Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Cytokinin-Dependent Photorespiration and the Protection of Photosynthesis during Water Deficit

Abstract: We investigated the effects of P(SARK)IPT (for Senescence-Associated Receptor KinaseIsopentenyltransferase) expression and cytokinin production on several aspects of photosynthesis in transgenic tobacco (Nicotiana tabacum cv SR1) plants grown under optimal or restricted (30% of optimal) watering regimes. There were no significant differences in stomatal conductance between leaves from wild-type and transgenic P(SARK)-IPT plants grown under optimal or restricted watering. On the other hand, there was a significant reduction in the maximum rate of electron transport as well as the use of triose-phosphates only in wild-type plants during growth under restricted watering, indicating a biochemical control of photosynthesis during growth under water deficit. During water deficit conditions, the transgenic plants displayed an increase in catalase inside peroxisomes, maintained a physical association among chloroplasts, peroxisomes, and mitochondria, and increased the CO(2) compensation point, indicating the cytokinin-mediated occurrence of photorespiration in the transgenic plants. The contribution of photorespiration to the tolerance of transgenic plants to water deficit was also supported by the increase in transcripts coding for enzymes involved in the conversion of glycolate to ribulose-1,5-bisphosphate. Moreover, the increase in transcripts indicated a cytokinin-induced elevation in photorespiration, suggesting the contribution of photorespiration in the protection of photosynthetic processes and its beneficial role during water stress.

Ethylene: biosynthesis and perception

Abstract: Ethylene is a plant hormone influencing plant processes such as seed germination, diageotropism, flowering, abscission, senescence, fruit ripening, and pathogenesis responses. Its biosynthesis involves multistep enzymatic pathway converting methionine to ethylene. Conjugated forms of ACC, l‐(malonylamino)cyclopropane‐1‐carboxylic acid and l‐(γ‐1‐glutamylamino)cyclopropane‐1‐carboxylic acid, and the enzymes catalyzing these reactions have also been demonstrated. The different ethylene biosynthesis enzymes are encoded each by a family of genes, which raises questions about their functional significance. In addition to transcriptional control of gene expression, posttranscriptional regulation seems to play an important role. Mutants of Arabidopsis and tomato have been used to dissect the ethylene signal transduction pathway. Analyses of ethylene‐insensitive mutants in Arabidopsis and tomato have identified ETR1 gene or its homologues, which codes for a protein similar to microbial two‐component regu...

Plant physiology and proteomics reveals the leaf response to drought in alfalfa (Medicago sativa L.)

Abstract: Despite its relevance, protein regulation, metabolic adjustment, and the physiological status of plants under drought is not well understood in relation to the role of nitrogen fixation in nodules. In this study, nodulated alfalfa plants were exposed to drought conditions. The study determined the physiological, metabolic, and proteomic processes involved in photosynthetic inhibition in relation to the decrease in nitrogenase (Nase) activity. The deleterious effect of drought on alfalfa performance was targeted towards photosynthesis and Nase activity. At the leaf level, photosynthetic inhibition was mainly caused by the inhibition of Rubisco. The proteomic profile and physiological measurements revealed that the reduced carboxylation capacity of droughted plants was related to limitations in Rubisco protein content, activation state, and RuBP regeneration. Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by Nase activity inhibition. In this context, drought induced the decrease in Rubisco binding protein content at the leaf level and proteases were up-regulated so as to degrade Rubisco protein. This degradation enabled the reallocation of the Rubisco-derived N to the synthesis of amino acids with osmoregulant capacity. Rubisco degradation under drought conditions was induced so as to remobilize Rubisco-derived N to compensate for the decrease in N associated with Nase inhibition. Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential (Ws). At the nodule level, drought had an inhibitory effect on Nase activity. This decrease in Nase activity was not induced by substrate shortage, as reflected by an increase in total soluble sugars (TSS) in the nodules. Proline accumulation in the nodule could also be associated with an osmoregulatory response to drought and might function as a protective agent against ROS. In droughted nodules, the decrease in N2 fixation was caused by an increase in oxygen resistance that was induced in the nodule. This was a mechanism to avoid oxidative damage associated with reduced respiration activity and the consequent increase in oxygen content. This study highlighted that even though drought had a direct effect on leaves, the deleterious effects of drought on nodules also conditioned leaf responsiveness.

