonpea) genotypes. The effects of interactions between Cd (25 and 50 mg/kg) and Pb (500 and 800 mg/kg) on plant dry mass, nitrogen metabolism, and production of phytochelatins (PCs) and glutathione (GSH) were monitored with and without AM fungus in genotypes Sel-85N (relatively tolerant) and Sel-141-97 (sensitive). Cd treatments were more toxic than Pb, and their combinations led to synergistic inhibitions to growth and nitrogen-fixing potential (acetylene reduction activity [ARA]) in both genotypes. However, the effects were less deleterious in Sel-85N than in Sel-141-97. Exposure to Cd and Pb significantly increased the levels of PCs in a concentration- and genotype-dependent manner, which could be directly correlated with the intensity of mycorrhizal infection (MI). Stimulation of GSH production was observed under Cd treatments, although no obvious effects on GSH levels were observed under Pb treatments. The metal contents (Cd, Pb) were higher in roots and nodules when compared with that in shoots, which was significantly reduced in the presence of AM fungi. The results indicated that PCs and GSH might function as potential biomarkers for metal toxicity, and microbial inoculations showed bioremediation potential by helping pigeonpea plants to grow in multimetal contaminated soils.
- Content Type Journal Article
- Pages 1-15
- DOI 10.1007/s00344-010-9191-7
- Authors
- Neera Garg, Department of Botany, Panjab University, Chandigarh, 160014 India
- Nalini Aggarwal, Department of Botany, Panjab University, Chandigarh, 160014 India
- Overexpression of NlgCycB Isolated from Interspecific Hybrid of N. langsdorffii × N. glauca Alters Root Growth and Root Hair Development
Abstract A cDNA clone encoding cyclin B ( NlgCycB ) was isolated from an interspecific hybrid of N. langsdorffii × N. glauca . The full-length cDNA had an open reading frame of 1,422 bp, with a deduced amino acid sequence of 473 residues. To investigate the role of NlgCycB , transgenic tobacco plants were constructed to overexpress NlgCycB . The transgenic plants showed premature root hair development in the elongation zone of the root tips. They had more and longer root hairs, which contained nuclei of increased size. Flow cytometric analysis revealed that the proportion of cells with 4C DNA content was increased in the transgenic plants. The NlgCycB gene in transgenic plants was coordinately enhanced with the expression of CDKA genes, especially in the root tips. The transgenic plants had greater growth than the wild-type in MS (1/10-strength) medium with reduced salt concentrations. Taken together, NlgCycB may play an important role in premature root hair development in the elongation zone of root tips and can aid in adaptation to low nutrient salt environments.
- Content Type Journal Article
- Pages 1-11
- DOI 10.1007/s00344-011-9198-8
- Authors
- Hye-Kyoung Kwon, Division of Forest Resources, Colleges of Forest Sciences, Kangwon National University, Chuncheon, 200-701 South Korea
- Yong-Eui Choi, Division of Forest Resources, Colleges of Forest Sciences, Kangwon National University, Chuncheon, 200-701 South Korea
- Myeong-Hyeon Wang, Department of Medical Biotechnology, College of Biomedical Science, Kangwon National University, Chuncheon, 200-701 South Korea
- Effect of Putrescine and Paclobutrazol on Growth, Physiochemical Parameters, and Nutrient Acquisition of Salt-sensitive Citrus Rootstock Karna khatta (Citrus karna Raf.) under NaCl Stress
Abstract Salinity is a serious problem in arid and semiarid areas and citrus trees are classified as salt-sensitive. Because putrescine (Put) and paclobutrazol (PBZ) are known to act as plant protectants under environmental stresses, we examined the effect of Put and PBZ on the physiochemical parameters of the salt-susceptible citrus rootstock Karna khatta under NaCl stress. PBZ was applied at 0, 250, and 500 mg L −1 as a soil drench 1 week prior to salinization. A computed amount of NaCl salt to develop soil salinity of 3 dS m −1 (3 g NaCl kg −1 soil) and foliar spray of Put at 0 or 50 mg L −1 were applied. The electrical conductivity (EC) of the garden soil (0.35 dS m −1 ) was used as control. Application of PBZ and/or Put reduced the membrane injury index and increased relative water content, photosynthetic rate, and pigments content under saline conditions compared to what occurred in plants exposed to NaCl in the absence of PBZ or Put. Application of PBZ or Put alone or in combination also improved the activities of SOD and peroxidase and proline content under saline conditions. Application of PBZ and/or Put also increased K + and reduced Na + and Cl − concentrations in leaf tissues. It is proposed that PBZ and/or Put could improve the tolerance of salt-susceptible Karna khatta by regulating absorption and accumulation of ions and improving antioxidant enzyme activities.
- Content Type Journal Article
- Pages 1-11
- DOI 10.1007/s00344-011-9192-1
- Authors
- Dew Kumari Sharma, Division of Fruits and Horticultural Technology, Indian Agricultural Research Institute, New Delhi, 110012 India
- A. K. Dubey, Division of Fruits and Horticultural Technology, Indian Agricultural Research Institute, New Delhi, 110012 India
- Manish Srivastav, Division of Fruits and Horticultural Technology, Indian Agricultural Research Institute, New Delhi, 110012 India
- A. K. Singh, Division of Fruits and Horticultural Technology, Indian Agricultural Research Institute, New Delhi, 110012 India
- R. K. Sairam, Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi, 110012 India
- R. N. Pandey, Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012 India
- Anil Dahuja, Division of Biochemistry, Indian Agricultural Research Institute, New Delhi, 110012 India
- Charanjeet Kaur, Division of Post Harvest Technology, Indian Agricultural Research Institute, New Delhi, 110012 India
- Nitric Oxide Induces Flowering in the Duckweed Lemna aequinoctialis Welw. (Syn. L. paucicostata Hegelm.) Under Noninductive Conditions
Abstract Nitric oxide (NO) plays diverse roles in the growth and development of plants and in their responses to various abiotic and biotic stresses. It has also been reported to repress flowering in Arabidopsis thaliana . In the present study, NO donors sodium nitroprusside (SNP), S -nitroso- N -acetyl penicillamine (SNAP), and 3-morpholinosydnonimine (SIN-1) induced flowering in Lemna aequinoctialis 6746 (a short-day strain) and in L. aequinoctialis LP 6 (a photoperiod-insensitive strain) under noninductive conditions. Nitrate and nitrite, two stable metabolites of NO, did not induce flowering. On the other hand, cyanide donors potassium ferricyanide {K 3 [Fe(CN) 6 ]} and potassium cyanide (KCN) induced flowering in both strains under noninductive conditions. The flowering induced under a 8-h daily photoperiod regime in the short-day strain L. aequinoctialis 6746 was inhibited by NO and cyanide donors. Vegetative multiplication of both strains was adversely affected by NO and cyanide donors, irrespective of the photoperiod conditions. The observed effects of NO donors on flowering were substantially negated by NO scavengers c-PTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and methylene blue. This confirmed the role of NO in induction of flowering. The inductive effect of CN − also appeared to be partly mediated through NO as NO scavengers partially negated the effect of CN − .
- Content Type Journal Article
- Pages 1-8
- DOI 10.1007/s00344-011-9199-7
- Authors
- Ashima Khurana, Department of Botany, University of Delhi, New Delhi, 110007 India
- Jitendra P. Khurana, Department of Plant Molecular Biology, University of Delhi, South Campus, New Delhi, India
- Shashi B. Babbar, Department of Botany, University of Delhi, New Delhi, 110007 India
- Plant-Growth-Promoting Fungicide-Tolerant Rhizobium Improves Growth and Symbiotic Characteristics of Lentil (Lensesculentus) in Fungicide-Applied Soil
Abstract The goal of this study was to identify lentil-specific rhizobial strains with the ability to tolerate fungicide and synthesize plant growth regulators even in soils contaminated with fungicides. A fungicide-tolerant and plant-growth-promoting rhizobial strain was used to assess its impact on lentil grown in fungicide-treated soils. The tebuconazole-tolerant Rhizobium sp. strain MRL3 produced plant-growth-promoting substances when grown in the presence and the absence of tebuconazole. Tebuconazole at the recommended and two and three times the recommended doses decreased consistently the dry biomass, symbiotic properties, nutrient uptake, and seed yields of lentil plants. In contrast, the fungicide-tolerant strain MRL3 significantly increased the measured parameters when lentil was grown in soils treated with varying concentrations of tebuconazole compared to uninoculated plants. As an example, strain MRL3 with 100 μg tebuconazole/kg soil significantly increased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, and seed yield by 31, 10, 41, 21, and 117%, respectively, compared to the uninoculated plants grown in soil treated solely with 100 μg tebuconazole/kg soil. In conclusion, the Rhizobium strain MRL3 may be applied as biofertilizer to enhance the performance of lentil plants in fungicide-applied soils.
- Content Type Journal Article
- Pages 1-9
- DOI 10.1007/s00344-011-9195-y
- Authors
- Munees Ahemad, Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, 202002 Uttar Pradesh India
- Mohammad Saghir Khan, Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, 202002 Uttar Pradesh India
- Phytohormone Changes and Carbohydrate Status in Sweet Orange Fruit from Huanglongbing-infected Trees
Abstract Huanglongbing (HLB) infection alters citrus fruit growth and development, resulting in small, misshapen, and poorly colored fruit containing aborted or partially developed seeds. Typically, symptomatic fruit have delayed maturation and abscise prematurely. We studied carbohydrate and phytohormone changes in HLB-affected fruit to explain symptom development because (1) carbohydrate shortage has been linked to fruit growth arrest and eventually abscission and (2) hormonal signals regulate, at least partially, fruit set and development. Symptomatic fruit (S), asymptomatic fruit (AS) from symptomatic trees, and healthy fruit (H) from asymptomatic trees were harvested from ‘Valencia’ sweet orange trees [ Citrus sinensis (L.) Osbeck] infected with the HLB pathogen or not, as verified by PCR. Mature S weighed less, had lower °Brix, were smaller, had more aborted seeds, and were greener than AS or H. Starch and sucrose contents were lower in mature S flavedo compared with that of H and AS. S and AS harvested 7 and 12 months after full bloom produced significantly less ethylene than H. Indole-3-acetic acid (IAA) and abscisic acid (ABA) contents in flavedo removed from the stylar end, middle section, or stem end of fruit generally were higher in S flavedo than in AS and H. ABA content was fourfold higher in flavedo from the middle section of S than in AS and H. Flavedo excised from the large shoulder of misshapen S had significantly higher IAA content when compared with the normal-sized area of the same fruit on the opposite side. This increase corresponded to an increase in hypodermal cell area in S flavedo. Overall, these data reveal an imbalance of carbohydrate and phytohormone status in fruit from HLB-infected trees and suggest a role of such changes in fruit symptom development.
- Content Type Journal Article
- Pages 1-10
- DOI 10.1007/s00344-011-9193-0
- Authors
- Raquel Rosales, Horticultural Sciences Department, University of Florida Institute of Food and Agricultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850-2299, USA
- Jacqueline K. Burns, Horticultural Sciences Department, University of Florida Institute of Food and Agricultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850-2299, USA
- Interplay Between Abscisic Acid and Jasmonic Acid and its Role in Water-oxidative Stress in Wild-type, ABA-deficient, JA-deficient, and Ascorbate-deficient Arabidopsis Plants
Abstract The interplay between jasmonic acid (JA) and abscisic acid (ABA) in plant responses to water stress and in water-stress-enhanced oxidative stress was investigated in Arabidopsis thaliana plants subjected to water stress by water deprivation. For this purpose a drought assay was conducted using Arabidopsis mutants impaired in ABA ( aba2 ), JA ( aos ), and ascorbate ( vtc1 ) biosynthesis. Our results show an interaction between ABA and JA during their biosynthesis. Moreover, the coordinated action of ABA and JA protected wild-type, aba2 , and aos plants from the effects of stress. However, this effect was not observed in the vtc1 mutant, which showed a distinct decrease in the F v / F m ratio, concomitant with a marked fall in relative water content (RWC), despite high endogenous concentrations of JA and ABA. This finding indicates the relevance of ascorbate metabolism in plant acclimation to stress. Despite the interaction between the two phytohormones, drought-associated stomatal closure is regulated mainly by ABA and weakly by JA, whereas JA plays a role in the formation of antioxidants regulating ascorbate and glutathione metabolism. A time course analysis revealed the relevance of plant age and stress duration in the responses of the mutants compared to wild-type plants. Here we discuss the relationship between ABA, JA, ascorbate, and glutathione in plants under water stress.
