【摘要】 镉胁迫使萝卜幼苗超氧阴离子(O2·)、过氧化氢 -(H2O2)和丙二醛(MDA)含量增加;随着镉浓度提高,超氧化物歧化酶(SOD)活性首先明显上升,然后逐渐下降,甚至低于对照;叶片过氧化氢酶(CAT)活性明显增加,根系CAT活性则减少;根系以及较高浓度镉处理后期叶片的谷胱甘肽还原酶(GR)活性均显著增加。由此推测:在胁迫初期可能主要由SOD和CAT发挥抗氧化作用,而在胁迫后期由于抗坏血酸 -谷胱甘肽(AsA-GsH)循环途径的激活,还原型谷胱甘肽和植物络合素含量的提高可能在清除活性氧或者直接螯合镉中起作用。更多还原

【Abstract】 When seedlings of radish were treated with Cd2+ from 125 to 500 μmol/L, for a period of 12 to 96 h in hydroponic system, increase in ratio of SOD to CAT and levels of Oˉ2· , H2O2, MDA indicate that Cd2+induces oxidative stress in radish plants （Table 1, Figs.1₃）. Antioxidant enzyme activities responded differently to the level and time of Cd2+ treatment. Under 125 μmol/L Cd2+treatment agradualincreaseinSOD activity was observed; at 250, 500 μmol/L Cd2+ treatment SOD activity increased first, then de- clined considerably to even lower than that of the control during later Cd2+ treatment （Fig.4）. A gradualdecrease inroots and a marked increase in leaves in CAT activity were detected （Fig.5）. GR activity in both leaves and roots were en- hanced significantly with the increase in content of Cd2+ and time of treatment （Fig.6）. The in- crease in GR activity suggests that AsA-GsH cycle may be activated to scavenge the AOS or the synthesis of PC may be stimulated to chelate cadmium.更多还原