Selenite mitigates cadmium-induced oxidative stress and affects Cd uptake in rice seedlings under different water management systems

Cadmium (Cd) is toxic throughout the food chain. Selenium (Se) can mitigate Cd accumulation in rice plants, although it is unclear why it has such effect. The objectives of this study were to investigate the effects of Se application on Cd-induced oxidative stress and antioxidant activities, and the combined effects of Se application and water management on the formation of iron plaque on the rice surface and Fe, Cd, and Se accumulation in rice plants. Rice seedlings were grown in Cd-contaminated soil with or without the addition of Se, and in aerobic or flooded conditions. Exogenous Se reduced Cd-induced oxidative stress. In the flooded treatment, exogenous selenite significantly decreased Cd concentrations in rice tissues, whereas it noticeably enhanced Cd concentrations in rice tissues in the aerobic treatment. Furthermore, selenite addition and flooding promote the formation of iron plaque and increase Fe concentrations in rice tissues. Pearson correlation analysis shows that plant Cd was significantly negatively correlated with Fe concentrations in rice tissues, and plant Fe was significantly positively correlated with Se concentrations in rice tissues, but no significant correlation was found between Cd and Se concentrations Thus, exogenous selenite may indirectly affect Cd uptake by influencing the formation of iron plaque on rice root surface, Fe uptake and Fe levels in rice.