The effects of nitrogen topdressing stage on photosynthesis, translocation and distribution of (14)~C assimilate and NR activity of wheat

The effects of nitrogen topdressing stage on photosynthesis,translocation and distribution of 14 C assimilate and NR activity in wheat were studied by combination experiments of pot culture and trough culture.The results showed that,compared with topdressing nitrogen fertilizer at double ridged stage,topdressing at jointing stage improved the chlorophyll content and photosynthetic rate of flag leaf.At filling stage,the proportion of 14 C assimilation translocated to grain remarkablely improved,while that remained at vegetative organs declined.The NR activities of flag leaf and root were increased significantly.As a result,the grain number per spike,the grain weight,the yield,and the content of protein improved remarkablely.