Effects Of Sodium Bisulfite On Rice Yield And The Mechanisms For Sodium Bisulfite Improving Rice Photosynthesis Efficiency

Rice(Oryza sativa L.)is one of the major food crops in China and even in the world.Increase rice yield has become a main goal in practice for rice workers,and improving photosynthesis is a key strategy for increasing the crop yield.The previous studies have shown that application of NaHSO3 is effective in improving plant photosynthesis,but the mechanisms involved are not completely clarified.By now the mechanisms about NaHSO3 enhancing photosynthesis include photorespiration inhibition,photophosphorylation promotion and photosynthesis system protection and so on.In order that NaHSO3 can be practically applied in the rice production,field experiments of different rice cultivars were conducted to investigate the effects of NaHSO3 application on rice yield.The results showed that spraying NaHSO3 at a concentration of 2mmol/L at booting significantly increased the setting rate and the grain yield.Furthermore,a pot experiment was conducted to explore the mechanisms involved in promoting rice photosynthesis by NaHSO3 through determining the leaf gas exchange parameters,the leaf chlorophyll florescence parameters,the content and activity of rubisco,RCA subunit content and its gene expression level.The result showed that,compared with the control group,the net photosynthetic rate(Pn),RuBP regeneration rate,initial Rubisco activity and RCA protein and mRNA concentration were significantly improved after spraying NaHSO3 on the leaf,suggesting that the NaHSO3 enhancement of PN could be directly attributed to induction of RCA gene expression both at the transcription and translation levels so as to regulate the initial Rubisco activity,and should not be attributed to inhibition of photorespiration,change in the stomatal conductance and the florescence characteristics of PS?.