Relationships Between Balance of Nitrogen Supply-Demandand Nitrogen Translocation and Senescenceof D

<正> By removing panicles and spikelets, the effects of nitrogen supply-demand balance(NSDB)on nitrogen translocation and senescence of leaves at different positions of the same stem in rice plant were studied. The results showed that under NSDB<0(CK), nitrogen translocation and senescence of the top 4 leaves was normal. Nitrogen exported from the top leaves(LFT)especially the top 4 leaves decreased remarkably with increase of NSDB. thus, their MDA contents and differences in color(SPAD value)decreased, while the activities of SOD and CAT increased. Under NSDB>0(panicle removal), N accumulation of the top 4 leaves increased significantly, and the leaf senescence process was delayed. The results also indicated that the color of the 4th LFT was mainly affected by NSDB among the top 4 leaves and was lighter than the 3rd LFT when nitrogen supply was insufficient for the sink need.