- Content Type Journal Article
- Pages 1-12
- DOI 10.1007/s00344-011-9194-z
- Authors
- Ricard Brossa, Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
- Marta López-Carbonell, Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
- Tana Jubany-Marí, Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
- Leonor Alegre, Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avda. Diagonal 645, 08028 Barcelona, Spain
- The AGL6-like Gene CpAGL6, a Potential Regulator of Floral Time and Organ Identity in Wintersweet (Chimonanthus praecox)
Abstract Wintersweet ( Chimonanthus praecox ), a deciduous aromatic shrub endemic to China, has high ornamental value for developing beautiful flowers with strong fragrance. The transition from the vegetative to the reproductive phase in wintersweet takes 4-5 years. The molecular mechanism regulating flower development in this basal angiosperm is largely unknown. Here we characterized the molecular features and expression patterns of the C . praecox AGL6 -like gene CpAGL6 and investigated its potential role in regulating floral time and organ development via ectopic expression in Arabidopsis thaliana . The expression of CpAGL6 is highly tissue-specific, with the highest level in the middle tepals, moderate levels in inner tepals and carpels, and weak levels in stamen and young leaf tissues. Its dynamic expression in the flower is coincident with tepal opening. Ectopic expression of CpAGL6 in Arabidopsis retarded the vegetative growth and led to precocious flowering, mainly correlated with the inhibition of the floral repressor FLC and promotion of the floral promoters AP1 and FT . Although no ectopic floral organs have been observed, transgenic plants exhibited abnormal stamen and carpel development in later-developing flowers, with fertility reduced to varying degrees. These results suggest that CpAGL6 , the AGL6 -like gene from the basal angiosperm C . praecox , is a potential E-function regulator involved in specifying floral time and organ identity, functionally homologous to those AGL6 -like genes from higher eudicots and monocots.
- Content Type Journal Article
- Pages 1-10
- DOI 10.1007/s00344-011-9196-x
- Authors
- Bei-Guo Wang, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Qiong Zhang, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Li-Gang Wang, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Ke Duan, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Ai-Hu Pan, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Xue-Ming Tang, Shanghai Key Laboratory of Agricultural Genetics and Breeding, Institute of Biotechnology, Shanghai Academy of Agricultural Sciences (SAAS), Beidi Road 2901, Minhang District, Shanghai, 201106 China
- Shun-Zhao Sui, College of Horticulture and Landscape, Institute of Ornamental Research, Southwest University, Chongqing, 400716 China
- Ming-Yang Li, College of Horticulture and Landscape, Institute of Ornamental Research, Southwest University, Chongqing, 400716 China
- Differential Transcript Expression of Wall-loosening Candidates in Leaves of Maize Cultivars Differing in Salt Resistance
Abstract
Salt-sensitive crop plants such as maize ( Zea mays L.) exhibit a strong and rapid growth reduction in response to NaCl stress. The unique salt-resistant maize hybrid SR03 and the salt-sensitive maize hybrid Lector provide good tools to characterize various genotypic responses to salinity in terms of shoot growth, shoot extensibility, and the expression pattern of wall-loosening candidates. The mRNA transcript levels of wall-loosening candidates such as xyloglucan endotransglucosylase (XET), endo-1,4-β-D-endoglucanase (EGase), α-expansins (EXPA), and the plasma membrane proton pump (PM-H + -ATPase) are correlated with cell-wall extensibility and with shoot growth under NaCl stress. We have found for the salt-sensitive maize that a decrease in the relative transcript abundance of ZmXET1, ZmEXPA1, and the composite PM-H + -ATPase mRNAs correlates with a decrease in wall extensibility and shoot growth. We suggest that this downregulation of wall-loosening candidates contributes to a reduction in extensibility and consequently in growth. In contrast, the decrease in wall extensibility is less strong in the salt-sensitive hybrid SR03. In the salt-resistant maize genotype, an upregulation of ZmXET1, ZmEXPA1 and PM-H +- ATPase transcripts possibly mitigates the salinity-induced decrease in wall extensibility and thus in shoot growth.
DOI: 10.1007/s00344-011-9201-4
- Jasmonic Acid-Mediated-Induced Resistance in Groundnut (Arachis hypogaea L.) Against Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)
Abstract
Jasmonic acid (JA) acts as a signal molecule to induce resistance in plants against herbivores and its levels are elevated in plants after wounding or insect damage. Groundnut is an important crop in many tropical and subtropical regions worldwide, but there is surprisingly little knowledge on its induced defenses against herbivores. The effect of JA as a spray on induced resistance in three groundnut genotypes, namely, ICGV 86699 (resistant), NCAc 343 (resistant), and TMV 2 (susceptible), against Helicoverpa armigera was studied. The activity of oxidative enzymes [peroxidase (POD) and polyphenol oxidase (PPO)] and the amounts of other host plant defense components [total phenols, hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), and protein content] were recorded at 24, 48, 72, and 96 h after pretreatment (1 day) with JA followed by infestation with H. armigera (PJA + HIN) and H. armigera infestation with simultaneous JA application (HIN + JA) to understand the consequences of induced resistance in groundnut. The plant damage, larval survival, and larval weights were also recorded. There was a significant increase in POD and PPO activities and in the amounts of total phenols, H 2 O 2 , MDA, and proteins in PJA + HIN- and JA + HIN-treated plants as compared to the plants treated with JA and infested with H. armigera individually and to untreated control plants. Among all the genotypes, the strongest induction of defense was observed in the ICGV 86699 genotype. It is concluded that pretreatment with JA and its application during low levels of insect infestation can increase the levels of host plant resistance against herbivorous insects and reduce the pest-associated losses in groundnut.
DOI: 10.1007/s00344-011-9213-0
- Effect of Selenium on Ascorbate–Glutathione Metabolism During PEG-induced Water Deficit in Trifolium repens L.
Abstract
To elucidate the effect of selenium (Se) on the ascorbate–glutathione (ASC–GSH) cycle under drought stress, the activities of antioxidant enzymes and the levels of molecules involved in ASC–GSH metabolism were studied in Trifolium repens seedlings subjected to polyethylene glycol (PEG)-induced water deficit alone or combined with 5 μM Na 2 SeO 4 . Compared to the control, H 2 O 2 , thiobarbituric acid reactive substances (TBARS), ascorbate (ASC), dehydroascorbate (DHA), and glutathione disulfide (GSSG) contents increased, whereas a constant content of glutathione (GSH) and decreases in ASC/DHA and GSH/GSSG ratios were observed in the presence of PEG. The activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were upregulated, except for monodehydroascorbate reductase (MDHAR) activity during PEG-induced water deficit. Se application decreased the contents of H 2 O 2 , TBARS, DHA, and GSSG, increased the levels of GSH and ASC, and inhibited the decreases of ASC/DHA and GSH/GSSG ratios. Although it did not affect APX activity significantly, Se addition improved the activities of MDHAR, DHAR, and GR. Furthermore, GR activity showed the highest increase followed by that of DHAR and MDHAR in decreasing order. These data indicated that fluctuations in ASC–GSH metabolism resulting from Se may have a positive effect on drought stress mitigation, and the regulation in the ASC–GSH cycle can be attributed mainly to GR and DHAR in PEG + Se-treated T. repens seedlings.
DOI: 10.1007/s00344-011-9206-z
- A Whole-Plant Microtiter Plate Assay for Drought Stress Tolerance-Inducing Effects
Abstract
The frequency and intensity of extreme weather events and global temperature are rising, which poses a potential threat to life, specifically crops, and therefore food and bioenergy supply. Reduced water availability has the most severe impact on potential grain yield. Negative effects of transient drought stress (dry spells) can be countered by drought tolerance-inducing chemicals. In search for useful compounds, biochemical assays are fast but limited in scope, whereas whole-plant assays are slow, require large amounts of compounds, and are usually not concentration-related. Here we report the development of a fast, concentration-dependent whole-plant assay using the fast growing duckweed Lemna minor L. 4-Amino-1,8-naphthalimide ( 1 ) and the imidacloprid metabolite 6-chloronicotinic acid ( 2 ) were affirmed as drought stress tolerance enhancers. Both also reduce oxidative stress-induced cell death in Arabidopsis thaliana (L.) Heynh. cell suspension culture but show differences in their mode of action.
DOI: 10.1007/s00344-011-9212-1
- Role of Salicylic Acid in Promoting Salt Stress Tolerance and Enhanced Artemisinin Production in Artemisia annua L.
Abstract
In the present investigation, the role of salicylic acid (SA) in inducing salinity tolerance was studied in Artemisia annua L., which is a major source of the antimalarial drug artemisinin. SA, when applied at 1.00 mM, provided considerable protection against salt stress imposed by adding 50, 100, or 200 mM NaCl to soil. Salt stress negatively affected plant growth as assessed by length and dry weight of shoots and roots. Salinity also reduced the values of photosynthetic attributes and total chlorophyll content and inhibited the activities of nitrate reductase and carbonic anhydrase. Furthermore, salt stress significantly increased electrolyte leakage and proline content. Salt stress also induced oxidative stress as indicated by the elevated levels of lipid peroxidation compared to the control. A foliar spray of SA at 1.00 mM promoted the growth of plants, independent of salinity level. The activity of antioxidant enzymes, namely, catalase, peroxidase, and superoxide dismutase, was upregulated by salt stress and was further enhanced by SA treatment. Artemisinin content increased at 50 and 100 mM NaCl but decreased at 200 mM NaCl. The application of SA further enhanced artemisinin content when applied with 50 and 100 mM NaCl by 18.3 and 52.4%, respectively. These results indicate that moderate saline conditions can be exploited to obtain higher artemisinin content in A. annua plants, whereas the application of SA can be used to protect plant growth and induce its antioxidant defense system under salt stress.
DOI: 10.1007/s00344-011-9205-0
- Salicylic Acid-induced Nitric Oxide and ROS Generation Stimulate Ginsenoside Accumulation in Panax ginseng Roots
Abstract
We evaluated the involvement of nitric oxide (NO) in salicylic acid (SA)-induced accumulation of ginsenoside in adventitious roots of Panax ginseng and its mediation by reactive oxygen species (ROS). Related effects of SA on components of the antioxidant system were also sought. Adventitious roots of P. ginseng were grown in suspension culture for 3 weeks in MS medium and treated over 5 days with SA (100 μM) alone, SA in combination with the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), or PTIO alone. Nitric oxide, the superoxide anion (O 2
·− ), H 2 O 2 , nitrite, nonprotein thiol, and ascorbate were monitored together with ginsenoside, NADPH oxidase activity, and several antioxidant enzymes. Salicylic acid did not inhibit root growth but induced accumulation of ginsenoside, lipid peroxidation, and generation of NO and O 2
·− . It also enhanced activities of NADPH oxidase, superoxide dismutase, catalase, and peroxidase, including ascorbate peroxidase. These effects were suppressed by PTIO. Salicylic acid also decreased glutathione reductase activity. Inclusion of PTIO with SA decreased the activity of glutathione reductase further. Treatment with SA plus PTIO also decreased nonprotein thiol and ascorbate contents but caused nitrite to overaccumulate. Salicylic acid applied to adventitious roots in culture induced accumulation of ginsenoside in an NO-dependent manner that was mediated by the associated increases in O 2
·− , which gave other antioxidant responses that were dependent on NO.
DOI: 10.1007/s00344-011-9202-3
- Fruit-set and Early Fruit Growth in Tomato are Associated with Increases in Indoleacetic Acid, Cytokinin, and Bioactive Gibberellin Contents
Abstract
Fruit-set, defined as the activation of a developmental program which converts the ovary into a developing fruit, depends on the crosstalk among plant hormones. Here we show that in pollinated ovaries fruit-set is associated with an increase in indole-3-acetic acid (IAA) content and high transcript levels of ToFZY , a gene involved in the tryptophan-dependent auxin biosynthesis pathway. In unpollinated ovaries developed parthenocarpically in response to the synthetic auxin chlorophenoxyacetic acid (4-CPA), ToFZY mRNA levels and IAA content slightly increase. The most likely sequence of events after fertilization involves auxin-mediated activation of gibberellin (GA) synthesis. Fertilization events not only strongly increase SlGA20ox1 and SlGA20ox3 message levels but also increase SlGA2ox2 , SlGA2ox4 , and SlGA2ox5 mRNA levels, suggesting a concerted regulation to modulate the level of bioactive GAs, GA 1 and GA 3 . 4-chlorophenoxyacetic acid was found to mimic the fertilization events in the stimulation of SlGA20ox1 and SlGA20ox3 mRNA levels, which were also enhanced and increased earlier, but in contrast with pollinated ovaries, SlGA2ox2 , SlGA2ox4 , and SlGA2ox5 mRNA levels were repressed leading to higher levels of bioactive GAs. We have also analyzed the content of abscisic acid (ABA) and its metabolites dihydrophaseic acid, phaseic acid, and ABA-glucosyl ester and the level of cytokinins (CKs) (free bases and their corresponding ribosides and ribotides) in pollinated and auxin-treated tomato fruits. We show that ABA levels decrease whereas the levels of free CKs increase immediately after pollination or auxin treatment.
