【摘要】 以电子自旋共振波谱技术,研究从水稻、玉米、花生和苋菜的成熟及衰老叶片分离的叶绿体中O₂^-的形成,以及干燥叶绿体和叶片粉末的有机自由基。经紫外光照射后老叶叶绿体的O₂^-浓度比成熟叶增大10～249％。冷冻干燥叶绿体及烘干叶片粉末在辐照前后皆有明显的单峰信号。辐照引发两种干样中形成更多的有机自由基。老叶制备的干样不论辐照或暗下都有较高水平的自由基。以上结果表明,叶片的衰老与自由基引起的损伤有关。更多还原

【Abstract】 Electron spin resonance spectroscopy wasused to study the formation of superoxide anion（O₂^?） and organic radical in chloroplasts anddry material from old and mature leaves of rice,corn, peanut and amaranth. The formationof O₂^? in UV radiated fresh chloroplasts wasobserved by detecting the ERS signal of tironsemiquinone radical （spin adduct）. Superoxidedismutase showed inhibitory effect on the for-mation of O₂^? Chloroplasts isolated from oldleaves produced 110～349% of O₂^? of that frommature leaves.A strong single peak of ESR was observedin both freeze-dried chloroplasts and dry mate-rial of leaves during exposure to ultraviolet lightand in the dark. The signal of an organicradical （G factor 2.0032） was enhanced by UVradiation. It is found that the higher levels offree radicals on chlorophyll content basis occurredin dry sample of old leaves before and after ra-diation. The data suggest that leaf senescenceis accompanied by damage caused by free radi-cals.更多还原