Selenium Alleviates the Arsenic Toxicity in Sunflower Seedling

Hydroponic experiments were performed to investigate physiological mechanisms of selenium (Se) mitigation of As toxicity in sunflower. The exposure of plants to 10 µM arsenic (As) inhibited biomass production and intensively increased accumulation of As in both roots and leaves. As also enhanced hydrogen peroxides (H2O2) content and lipid peroxidation as indicated by malondialdehyde (MDA) accumulation. Presoaking seeds with Se (5, 10 and 20 μM) markedly alleviated the negative effect of As on plan growth and led to a decrease in oxidative damages as evidenced by the lowered H2O2 and MDA content. Se particularly enhanced the activities of catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX), but lowered that of superoxide dismutase (SOD). As important antioxidants, ascorbate (AsA) and glutathione (GSH) contents in sunflower leaves exposed to As were significantly decreased by Se treatment. These results reveal the potentiating effect of selenium in regulating Arsenic induced oxidative stress in sunflower seedling.