DOI: 10.1007/s00344-011-9204-1
- CML24 is Involved in Root Mechanoresponses and Cortical Microtubule Orientation in Arabidopsis
Abstract
Mechanostimuli can influence plant root system architecture by causing alterations in the root tip growth direction and triggering lateral root initiation. However, how a plant root senses and translates mechanostimulation into appropriate growth and/or developmental responses remains largely unclear. The fast expression induction and transcript turnover of the Arabidopsis TCH genes by touch stimulation suggest that the TCH genes may function in mechano-related events. However, the physiological functions of the TCH genes in Arabidopsis mechanoresponses remain undetermined. Here we screened a suite of tch mutants by characterizing their root growth behaviors on hard-agar surfaces. Two calmodulin-like 24 ( CML24 or TCH2 ) mutants, cml24-2 and cml24-4 , exhibited reduced root length, biased skewing, and altered epidermal cell file rotation (CFR) phenotypes compared with wild type (Col-0). The mutant phenotypes were dependent on hard-agar surface contact and disappeared when seedlings were grown in liquid medium. Abnormal glass barrier responses of cml24 mutants further indicate touch response defects. Pharmacological tests revealed differential sensitivity of cml24 mutants to microtubule-targeted agents. Nonadditive effects of mutations in CML24 and transgenic expression of a functional microtubule label, MBD-GFP, on root skewing and CFR phenotypes suggest a potential microtubule-related role of CML24 . In vivo visualization of microtubule structures with the MBD-GFP reporter revealed altered cortical microtubule orientation in the epidermal cells in cml24-4 . Our observations indicate that CML24 has a role in Arabidopsis root mechanoresponses, possibly through the regulation of cortical microtubule orientation.
DOI: 10.1007/s00344-011-9209-9
- The aba3-1 Mutant of Arabidopsis thaliana Withstands Moderate Doses of Salt Stress by Modulating Leaf Growth and Salicylic Acid Levels
Abstract
The role of abscisic acid (ABA) and salicylic acid (SA) in salt stress tolerance was studied in Arabidopsis thaliana using mutants that show a defect in hormone biosynthesis or signaling. Plants were subjected to either control conditions (irrigated with nutrient solution) or a moderate salt stress (nutrient solution + 100 mM NaCl), and the response of the aba3 , abi4 , sid2 , and eds5 mutants (with defective ABA or SA biosynthesis/signaling) was compared to that of the wild type (WT). A particular phenotype was observed in the aba3 mutant, which was characterized by reduced plant biomass and lower relative leaf water contents (RWC) under control conditions. However, salt stress reduced growth in the WT, sid2 , and eds5 mutants, and to a lesser extent in the abi4 mutant, but not in the aba3 mutant. An analysis of the hormonal balance of leaves revealed that altered SA levels may explain, at least partly, growth changes in the aba3 mutant, under both control and salt stress conditions. The aba3-1 mutant showed higher SA levels than the WT under control conditions and a drastic decrease in the levels of this plant growth regulator under salt stress, an aspect that was not observed in the WT. However, reductions in endogenous SA levels in sid2 and eds5 mutants did not result in increased growth either under control or salt stress conditions. Among the tested genotypes, the aba3 mutant was the only one in which jasmonic acid (JA) levels did not increase in response to salt stress. It is concluded that although ABA deficiency can severely affect plant growth and water relations in aba3 mutants, these plants modulate, among other processes, leaf growth and SA levels, which help them withstand moderate doses of salt stress.
DOI: 10.1007/s00344-011-9208-x
- The Effects of Salinity on Nitrogen Fixation and Trehalose Metabolism in Mycorrhizal Cajanus cajan (L.) Millsp. Plants
Abstract
Arbuscular mycorrhizal (AM) fungi exist widely in natural ecosystems as well as in salt-affected soils and are considered suitable candidates for bio-amelioration of saline soils. Plants respond to salinity by accumulating sugars and other low-molecular-weight compatible solutes. One such compound is trehalose, which has been found to play an important role as a stress protectant. The aim of the present investigation was to study interactions between an AM fungus and salinity stress on growth, nitrogen fixation, and trehalose metabolism in Cajanus cajan (L.) Millsp. (pigeonpea). Two genotypes [Sel 85N (salt-tolerant) and ICP 13997 (salt-sensitive)] were subjected to saline treatments with and without mycorrhizal inoculations. Salinity reduced plant biomass (shoot and root) in both genotypes and resulted in a decline in shoot-to-root ratio (SRR); however, a smaller decline was observed in Sel 85N than in ICP 13997. AM colonization was reduced with increasing salinity levels but mycorrhizal responsiveness (MR) increased. Genotypic variability in nitrogen fixation and trehalose metabolism in response to salinity and mycorrhization was observed. An increment in nodule number was accompanied by a reduction in dry mass. Subsequently, nodular activity (leghemoglobin, acetylene-reduction activity [ARA], nitrogen content) was reduced under soil salinity, which was more profound in ICP 13997 than in Sel 85N. The symbiotic association with Glomus mosseae led to significant improvement in plant dry mass and nitrogen-fixing potential of nodules under salt stress. Salinity led to an increase in trehalose-6-P synthetase (TPS) and trehalose-6-P phosphatase (TPP) activities resulting in increased trehalose content in nodules, which was accompanied by inhibition of trehalose catabolism (trehalase activity). AM plants had lower trehalase activity under saline and nonsaline conditions. Thus, a symbiotic relationship between plant roots and G. mosseae might have resulted in salinity tolerance in a genotype-dependent manner.
DOI: 10.1007/s00344-011-9211-2
- Nodule Senescence in Medicago truncatula–Sinorhizobium Symbiosis Under Abiotic Constraints: Biochemical and Structural Processes Involved in Maintaining Nitrogen-Fixing Capacity
Abstract
Nitrogen-fixing capacity (NFC) in nodules of four Medicago truncatula lines inoculated with four strains of Sinorhizobium was assessed, during the plant life cycle, in relation to parameters identified as indices of plant growth, photosynthetic capacity, nodule integrity, and functioning. Differences in duration of the NFC period were observed among symbiotic associations and were correlated with variability on plant biomass production. Senescence appearance and vigor varied in parallel with structural, physiological, and biochemical stability of nodules. Maintenance of a longer high-NFC period was correlated to a higher stimulation of antioxidant enzymes, mainly superoxide dismutase (SOD, EC 1.15.1.1) and guaiacol peroxidase (POX, EC 1.11.1.7), and a consequent longer maintenance of membrane integrity and nodule structure within the first stages of senescence. Salinity and drought stresses interfered with nodule functioning and triggered fast and global nodule senescence, albeit a superiority of nodules having a long high-NFC period. The protective role of POX activity on salt- and drought-stressed nodules was revealed. On the other hand, SOD stimulation was independent of stress application. Another strategy allowing the maintenance of longer NFC in salt-stressed nodules could be the accumulation of starch granules in the senescence-functioning interface of nodules. This finding is currently under investigation. Interestingly, the symbioses with different behaviors of nodule senescence identified in this work would be useful bases for biochemical, genomic, and proteomic studies dissecting nodule senescence.
DOI: 10.1007/s00344-011-9210-3
- Cloning and Characterization of the H Subunit of a Magnesium Chelatase Gene (PpCHLH) in Peach
Abstract
It has been suggested that the phytohormone abscisic acid (ABA) plays an important role in the ripening of climatic fruit, although relevant genetic/molecular evidence is lacking. In the present study, a peach gene homologous to the putative Arabidopsis ABA receptor gene ABAR/CHLH , named PpCHLH , was isolated and characterized. PpCHLH is expressed ubiquitously as a single-copy gene in peach. Using tobacco rattle virus-induced gene silencing (VIGS), the PpCHLH gene was silenced in both peach leaves and fruit. The silenced PpCHLH gene affected leaf stomatal movement and delayed fruit ripening significantly. Although exogenously applied ABA promoted the ripening of the wild-type fruits, it could not rescue the RNAi chimeric fruit ripening. Collectively, these results demonstrate that PpCHLH plays a critical role in peach fruit ripening, and suggest that ABA might function as an important signal in the regulation of climacteric fruit development.
DOI: 10.1007/s00344-011-9207-y
- Expression and Subcellular Localization of Arabidopsis thaliana Auxin-Binding Protein 1 (ABP1)
Abstract
Expression of Arabidopsis thaliana ABP1 ( AUXIN-BINDING PROTEIN 1 ) was studied using a promoter:GUS approach. Two promoter regions were analyzed. The 1585-bp promoter region upstream of the translation start site (P ABP1 ) showed different activity compared to the promoter region that included, in addition, the first two introns and three exons of the transcribed ABP1 sequence (P ABP1 i1,2 ), indicating that cis elements were present downstream of the start codon. P ABP1 i1,2 -driven β -glucuronidase activity was highest in growing leaves, in the root meristem, in vascular tissues, and in hydathodes. ABP1 promoter activities overlapped largely but not completely with that of DR5, which is a marker for the ARF-AuxRE-dependent auxin response. Subcellular ABP1 localization was studied using a constitutively overexpressed EGFP-ABP1 fusion protein. Results confirmed predominant localization to the endoplasmic reticulum as was concluded previously.
DOI: 10.1007/s00344-011-9203-2
No Issue Number - Fruit Load and Root Development in Field-Grown Loquat Trees (<em class="a-plus-plus">Eriobotrya japonica</em> Lindl)
Abstract Photosynthate translocation to the root in loquat trees decreases as fruit develops. Thus, during the most active period of fruit development, that is, from 50 % of its final size to the beginning of fruit color change, which correspond to BBCH growth scale stages 705 and 801, both translocating and reducing carbohydrate concentrations diminish greatly. Concomitantly, the results from our experiment show an increased abscisic acid (ABA) concentration and a decrease in the respiration rate detected by an accumulation of glucose-6-phosphate, which paralleled a reduced indole-3-acetic acid (IAA) concentration in roots. As a consequence, root development was strongly and significantly reduced. Because loquat fruit develops in winter and nonshoot growth takes place at this time, our results show that root development in loquat trees is controlled by the fruit, mediated by competition for carbohydrates and modulated by hormones. The experiment was conducted using field-grown loquat during two consecutive years and by comparing fruiting and defruited trees. Fruits were detached from the trees in the early fruit developmental stage (10 % of final size, 701 BBCH growth scale), and carbohydrate concentrations in leaves, shoot bark, and roots, as well as nitrogen fractions (N–NO 3 − , N–NH 4 + , and N–proteinaceous) and hormone (IAA, zeatin, and ABA) concentrations in roots, were analyzed throughout the period of fruit development. Root development was evaluated by counting the emerging lateral root primordia during the fruit developmental stages BBCH growth scale 701–809 (fruit color fully developed).
- Regulation of Phytohormone Biosynthesis and Accumulation in <em class="a-plus-plus">Arabidopsis</em> Following Treatment with Commercial Extract from the Marine Macroalga <em class="a-plus-plus">Ascophyllum nodosum</em>
Abstract Seaweeds and their extracts have been used for centuries in agriculture to improve plant growth and impart stress tolerance. There has been historical evidence that phytohormones present in seaweeds lead to these effects, but questions of this mode of action have always been raised. By quantifying phytohormones in seaweed extracts coupled with the use of phytohormone biosynthetic and insensitive mutants, we conclude that the phytohormone levels present within the extracts are insufficient to cause significant effects in plants when extracts are applied at recommended rates. However, components within seaweed extracts may modulate innate pathways for the biosynthesis of phytohormones in plants. Phytohormone profiles of plant tissue extracts were analyzed following root application of a commercial seaweed extract produced from Ascophyllum nodosum (ANE) to in vitro-grown Arabidopsis plants. We found an increase in total concentration of cytokinins (CKs), in particular, of trans -zeatin-type CKs, 24 and 96 h after ANE application, with an increase in cis -zeatin-type CKs observed at 144 h. Concomitantly, increases in abscisic acid (ABA) and ABA catabolite levels were observed whereas auxin levels were reduced. Additionally, the profile of transcripts revealed that CK biosynthetic genes were upregulated, whereas the CK catabolic genes were repressed at 24 and 96 h following ANE application. Not surprisingly, the transcripts of ABA biosynthetic genes were increased whereas the auxin biosynthetic genes were repressed. These corroborated findings are the first to help explain the underlying physiological benefits derived from the application of ANE to plants.
