Effects Of Temperature And Light On Photosynthetic Characteristics,Grain Filling And The Related Enzymes Of Carbon & Nitrogen Metabolism In The Double-cropping Indica Rice

Under the background of global warming,extreme weather appears frequently.High temperature and strong light in early rice filling stage and continuous low temperature and weak light in late rice filling stage restricted the improvement of yield and quality of high-quality indica rice in southern double cropping rice system.In this study,the early indica double-season rice xiangzaoxian 45(high-quality rice),Zhongjiazao 17(commen quality rice)and the late indica rice Taiyou 871(high quality)and Tianyouhuazhan(high quality)were used as the research materials.Pot experiment and artificial climate chamber were used to set three treatments: control(CK),high temperature normal light(HT)treatment and high temperature strong light(HT+SL)treatment at the early rice filling stage;three treatments,control(CK),low temperature normal light(LT)treatment and low temperature weak light(LT+LL)treatment were used to analyze the effects of these treatments on photosynthetic characteristics of rice leaves,grain filling and the activities of key enzymes in carbon and nitrogen metabolism.The main results are as follows:1.Compared with CK,HT and HT+SL treatments significantly decreased the net photosynthetic rate,transpiration rate,stomatal conductance and maximum photochemical efficiency of early rice leaves.Compared with HT treatment,HT+SL treatment increased transpiration rate and decreased the maximum photochemical efficiency of leaves.HT and HT+SL treatments significantly increased the initial filling rate in the upper part of grain,but it had no significant effect on grain weight in the upper and lower parts of early rice,the reason was that the time to reach the maximum filling rate was significantly decreased.In conclusion,HT and HT+SL treatments significantly inhibited photosynthesis and grain filling of early rice during grain filling.Under HT and HT+SL treatments,the activities of SSS,GBSS and SBE increased significantly in the early stage of filling,but decreased significantly in the late stage of filling,and the HT+SL treatment had a higher effect on the activities of SSS and GBSS in the early stage of filling.SBE activity continued to increase throughout the filling stage,but there was no significant difference for DBE.Under HT and HT+SL treatments,GOT activity increased significantly only in the early stage of filling,while GPT activity increased significantly in the whole growth stage,and there was no significant difference between HT treatment and HT+SL treatment.2.Compared with CK,LT and LT+LL treatments significantly decreased net photosynthetic rate,transpiration rate,stomatal conductance and maximum photochemical efficiency of leaves of late rice.Compared with LT treatment,LT+LL treatment had a significant effect on the reduction of net photosynthetic rate.LT and LT+LL treatments tended to decrease the grain weight of the upper and lower parts,and the LT+LL treatment had significant decreasing effect compared with LT treatment,because the initial filling rate was significantly decreasesd.Under LT and LT+LL treatments,the activities of SSS,GBSS and SBE decreased significantly in the early stage of filling,and the activities of GBSS increased significantly in the late stage of filling,while the activities of SBE decreased significantly in the whole stage.GBSS had no significant difference under LT+LL treatment,while SBE activity decreased significantly under LT+LL treatment compared with LT treatment.Under LT and LT+LL treatments,GOT activity decreased significantly during the whole grain filling stage,while GPT activity increased first and then decreased.In conclusion,LT and LT+LL treatments significantly inhibited photosynthesis,grain filling and activities of enzymes related to carbon and nitrogen metabolism in late rice during grain filling.