The aim of our study was to investigate the underlying molecular mechanisms of exogenously supplied trehalose affecting wheat photosynthesis under heat stress. The amount of ATP synthase (ATPase), oxygen-evolving enhancer protein (OEE), PsbP, Rubisco, chloroplast fructose-bisphosphate aldolase (FBPA), and ferredoxin-NADP(H) oxidoreductase (FNR) were downregulated, while PSI reaction center subunits were upregulated under heat stress. However, in the trehalose-pretreated groups, the amount of FNR, cytochrome b6f complex, PSI reaction center subunits, ATPase, FBPA, and Rubisco were upregulated under normal growth conditions and heat stress. Besides, during the recovery period, the upregulation in CAB, PsbP, OEE2, and ATPase suggested that trehalose pretreatment might help to the recovery of PSII and PSI. These results indicate that trehalose pretreatment effectively regulates the levels of the photosynthesis-related proteins and relieves the damage of heat stress to wheat chloroplast., Y. Luo, H. Y. Liu, Y. Z. Fan, W. Wang, Y. Y. Zhao., and Obsahuje bibliografii
We investigated the different responses of wheat (Triticum aestivum L.) plants to drought- (DS) and heat stress (HS), and analyzed the physiological mechanisms of glycine betaine (GB) involved in the improvement of wheat tolerance to the combination of these stresses. The transgenic wheat T6 line was generated by introducing a gene encoding betaine aldehyde dehydrogenase (BADH) into the wild-type (WT) Shi4185 line. The gene was cloned from the Garden Orache plant (Atriplex hortensis L.). Wheat seedlings were subjected to drought stress (30%, PEG-6000), heat stress (40°C), and their combination. Photosynthetic gas exchange, water status and lipid peroxidation of wheat leaves were examined under different stresses. When subjected to a combination of drought and heat, the inhibition of photosynthesis was significantly increased compared to that under DS or HS alone. The increased inhibition of photosynthesis by the combined stresses was not simply the additive stress effect of separate heat- and drought treatments; different responses in plant physiology to DS and HS were also found. HS decreased the chlorophyll (Chl) content, net photosynthetic rate (PN), carboxylation efficiency (CE) and apparent quantum yield (AQY) more than DS but DS decreased the transpiration rate (E), stomata conductance (gs) and intercellular CO2 concentration (Ci) more than HS. GB over-accumulation led to increased photosynthesis not only under individual DS or HS but also under their combination. The enhancement of antioxidant activity and the improvement of water status may be the mechanisms underlying the improvement of photosynthesis by GB in wheat plants. and G. P. Wang ... [et al.].
Low temperature during the vegetative stage affects rice (Oryza sativa L.) seed-setting rate in Heilongjiang province at Northeast China. However, little is known about changes of the photosynthetic rate and physiological response in contrasting rice cultivars during chilling periods. In this study, two rice cultivars with different chilling tolerance were treated with 15°C from June 27 to July 7. The chilling-susceptive cultivar, Longjing11 (LJ11), showed a significant decrease in a ripening rate and seed-setting rate after being treated for four days, whilst chilling-tolerant cultivar, Kongyu131 (KY131), was only slightly affected after 4-d treatment. The photosynthetic activities, chlorophyll contents, and antioxidative enzyme activities in LJ11 decreased significantly along with the chilling treatment. The decrease in ß-carotene contents might play a role as it could cause direct photooxidation of chlorophylls and lead to the inhibition of the photosynthetic apparatus. In the meantime, no significant damage was found in leaves of KY131 from June 27 to July 11. In conclusion, the chilling-tolerance mechanism of rice is tightly related to the photosynthetic rate, metabolism of reactive oxygen species, and scavenging system in the vegetative stage., L.-Z. Wang, L.-M. Wang, H.-T. Xiang, Y. Luo, R. Li, Z.-J. Li, C.-Y. Wang, Y. Meng., and Obsahuje bibliografii