关键词: 镉, 墨旱莲, 富集, 耐性, 光合作用

Abstract: To screen new cadmium (Cd)-accumulating plants, eight Asteraceae species were cultured in nutrient solution containing 10 mg·L^-1 Cd. Eclipta prostrata exhibited the strongest capacity of Cd accumulation. Consequently, the accumulation, tolerance and photosynthetic response of Cd in E. prostrata were further determined by pot experiment with different soil Cd concentrations (0, 5, 15, 35 and 50 mg·kg^-1). The results showed that higher Cd concentrations in the shoot (64.01 mg·kg^-1) and root (45.84 mg·kg^-1) of E. prostrata were detected when treated with 50 mg·kg^-1 Cd. Both the bioconcentration factor and translocation factor of Cd were higher than 1. The subcellular distribution of Cd concentration in the leaves was as follows: cell wall > soluble component > mitochondria and chloroplasts ≈ nucleus. Furthermore, plant height, chlorophyll b and total chlorophyll contents increased significantly under 5 mg·kg^-1 Cd treatment, but the aboveground biomass and photosynthetic pigment contents in leaves decreased significantly under the treatments of 35 and 50 mg·kg^-1 Cd. Further analysis revealed that 5-35 mg·kg^-1 Cd treatments induced a significant increase in the level of malondialdehyde (MDA) in the leaves. The stomatal conductance, transpiration rate, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly increased under 50 mg·kg^-1 Cd treatment in comparison to the control, but without significant difference in net photosynthetic rate. The results of stepwise regression analysis showed that shoot Cd concentration was positively correlated with leaf CAT activity but negatively correlated with leaf MDA content. In conclusion, although E. prostrata is not a Cd hyperaccumulator, it shows a strong capacity to accumulate and translocate Cd, which could be useful for phytoremediation of Cd-contaminated soils.

Key words: cadmium (Cd), Eclipta prostrata, accumulation, tolerance, photosynthesis