Effect of H_2O_2 Pretreatment on Cd Tolerance of Different Rice Cultivars

The effect of H2O2 pretreatment on Cd tolerance and translocation of rice seedlings were studied using two rice cultivars (N07-6 and N07-63) differing in Cd tolerance. The contents of malondialdehyde (MDA), reduced glutathione (GSH), non-protein thiols (NPT), phytochelatins (PCs) and the activity of glutathione S-transferase (GST) were compared between the two cultivars exposed to various treatments. The results showed that 50 μmol/L Cd exposure significantly inhibited rice growth, enhanced the production of GSH, NPT, PCs and MDA, and increased the activity of GST, and there were significant differences between the two cultivars. More Cd was transported into the shoot of N07-6. The H2O2 pretreatment alleviated Cd toxicity by further increasing GSH, NPT and PCs contents, as well as the GST activity in roots. The increase degrees of these parameters in N07-63 were higher than those in N07-6, suggesting that the tolerance of N07-63 was enhanced more significantly than N07-6. Hydrogen peroxide reduced Cd translocation to rice shoot but affected the Cd content in root differently. From the above results, it may be speculated that there were remarkable differences in the Cd detoxification and response to the H2O2 pretreatment between the two cultivars.