小麦叶片老化过程中光合功能衰退的可能机制

在小麦旗叶自然老化过程中，叶绿素含量和光合速率在叶片全展时达最大值，以后至叶片枯黄不断降低，ＲｕＢＰｃａｓｅ活性于全展后１０天达到最大值，ＰＳⅠ，ＰＳⅡ活性在老化前期保持平稳，以后不断下降。ＲｕＢＰｃａｓｅ活性与ＰＳⅠ活生，ＰＳⅡ活性比值也均于全展扣１０天达最大值，以后呈迅速降低趋势，表明在叶片老化中后期，光合机构的光暗反应出现失衡现象。

Studieson Deterioration of Photosynthetic Function and Its Probable Mechanism in Natural Aging of Leaf in Wheat

During flag leaf growth span of wheat, chlorophyll content (Chl) and photo-synthetic rate (Pn) reached the highest values at leaf full expansion, then decreased gradually.The RuBPcase activity peaked at 10 th day after leaf full expansion. During early aging process(before the 20 th day after leaf full expansion), PS I , PS II activity maintained stable, then declined. The ratios of RuBPcase activity to PS I , PS II activity also reached the maximum at the10 th day after leaf full expansion, then decreased sharply. It is suggested that the balance between photochemical reactions and photosynthetic dark reactions is broken during the middle-lateaging process. O2- producing rate and H2O2 content increased, while SOD activity gradually declined during leaf aging process. These results indicate that during leaf natural aging process, theimbalance between photochemical reactions and photosynthetic dark reactions gradually increases, Which may cause an increase in active oxygen production and finally result in the deterioration of photosynthetic function. The leaves of hybrid wheat showed much longer function duration and higher scavenging capacity for active oxygen.