Plant physiology

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

Genetic dissection of blue-light sensing in tomato using mutants deficient in cryptochrome 1 and phytochromes A, B1 and B2

Abstract: Several novel allelic groups of tomato (Solanum lycopersicum L.) mutants with impaired photomorphogenesis have been identified after gamma-ray mutagenesis of phyA phyB1 double-mutant seed. Recessive mutants in one allelic group are characterized by retarded hook opening, increased hypocotyl elongation and reduced hypocotyl chlorophyll content under white light (WL). These mutants showed a specific impairment in response to blue light (BL) resulting from lesions in the gene encoding the BL receptor cryptochrome 1 (cry1). Phytochrome A and cry1 are identified as the major photoreceptors mediating BL-induced de-etiolation in tomato, and act under low and high irradiances, respectively. Phytochromes B1 and B2 also contribute to BL sensing, and the relative contribution of each of these four photoreceptors differs according to the light conditions and the specific process examined. Development of the phyA phyB1 phyB2 cry1 quadruple mutant under WL is severely impaired, and seedlings die before flowering. The quadruple mutant is essentially blind to BL, but experiments employing simultaneous irradiation with BL and red light suggest that an additional non-phytochrome photoreceptor may be active under short daily BL exposures. In addition to effects on de-etiolation, cry1 is active in older, WL-grown plants, and influences stem elongation, apical dominance, and the chlorophyll content of leaves and fruit. These results provide the first mutant-based characterization of cry1 in a plant species other than Arabidopsis.

Nitrogen Metabolism and Photosynthesis in Leymus chinensis in Response to Long-term Soil Drought

Abstract: Key enzyme activities related to nitrogen metabolism, gas-exchange, chlorophyll fluorescence, and lipid peroxidation were determined in Leymus chinensis (Trin) Tzvel plants under four soil moisture regimes (control: 75%–80% of field moisture capacity, mild drought: 60%–65%, and moderate drought: 50%–55% as well as severe drought: 35%–40%) Severe drought significantly decreased the key enzyme activities of nitrogen anabolism such as nitrate reductase (NR, EC 1661), glutamine synthetase (GS, EC 6312), and glutamate dehydrogenase (GDH, EC 1412) but increased the key enzyme activities of nitrogen catabolism such as asparaginase (AS, EC 6354) and endopeptidase (EP, EC 342411), especially after long-term soil drought Plant biomass, leaf-biomass ratio between the green leaf and total plant biomass, net photosynthetic rate, stomatal conductance, the maximal efficiency of PSII photochemistry, the actual quantum yield, and the photochemical quenching were significantly reduced by severe water stress Plant malondialdehyde (MDA) concentration increased with the increase in water stress, particularly at the late-growth stage Our results suggest that the key enzymes of nitrogen metabolism may play an important role in the photosynthetic acclimation of L chinensis plants to long-term soil drought

Jasmonic Acid and Ethylene Modulate Local Responses to Wounding and Simulated Herbivory in Nicotiana attenuata Leaves

Abstract: Jasmonic acid (JA) and ethylene (ET) are known to play important roles in mediating plant defense against herbivores, but how they affect development in herbivore-attacked plants is unknown. We used JA-deficient (silenced in LIPOXYGENASE3 [asLOX3]) and ET-insensitive (expressing a mutated dominant negative form of ETHYLENE RESPONSE1 [mETR1]) Nicotiana attenuata plants, and their genetic cross (mETR1asLOX3), to examine growth and development of these plants under simulated herbivory conditions. At the whole plant level, both hormones suppressed leaf expansion after the plants had been wounded and the wounds had been immediately treated with Manduca sexta oral secretions (OS). In addition, ectopic cell expansion was observed around both water- and OS-treated wounds in mETR1asLOX3 leaves but not in mETR1, asLOX3, or wild-type leaves. Pretreating asLOX3 leaves with the ET receptor antagonist 1-methylcyclopropane resulted in local cell expansion that closely mimicked the mETR1asLOX3 phenotype. We found higher auxin (indole-3-acetic acid) levels in the elicited leaves of mETR1asLOX3 plants, a trait that is putatively associated with enhanced cell expansion and leaf growth in this genotype. Transcript profiling of OS-elicited mETR1asLOX3 leaves revealed a preferential accumulation of transcripts known to function in cell wall remodeling, suggesting that both JA and ET act as negative regulators of these genes. We propose that in N. attenuata, JA-ET cross talk restrains local cell expansion and growth after herbivore attack, allowing more resources to be allocated to induced defenses against herbivores.

Bacterial-Mediated Induction of Systemic Tolerance to Salinity with Expression of Stress Alleviating Enzymes in Soybean ( Glycine max L. Merrill)

Abstract: This study explored several features related to salt tolerance in soybean plants through plant growth-promoting rhizobacteria (PGPR; Pseudomonas sp. strain AK-1, and Bacillus sp. strain SJ-5). We report the significant effect of 1-aminocyclopropane-1-carboxylate deaminase, indole-3-acetic acid production and exopolysaccharide production from both bacterial strains on physical parameters and biochemical activities in Glycine max plants under salt stress. In this report, we investigated the leaf water content, osmolyte accumulation, and activities of stress-responsive enzymes in the absence and presence of salt stress. Control (plants devoid of bacterial strains) and PGPR-inoculated soybean plants were grown in half Murashige and Skoog medium subjected to saline and non-saline conditions. Results showed that PGPR-inoculated plants had superior tolerance against salt stress, as shown by their enhanced plant biomass (fresh weight), higher water content, higher photosynthesis activity, and lower osmotic stress injury. The increased proline accumulation and lipoxygenase activity in PGPR-inoculated plant roots contributed to increased plant tolerance to salt stress. SJ-5-inoculated plants (0.414 U/mg protein) and AK-1-inoculated plants (0.403 U/mg protein) showed higher LOX activity than control plants (0.366 U/mg protein). Proline content was higher in SJ-5-(120 µg/g f.w.) and AK-1-(135 µg/g f.w.)inoculated plants than control plants (90 µg/g f.w.). Peroxidase activity was also higher in PGPR-inoculated plant roots during salinity. These results suggest that, in PGPR-inoculated roots, lipoxygenase plays a role in mitigating the adverse effect of salt stress. Furthermore, enhanced proline maintains osmotic balance and a positive water potential for water entrance into the roots, and peroxidase enzyme reduces oxidative damage by lowering reactive oxygen species level under salt stress. Our results indicated that both Pseudomonas and Bacillus are multifunctional PGPR strains that can promote plant growth, development and reduce salinity stress. However, our Bacillus bacterium strain had more ACC deaminase, phosphate solubilization, and siderophore activity under salt stress as compared to the Pseudomonas strain.