Effects of Post-anthesis Drought and Waterlogging on Photosynthetic Characteristics,Assimilates Transportation in Winter Wheat

Four winter wheat( Triticum aestivum L.) genotypes differing in grain protein content, Heixiaomai 76, Wanmai 38, Yangmai 10 and Yangmai 9, were used in pot experiment in greenhouse to investigate the effects of drought (Soil relative water content, SRWC=45%-50%), waterlogging and moderate soil water status (SRWC=75%-80%) after anthesis on net photosynthesis and chlorophyll contents of flag leaves, remobilization of assimilates stored before anthesis, transportation of post-anthesis assimilates, and contents and yields of starch and protein in grain at maturity. It was found that the photosynthetic active duration (PAD) and the relative steady phase of chlorophyll content( RSP) of flag leaves of four wheat genotypes were shortened by both drought and waterlogging. Values of PAD and RSP declined from CK, via waterlogging then drought. The remobilization rate of pre-anthesis stored assimilates was the highest for CK, while the lowest for waterlogging. The amounts of post-anthesis assimilates and accumulated nitrogen transferring into grain were declined as CKwaterloggingdrought and CKdroughtwaterlogging, respectively. The yield of grain protein significantly decreased at 5% level with the order of CK drought waterlogging in four wheat genotypes. The contents of grain protein increased significantly under drought, but had no significant difference between CK and waterlogging. Compared with CK, starch yield significantly decreased under drought and waterlogging in four wheat genotypes, but starch content was various among four wheat genotypes. These results showed that the amount of post-anthesis assimilates transferring into grain decreased distinctly under drought, while the remobilization of pre-anthesis stored nitrogen and the transferring of post-anthesis accumulated nitrogen into grain declined distinctly under waterlogging, which led to differences in protein and starch contents of wheat grains under post-anthesis drought and waterlogging. It is inferred that the transferring of post-anthesis accumulated nitrogen into grain and the remobilization of pre-anthesis stored nitrogen were vital factors to determine protein yield under the drought and waterlogging condition, respectively.