【摘要】 黄瓜幼苗子叶SOD活性在细胞内的分布是细胞溶质部份最高(占总活性的85％左右),其次是线粒体(占10％)和叶绿体(约4％)。各细胞器的SOD同工酶酶谱均为三条同工酶活性带,迁移率较慢的一条是Mn-SOD同工酶,迁移率较快的二条为CuZn-SOD同工酶。各细胞器的SOD对低温的敏感程度不同,依次为:叶绿体>线粒体>细胞溶质部份。叶绿体和线粒体周工酶酶谱的CuZn-SOD活性带,随着处理温度的降低而减弱或接近消失。随着温度的降低,黄瓜幼苗子叶SOD活性的下降和电解质泄漏增加,幼苗逐渐呈现出伤害症状,而SOD活性的显著下降却比细胞电解质大量泄漏的出现要早。耐寒力不同的两个品种在SOD活性及电解质泄漏的变化上有差异。更多还原

【Abstract】 The localization and isoenzyme pattern of superoxide dismutase(SOD) in various organelles of cotyledons of etiolated cucumber seedlings were characterized. The changes in electrolyte leakage, SOD activity and electropherogram in cotyledons of cucumber seedlings with different cold tolerance during cold treatment were also studied, The experimental results are as follows:(1) Approximately 4% of the total SOD activity was present in the 1000×g precipitate fraction (chloroplast); about 9～10% of the activity was in the 11000×g pellet fraction (mitochondria); and nearly 86% was in the 11000×g supernatant (cell solute). There were three isoenzyme bands of SOD in these three organelles among which the one with relatively slow migrating rate was Mn-SOD isoenzyme and the others were Cu-Zn-SOD isoenzymes.(2) The sensitivities of SOD to low temperature in various organelles were different, with the highest being in chloroplast, then in mitochondria and in cell solute. The activity of Cu-Zn-SOD zymogram in chloroplasts and mitochondria decreased or disappeared as the temperature decreased.(3) As temperature decreased, the activity of SOD in cucumber seedling cotyledons decreased and the leakage of electrolytes out of the cell increased; subsequently, the injury symptoms of cucumber seedlings gradually appeared. However, a significant reduction of SOD activity appeared before the leakage of electrolytes from the cell began. The seedlings of two cucumber cultivars with different cold tolerance exhibited some differences in both SOD activity and leakage of electrolytes.Finally, the correlation between the SOD activity and the breakdown of the structure and function of the cell membrane system under low temperature stress in plant has been discussed.更多还原