[Effects of drought and waterlogging on flag leaf post-anthesis photosynthetic characteristics and assimilates translocation in winter wheat under high temperature].

With winter wheat varieties Yangmai 9 and Yumai 34 as test materials, this paper studied post-anthesis photosynthetic characteristics in flag leaves, the translocation of assimilates and nitrogen stored in vegetative organs before and after anthesis and their relationships with grain yield and quality under different temperature and water conditions. The results showed that high temperature, drought, and waterlogging all had significant negative effects on photosynthetic rate and chlorophyll content (SPAD value) of flag leaves, and the effects of drought and waterlogging were greater under high temperature than under optimum temperature. The translocation amount and rate of assimilates and nitrogen stored in vegetative organs before anthesis declined in the order of drought > normal soil moisture content > waterlogging under optimum temperature, but normal soil moisture content > drought > waterlogging under high temperature. The amount of post-anthesis assimilates translocated into grain declined in the order of normal soil moisture content > waterlogging > drought under optimum temperature, but normal soil moisture content > drought > waterlogging under high temperature, while that of post-anthesis accumulated nitrogen declined in the order of normal soil moisture content > waterlogging > drought under both high and optimum temperature. The starch and protein contents in grains were the lowest under high temperature x waterlogging, but the highest under optimum temperature x normal soil moisture content. Overall, the decrease of grain mass and starch content under high temperature and water stresses was associated with the lower photosynthetic rate and less post-anthesis assimilates accumulation, while grain protein content was related to the translocation amount and rate of nitrogen stored before anthesis.