萝卜离体子叶衰老与膜脂过氧化的关系

萝卜离体子叶在光下或暗中衰老及激素调节衰老过程中,作为叶片衰老指标的叶绿素和蛋白质含量的降低,发生在MDA含量增高之前,更早于SOD活性的下降。表明由SOD活性降低所导致的膜脂过氧化的增强,并非衰老的原初反应,而是叶片衰老到一定程度的生理变化。因此,至少在萝卜离体子叶上,不能将其衰老的启动归因于受SOD控制的膜脂过氧化作用导致的膜累积性质变。

The Relationship Between Senescence and Membrane Lipid Peroxidation in Detached Cotyledons of Radish

The causality between radish cotyledon senescence and membrane lipid peroxidation was investigated. The results showed that, whether under illumination or in the dark, the contents of protein and chlorophyll in detached cotyledons floated on water and treated with 6-BA or ABA markedly decreased during 2 d of senescence. However, MDA content and SOD activity remained at relatively stable values during the same periods. Increase of MDA content and decrease of SOD activity did not occur until the 3rd day and 4th day of cotyledon senescence respectively. From the fact that the accumulation of MDA and decline of SOD activity lag behind the decline of protein and chlorophyll content in detached radish cotyledons floated on water or treated with exogenous phytohormones, it is evident that they are the results of physiological changes after senescence hasstartedin detached cotyledons. Once membrane injury occurred as a result of membrane lipid peroxidation, metabolism deterioration and senescence of leaves will be accelerated.