- Transcriptional Regulation of Genes Encoding Key Enzymes of Abscisic Acid Metabolism During Melon (<em class="a-plus-plus">Cucumis melo</em> L.) Fruit Development and Ripening
Abstract The ‘Elizabeth’ melon ( Cucumis melo L. cv. Elizabeth) is regarded as a climacteric fruit, but it has characteristics of both climacteric and nonclimacteric fruits during the ripening stage. To clarify whether the ethylene-independent pathways during ripening were related to abscisic acid (ABA), four cDNAs that encode for key enzymes of ABA metabolism ( CMNCEDs , CMCYP707A1 , and CMBG1 ) were cloned and their transcription expression levels were analyzed. The levels of endogenous ABA and ethylene production in fruit ripening and the effect of exogenous ABA or nordihydroguaiaretic acid (NDGA) treatment on fruit senescence post-harvest were also investigated. The results showed that the ABA levels in young fruit were initially high then gradually decreased. At 20 days after fruit setting (DAFS) there was a rapid increase that peaked at 30 DAFS. Ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and ACC oxidase (ACO) activity were all at low levels at the early stages of fruit setting, and their peaks were observed 5 days after the ABA peak. The CMNCED3 gene and the β-glucosidase gene CMBG1 had similar expression patterns, with expression peaks that occurred at 30 DAFS, which was consistent with the accumulation of ABA. The expression of CMNCED2 was relatively high during the early stages and no peak value occurred in the ripening stage. The CMCYP707A1 gene was expressed mainly at the late ripening stage. The exogenous ABA treatment promoted fruit ripening and softening by the upregulation and expression of the ethylene synthesis genes CmACS1 and CmACO1 and the cell wall catabolic enzyme gene CmPG1 . The effect was proportional to the concentration of ABA, but too much ABA (>500 μmol/L) had a negative effect on fruit development. The NDGA treatment also had a negative effect on fruit ripening and development. ABA and ethylene have a synergistic effect on the regulation of melon fruit ripening. ABA mainly acted in the early stages of development, whereas ethylene played a major role in later stages of ripening. The endogenous ABA levels were maintained in a dynamic balance of biosynthesis and catabolism, which were regulated by CMNCEDs , CMBG1 , and CMCYP707A1 .
- Molecular Characterization and Expression of Ethylene Biosynthetic Genes During Cut Flower Development in Tree Peony (<em class="a-plus-plus">Paeonia suffruticosa</em>) in Response to Ethylene and Functional Analysis of <em class="a-plus-plus">PsACS1</em> in <em class="a-plus-plus">Arabidopsis thaliana</em>
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">Our previous studies have suggested that ethylene is likely to be involved in the regulation of opening and senescence of cut flowers of tree peony. In the present work, to understand the molecular regulation of ethylene biosynthesis in cut tree peony flower development, we isolated two full-length cDNAs encoding ethylene synthetic enzymes, termed <em class="a-plus-plus">PsACS1</em> and <em class="a-plus-plus">PsACO1</em>, from tree peony flower petals and investigated the effects of exogenous ethylene and 1-methylcyclopropene (1-MCP) on their expressions during vase life. Northern blot analysis revealed that in untreated flowers slight expression of <em class="a-plus-plus">PsACS1</em> was initiated until flowers half opened and reached the maximum when flowers fully opened, whereas <em class="a-plus-plus">PsACO1</em> exhibited constitutive levels during flower opening. <em class="a-plus-plus">PsACS1</em> expression was substantially induced by ethylene and inhibited by 1-MCP during flower development, and no significant alteration was found in the accumulation of <em class="a-plus-plus">PsACO1</em> transcript in the petals of differently treated flowers. These results suggest that the <em class="a-plus-plus">PsACS1</em> gene and its resultant protein may be involved in flower opening and senescence, whereas <em class="a-plus-plus">PsACO1</em> seems constitutively expressed in tree peony. Via <em class="a-plus-plus">Agrobacterium</em>-mediated transformation, <em class="a-plus-plus">PsACS1</em> was successfully inserted into <em class="a-plus-plus">Arabidopsis</em> and T3 transgenic lines were used for functional analysis of <em class="a-plus-plus">PsACS1</em>. Compared with the wild-type control, <em class="a-plus-plus">PsACS1</em>-overexpressing plants showed a discrepant phenotype, including shorter hypocotyls, fewer leaves, smaller rosette diameter, and later flowering, which were all attributed to the higher ethylene production caused by the ectopic expression of <em class="a-plus-plus">PsACS1</em> in <em class="a-plus-plus">Arabidopsis</em>. This result provides support of the hypothesis that <em class="a-plus-plus">PsACS1</em> is an important gene involved in ethylene biosynthesis during cut flower opening and senescence of tree peony.</p>
- Auto- and Cross-repression of Three<em class="a-plus-plus"> Arabidopsis</em> WRKY Transcription Factors WRKY18, WRKY40, and WRKY60 Negatively Involved in ABA Signaling
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">Some members of the WRKY transcription factor family are known to be involved in ABA signaling. However, it remains unclear how the WRKY transcription factors cooperate to regulate ABA signaling. In the present study, we showed that three <em class="a-plus-plus">Arabidopsis</em> (<em class="a-plus-plus">A. thaliana</em>) WRKY proteins previously identified as ABA signaling regulators, WRKY18, WRKY40, and WRKY60, directly target the W-box regions in various domains of the promoters of all their own encoding genes <em class="a-plus-plus">WRKY18</em>, <em class="a-plus-plus">WRKY40</em>, and <em class="a-plus-plus">WRKY60</em>, which was evidenced by chromatin immunoprecipitation and gel shift assays. Furthermore, we showed that the three WRKY proteins inhibit expression of all three <em class="a-plus-plus">WRKY</em> genes, which was evidenced in both an in vivo assay of coexpression of the WRKY proteins with the three <em class="a-plus-plus">WRKY</em> promoters and expression analysis of the three <em class="a-plus-plus">WRKY</em> genes in various <em class="a-plus-plus">wrky</em> mutants. Additionally and importantly, we provide new evidence, with three different testing systems, that WRKY18, WRKY40, and WRKY60 are negative, not positive, ABA signaling regulators, and that ABA treatment represses all three <em class="a-plus-plus">WRKY</em> genes through a mechanism partly independent of the WRKY proteins, in which the response of the <em class="a-plus-plus">WRKY60</em> gene to ABA partly requires WRKY18 and WRKY40. These findings describe a mechanism of auto- and cross-repression of the WRKY transcription repressors that suggests a sophisticated mechanism to balance the negative functions of the WRKY transcription repressors in ABA signaling and helps to understand the WRKY-mediated complex events in ABA signaling pathways.</p>
- Effects of Drought and Warming on Biomass, Nutrient Allocation, and Oxidative Stress in <em class="a-plus-plus">Abies fabri</em> in Eastern Tibetan Plateau
Abstract Abies fabri (Mast.) Craib is an endemic and dominant species in typical subalpine dark coniferous forests distributed in the eastern Tibetan Plateau. To assess how A. fabri may respond and adapt to future climate changes, we investigated the effects of drought and warming on the growth, resource allocation in biomass, membrane stability, and oxidative stress of the seedlings over two growing seasons. Drought (11.4 % average reduction in soil moisture) was created by excluding natural precipitation with a plastic roof and warming was performed by an infrared heater above the plots. Drought increased root length, the root-to-shoot ratio, N concentration, and N/P ratio in all organs, and decreased seedling height and C/N ratio in all organs. Moreover, warming (2 °C) decreased seedling height, root length, total biomass, and N concentration in stems but increased the C/N ratio. Furthermore, the combination of drought and warming decreased seedling height and biomass in all organs, which further increased the N concentration and N/P ratio in all organs. A significant decrease in the membrane stability index and an increase in malondialdehyde, superoxide radical (O 2 − ), and hydrogen peroxide (H 2 O 2 ) were exactly matched with a dramatic decrease of total biomass under the combination of drought and warming treatment. Together these results implied that drought alone and warming alone were unfavorable for the early growth of A. fabri , and drought plus warming will intensify the opposite effect of drought alone or warming alone. Moreover, N will be a limited nutrient under extant and future climate changes.
- Physiological and Biochemical Responses Reveal the Drought Tolerance Efficacy of the Halophyte <em class="a-plus-plus">Salicornia brachiata</em>
Abstract The drought tolerance of Salicornia brachiata seedlings was assessed by monitoring growth, nutrient uptake, electrolyte leakage, lipid peroxidation, and biochemical responses under drought conditions simulated with 0, 10, 20, and 30 % polyethylene glycol (PEG 6000). After 7 days of drought induction, plants were harvested for measurement of various parameters. The biomass decreased and the plant height remained unchanged with PEG treatment. The total plant water content (TWC%) decreased by 11 % at the highest concentration of PEG (30 %). The electrolyte leakage and lipid peroxidation of shoots increased by 17 and 5 %, respectively, in 30 % PEG-treated plants. K + and Ca 2+ contents of shoots increased in a dose-dependent manner. However, in roots K + content decreased and Ca 2+ content remained unaffected by PEG treatment. Mg 2+ content increased at high concentrations of PEG (20–30 %) in shoots and decreased at the highest concentration of PEG (30 %) in roots. Total free amino acids, proline, and polyphenol contents increased progressively with increase in severity of the drought stress. Total sugar content and reducing sugar content increased in 10 and 20 % PEG-treated plants and decreased in 30 % PEG-treated plants. Our results suggest that proline and other free amino acids, sugars, and polyphenols are the main compatible solutes in S. brachiata for maintenance of osmotic balance, protection of cellular macromolecules, detoxification of the cells, and scavenging of free radicals under drought stress. A greater accumulation of compatible solutes also facilitates the maintenance of nutrient uptake and adequate tissue water status and protection of membranes under drought conditions in S. brachiata . The results from the present study suggest that S. brachiata can be used for restoration of arid and semiarid lands of coastal ecosystems.
- Differences in Cowpea Root Growth Triggered by Salinity and Dehydration are Associated with Oxidative Modulation Involving Types I and III Peroxidases and Apoplastic Ascorbate
Abstract The aim of this work was to investigate the balance between the activities of ascorbate peroxidase (APX) and phenol peroxidases (POD) and cowpea root growth in response to dehydration and salt stress. Root growth and indicators of oxidative response were markedly changed in response to salinity and dehydration. Salt treatment strongly inhibited root elongation, which was associated with an increase in lignin content and a significant decrease in the concentrations of apoplastic hydrogen peroxide (H 2 O 2 ) and ascorbate. In conditions of extreme salinity, cytosol–APX activity was significantly decreased. In contrast, cell-wall POD activity was greatly increased, whereas lipid peroxidation was unchanged. These results indicate that POD could be involved in both H 2 O 2 scavenging and the inhibition of root elongation under high salinity. In contrast, dehydration stimulated primary root elongation and increased lipid peroxidation and apoplastic ascorbate content, but it did not change APX and POD activities or H 2 O 2 concentration. When cowpea roots were subjected to salinity followed by dehydration, the water and pressure potentials were decreased, and lipid peroxidation was markedly increased, highlighting the additive nature of the inhibitory effects caused by salt and dehydration. The proline concentration was markedly increased by dehydration alone, as well as by salt followed by dehydration, suggesting a possible role for proline in osmotic adjustment. Salinity and dehydration induce contrasting responses in the growth and morphology of cowpea roots. These effects are associated with different types of oxidative modulation involving cytosolic-APX and cell-wall POD activities and apoplast H 2 O 2 and ascorbate levels.
