Effects of Cd and Zn Combined Stress on Membrane Lipid Peroxidation and Antioxidant Enzyme System of Maize Seedlings

Under different concentrations of Cd2+(0, 5, 15, 50 mg·L-1) and Zn2+(0, 5, 50, 200 mg·L-1) stress, the effects of single and combined stress of Cd and Zn on growth, active oxygen generation, membrane lipid peroxidation and antioxdant enzyme activities of maize seedlings were studied by hydroponic experiment. The results showed that after 10 days of Cd and Zn single or combined stress, compared to the control, the contents of O2-·, H2O2 and MDA increased by 3.4%~66.2%, 6.7%~95.9% and 0.9%~282.2%, respectively, while the root length, shoot height and dry weight of seedling decreased by 2.1%~84.8%, 2.0%~69.5%, 2.3%~39.7% and 0.5%~36.5%, respectively, and the biomass were declined (except for Cd5Zn0, Cd0Zn5), Which proved that the interaction effect of Cd-Zn combined stress on membrane lipid peroxidation was mainly displayed as mutualism, or antagonism at high level of combined stress (Zn200Cd50). With the increase of Cd2+, Zn2+ concentrations, the activities of SOD, CAT and GR increased first then declined, higher than those of the control when Cd2+ and Zn2+ concentrations were 5 mg·L-1, but decreased considerably by 1.36%~94.8%, 5.0%~57.1% and 6.2%~53.3%, respectively, when Cd2+, Zn2+ concentration exceeding 15 mg·L-1 and 50 mg·L-1. Numerical expression of some isozyme of peroxidase was raised under Cd (Cd15 Zn5, Cd50 Zn0), Zn (Cd0 Zn50) and Cd-Zn combined stress (Cd0 Zn200, Cd5 Zn200, Cd15 Zn200, Cd50 Zn200). The toxic effect of Cd-Zn combined stress was more than that of single element stress at same levels. So the danger of compound pollution must be emphasized.