Keywords: 
• Cd /
• Pb /
• water mimosa /
• antioxidant enzyme /

Abstract: Soil heavy metal (HM) pollution has received wide concern because HMs could be enriched in crops to threaten human health. Phytoremediation is a popular and efficient approach for soil HMs remediation due to its advantage of wide adaptability. In this study, a pot experiment was conducted, with an aquatic legume plant Neptunia olerace as the experiment material, to study its tolerance and absorption to two HMs of Cd (0, 50, 100, 180 mg·kg^-1) and Pb (0, 500, 1 000, 1 800 mg·kg^-1) in soil. Results showed that: (1) Cd pollution significantly depressed the growth of Neptunia olerace. Although the total biomass and length of Neptunia olerace were significantly decreased (P<0.05), the Cd treatments did not significantly affect the content of soluble protein, chlorophyll, and the malondialdehyde (MDA) in root and stem. The activity of catalase (CAT) in the leaves was significantly improved, while the activity of superoxide dismutase (SOD) in the stem, CAT in the root and peroxidase (POD) in the leaves, and the content of MDA in the leaves were first decreased and then increased. (2) Neptunia olerace is highly tolerant to Pb stress, because there were no significant differences in the biomass, plant length, soluble protein, chlorophyll and MDA content. However, the activity of CAT in leaves was significantly increased (P<0.05). Besides, the SOD activity in root and stem, CAT activity in stem and POD activity in leaves were all first decreased and then increased (P<0.05). (3) The bioconcentration factors of Neptunia olerace under different Cd concentrations (50, 100, 180 mg·kg^-1) were 0.28, 0.32 and 0.29, respectively, while the translocation factors were 0.05, 0.06 and 0.08, respectively. The bioconcentration factors for Pb were 0.02, 0.04 and 0.02 at different Pb concentrations (500, 1 000, 1 800 mg·kg^-1), and the translocation factors were 0.04, 0.08 and 0.05, respectively. These results suggest that Neptunia olerace is not a hyperaccumulator for Cd and Pb. However, we found that the Cd and Pb concentrations in the below-ground part of Neptunia olerace were greatly higher than those in the above-ground part. Considering that the root of Neptunia olerace is tap root system and shallow to easily harvest. Therefore, Neptunia olerace could be recommended to interplant with aquatic crops such as rice, since it would not only fix nitrogen, but also alleviate the risk of soil heavy metal pollution to produce safe rice and other agricultural products.