- Plant Growth-Promoting Rhizobacteria Enhance Abiotic Stress Tolerance in <em class="a-plus-plus">Solanum tuberosum</em> Through Inducing Changes in the Expression of ROS-Scavenging Enzymes and Improved Photosynthetic Performance
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">In this report we address the changes in the expression of the genes involved in ROS scavenging and ethylene biosynthesis induced by the inoculation of plant growth-promoting rhizobacteria (PGPR) isolated from potato rhizosphere. The two <em class="a-plus-plus">Bacillus</em> isolates used in this investigation had earlier demonstrated a striking influence on potato tuberization. These isolates showed enhanced 1-aminocyclopropane-1-carboxylic acid deaminase activity, phosphate solubilization, and siderophore production. Potato plants inoculated with these PGPR isolates were subjected to salt, drought, and heavy-metal stresses. The enhanced mRNA expression levels of the various ROS-scavenging enzymes and higher proline content in tubers induced by PGPR-treated plants contributed to increased plant tolerance to these abiotic stresses. Furthermore, the photosynthetic performance indices of PGPR-inoculated plants clearly exhibited a positive influence of these bacterial strains on the PSII photochemistry of the plants. Overall, these results suggest that the PGPR isolates used in this study are able to confer abiotic stress tolerance in potato plants.</p>
- Regulation of Metabolites, Gene Expression, and Antioxidant Enzymes to Environmentally Relevant Lead and Zinc in the Halophyte <em class="a-plus-plus">Suaeda salsa</em>
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">As a pioneer halophyte, <em class="a-plus-plus">Suaeda salsa</em> can grow in the intertidal zones, which are often polluted by heavy metals from both terrigenous wastewater and tidewater containing high concentrations of heavy metals. Therefore <em class="a-plus-plus">S. salsa</em> is potentially suitable as a biomonitor for heavy-metal pollution in the intertidal zones. In this study, regulation of metabolites, gene expression, and antioxidant status of environmentally relevant lead and zinc were characterized using NMR-based metabolomics, real-time quantitative reverse transcription polymerase chain reaction, and antioxidant enzyme activities. In Pb-exposed <em class="a-plus-plus">S. salsa</em> samples, only decreased tyrosine was observed, with statistical significance approaching 0.05. Metabolic biomarkers in Zn-exposed <em class="a-plus-plus">S. salsa</em> samples included increased amino acids (valine, isoleucine, leucine, threonine, asparagine, and phenylalanine), and decreased acetate, glucose, ferulate, and fumarate. Increased succinate, aspartate, and malonate and decreased fructose were uniquely found in mixed Pb- and Zn-exposed samples in addition to the similar metabolic changes such as alanine, glucose, fumarate, and ferulate in Zn-exposed samples. Based on the metabolic biomarkers, gene expressions, and antioxidant enzyme activities, both Zn and mixed Pb and Zn induced significant oxidative stress and disturbances in energy metabolism, photosynthesis/glucogenesis, and protein biodegradation in <em class="a-plus-plus">S. salsa</em>. However, environmentally relevant Pb could induce slight oxidative stress in <em class="a-plus-plus">S. salsa</em> as indicated by increased catalase gene expression levels and catalase activities.</p>
- The Effects of Plant Growth Substances and Mixed Cultures on Growth and Metabolite Production of Green Algae <em class="a-plus-plus">Chlorella</em> sp.: A Review
Abstract Recent interest in the use of microalgae for the production of biofuels and bioproducts has stimulated an interest in methods to enhance the growth rate of microalgae. This review examines past work involving the stimulation of Chlorella sp. growth and metabolite production by plant growth substances as well as by mixed cultures of Chlorella sp. with bacteria. Plant growth substances known to regulate Chlorella sp. growth and metabolite production include auxins, cytokinins, abscisic acid, polyamines, brassinosteroids, jasmonic acid, salicylic acid, and combinations of two or three of the aforementioned substances. Mixed cultures of bacteria are examined, including both natural bacteria–algae consortia and artificially induced symbioses. For natural consortia, commonly occurring bacterial species, including the genera Brevundimonas and Sphingomonas , are discussed. For artificially induced symbioses, the use of the nitrogen-fixing bacterium Azospirillum is examined in detail. In particular, a variety of studies have involved the coimmobilization of Chlorella sp. with Azospirillum sp. in alginate beads, with the goal of using the mixed culture to treat wastewater. In summary, the use of plant growth substances and mixed cultures provides two methods to increase the growth of Chlorella sp., whether for the production of lipids for biofuels, the production of bioproducts, the treatment of wastewater, or a variety of other reasons.
- Defensive Responses in Groundnut Against Chewing and Sap-Sucking Insects
Abstract Induced resistance is one of the important components of host plant resistance to insects. We studied the induced defensive responses in groundnut genotypes with different levels of resistance to the leaf defoliator Helicoverpa armigera and the sap-sucking insect Aphis craccivora to gain an understanding of the induced resistance to insects and its implications for pest management. The activity of the defensive enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, superoxide dismutase, ascorbate peroxidase, and catalase) and the amounts of total phenols, hydrogen peroxide, malondialdehyde, and proteins were recorded at 6 days after infestation. Induction of enzyme activities and the amounts of secondary metabolites were greater in the insect-resistant genotypes ICGV 86699, ICGV 86031, ICG 2271, and ICG 1697 infested with H. armigera and A. craccivora than in the susceptible check JL 24. The resistant genotypes suffered lower insect damage and resulted in lower Helicoverpa larval survival and weights than those larvae fed on the susceptible check JL 24. The number of aphids was significantly lower on insect-resistant genotypes than on the susceptible check JL 24. The results suggested that groundnut plants respond to infestation by H. armigera and A. craccivora in a similar way; however, the degree of the response differed across the genotypes and insects, and this defense response is attributed to various defensive enzymes and secondary metabolites.
- 2012 Reviewer Thank You
- Microbial Consortium-Induced Changes in Oxidative Stress Markers in Pea Plants Challenged with <em class="a-plus-plus">Sclerotinia sclerotiorum</em>
Abstract The ability for rhizobacteria and fungus to act as bioprotectants via induced systemic resistance has been demonstrated, and considerable progress has been made in elucidating the mechanisms of plant–biocontrol agent–pathogen interactions. Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27, and Bacillus subtilis BHHU100 from rhizospheric soils were used singly and in consortium and assessed on the basis of their ability to provide disease protection by relating changes in ascorbic acid and hydrogen peroxide (H 2 O 2 ) production, lipid peroxidation, and antioxidant enzymes in pea under the challenge of Sclerotinia sclerotiorum . Increased production of H 2 O 2 24 h after pathogen challenge was observed and was 254.4 and 231.7–287.7 % higher in the triple consortium and singly treated plants, respectively, when compared to untreated challenged control plants. A similar increase in ascorbic acid content and ascorbate peroxidase activity was observed 24 and 48 h after pathogen challenge, respectively, whereas increased activities of catalase, guaiacol peroxidase, and glutathione peroxidase were observed 72 h after pathogen challenge. Similarly, lipid peroxidation reached a maximum at 72 h of pathogen challenge and was 61.2 and 11.2–32.1 % less in the triple consortium and singly treated plants, respectively, when compared to untreated challenged control plants. These findings suggest that the interaction of microorganisms in the rhizosphere enhanced protection from oxidative stress generated by pathogen attack through induction of antioxidant enzymes and improved reactive oxygen species management.
- Synthesis, Characterization, and Theoretical and Experimental Investigations of Zinc(II)–Amino Acid Complexes as Ecofriendly Plant Growth Promoters and Highly Bioavailable Sources of Zinc
Abstract Amino acids (AA) as metal complexing agents have the ability to form relatively stable complexes with zinc (Zn) and thereby increase its availability for plants. In this study, the complexes of Zn(II), [Zn(L–L′) 2 ] [where L–L′ = monoanion of arginine (Arg), glycine (Gly), glutamine (Gln), histidine (His), and methionine (Met)], were synthesized and characterized by different analytical techniques. The results of elemental analysis support the formation of Zn(II)–AA complexes (ZnAAC) with a 2:1 ligand-to-metal molar ratio. The computational results indicated that the AA ligands coordinated to the Zn(II) ion via their nitrogen and oxygen atoms and support the coordination mode obtained from IR spectroscopy. For the first time, the semiempirical calculations were also performed to investigate the passive uptake of ZnAAC by root cells. The proposed transport pathway indicated that ZnAAC can pass via plant root cell wall pores without any strict hindrances. The efficacy of ZnAAC as a Zn source was evaluated for two lettuce cultivars ( Lactuca sativa L., cvs. ‘Lollo Bionda’ and ‘Lollo Rossa’) grown in nutrient solution. The results confirmed the higher efficacy of ZnAAC in supplying Zn for lettuce in comparison with ZnSO 4 . The synthesized ZnAAC also had a stimulating effect on root and shoot growth of both lettuce cultivars. According to the results, ZnAAC can be used as ecofriendly plant growth stimulators and sources of Zn to supply plants with readily available Zn.
- Seaweed Oligosaccharides Stimulate Plant Growth by Enhancing Carbon and Nitrogen Assimilation, Basal Metabolism, and Cell Division
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">It is now well established that plant cell wall oligosaccharides can stimulate or inhibit growth and development in plants. In addition, it has been determined that seaweed (marine algae) cell wall polysaccharides and derived oligosaccharides can enhance growth in plants. In particular, oligo-alginates obtained by depolymerization of alginates from brown seaweeds increase growth of different plants by enhancing nitrogen assimilation and basal metabolism. Interestingly, oligo-alginates also stimulate growth of marine and fresh water green microalgae, increasing the content of fatty acids. On the other hand, oligo-carrageenans obtained by depolymerization of carrageenans from red seaweeds increase growth of tobacco plants by enhancing photosynthesis, nitrogen assimilation, basal metabolism, and cell division. In addition, oligo-carrageenans increase protection against viral, fungal, and bacterial infections in tobacco plants, which is determined, at least in part, by the accumulation of several phenylpropanoid compounds (PPCs) with antimicrobial activity. Moreover, oligo-carrageenans stimulate growth of 3-year-old <em class="a-plus-plus">Eucalyptus globulus</em> trees by increasing photosynthesis, nitrogen assimilation, and basal metabolism. Furthermore, oligo-carrageenans induce an increase in cellulose content and in the level of essential oil and some PPCs with antimicrobial activities, suggesting that defense against pathogens may be also enhanced. Thus, seaweed oligosaccharides induce a dual beneficial effect in plants and trees, enhancing growth, which is determined by the increase in carbon and nitrogen assimilation, basal metabolism, and cell division, and defense against pathogens, which is determined by the accumulation of compounds with antimicrobial activities. In this sense, molecular mechanisms that potentially interconnect activation of plant growth and defense responses are discussed.</p>
- Synthesis of 3-Aryl-1<em class="a-plus-plus">H</em>-Indazoles and Their Effects on Plant Growth
Abstract Indazoles are valuable because of their biological activities. A series of 3-aryl-1 H -indazoles have been synthesized by condensing bisulfite adduct of aromatic aldehydes with phenyl hydrazine in good yield. Different concentrations of indazoles were employed to check their effects on seed germination and early growth. The arylindazoles were proved to be growth inhibitors of root and shoot lengths of wheat and sorghum, especially at a high concentration (100 ppm). At lower concentrations growth inhibition was found to be less prominent. Seed germination and early growth of plantlets also depended on the nature of substitution on the aryl group.
- Responses of ‘Conference’ Pear to Deficit Irrigation: Water Relations, Leaf Discrimination Against <sup class="a-plus-plus">13</sup>CO<sub class="a-plus-plus">2</sub>, Tree Starch Content, Growth, and Recovery After Rewatering
Abstract Responses to deficit irrigation (DI) throughout the fruit-growing season were studied in ‘Conference’ pear grafted onto quince M-A rootstock and grown in large containers. The treatments were (1) full irrigation (FI), (2) DI during Stage I of fruit growth (DI-Stage I), and (3) DI during Stage II of fruit growth (DI-Stage II). Four whole trees were sampled before Stage I and from all treatments at the end of Stage I, end of Stage II (fruit harvest), and before leaf fall. There was less discrimination against 13 CO 2 in DI leaves, indicative of reduced photosynthetic capacity. DI treated trees had lower starch content in branches and trunks but root starch concentration was the same between DI- and FI-treated trees. Compared to FI-treated trees, leaf, shoot, branch, and trunk dry biomass was reduced by 34, 50, 37, and 32 %, respectively, in DI-Stage I and by 45, 73, 37, and 22 % in DI-Stage II. Root growth was not affected by DI. Trees had limited capacity for storing starch in roots. Recovery of the aboveground starch concentration for DI treatments occurred within 1 month after rewatering but total starch content never recovered.
- Erratum to: Regulation of Phytohormone Biosynthesis and Accumulation in <em class="a-plus-plus">Arabidopsis</em> Following Treatment with Commercial Extract from the Marine Macroalga <em class="a-plus-plus">Ascophyllum nodosum</em>
- α-Tocopherol Application Modulates the Response of Wheat (<em class="a-plus-plus">Triticum aestivum</em> L.) Seedlings to Elevated Temperatures by Mitigation of Stress Injury and Enhancement of Antioxidants
Abstract Wheat seedlings (4 days old) were subjected to varying temperatures of 25, 30, and 35 °C for 7 days in a growth chamber under hydroponic conditions in the absence or presence of α-tocopherol (5 μM). The growth of shoots and roots was inhibited severely at 35 °C. The endogenous α-tocopherol increased in the shoots at 30 °C over the controls but decreased significantly at 35 °C over the previous temperature. The exogenous application of α-tocopherol elevated the endogenous levels in the heat-stressed plants, which were consequently able to maintain significantly greater growth associated with reduction in damage to membranes, cellular oxidizing ability, chlorophyll content, and photochemical efficiency in shoots. The relative leaf water content and stomatal conductance were not affected significantly with the application of tocopherol. The oxidative stress induced by high temperature (35 °C) in terms of malondialdehyde and hydrogen peroxide contents was significantly lower in the presence of α-tocopherol. The enzymatic antioxidants such as superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase showed considerable reduction in their activities at 35 °C compared to those at 30 °C, with greater effects on APX and GR. The nonenzymatic antioxidants like ascorbate, glutathione, and proline increased at 30 °C but decreased appreciably at 35 °C, suggesting impairment in their synthesis at stressful temperatures. α-Tocopherol-treated plants, especially those growing at 35 °C, had improved levels of enzymatic and nonenzymatic antioxidants. These observations provided evidence about the involvement of α-tocopherol in governing heat sensitivity in wheat and suggested manipulation of its endogenous levels to induce heat tolerance in this crop.
