Physiological Responses of Radish (Raphanus Sativus L.) to Lead Stress

To investigate the phytotoxicity and tolerance responses of radish (Raphanus sativus L.) to Lead (Pb), plants of two genotypes were exposed to various concentrations of Pb (0, 100, 400 and 800 mg L
^-1
) for up to 8 days by hydroponics culture. The plant growth was inhibited under Pb stress, with the decrease of root length, fresh and dry weights. Excess Pb induced MDA contents increasing significantly and MDA in shoot was much higher than that in root, while the content of MDA in Nau-Rg05 was higher than that in Nau-Zdcb05. The antioxidant activities (SOD, POD, CAT and APX) increased in the roots at 100 mg L
^-1
Pb compared to control and followed by decreasing with the increasing Pb concentrations, indicating a direct correlation with Pb accumulation. Moreover, the antioxidant activities in root of Nau-Rg05 were higher than that in Nau-Zdcb05. It can be suggested that Pb induces oxidative stress in growing radish plants and the SOD, POD, CAT and APX could serve as important components of antioxidative defense mechanism against Pb stress in radish.