叶绿体衰老过程中产生超氧阴离子的研究

STUDIES ON THE GENERATION OF SUPEROXIDE ANION IN THE CHLOROPLASTS DURING SENESCENCE

以Tiron为探针的电子顺磁共振波谱法,研究了小麦叶绿体衰老时(?)产量的变化和来源.暗诱导和自然衰老叶绿体生成(?)的能力增大,分别在第5和21天达到高峰;而这种升高恰与MDA的积累,Fv/Fo比值下降相同步,推测是(?)和其它活性氧作用的结果.同时衰老时内源SOD的活性却不能清除这种增高的(?)水平.100℃的热变性处理后,叶绿体TH·信号大大增加,DCMU的处理却不改变(?)的生成,表明衰老时(?)的升高可能是叶绿素光氧化后电子接受体如PQ减少之故,而非酶促反应.并由此探讨了叶绿体衰老时(?)的来源和转化的可能途径.

Electron paramagnetic resonance spectroscopy was used to determine the changes of concentration and origin of superoxide radical in chloroplasts during wheat (Triticum aestivum L.) leaf senescence through measuring Tiron semiquinone radical, which formed when Tiron reacts with O2. The production of O2 by illu-minated chloroplasts increases during attached and detached leaf senescence, wh h reachs peak at 5 and 21-day respectively, and declines again with intensifing senescence. Moreover, this peak exactly coincides with the accumulation of MDA and decreases of Fv/Fo ratio. These results may be induced by O2 and other activated oxygen. At the same time, the specific activity of SOD does not scavenge the increased levels of O2 with advancing senescence. In addition, heat denaturati-on of isolated chloroplasts at 100℃ greatly increases the ability to form O2 upon illumination. This suggests that the rise in O2 production during senescence is caused through photochemical reaction involving PQ, rather than enzymatically. The mode of generation and conversion of O2 by chloroplasts are also discussed.