- The Ethylene Signaling Pathway is Needed to Restrict Root Gall Growth in <em class="a-plus-plus">Arabidopsis</em> after Infection with the Obligate Biotrophic Protist <em class="a-plus-plus">Plasmodiophora brassicae</em>
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">A possible role for ethylene in the interaction of <em class="a-plus-plus">Arabidopsis thaliana</em> and the obligate biotrophic protist <em class="a-plus-plus">Plasmodiophora brassicae</em>, causing clubroot disease, has been investigated. The ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC) was lower in infected compared to control roots during early time points of the interaction. We therefore analyzed the transcription of selected genes encoding proteins involved in ET synthesis. One gene for ACC oxidase was consistently upregulated in infected roots, whereas transcriptional regulation of other ET biosynthesis genes varied according to the time point during infection. The ET-overproducing mutant <em class="a-plus-plus">eto2</em> was slightly less susceptible to the clubroot pathogen. The analysis of mutants within the ET signaling pathway showed that they were more susceptible to the clubroot pathogen than wild-type Columbia, that is, they formed larger galls. The findings are discussed in relation to a potential effect of ET on <em class="a-plus-plus">Arabidopsis</em> root infection by <em class="a-plus-plus">P. brassicae</em>.</p>
- Special Solutions to the Ortega Equation
Abstract The previously established augmented growth equation (Cosgrove, Plant Physiol 78:347–356, 1985; Ortega, Plant Physiol 79:318–320, 1985), suitable for description of pressure relationships in the growing plant cell, is revised with respect to the inclusion of changing cell wall properties hitherto represented by two constants, Φ and ε, connected with viscoelastic behavior. This phenomenological equation in the modified form is capable of appropriate description of volumetric extensibility, growth rate, and pressure changes in growing plant cells. This concerns deposition of new material in the polymer cell wall intercalation process, but it can also be used successfully for induced cell wall loosening, for example, by expansin EXPA (EXPB) proteins. In this context, a specific shape of the proposed equations, armed with a small number of physiologically explained parameters, opens up an experimental perspective for determining vital numbers connected with interactions at the nanoscale (polymer bonds “dilution” of an extending cell wall), or even at the molecular level in the cell wall (calculating numbers proportional to the expansin molecule’s active surface area). A systematic survey of ready-to-use deterministic solutions originating from the Ortega equation, reporting on both reversible (elastic) and irreversible (plastic) features of a growing plant cell, is presented. These findings also provide a quantitative cytomechanical model able to account for the important role of mechanical properties of the cell wall in cellular growth processes. An important feature of the analytical approach is that all model equations, after calibrating on existing data, allow new results to be inferred without further experimental work.
- RNAi-Mediated Silencing of the Flavanone 3-Hydroxylase Gene and Its Effect on Flavonoid Biosynthesis in Strawberry Fruit
Abstract Anthocyanin biosynthesis requires the activities of several enzymes in vivo. Flavanone 3-hydroxylase (F3H) converts flavanone into dihydroflavanol at an early step in the anthocyanin biosynthesis pathway. In this study we constructed an RNAi gene-silencing vector that encodes a hairpin F3H RNA. Agrobacterium strain GV3101 harboring the F3H RNAi vector was injected into strawberry fruits which were still attached to the plants 14 days after pollination. The phenotype was observed 10 days postinjection, and fruits were tested by RT-PCR and northern blot assays. The results showed that the F3H gene was downregulated by approximately 70 % in the agroinfiltrated fruits compared with the control. HPLC–MS analysis showed that anthocyanin content was greatly reduced, flavonol was also decreased, and the levels of p -coumaroyl glucoside and p -coumaroyl-1-acetate were markedly increased. We conclude that the precursors were shunted to the phenylpropanoid pathway, and that F3H is one of the key enzymes required for the biosynthesis of flavonoids in strawberry fruit. According to our results, reducing gene function via RNA interference is a rapid, simple, and effective way to identify gene function in strawberry fruit.
- Spermine Promotes Acclimation to Osmotic Stress by Modifying Antioxidant, Abscisic Acid, and Jasmonic Acid Signals in Soybean
Abstract The possible involvement of spermine (Spm) in the acclimation of soybean to osmotic stress was investigated by determining the changes in photosynthetic pigments, antioxidants, and plant hormone levels in response to applied Spm. Plants were exposed to 9 % PEG-induced osmotic stress with or without 0.4 μM Spm. Osmotic stress reduced the relative water content, chlorophyll a , chlorophyll b , carotenoid, and protein contents in leaves, and these detrimental effects were alleviated by treatment with Spm. Moreover, the significant increase in the content of abscisic acid and decrease in that of jasmonic acid in plants subjected to osmotic stress was attenuated by treatment with Spm. Osmotic stress caused a significant increase in lipid peroxidation when compared to controls, and that was accompanied by a slight reduction in the level of antioxidants and reduced glutathione and in the activities of catalase, superoxide dismutase, peroxidase, and polyphenol oxidase. Spm treatment ameliorated these osmotic stress effects by reducing lipid peroxidation and increasing catalase, superoxide dismutase, peroxidase, and polyphenol oxidase activities. These results indicate that application of Spm could be exploited to alleviate a moderate level of osmotic stress through the regulation of stress-related components such as photosynthetic pigments, plant hormones, and antioxidants.
- Pyridine 2,4-Dicarboxylate Downregulates Ethylene Production in Response to Mechanical Wounding in Excised Mature Green Tomato Pericarp Discs
Abstract Pyridine 2,4-dicarboxylate (PDCA) is a structural analog of 2-oxoglutarate and a potent inhibitor of 2-oxoacid-dependent dioxygenases (2-ODDs), such as prolyl 4-hydroxylases (P4Hs). It has been reported that PDCA inhibited the in vitro activity of P4Hs in cut carnation flowers and delayed petal senescence due to suppression of climacteric ethylene production. In this study, the effect of PDCA on ethylene evolution in response to mechanical wounding due to excision of mature green tomato pericarp discs was investigated. Ethylene evolution was induced within 1 h of mechanical wounding in control discs and gradually increased throughout 24 h, whereas it was partially suppressed in PDCA-treated discs during the first 12 h of a 24-h experimental period. This transient, partial suppression of ethylene production can be attributed to the lack of induction and the downregulation of ethylene biosynthetic genes within 1 h and after 12 h of wounding, respectively. However, it cannot be attributed to the suppression of ACC oxidase, a well-known 2-ODD, because no significant change in enzymatic activity was observed in PDCA-treated discs. In addition, the transcript abundance of wound-induced and ethylene-regulated PIN1 , PIN2 , and E4 genes was also partially suppressed in PDCA-treated discs. PDCA was also shown to be involved in ethylene evolution and color development of mature green and turning fruit discs. Overall, these results indicate that PDCA downregulates ethylene production in response to mechanical wounding and during ripening of preclimacteric and climacteric tomato fruit discs.
- Growth and Fatty Acid Composition of Borage (<em class="a-plus-plus">Borago officinalis</em> L.) Leaves and Seeds Cultivated in Saline Medium
Abstract The effects of salinity on growth and fatty acid composition of borage ( Borago officinalis L.) leaves and seeds grown in hydroponic medium were investigated. Three different levels of NaCl (25, 50, and 75 mM) were applied. The first results showed that salinity significantly reduced plant growth by 56.5 % at 75 mM compared with the control, suppressed seed yield at 50 and 75 mM, and increased lipid peroxidation. Raising NaCl concentrations led to an important decrease in total fatty acid (TFA) content by 77 % at 75 mM NaCl. Moreover, the polyunsaturated fatty acid (PUFA) content decreased, whereas the saturated fatty acids increased with respect to increasing salinity. The 25 mM NaCl level did not modify the fatty acid composition of seeds and their contents.
- Coexpression of <em class="a-plus-plus">ScNHX1</em> and <em class="a-plus-plus">ScVP</em> in Transgenic Hybrids Improves Salt and Saline-Alkali Tolerance in Alfalfa (<em class="a-plus-plus">Medicago sativa</em> L<em class="a-plus-plus">.</em>)
Abstract Salt and saline-alkali are major environmental factors limiting the growth and productivity of alfalfa, the most economically important forage legume worldwide. In this study, alfalfa plants transgenic for both ScNHX1 (encoding vacuolar membrane Na + /H + antiporter from Suaeda corniculata ) and ScVP (encoding vacuolar H + -PPase from S. corniculata ) were produced by cross-pollination. Transgenic alfalfa plants coexpressing ScVP / ScNHX1 showed enhanced salt and saline-alkali tolerance to 300 or 200 mM NaCl with 100 mM NaHCO 3 treatments, compared with wild-type plants. In addition, ScVP / ScNHX1 -coexpressing alfalfa plants accumulated more Na + in leaves and roots than wild-type plants and showed increased tolerance to higher salt and saline-alkali stress. Using the fluorescent carboxy-SNARF probe, the intracellular pH was visualized in the transgenic and wild-type plants under salt and saline-alkali stress. The results showed that the overnight treatment caused a massive change in pH in ScVP / ScNHX1 -coexpressing alfalfa plants and they showed that there was significantly higher vacuolar alkalization under salt stress compared with wild-type plants. However, saline-alkali treatment enhanced vacuolar acidification more in the wild-type plants than in transgenic plants. Taken together, our results indicate that coexpression of multiple, effective genes in transgenic plants can enhance resistance to salt and saline-alkali stress.
- 5-Aminolevulinic Acid Ameliorates the Growth, Photosynthetic Gas Exchange Capacity, and Ultrastructural Changes Under Cadmium Stress in <em class="a-plus-plus">Brassica napus</em> L.
Abstract Heavy-metal toxicity in soil is one of the major constraints for oilseed rape ( Brassica napus L.) production. One of the best ways to overcome this constraint is the use of growth regulators to induce plant tolerance. Response to cadmium (Cd) toxicity in combination with a growth regulator, 5-aminolevulinic acid (ALA), was investigated in oilseed rape grown hydroponically in greenhouse conditions under three levels of Cd (0, 100, and 500 μM) and three levels of foliar application of ALA (0, 12.5, and 25 mg l −1 ). Cd decreased plant growth and the chlorophyll concentration in leaves. Foliar application of ALA improved plant growth and increased the chlorophyll concentration in the leaves of Cd-stressed plants. Significant reductions in photosynthetic parameters were observed by the addition of Cd alone. Application of ALA improved the net photosynthetic and gas exchange capacity of plants under Cd stress. ALA also reduced the Cd content in shoots and roots, which was elevated by high concentrations of Cd. The microscopic studies of leaf mesophyll cells under different Cd and ALA concentrations showed that foliar application of ALA significantly ameliorated the Cd effect and improved the structure of leaf mesophyll cells. However, the higher Cd concentration (500 μM) could totally damage leaf structure, and at this level the nucleus and intercellular spaces were not established as well; the cell membrane and cell wall were fused to each other. Chloroplasts were totally damaged and contained starch grains. However, foliar application of ALA improved cell structure under Cd stress and the visible cell structure had a nucleus, cell wall, and cell membrane. These results suggest that under 15-day Cd-induced stress, application of ALA helped improve plant growth, chlorophyll content, photosynthetic gas exchange capacity, and ultrastructural changes in leaf mesophyll cells of the rape plant.
- Growth Promotion and Flowering Induction in Mango (<em class="a-plus-plus">Mangifera indica</em> L. cv “Ataulfo”) Trees by <em class="a-plus-plus">Burkholderia</em> and <em class="a-plus-plus">Rhizobium</em> Inoculation: Morphometric, Biochemical, and Molecular Events
Abstract Inoculation of mango trees with Burkholderia caribensis XV and Rhizobium sp. XXV led to mango growth promotion (dry biomass increased in root 89 %, stem 34 %, leaves 51 %, and foliar area 53 %), floral fate (floral buds 100 %), and increased number of flowers (100 %). Nitrogen content in leaves was similar in inoculated and noninoculated trees, around 1.4 % (optimal condition for floral induction). The total foliar nitrogen content increased significantly (56 %) when the microbial inoculation treatment was applied. In addition, the initial content of sucrose, glucose, and fructose in leaves was higher in the microbial inoculation treatment trees but decreased during the evaluated period. The sucrose content in the noninoculated trees presented similar dynamics compared to the microbial inoculation treatment trees, but glucose and fructose showed increased values compared to those of the microbial inoculation treatment. FLOWERING LOCUS T ( FT ) expression profiles normalized to ACTIN showed similar dynamics but different expression levels: RQ values of 0.03 and 0.05 for noninoculated and microbial inoculation treatments, respectively. In addition, FT expression profiles in microbial inoculation, normalized to the noninoculated treatment, showed an increased FT expression dynamic over time (up to RQ = 2.2), although a drastic decrease in the last sampling date, when all trees presented developed panicles and flowers, was observed. This FT upregulation was in accordance with the flowering induction in that treatment. Temperature had an important influence on mango flowering induction, which was observed for a 1-month period (~10 °C at night and 20 °C during the day). Bud growth that occurred during that period generated mixed and floral buds depending on the exposure time to these inductive temperatures, less than 2 weeks and more than 3 weeks, respectively. Data indicate that inoculation of mango trees with plant growth-promoting rhizobacteria (associated with this crop) is a potential alternative way to promote growth and induce flowering in mango, greatly reducing the high economical costs and environmental contamination associated with traditional agricultural practices.
