Synergistic Effects of Selenium and Silicon Mitigate Arsenic Toxicity in Oryza sativa L.

Arsenic (As) is a toxic element for plants, animals and humans. The mitigation of As stress has been achieved via selenium (Se) and silica (Si) supplementations. However, the effects of combined application of Se and Si against As stress are not known. The present study was conducted to evaluate the effect of Se (0.5 and 1 mg L-1) and Si (10 and 30 mg L-1) on Oryza sativa L. (rice) subjected to during As (4 mg L-1) stress. The rice plants showed reduction in As accumulation in co-treatment of As + Se, As + Si and As + Se + Si in comparison to As alone treated plants (7 d). The maximum reduction of As accumulation in root and shoot was 57% and 64%, respectively in As + Se + Si treatment. The increase in enzymatic antioxidant system (superoxide dismutase, ascorbate peroxidase, glutathione peroxidase, glutathione reductase and glutathione-s-transferase) along with decrease in oxidative stress markers (lipid peroxidation, dehydroascorbate reductase, ascorbate oxidase and hydrogen peroxide) in As + Se + Si treatment as compared to As treatment signified elevated tolerance of rice plants to As stress. Gene expressions of enzymes involved in antioxidant defence and thiol metabolism were found to be significantly positively correlated with their respective biochemical activities. In conclusion an optimum combination of Se and Si can be used to effectively mitigate As toxicity in plants.