Plant biochemistry and molecular biology

Abstract: Contents : 1. A leaf cell consists of several metabolic compartments -2. The use of energy from sunlight by photosynthesis -3. Photosynthesis is an electron transport process -4. ATP generation by photosynthesis -5. Mitochondria, the power stations of cell -6. Photosynthetic CO2 assimilation by the Calvin cycle -7. Photorespiration -8. Photosynthesis and water consumption -9. Polysaccharides -10. Nitrate assimilation -11. Nitrogen fixation -12. Sulfate assimilation -13. Phloem transport -14. Plant storage proteins -15. Glycerolipids -16. The function of secondary metabolites in plants -17. Isoprenoids -18. Phenylpropanoids -19. Signals regulating the growth and development of plant organs -20. The genomes of plant cells -21. Protein biosynthesis -22. Gene technology in plants.

Physiology of Crop Production

Abstract: * Preface and Acknowledgments * Chapter 1. Plant Canopy Architecture * Introduction * Plant Height * Tillering * Leaf Characteristics * Breeding and Management Strategies for Ideal Plant Architecture * Conclusion * Chapter 2. Root Architecture * Introduction * Root Morphology * Shoot-Root Ratios * Root Growth Parameters and Methods of Measurement * Root Distribution in Soil * Root Development Relative to Plant Growth Stage * Root Characteristics Related to Drought Resistance * Soil Environment * Management Strategies for Maximizing Root Systems * Conclusion * Chapter 3. Physiology of Growth and Yield Components * Introduction * Theory of Growth and Yield Components Analysis * Yield Components Analysis * Dry Matter Production and Grain Yield * Duration of Reproductive Growth Period * Duration of Grain-Filling Period * Management Strategies for Ideal Yield Components * Conclusion * Chapter 4. Photosynthesis and Crop Yield * Introduction * Crop Photosynthesis * Canopy Photosynthesis * C3 and C4 Photosynthesis * Radiation Use Efficiency * Leaf Area Index * Partitioning of Assimilates * Respiration During Photosynthesis * Management Strategies for Maximizing Photosynthesis * Conclusion * Chapter 5. Source-Sink Relationships and Crop Yield * Introduction * Source-Sink Transitions * Physiological Aspects of Source-Sink Relationships in Annual Crop Plants * An Example of Yield Manipulation Using Source-Sink Concepts Relative to Nitrogen and Crop Development * Relationship Between Sink and Respiration * Formation of Yield Sinks * Modification in Source-Sink Relationships with Cultivar Improvement * Management Strategies for Maximizing Source-Sink Relationships * Conclusion * Chapter 6. Carbon Dioxide and Crop Yield * Introduction * Total Carbon in Soils of the World * Carbon Dioxide and Plant Growth * Carbon Dioxide and Photosynthesis * Carbon Dioxide and Water Use Efficiency * Carbon Dioxide and Radiation Use Efficiency * Management Strategies in Sequestration of CO2 * Conclusion * Chapter 7. Physiology of Drought in Crop Plants * Introduction * Water Use Efficiency * Crop Yield Relative to Water Stress * Drought and Nutrient Acquisition * Drought Resistance Mechanisms * Management Strategies for Reducing Drought * Conclusion * Chapter 8. Physiology of Mineral Nutrition * Introduction * Root Morphology * Active and Passive Ion Transport * Ion Uptake Mechanisms * Ion Absorption Measurement * Ion Translocation from Roots to Shoots * Physiological Functions of Nutrients * Beneficial and Toxic Elements * Conclusion * Appendix. Plant Species * References * Index