- Plant Thin Cell Layers: A 40-Year Celebration
Abstract The concept of a thin cell layer (TCL) was initially presented by Tran Thanh Van in two key papers exactly 40 years ago. At that time, Nicotiana tabacum was the model plant used to establish three main pathways for de novo organogenesis by developing a flower, vegetative bud, and root “programme” from pedicel tissue. Over the last 40 years, a wealth of research in plant tissue culture based on TCLs has emerged, fortifying the importance of this very simple technique, and highlighting its fundamental importance as a key tool in plant cell and tissue differentiation as well as organ development. This review not only highlights the achievements made using TCLs in the plant kingdom over these 40 years, it also reports on the success of this technique in ornamentals, fruit and forestry species, vegetables, and medicinal plants. There is overwhelming evidence of the importance of this technique for plant biotechnology, and it provides one solution for the mass clonal propagation of plants, use in bioreactors, genetic transformation, or micropropagation.
- Interactive Effects of Elevated CO<sub class="a-plus-plus">2</sub>, Drought, and Warming on Plants
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">Adverse climate change attributed to elevated atmospheric carbon dioxide concentration (CO<sub class="a-plus-plus">2</sub>) and increased temperature components of global warming has been a central issue affecting economic and social development. Climate change, particularly global warming, imposes a severe impact on the terrestrial ecosystem. Elevated CO<sub class="a-plus-plus">2</sub>, drought, and high temperature have been extensively documented individually; however, relatively little is known about how plants respond to the interaction of these factors. To summarize current knowledge on the response of plants to global change factors, we focus on the interactive effects of CO<sub class="a-plus-plus">2</sub> enrichment, warming, and drought on plant growth, carbon allocation, and photosynthesis. Stimulation due to elevated CO<sub class="a-plus-plus">2</sub> might be suppressed under other negative climatic/environmental stresses such as drought, high temperature, and their combination. However, elevated CO<sub class="a-plus-plus">2</sub> could alleviate deleterious effects of moderate drought via reducing stomatal conductance, altering leaf surface, and regulating gene expression. High CO<sub class="a-plus-plus">2</sub> levels and rising temperatures may result in opposite responses in plant water use efficiency. Stimulation of plant growth due to elevated CO<sub class="a-plus-plus">2</sub> for C<sub class="a-plus-plus">3</sub> species occurs regardless of water conditions, but only under a water deficit for C<sub class="a-plus-plus">4</sub> species. The positive effect of elevated CO<sub class="a-plus-plus">2</sub> on C<sub class="a-plus-plus">4</sub> species is derived mainly from the improved water status. Plant adaptive or maladaptive responses to multivariate environments are interactive; thus, researchers need to explore the ecological underpinnings involved in such responses to the multiple factors involved in climate change.</p>
- Regulation in Plant Stress Tolerance by a Potential Plant Growth Regulator, 5-Aminolevulinic Acid
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">Exogenous application of different plant growth regulators is a well-recognized strategy to alleviate stress-induced adverse effects on different crop plants by regulating a variety of physiobiochemical processes such as photosynthesis, chlorophyll biosynthesis, nutrient uptake, antioxidant metabolism, and protein synthesis, which are directly or indirectly involved in the mechanism of stress tolerance. Of various environmental factors, salinity, drought, and extreme temperature (low or high) considerably diminish plant growth and yield by modulating endogenous levels as well as signaling pathways of plant hormones. Of various plant hormones/regulators, a potential plant growth regulator, 5-aminolevulinic acid (ALA), is known to be effective in counteracting the injurious effects of various abiotic stresses in plants. Until now the mechanisms behind ALA regulation of growth under stress have not been fully elucidated. It is also not yet clear how far growth and yield in different crops can be promoted by exogenous application of ALA and whether this ALA-induced growth and yield promotion is cost-effective. Thus, in this review we discuss at length the effects of ALA in regulating growth and development in plants under a variety of abiotic stress conditions, including salinity, drought, and temperature stress. Furthermore, advances in the functional and regulatory interactions of this plant growth regulator with plant stress tolerance, as well as the effective mode of exogenous application of ALA in inducing stress tolerance in plants are also comprehensively discussed in this review. In the future, overaccumulation of ALA in plants through manipulation of gene(s) could enhance plant stress tolerance. Thus, genetic manipulation of plants with the goal of attaining increased synthesis/accumulation of ALA and hence improved stress tolerance under stress conditions is an important area for research.</p>
- Carbon–Nitrogen Interaction Modulates Plant Growth and Expression of Metabolic Genes in Rice
Abstract Carbon (C) and nitrogen (N) interact to coordinate their metabolism in achieving C:N homeostasis in all cellular organisms. Plant shoots and roots take up C and N, respectively, and the coordinated C and N assimilation is essential for normal plant growth and development. In this study, rice was used as a model system for the investigation of molecular mechanisms underlying C–N interactions and coordination in cereal species. We investigated the growth response of rice seedlings to a wide range of exogenous C:N availabilities and established balanced exogenous C:N that was optimal for rice seedling growth. To assess correlations between the modulation of plant growth and the regulation of metabolic gene expression by C:N availabilities, we examined the expression of PEPC , PK , NR , GS , and GOGAT in rice seedlings treated with four C:N availabilities: low C/low N, low C/high N, high C/low N, and high C/high N. It was found that their expression was subjected to complex regulation by C:N availabilities. Our results demonstrate that growth of shoot and root rice seedlings is regulated by C–N interaction and growth modulations are associated with changes in metabolic gene expression. Our findings suggest that rice is a useful model system for the investigation of regulation mechanisms responsible for C–N interaction and coordination in plants.
- Characterizing Penetration of Aminoethoxyvinylglycine (AVG) through Isolated Tomato Fruit Cuticles
Abstract Aminoethoxyvinylglycine (AVG) is an ethylene biosynthesis inhibitor that is commonly applied to apple trees prior to harvest to delay ripening and reduce fruit drop. To help understand how selected environmental factors and spray adjuvants affect AVG uptake, penetration of 14 C-AVG through enzymatically isolated tomato ( Solanum lycopersicon L.) fruit cuticular membranes (CM) was studied using a finite-dose diffusion system in which penetration is monitored from a drying spray droplet/deposit through an interfacing CM into a receiver solution. Penetration of AVG was initially rapid (4.1 % at 1 h after application), slow after droplet drying (12.5 % by 120 h after application), and averaged 20.7 % of the amount applied at 37 days after application. Rate and amount of AVG penetration were positively related to AVG concentration. Rewetting the dried droplet deposit with deionized water caused a transient increase in penetration that ceased when the droplet dried again. Increasing relative humidity from 50 to 100 % above the dried droplet deposit markedly increased penetration. Increasing temperature from 10 to 30 °C at constant water vapor pressure deficit (0.35 kPa) increased AVG penetration between 0 and 6 h after application but had little effect on penetration thereafter. LiCl, CaCl 2 , and MgCl 2 at 100 mM increased AVG penetration at 120 h after application; lower concentrations had no effect. Our results indicate that AVG penetration was enhanced by increasing humidity above the droplet deposit or by the addition of hygroscopic salts to the spray solution, thereby maintaining the AVG mobility in the droplet deposit.
- Evidence that Tuber Respiration is the Pacemaker of Physiological Aging in Seed Potatoes (<em class="a-plus-plus">Solanum tuberosum</em> L.)
Abstract Storage temperatures greater than 4 °C (that is, heat-unit accumulation) increase respiration and accelerate physiological aging of seed tubers. The degree of apical dominance is a good indicator of physiological age (PAGE). As seed age advances, apical dominance decreases, resulting in more stems, greater tuber set, and shifts in tuber size distribution. Herein we provide evidence that tuber respiration rate may constitute the “pacemaker” of aging. Tubers exposed to a brief high-temperature age-priming treatment initially in storage, followed by holding at 4 °C for the remainder of a 190–200-day storage period, maintained a higher basal metabolic (respiration) rate throughout storage compared with tubers stored the entire season at 4 °C. Tubers thus “remembered” the age-priming treatment as reflected by their elevated respiration rate. Moreover, reducing the respiration rate of age-primed seed by subsequently storing it at 3.5 % O 2 (4 °C) until planting significantly attenuated the effects of the aging treatment on apical dominance, tuber set, and size distribution. The effect of the age-priming treatment on the magnitude of the respiratory response was the same whether given at the beginning or toward the end of storage. However, moving the age-priming treatment progressively later in the storage season effectively decreased its impact on plant growth and development. These results underscore the importance of time in the aging process. Exposure of seed to a high-temperature age-priming treatment at the beginning or end of storage elevated respiration (the pacemaker) to the same extent; however, the timing of these treatments resulted in vastly different physiological ages. The longer the respiration rate of tubers remains at an elevated level, the greater their PAGE at planting. Thus, an accurate but impractical measure of PAGE may be the respiratory output from vine kill to subsequent planting. Respiration appears to be the pacemaker of PAGE and production, and storage conditions that affect respiration may “set the clock speed” that will ultimately determine the PAGE at planting.
- Multivariate Statistical Analysis of Low-Light Tolerance in Tomato (<em class="a-plus-plus">Solanum lycopersicum</em> Mill.) Cultivars and Their Ultrastructural Observations
Abstract This research used multivariate statistical analysis to evaluate the tolerance of 11 tomato cultivars to low light at the seedling stage. The low-light condition (200–420 μmol/m 2 s) was simulated by a shade net. It was found that 11 of 16 character indices of different cultivars, such as dropping angle, bend degree, and accumulation of leaf area, showed a significant difference by using multiple variance analysis. After factor analysis, the 11 character indices could be summarized into 5 main factors with a cumulative contribution rate of 84.968 %. According to the factor scores after varimax rotation, the 11 tomato cultivars could be classified into three categories by using cluster analysis. The severely low-light-sensitive cultivars were T1, T5, T6, T10, and T11 and the moderately low-light-sensitive cultivars were T4, T7, and T9. Cultivars T2, T3, and T8 were resistant to low light. In accordance with the appraisal result, the light-sensitive cultivars T5 and T10, the moderately low-light-sensitive cultivar T4, and the low-light-tolerant cultivar T8 were randomly selected to observe the variation in the ultrastructure of leaves of different tomato cultivars with the aid of a transmission electron microscope (TEM). In chloroplasts of T5 and T10, membranes were heavily damaged and mitochondria were vacuolated, whereas the chloroplast structure of T4 was slightly damaged and its mitochondria grew normally. In the chloroplasts of T8, the organelle membranes were intact, the degree of thylakoid stacking was high, and mitochondria grew normally. Our results showed that multivariate statistical analysis of low-light tolerance in tomatoes has certain scientific applicability.
- β-Estradiol Protects Embryo Growth from Heavy-Metal Toxicity in Germinating Lentil Seeds
Abstract Mammalian sex hormones spread in the environment from both natural and anthropogenic origin. In the present study, we found that treatment with β-estradiol (E) could improve embryo growth and alleviate unsuitable availability of nutrients imposed by cadmium and copper toxicity during germination of lentil ( Lens culinaris Medik.) seeds. The length of embryonic axes decreased in the presence of 100 μM CdCl 2 or 200 μM CuCl 2 . Addition of 10 −6 M E in the germination media could greatly reverse the inhibitory effect of heavy-metal (HM) stress on post-germination events. The cotyledons of E-treated seeds also tended to (1) retain higher protease and amylase activities, (2) breakdown more storage compounds (albumin, globulin, and starch), and (3) have higher contents of free amino acids and glucose than controls without added E (Cd or Cu applied individually). Further investigations showed that exposure to HM dramatically provoked the solute leakage in imbibition medium, whereas the combination of HM with E significantly reduced the loss of nutrients. Moreover, the seed Cd and Cu contents were not significantly different between the cotreatment of Cd or Cu with E and no treatment, meaning that E was not responsible for preventing HM accumulation in seed tissues.
