镉诱导萝卜幼苗活性氧产生、脂质过氧化和抗氧化酶活性的变化

通过水培试验,研究Cd2+胁迫对萝卜幼苗活性氧的产生、脂质过氧化和抗氧化酶活性的影响。超氧 阴离子(O 2)的产生速率和丙二醛(MDA)的含量与对照相比有不同程度的增加,表明Cd2+胁迫能导致萝卜体 内的氧化胁迫;超氧化物歧化酶(SOD)的活性,随着Cd2+浓度提高,首先明显上升,然后逐渐下降,甚至低于 对照,叶片过氧化氢酶(CAT)的活性明显增加,根系CAT活性则减少,根系以及较高浓度Cd2+处理后期叶片 谷胱甘肽还原酶(GR)的活性均显著增加。推测:胁迫初期可能主要由SOD和CAT发挥抗氧化作用;后期由 于抗坏血酸—谷胱甘肽(AsA GsH)循环途径的激活,以及还原型谷胱甘肽(GSH)和植物络合素(Phytochela tins,PCs)的合成,可能在清除活性氧或者直接鏊合Cd2+中起作用。

Cadmium-induced superoxide anion generation,lipid peroxidation and changes of antioxidant enzyme activities in radish seedlings

While seedlings of radish raised in increasing contents of Cd2+ in hydroponic system,increment in ratio of superoxide dismutase(SOD)/catalase(CAT)and levels of superoxide anion(O2)and lipid peroxides were observed;125 μmol/L Cd2+ treatment resulted in a gradual elevation in SOD activity; while at Cd2+ level of 250 and 500 μmol/L,SOD activity considerably increased at first,then declined to even lower than that of the control. CAT activity showed enhancement in leaves whereas decrease in roots. Cd2+ induced an obvious elevation in GR activity in both roots and leaves. A marked elevation in GR activity suggests that ascorbate-glutathione(AsA-GsH)cycle may be activated to scavenge AOS and the synthesis of reduced glutathione(GSH)may be stimulated for subsequent synthesis of phytochelatins(PCs)to chelate Cd2+ directly.