To investigate how bisulfite promotes photosynthesis, a pot experiment was conducted with rice (Oryza sativa L.) plants to determine Rubisco activity and content, and Rubisco activase (RCA) gene expression after spraying NaHSO3 on rice leaves. The NaHSO3 treatment promoted significantly net photosynthetic rate (PN), carboxylation efficiency, maximum carboxylation rate, ribulose-1,5-bisphosphate regeneration rate, initial Rubisco activity, and RCA protein and mRNA concentrations. Therefore, the NaHSO3 enhancement of PN could be directly attributed to induction of RCA gene expression both at the transcription and translation levels. Thus, the increased RCA regulated the initial Rubisco activity in vivo., Y. Chen, J.-H. Jin, Q.-S. Jiang, C.-L. Yu, J. Chen, L.-G Xu, D.-A. Jiang., and Obsahuje bibliografii
The effects of submergence on chlorophyll (Chl) a fluorescence were compared in seven Oryza sativa (L.) cultivars, namely FR 13A, Khoda, Khadara, Kalaputia (tolerant), Sabita, and Hatipanjari (avoiding type), and IR 42 (susceptible). Seedlings were submerged for 4 d under complete darkness. Oxygen concentration of flood water decreased with the period of submergence with concomitant increase in concentration of carbon dioxide. Submergence caused diminution in the amount of total Chl. Genotypic differences were observed for Chl content and survival percentage. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of photosystem 2 (PS2) to submergence. The kinetics of Chl a fluorescence rise showed complex changes in the magnitudes and rise of O-J, J-I, and I-P phases caused by submergence. The selective suppression of the J-I phase of fluorescence especially after 2 d of submergence provided evidence for weakened electron donation from the oxygen evolving complex whereas under severe submergence stress (4 d) both O-J and J-I steps were suppressed greatly with highly suppressed P-step, which resulted in lowering of variable fluorescence. Grouping probability or energetic connectivity between PS2 obtained through JIP-test from the data after 2 d of submergence showed a direct relation with survival percentage, i.e. fluorescence measurements contained the information of the survival chance of a plant under submerged conditions. The information could be used in identifying the submergence tolerant cultivars when the damage is not very severe. and D. Panda ... [et al.].
Plants experience multiple abiotic stresses during the same growing season. The implications of submergence with and without saline water on growth and survival were investigated using four contrasting rice cultivars, FR13A (submergence-tolerant, salinity-susceptible), IR42 (susceptible to salinity and submergence), and Rashpanjor and AC39416 (salinity-tolerant, submergence-susceptible). Though both FR13A and IR42 showed sensitivity to salinity, FR13A exhibited higher initial biomass as well as maintained greater dry mass under saline condition. Greater reduction of chlorophyll (Chl) contents due to salinity was observed in the susceptible cultivars, including FR13A, compared to the salinity-tolerant cultivars. Exposure of plants to salinity before submergence decreased the survival chance under submergence. Yet, survival percentage under submergence was greater in FR13A compared to other cultivars. Generally, the reduction in the Chl content and damage to PSII were higher under the submergence compared to salinity conditions. The submergence-tolerant cultivar, FR13A, maintained greater quantities of Chl during submergence compared to other cultivars. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of PSII to submergence in saline and nonsaline water. The submergence-tolerant cultivar maintained greater chloroplast structural integrity and functional ability irrespective of the quality of flooding water., R. K. Sarkar, Anuprita Ray., and Obsahuje seznam literatury
At the vegetative growth stage (40 d), the mean photosynthetic rate (PN) and canopy photosynthesis (PN × LAI) in F1 hybrids and their parents were similar, whereas the maintenance respiration rate (RM) was considerably higher and PN/RM lower in the F1 hybrids than in the parents. Yet at the flowering stage, the hybrids showed higher PN and PN × LAI values, while RM and PN/RM were similar in both. A specific F1 hybrid like IR 62829A×Vajram showed high readings in PN, PN/RM, and PN × LAI at the flowering stage, while IR 62829A×Swarna followed by IR 62829A×Vajram had high values 40 d after planting. The parents Swarna and Vajram, although moderate in PN, had the highest PN × LAI at the flowering stage due to a greater LAI. and M. J. Baig, P. Swain, K. S. Murty.
Rice being the major food crop for more than half of the world population is severely affected by drought stress starting from the establishment of the seedling. We focused on the UV-B priming mediated transgenerational drought tolerance of a drought-tolerant rice variety (Vaisakh) towards polyethylene glycol (PEG) 6,000 (20%)-induced drought. Results showed that priming in F0 generation and re-priming in F1 generation with UV-B enhanced the PEG stress tolerance potential of rice seedlings with increased expression of genes encoding antioxidant enzymes and stress-related proteins offering better protection to primed plants. UV-B priming maintained oxidative homeostasis of the plant cell thus ensuring uninterrupted mitochondrial and photosynthetic activities. Cumulatively, our results suggest that the transgenerational priming memory retained in the seeds is transferred to offspring without any loss. Moreover, re-priming in F1 generation further boosted the innate tolerance potential of a tolerant variety resulting in stable cellular redox homeostasis.