Influence of cadmium toxicity on growth and antioxidant enzyme activity in rice cultivars with different grain cadmium accumulation

The effect of cadmium (Cd) toxicity on growth, lipid peroxidation, and antioxidant enzymes was studied using two rice cultivars, Bing 97252 with low and Xiushui 63 with high grain Cd accumulation. Plants were exposed to 0-5 micromolar Cd in hydroponic culture. Cadmium stress inhibited plant height and chlorophyll content and altered melondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Roots and shoots responded differently to Cd in terms of antioxidant enzyme activity. Generally, the activities of SOD, POD, and CAT decreased with increase in Cd level, while the activity of MDA increased with increase in Cd level. With the increase in Cd concentration in nutrient solution, MDA content in shoots and roots of Xiushui 63 increased at a much higher rate than did that of Bing 97252 at both growth stages. At booting stage, a decrease of 46%-52% in SOD activity was noted in plant roots grown under 5 micromolar Cd, while at tillering stage the decrease was 13%-19% compared with the control. A significant decrease in chlorophyll content and plant height was noted under higher Cd treatment (1.0 and 5.0 micromol) at two stages. The higher MDA and lower chlorophyll content in the cultivar Xiushui 63 showed that it is more sensitive to Cd than the cultivar Bing 97252.