[Changes of key enzyme activities in rice cultivars with different photooxidation-tolerance during grain-filling stage in early and late seasons].

Four rice cultivars with different photooxidation-tolerance characteristics during grain-filling stage in early and late seasons were selected to uncover the physiological and biochemical mechanisms of the correlation between rice photooxidation-tolerance and grain quality.The results showed that the parameters mean grain-filling rate (G_ mean ),time arrived to maximum grain-filling rate (T_ max.G ),and 100-grain weight at the maximum grain-filling rate (W_ max.G ) were relatively stable for the varieties adaptable to high light intensity,while on the contrary for those sensitive to photooxidation.The ADP glucose pyrophosphorylase and starch synthase activities of the varieties adaptable to high light intensity after grain-filling peaks had a less difference between early and late seasons than those sensitive to photooxidation,and the relative enzyme activities in the varieties adaptable to high light intensity changed coequally in early and late seasons.