水稻叶片衰老过程中氨肽酶活性的变化

水稻叶片中存在着氨肽酶,其最适反应pH和最适反应温度分别为8.2℃和40℃,酶促反应的产物量在最初30min内与时间呈直线相关。 水稻叶片衰老过程中叶绿素和蛋白质含量下降,而氨肽酶比活上升;用植物激素延缓或促进叶片衰老蛋白质降解的同时也抑制或促进了氨肽酶比活的上升,说明氨肽酶在水稻叶片衰老蛋白质降解过程中起一定的作用。根据水稻叶片衰老过程中大分子化合物和叶片外部形态的变化,可将叶片衰老过程划分为缓衰期、急衰期和竭衰期。

CHANGES OF AMINOPEPTIDASE ACTIVITY DURING LEAF SENESCENCE IN RICE

The specific activity of aminopeptidase increased during the course of senescenceof attached rice leaves in parallel with the decrease of protein and chlorophyll con-tents. Sprayed the plants with plant hormones everyweek after heading, GA_3 (10ppm) and 6-BA (10 ppm) delayed the rate of protein degradation and the increasingof specific activity of aminopeptidase during leaf senescence while ethrel (100 ppm)promoted the rate of protein degradation and specific activity of aminopeptidase.There existed a negative correlation between the specific activity of aminopeptidaseand protein content. Therefore, aminopeptidase must play an active role in riceleaf senescence.The specific activity of hemoglobin-digesting proteinase in attached rice leavesduring senescence increased by as much as 12.5-fold while aminopeptidase, 5.4-fold. Accordingly hemoglobin-digesting proteinase might play a more importantrolethan aminopeptidase in degradation of leaf protein during senescence in rice.According to changes of some macromoleculars in the leaf with changes ofleaf color it was proposed that the senescent process of rice leaves might be dividedinto three stages, namely slow quick and complete senescent stages.