- The Microtubule-Associated Protein END BINDING1b, Auxin, and Root Responses to Mechanical Cues
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">The ability of roots to penetrate through the soil and maneuver around rocks and other impenetrable objects requires a system for modulating output from mechanosensory response networks. The microtubule-associated protein END BINDING1b (EB1b) has a role in this process; it represses root responses to mechanical cues. In this study, a possible relationship between EB1b and auxin during root responses to mechanical cues was investigated. We found that <em class="a-plus-plus">eb1b-1-</em>mutant roots are more sensitive than wild-type roots to chemicals that disrupt auxin transport, whereas the roots of mutants with defects in auxin transport are resistant to these treatments. Using seedlings that express the auxin-sensitive <em class="a-plus-plus">DR5rev::GFP</em> construct, we also found that wild-type and <em class="a-plus-plus">eb1b-1</em> roots treated with the auxin transport inhibitor naphthylphthalamic acid exhibited dose-dependent reductions in basipetal auxin transport that were indistinguishable from each other. The responses of <em class="a-plus-plus">eb1b-1</em> roots to mechanical cues were also enhanced over wild type in the presence of <em class="a-plus-plus">p</em> <strong class="a-plus-plus">-</strong>chlorophenoxyisobutyric acid, a chemical thought to inhibit auxin signaling. Finally, roots of <em class="a-plus-plus">eb1b-1</em> and wild-type plants exhibited slight increases in loop formation in response to increasing levels of exogenously applied indole-3-acetic acid or 1-naphthalene acetic acid. Taken together, these results suggest that the repression of loop formation by EB1b and auxin transport/signaling occurs by different mechanisms.</p>
- Nitric Oxide Modulates the Expression of Proteins and Promotes Epiphyllous Bud Differentiation in <em class="a-plus-plus">Kalanchoe pinnata</em>
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">Nitric oxide (NO), a recent addition to the signaling molecules in plants, plays an important role in mediating both biotic and abiotic stress responses. The occurrence of reproductive/vegetative structures, known as epiphylly, on the surface of leaves is a stress survival mechanism exhibited by some plants, including <em class="a-plus-plus">Kalanchoe pinnata</em>. In the present study the role of NO during epiphyllous bud differentiation was investigated. NO donors <span class="a-plus-plus emphasis type-small-caps">l</span>-arginine, NaNO<sub class="a-plus-plus">2</sub>, and SNP promoted epiphyllous bud differentiation in a dose-dependent manner, whereas NO inhibitors reversed the effect, suggesting the involvement of NO in the process. Albeit numerous physiological processes are reported to be modulated by NO, but their correlation with NO-responsive genes and proteins needs to be established. To address this issue, NO-responsive proteins (NORPs) were identified using 2D-PAGE and MS analysis. Major NORPs that were identified belonged to photosynthesis, oxidative phosphorylation, signaling, and stress metabolism, aptly indicating their probable role in this stress-induced growth process. The present study clearly indicates the role of NO in this stress survival mechanism, thus strongly affirming its role in stress responses.</p>
- Control of Drought Stress in Wheat Using Plant-Growth-Promoting Bacteria
Abstract Abiotic stress conditions are the main limiting factors for crop cultivation around the world. In the present study we aimed to improve wheat growth under drought stress conditions through priming with beneficial bacteria considered as plant-growth promoting bacteria (PGPB). Two bacterial strains, Bacillus amyloliquefaciens 5113 and Azospirillum brasilense NO40, were used to prime the wheat cv. Sids1. To generate drought stress for 12-day-old seedlings, water was withheld for 4, 5, or 7 days while growth and survival were recorded. Furthermore, several stress markers were examined by molecular and biochemical assays to study the role of priming on different stress tolerance mechanisms. Priming significantly alleviated the deleterious effect of drought stress on wheat. Drought resulted in the upregulation of some stress-related genes ( APX1 , SAMS1 , and HSP17.8 ) in the leaves and increased activity of enzymes involved in the plant ascorbate–glutathione redox cycle. Bacteria-treated plants showed attenuated transcript levels suggesting improved homeostatic mechanisms due to priming. The present study reports on the ability of certain PGPB to attenuate several stress consequences in plants which strongly supports the potential of such an approach to control drought stress in wheat.
- Carbohydrates Modulate the In Vitro Growth of Olive Microshoots. I. The Analysis of Shoot Growth and Branching Patterns
Abstract The rate of microshoot proliferation during the micropropagation of olive ( Olea europaea L . ) plants is limited by the low rates of both bud sprouting and growth of secondary shoots following subculturing. The aim of this study was to determine (1) the effects of sucrose and mannitol on shoot growth, (2) whether either of these sugars modifies the pattern of shoot development of the explants, and (3) the influence of apical dominance on explant development. Working with single-node microcuttings of Olea europaea L. cv. Maurino with two opposite axillary buds, we added 17, 34, or 68 g L −1 of sucrose or mannitol to the medium as the primary carbon source. Shoot development was classified as either (a) an outgrowth of the first bud on an explant (shoot-type A), (b) an outgrowth of the second bud (shoot-type B), or (c) an outgrowth of an axillary bud on either an A- or B-type shoot (shoot-type C). Explant survival, fresh-mass production, and patterns of shoot development were influenced by the type and concentration of sugar used. Mannitol promoted the sprouting and growth of A-, B-, and C-type shoots more than sucrose. The developmental responses observed indicate that the growth of axillary meristems of in vitro olive explants is not regulated by apical dominance. The results demonstrate that the sugar alcohol plays an important role in the developmental regulation of olive explants. Mannitol may also protect against detrimental effects associated with in vitro growth conditions.
- Negative Regulation of Methyl Jasmonate-Induced Stomatal Closure by Glutathione in <em class="a-plus-plus">Arabidopsis</em>
Abstract Glutathione (GSH) has been shown to negatively regulate methyl jasmonate (MeJA)-induced stomatal closure. We investigated the roles of GSH in MeJA signaling in guard cells using an Arabidopsis mutant, cad2 - 1 , that is deficient in the first GSH biosynthesis enzyme, γ-glutamylcysteine synthetase. MeJA-induced stomatal closure and decreased GSH contents in guard cells. Decreasing GSH by the cad2 - 1 mutation enhanced MeJA-induced stomatal closure. Depletion of GSH by the cad2 - 1 mutation or increment of GSH by GSH monoethyl ester did not affect either MeJA-induced production of reactive oxygen species (ROS) or MeJA-induced cytosolic alkalization in guard cells. MeJA and abscisic acid (ABA) induced stomatal closure and GSH depletion in atrbohD and atrbohF single mutants but not in the atrbohD atrbohF double mutant. Moreover, exogenous hydrogen peroxide induced stomatal closure but did not deplete GSH in guard cells. These results indicate that GSH affects MeJA signaling as well as ABA signaling and that GSH negatively regulates a signal component other than ROS production and cytosolic alkalization in MeJA signal pathway of Arabidopsis guard cells.
- Dynamics of Endogenous Phytohormones during Desiccation and Recovery of the Resurrection Plant Species <em class="a-plus-plus">Haberlea rhodopensis</em>
Abstract Drought is one of the most significant threats to world agriculture and hampers the supply of food and energy. The mechanisms of drought responses can be studied using resurrection plants that are able to survive extreme dehydration. As plant hormones function in an intensive cross-talk, playing important regulatory roles in the perception and response to unfavorable environments, the dynamics of phytohormones was followed in the resurrection plant Haberlea rhodopensis Friv. during desiccation and subsequent recovery. Analysis of both leaves and roots revealed that jasmonic acid, along with and even earlier than abscisic acid, serves as a signal triggering the response of the resurrection plants to desiccation. The steady high levels of salicylic acid could be considered an integral part of the specific set of parameters that prime H. rhodopensis desiccation tolerance. The dynamic changes of cytokinins and auxins suggest that these hormones actively participate in the dehydration response and development of desiccation tolerance in the resurrection plants. Our data contribute to the elucidation of a global complex picture of the resurrection plant’s ability to withstand desiccation, which might be successfully utilized in crop improvement.
- Differential Suppression of Ethylene Biosynthesis and Receptor Genes in ‘Golden Delicious’ Apple by Preharvest and Postharvest 1-MCP Treatments
Abstract Harvista™, a sprayable formulation of 1-methylcyclopropene (1-MCP), has recently been developed for preharvest use on horticultural products, whereas SmartFresh™ is a widely used 1-MCP treatment for products after harvest. The effects of Harvista™ on apple fruit ripening when sprayed at different maturities and on expression patterns of ethylene biosynthesis and receptor genes during storage have been investigated. Harvista™ applied to on-tree maturing apple fruit at an average starch pattern index of 2.5 resulted in a higher at-harvest firmness value compared with those treated at a starch pattern index of 1.5 and 3.5. This indicates that the timing of the Harvista™ application is critical. An application of Harvista™ led to better postharvest fruit firmness retention as well as reduced ethylene production. In addition, both preharvest and postharvest 1-MCP treatments resulted in contrasting responses in the expression patterns of two ethylene biosynthesis genes and in differentially suppressing effects on four ethylene receptor genes. Furthermore, the combined application of Harvista™ + SmartFresh™ resulted in greater fruit firmness retention and longer ethylene suppression. The expression profiles of these genes during on-tree fruit maturation prior to Harvista™ application were also characterized. Different regulation patterns of receptor genes could contribute to differential effects by 1-MCP treatments. The potential roles of Harvista™ to manipulate the ripening process as well as the molecular mechanism influencing 1-MCP treatment efficacy are discussed.
- Improving Soybean (<em class="a-plus-plus">Glycine</em>
<em class="a-plus-plus">max</em> L.) N<sub class="a-plus-plus">2</sub> Fixation under Stress
Abstract Soybean is a major leguminous plant that has the ability to establish a symbiotic association with the N-fixing bacteria, Bradyrhizobium japonicum . Soils are usually subjected to stress including salinity, drought, acidity, and suboptimal root zone temperature, adversely affecting the symbiotic process between soybean and the bacteria. One of the important processes affecting the performance of soybean under stress is the inhibited exchange of symbiosis-related signaling molecules, specifically genistein, between the host legume and B . japonicum during the initiation of symbiosis. Interestingly, inoculation of B . japonicum with the signal molecule genistein can partially or completely alleviate the stress. Understanding the techniques and the precise molecular pathways, which may be influenced by the signaling molecules during the stress, can be useful to determine parameters that enhance the plant’s ability to cope with stress. For example, the use of proteomic techniques to identify proteins expressed under stress can help characterize those proteins and their involvement in stress. Biotechnological-genetic techniques, either breeding or transformation, are also among the effective methods of improving soybean’s ability to fix N 2 under stress. This can be achieved by identifying the genes, which may be expressed under stress in tolerant bacterial and plant species, and inserting them into the non-tolerant species. This article highlights some important advances in soybean N 2 fixation under different stress conditions, and reviews some of the techniques used to improve the ability of plants and bacteria to efficiently fix N 2 under stress.
- Characterization of Phospholipase D from <em class="a-plus-plus">Arabidopsis thaliana</em> Callus in Response to <em class="a-plus-plus">Ent</em>-Kaurene Diterpenoid Leukamenin E
Abstract A variety of components have been isolated from various higher plants and characterized as allelochemicals, which can play an important role in natural plant communities. Leukamenin E is an ent -kaurene diterpenoid isolated from Isodon racemosa (Hemsl) Hara. Phospholipase D (PLD) is a key enzyme involved in membrane phospholipid catabolism during plant growth, development, and stress responses. To further explore and elaborate the responses of PLD to leukamenin E treatment, the activities and expression patterns of the PLD gene in Arabidopsis thaliana ( A. thaliana ) callus were researched. When A. thaliana callus was incubated with leukamenin E at concentrations of 100 and 200 μM for 48 h, the activities of PLD in microsomal and mitochondrial membranes exhibited an upregulation behavior, with the highest levels at 24 and 36 h, respectively. RT-PCR analyses suggested that PLD activity partially corresponded to the A. thaliana PLD gene transcript level. As indicators of membrane damage, electrolyte leakage and malondialdehyde contents increased significantly and peaked at hour 36 and then decreased when A. thaliana callus was treated by leukamenin E. The contents of osmotic adjustment components proline and soluble sugar also shared similar trends. These results demonstrated that the specific mechanism of the A. thaliana response to leukamenin E was linked to PLD.
- Wood Anatomy and the Development of Interxylary Phloem of <em class="a-plus-plus">Ipomoea</em>
<em class="a-plus-plus">hederifolia</em> Linn. (Convolvulaceae)
<h3 class="a-plus-plus">Abstract</h3> <p class="a-plus-plus">In <em class="a-plus-plus">Ipomoea hederifolia</em> Linn., stems increase in thickness by forming successive rings of cambia. With the increase in stem diameter, the first ring of cambium also gives rise to thin-walled parenchymatous islands along with thick-walled xylem derivatives to its inner side. The size of these islands increases (both radially and tangentially) gradually with the increase in stem diameter. In pencil-thick stems, that is, before the differentiation of a second ring of cambium, some of the parenchyma cells within these islands differentiate into interxylary phloem. Although all successive cambia forms secondary phloem continuously, simultaneous development of interxylary phloem was observed in the innermost successive ring of xylem. In the mature stems, thick-walled parenchyma cells formed at the beginning of secondary growth underwent dedifferentiation and led to the formation of phloem derivatives. Structurally, sieve tube elements showed both simple sieve plates on transverse to slightly oblique end walls and compound sieve plates on the oblique end walls with poorly developed lateral sieve areas. Isolated or groups of two to three sieve elements were noticed in the rays of secondary phloem. They possessed simple sieve plates with distinct companion cells at their corners. The length of these elements was more or less similar to that of ray parenchyma cells but their diameter was slightly less. Similarly, in the secondary xylem, perforated ray cells were noticed in the innermost xylem ring. They were larger than the adjacent ray cells and possessed oval to circular simple perforation plates. The structures of interxylary phloem, perforated ray cells, and ray sieve elements are described in detail.</p>
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