Cadmium-Induced Oxidative Stress 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(center dot-)) and lipid peroxides was observed; 125 mu mol.L-1 Cd2+ treatment resulted in a gradual elevation in SOD activity; while at Cd2+ level of 250 and 500 mu mol-L-1 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.