Respective and interactive effects of doubled CO2 and O3 concentration on membrane lipid peroxidation and antioxidative ability of soybean

Effects of doubled CO₂ and O₃ concentration on Soybean were studied in open-top chambers (OTC). Under doubled CO₂ concentration, grain yield and biomass increased, the SOD activity, vitamin C (Vc) and carotenoid (Car) content also increased; Superoxide (O₂ ⁻) generating rate decreased, relative conductivity and malondialdehyde (MDA) content significantly declined. But under doubled O₃ concentration, the SOD activity, Vc and Car contents declined, resulting in imbalance of activated-oxygen production, enhanced O₂ ⁻ generating rate and accelerated process of lipid peroxidation and increase in MDA content and ion leakage of leaves. The final result was decreased grain yield and plant biomass. Interactive effects of doubled CO₂ and O₃ concentrations on soybean were mostly counteractive. However, the beneficial effects of concentration-doubled CO₂ are more than compensate the negative effects imposed by doubled O₃, and the latter in its turn partly counteracted the positive effects of the former.