Oxidative stress during phosphate deficiency in roots of bean plants (Phaseolus vulgaris L.)

The oxidative stress symptoms were studied during phosphate deficiency. Prolonged phosphate starvation of bean plants (Phaseolus vulgaris L.) and severe decrease of inorganic phosphate concentration resulted in increased lipid peroxidation and hydrogen peroxide concentration in root tissues. The ratio of reduced to total ubiquinone was also higher in whole roots and isolated mitochondria from the roots of phosphate-deficient plants. No effect of phosphate deficiency on ascorbate peroxidase and superoxide dismutase activities was detected. However, the activities of catalase and total peroxidase were higher in extracts of phosphate-deficient roots compared to control roots. These results indicate that phosphate starvation is an abiotic stress that imposes an oxidative stress in bean root cells. The role of alternative oxidase in stabilizing the reduction level of ubiquinone, and thus preventing active oxygen species formation, is discussed.