Cadmium-induced physiological response and antioxidant enzyme changes in the novel cadmium accumulator, Tagetes patula

The accumulation and effect of cadmium (Cd) on the growth and enzymatic activities changes of antioxidants in Tagetes patula, French marigold, were investigated to reveal the physiological mechanisms corresponding to its Cd tolerance and accumulation. Hydroponically grown T. patula plants were treated with different concentrations of Cd (0, 10, 25, 50 μM CdCl2) at various regime of times. T. patula accumulated Cd to a maximum of 450 mg Cd kg−1 dry weight (DW) in shoot and 3500 mg Cd kg−1 DW in root after 14 days' exposure at 10 and 50 μM CdCl2, respectively. The translocation factors of Cd were greater than 1 in plants exposed to 10 μM CdCl2. Toxic effects were gradually observed with increasing Cd concentration (25 and 50 μM) accompanied with the reduction of biomass, chlorophyll content, decrease of cell viability and the increase level of lipid peroxidation. In leaves of T. patula, the activities of ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD) were induced by Cd. However, in roots, activities of APX, GR, SOD and catalase (CAT) were significantly reduced by 25 and 50 μM Cd treatment but not 10 μM Cd. In-gel zymography analysis revealed that Cd induced the enzymatic activities of APX, MnSOD, CuZnSOD and different isozymes of GR in leaves. These results indicate that T. patula is a novel Cd accumulator and able to tolerate with Cd-induced toxicity by activation of its antioxidative defense system.