Differences in responses of Liriodendron chinense (Hemsl.)Sarg. seedlings from different provenances to cadmium stress and cadmium tolerance evaluation

Liriodendron chinense (Hemsl.)Sarg. is a good timber and landscape tree species. In the current study, we investigated the physiological responses of L. chinense seedlings from three provinces and seven provenances under cadmium stress (concentration of 10 mg/kg) at four different time points (0, 5, 10, and 15 d) in hydroponic experiments. The characteristics of Cd²⁺ absorption and distribution in roots, stems, and leaves were measured. Cadmium tolerance (Cd) of the different provenances were evaluated by the membership function method based on the physiological indices of the leaves. Results showed that the growth of seedlings from different provenances was inhibited to varying degrees with prolonged cadmium stress. Chlorophyll content decreased significantly and malondialdehyde content increased, but the change ranges differed significantly among provenances. Superoxide dismutase (SOD) and peroxidase (POD) activities were increased significantly, but the trend patterns in different provenances varied with prolongation of stress time. Based on physiological and biochemical indices, the order of cadmium tolerance of L.chinense from different provenances was: GZJH > GZST > ZJSC > YNHK > YNMLP > GZDZ > YNJP. After 15 d of Cd stress, the order of cadmium concentration in the plants was root > stem > leaf. Furthermore, cadmium concentrations in the roots, stems, and leaves of the GZJH and GZST provenances from Guizhou were significantly lower than that in the YNHK and YNJP provenances from Yunnan. Cadmium tolerance of the L. chinense provenances differed from each other and showed strong correlation with the concentration of cadmium in the plant organs. Seedlings from resistant provenances may alleviate cadmium-induced damage by separating old leaves, regulating antioxidant enzyme activity, and restricting cadmium absorption of the root, which could be used for the ecological restoration of cadmium-polluted soil.