Influences of silicon on activities of antioxidant enzymes in rice leaves infected by Xoo strain in relation to bacterial blight resistance

Hydroponics experiments were performed with an Xoo-susceptible rice cultivar (Oryza sativa L. cv. Nipponbare) to study the effects of silicon(Si) on disease development, concentrations of malondialdehyde(MDA) and hydrogen peroxide (H2O2), activities of superoxide dismutase(SOD), catalase(CAT), lipoxygenase(LOX), peroxidase (POD) and ascorbate peroxidase (APX) in leaves inoculated with Xoo strain. Si addition could significantly decrease the rice severity index of bacterial blight, with the relative immunization efficiency of 62.86%. The concentrations of MDA and H2O2 in Si-amended rice plants were increased significantly during a 48-h-period of time after inoculation with Xoo strain. Activities of SOD and LOX were significantly higher but those of CAT, POD and APX were lower in Si-amended plants than in Si-deprived plants, resulting in accumulation of H2O2 in plants and intensification of membrane lipid peroxidation. It is concluded that Si can enchance rice resistance to bacterial blight through regulating the antioxidant defense system and trigering hypersensitive reaction(HR) and Si is involved in physiological and biochemical metabolisms in plants.