氮素对水稻叶片衰老的调节作用

氮素营养可调节水稻叶片衰老过程中叶绿素降解的缓降期和迅降期。缺氮促使迅降期提前,而对迅降期中叶绿素降解的速率无影响。在缓降期内恢复供氮可使叶绿素和蛋白质含量恢复到对照(正常供氮)的同期水平。 叶片衰老时内源ABA含量增加。缺氮促使内源ABA急剧上升;恢复供氮可延缓衰老,同时推迟ABA含量的上升。衰老过程中叶绿素、蛋白质含量下降的速度与内源ABA含量的上升呈极显著的负相关。 氮素除作为营养物质外,可通过对叶片内源ABA水平的调节,延缓衰老的进程。

RFFECT OF NITROGEN DEFICIENCY ON LEAF SENESCENCE OF RICE SEEDLING

The effects of N-deficiency on the leaf senescence of rice seedling and the change in ABA content determined by radioimmunoassay were studied. In N-deficiency leaf, the onset of log phase was shifted to an earlier date as compared with the control on a full nutrient solution. Nitrogen supply in log phase of N-deficiency leaf could not reverse the loss of chlorophyll or protein.Nitrogen deficiency promoted the increase of endogenous ABA level and the senescence of rice leaves. Supply of nitrogen after 4 days in N-free solution retarded the increase of ABA level. Meanwhile it also delayed the leaf senescence. There was an extremely significant negative correlation between the loss of chlorophyll or protein and the increase of ABA content in rice leaf senescence. It was concluded that the early senescence of N-deficiency leaf may be resulted from rapid increase of endogenous ABA level.