Abstract:Dynamic changes in content of chlorophll and proline,and activity of protective enzymes such as superoxide (SOD),peroxidase (POD) and chloramphenicol acetyltransferase (CAT) in the leaves of Trapa bispinosa treated,respectively,with Cd2+ at varying rates and Cd2+ plus 5 mg L-1 Ce3+ were studied.Results show that chlorophyll contents decreased with increasing Cd2+ concentration,while the activity of both SOD and POD,and the content of proline increased when Cd2+ concentration was low and decreased when it was high.In contrast,CAT activity decreased when it was low and increased when it was high.Compared with the single ion treatments,the Cd2++Ce3+ treatments increased cholorophyll contents,and stimulated activity of SOD and POD,especially,that of the latter,which was 8.33 times higher than its control when the combination was 5 mg L-1 Ce3+ plus 1 mg L-1 Cd2+.The results suggest that the addition of 5 mg L-1 Ce3+ can relieve the toxicity of a low concentration Cd2+ on leaves of Trapa bispinosa.