Effects of sulfur supply and hydrogen peroxide pretreatment on the responses by rice under cadmium stress

A hydroponic experiment was carried out to investigate the effects of sulfur (S) supply and hydrogen peroxide (H2O2) pretreatment on the growth and physiological responses by rice under cadmium (Cd) stress. Seedlings were grown with normal S level (3.4 mmol center dot L-1 sulfate), S deficiency (0 mmol center dot L-1 sulfate) for 6 days, or H2O2 (100 mu mol center dot L-1) pretreatments for 1 day and subsequently exposed to 1.0 mu mol center dot L-1 Cd for 7 days. In the S-deficient rice, both shoot and root Cd contents were increased 8.9 and 24.3 % respectively. In addition, cysteine (Cys), glutathione (GSH) and phytochelation (PC2-4) levels were increased significantly, while opposite effects were observed in the S-deficient rice. H2O2 pretreatment induced stronger Cd resistance in rice, as the amounts of thiols and the activity of glutathione S-transferase (GST) were all increased and the seedling growth was not inhibited by Cd stress. In conclusion, the results in this study demonstrated the adequate S supply and H2O2 pretreatment were important in Cd detoxification in rice through maintenance of cellular thiol levels and GST activity.