衰老叶片叶绿素荧光动力学变化及6-BA延缓衰老的机理研究

观测了离体小麦叶片衰老进程中685nm光诱导荧光动力学的变化,发现曲线的第二峰首先消失,F_v(F_p-F_t)、F_p-F_t和F_v/F_o比值迅速下降,达最大荧光P点的时间缩短。推测衰老叶片中PQ分子数目的减少是光合能力丧失的主要原因。用6-BA处理叶片,阻止了F_v和F_v/F_o比值的下降,与对照相比,衰老第三天仍保持第二峰;此外,核黄素使第二峰消失,而核黄素+BA与BA效果相似;同时叶片衰老时SOD活性的下降和膜脂过氧化作用均被延缓,据此探讨了BA作为自由基清除剂延缓叶片衰老的可能机理。

Studies on the Changes of Kinetics of Chlorophyll Fluorescence from Intact Leaves During Senescence and the Mechanism of Inhibiting Aging by 6-BA

The kinetics of 685 nm chlorophyll fluorescence emission from wheat (Triticum aestivum L.) leaves were measured during senescence. It were found that the second peak (S to M rise) in induction curves disappered firstly, variable fluorescence (Fv:Fp-Fo), Fp-Ft and the ratio of Fv/Fo were decreased rapidly, and the time taken to reach P posnt of the curve reduced. All these indicated that fewer plastoquinone (PQ) molecules in old leaves were responsible for this decline in photosynthetic capability. Treatments of detached wheat and maize (Zea mays L.) leaves with 6-BA, not only could strongly inhibit the decrease of the ratio of Fv/Fo and Fv, but also sustain the second peak. In addition, the second peak disappered when the leaves were treated with riboflavin after 3 days in darkness, but BA + riboflavin kept it. Meanwhile the decrease of superoxide dismutase activity and the increase of lipid peroxidation was also delayed. Thus, the possible mechanism of BA in preventing senescence as the scavenger of free radicals was discussed.