Abstract: The study with pot experiment showed that low concentrations of Cu (<500 mg·kg ^-1) had no obvious inhibitory effects on the seedlings growth of Medicago lupulina L., while in adverse, could promote it. The leaf electric conductivity increased slightly, and the plant fresh and dry weights as well as the leaf soluble protein and pigments contents all reached their highest values at 500 mg Cu·kg^-1.In the meantime, leaf MDA content decreased,superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities slightly increased, and protective enzy me system still kept in balance. However, definite negative effects of Cu were o bserved with the increase of Cu concentration (500—3000 mg·kg^-1). Compared with the control,the plant fresh and dry weights as well as the leaf soluble protein and pigments contents decreased drastically, and leaf electric conductivity and malondialdehyde (MDA) content increased rapidly. Meanwhile, the POD activity increased obviously while SOD and CAT activities decreased markedly, which indicated that the active oxygen metabolism system was destroyed, and the balance of protective enzyme system was broken.

Key words: Cultivation practices, Indica, Japonica, Iron plaque outside roots, Cd-polluted soil