Antioxidant responses of rice seedling to Ce4+ under hydroponic cultures

Since the 1980s, rare earth elements have been commonly used in China because of their enriched fertilizers. To understand the potential benefits or damages of Ce4+ on rice, the antioxidant responses (superoxide dismutase, ascorbate peroxidase, catalase activities, and ascorbate and glutathione contents) of rice seedling to Ce4+ under hydroponic cultures were investigated. The results showed that Ce4+ induced H2O2 and O2− production of rice seedling. The inhibition studies with diphenylene iodonium suggested that the key enzyme responsible for oxidative bursts was primarily NADPH oxidase. Ce4+ (0.02 mM) increased the antioxidant capacity of reduced ascorbate and glutathione and the levels of superoxide dismutase, ascorbate peroxidase, and catalase. However, antioxidant enzymes and antioxidant capacity of rice seedling were decreased by 0.2 mM Ce4+ treatment, indicating that higher content of Ce4+ damaged the mechanism of defense responses and emerged the peroxidation of membrane lipids. These results will help us to understand the mechanism of Ce4+ on rice and concern about its environmental impact in agricultures.