Zn phytotoxicity induces oxidative stress in primary leaves of Phaseolus vulgaris

Abstract

We studied the sequence of several metabolic reactions representative for oxidative damage and protection in primary leaves of Phaseolus vulgaris (cv. Limburgse vroege) after root uptake of a toxic sublethal amount of Zn. An immediate increase of membrane peroxidation products was observed as soon as Zn was assimilated by the primary leaf. This rise could be explained by activation of the enzyme lipoxygenase (EC 1.13.11.12). In our experimental conditions, membrane lipid peroxidation and K+-leakage were not directly related. Zn treatment had no effect on the capacity of catalase (EC 1.11.1.6) and superoxide dismutase (EC 1.15.1.1), while the capacity of ascorbate peroxidase (EC 1.11.1.11) was increased. Zn toxicity further leads to enhanced levels of hydrogen peroxide which could not be efficiently removed by the antioxidative system. Therefore, it seems that an excess of Zn can cause oxidative damage.