Quantitative and qualitative changes in peroxidase of Cucurbita pepo cultivars stressed with heavy metals

Seedlings of two cultivars of zucchini (Cucurbita pepo L.) Courgette d'Ital ie (CI) and Courgette d'Alger (CA) were pre-treated with various concentrat ions of cadmium, copper and zinc for 30 d. High accumulation of heavy metal s especially in the roots was showed. Peroxidase activity was affected acco rding to the type of metal added, concentration, and the plant cultivar use d. In leaves and roots of the CI control plants peroxidase activities were 50 and 17 % higher than in the CA control plants. Treatment with Cd (5 mu g g(-1)), Cu (200 mu g g(-1)), and Zn (500 mu g g(-1)) increased peroxidase activities in CA but decreased it in CI both in leaves and roots. Heavy met als tested lead also to some qualitative changes characterized by appearanc e of new isoforms of peroxidase. The results show the possibility to use th e activities of peroxidase as biomarkers for Cd, Cu and Zn stresses.