Abstract:In order to evaluate the responses of physiological indexes of Iris lactea var. chinensis to cadmium stress and provide theoretical instructions to the further research of cadmium tolerance and tolerance mechanism for I. lactea var. chinensis, we carried out a water culture experiment to study the effects of different concentration of cadmium (0,10,25,50,100 and 150 mg·L-1) on the growth, root morphology and partial physiological indexes of I. lacteal seedlings. The results showed that: (1) at lower Cd2+ treatments (10~25 mg·L-1), the plant height, the shoot dry weight, root dry weight, total root length, root surface area, root volume and root activity of I. lactea var. chinensis were higher than those of the control and all of them decreased at higher Cd2+ levels (50~150 mg·L-1), which mainly manifested as the plant height, root dry weight and total root length were lower than that of control, and root surface area, root volume and root activity of I. lactea var. chinensis were significantly lower than that of control. (2) With increasing concentrations of Cd2+, the relative conductivity, malondialdehyde content (MDA), peroxidase activity (POD), catalase activity (CAT) and proline content (Pro) of I. lactea var. chinensis in both roots and leaves increased, but soluble protein content (SP) increased firstly and decreased afterwards. The superoxide dismutase activity (SOD) increased firstly and decreased in roots with increasing concentrations of Cd2+, while the activity of SOD in leaves increased continuously. (3) When the Cd2+ concentration rises, the Cd2+ content in both roots and leaves increased, and the Cd2+ content in roots was 829.39~8 944.54 mg·kg-1, while the Cd2+ content in shoots was 200.60~519.76 mg·kg-1, and the Cd2+ translocation factors were always less than 1 (0.06~0.32), suggesting that cadmium is mainly accumulated in the root of I. lactea var. chinensis seedlings, and only a few Cd2+ of roots were transferred to shoots. Overall, the findings suggest that I. lactea var. chinensis could increase the antioxidant enzyme activities, maintain osmotic equilibrium and scavenge excess free radicals by limiting translocation of Cd2+ from roots to shoots, thereby improving its Cd2+ tolerance.