Effect of copper excess on H2O2 accumulation and peroxidase activities in bean roots.

We studied oxidative stress and peroxidase activity resulting from application of excess copper in the nutrient medium on the roots of young bean seedlings. The change in H2O2 content, lipid peroxidation and antioxidant enzymes activities were quantified and located. Excess of copper caused a loss of membrane integrity and the formation of hydrogen peroxide (H2O2) as visualized in the transmission electron microscopy and measured using spectrophotometry. H2O2 accumulated in the intercellular spaces and in the cell wall. The production of H2O2 was accompanied by an increase in the activity of soluble and ionic GPX (guaiacol peroxidase, EC 1.11.17), CAPX (coniferyl alcohol peroxidase) and NADH oxidase.