Effects of CaCl2 pretreatment on antioxidant enzyme and leaf lipid content of faba bean (Vicia faba L.) seedlings under cadmium stress

In the present investigation we studied the role of CaCl2 pretreatment on physiological and biochemical characteristics in faba bean (Vicia faba L.) seedlings subjected to cadmium (Cd) stress. The seeds of faba bean were treated with H2O and 2 % CaCl2 before germination for 6 h. Primed or nonprimed (control) seeds were then germinated under increasing concentrations of Cd (0, 10, 50 and 100 mu M) for 21 days. The contents of Cd, soluble protein (SP), malondialdehyde (MDA), total membrane lipid contents, fatty acid composition and the activities of superoxide dismutase (SOD EC 1.15.1.1), catalase (CAT EC 1.11.1.6), guaiacol peroxidase (GPX EC 1.11.1.7), lipoxygenase (LOX) in the seedlings leaves were tested. Exposure of the plants to Cd caused a gradual decrease in the shoot and root dry weight. Seed pretreatment with CaCl2 alleviated the negative effect of Cd on plant growth parameters. The same tendency was observed for the chlorophyll content. The level of lipid peroxidation (as indicated by MDA content) was higher in Cd-treated plants, and remained unchanged in CaCl2-pretreated plants. The same results for the total lipid content, fatty acids composition and SP level were observed. Treatment of plants with Cd drastically decreased CAT activity and caused an increase in both SOD and GPX activity. However, in CaCl2-pretreated plants, CAT activity exhibited a slight decrease under Cd treatment. An increased of SOD and GPX activity in leaves of pretreated plants was also demonstrated. The data suggest that CaCl2 pretreatment may protect faba bean seedlings against Cd toxicity.