Abstract: A pot experiment was conducted to explore effects of bentonite on physiological and biochemical characteristics, such as chlorophyll content, shoot biomass, SOD and POD activities, and MDA content of rice seedlings growing in Cd contaminated soil. Results show that the amendment of bentonite increased the content of chlorophyll in leaves of the rice seedlings and promoted growth and development of the seedlings.The dry biomass of rice shoots increased with rising bentonite application rate. In the soil contaminated only with Cd, SOD activity remained almost unchanged in leaves of the rice seedlings, but did significantly in roots of the plants, SOD lowered with rising Cd concentration in the soil (P < 0.05), and application of bentonite increased SOD activity in the roots as a whole. However, POD activities in leaves and roots of the plants rose sharply first and then declined with the increase in Cd concentration in the soil treated only with Cd. Application of bentonite reduced POD activity in leaves of the plants. However, the application of 5~50 g•kg^-1 bentonite significantly increased POD activity in roots of the rice seedlings, by 13.2%-22.4%, 4.9%-9.5%, 44.8%-80.6%, and 6.9%-49.6%, respectively, over that in the control. MDA contents in leaves and roots of the plants rose with rising Cd concentration and were 139.0% and 158.1% higher, respectively than that in control. Application of bentonite significantly lowered MDA contents in the rice, and weakened the effect of membrane lipid peroxidation. To sum up, application of bentonite can effectively alleviate Cd toxicity to rice seedlings, thus it can be used as an approach to the remediation of Cd contaminated soils.

Key words: rice, bentonite, Cd, physiological and biochemical characteristics