Genotypic Difference in the Responses of Seedling Growth and Cd Toxicity in Rice (Oryza sativa L.)

The experiment was carried out to study the genotypic difference in the responses of seed germination, growth andphysiological characters of rice seedlings to Cd toxicity. The result showed that the germination was slightly stimulatedunder low Cd concentration (0.01-1.5 mM Cd), while severely depressed under higher Cd concentration (2.0 mM). Riceseedlings exposed to 0.01 mM Cd showed slight increases in plant height, root volume, biomass and chlorophyllconcentration. These parameters were significantly reduced when Cd level in the medium was increased to 0.5 mM, andmeanwhile corresponding increase in superoxide dismutase (SOD) and peroxidase (POD) activities, and MDA(malondialdehyde) content was observed. However, SOD and POD activities declined when plants were exposed to 1 mMCd when compared with those under 0.5 mM Cd. Cadmium addition lowered Fe, Cu and Mn concentrations in roots andshoots. There was significant genotypic difference in the response of these parameters to Cd stress. Under Cd stress,Xiushui 110 had the least inhibition of growth and increase in MDA content, higher shoot Cd concentration, and greatestincrease in POD and SOD activities, indicating its higher tolerance to Cd toxicity, while Bing 9914 had the greatestreduction of growth, and Zn, Cu, Fe, and Mn contents, but greatest increase in MDA content, and least increase inactivities of antioxidative enzymes, indicating its sensitivity to Cd toxicity.