Effects of copper ion on antioxidant function of Vallisneria asiatica

The objective of this research is to demonstrate the antioxidant ecological response of Vallisneria asiatica to the heavy metal Cu²⁺ pollution which is recently a serious problem in the lakes. Batch experiments with five different concentrations of Cu²⁺ (0, 5, 10, 20, 40, 80 mg·L^-1) were carried out. After the 12th day, the roots and leaves of Vallisneria asiatica dipped in the solution with Cu²⁺ were removed and the physiological and biochemical indexes, chlorophyll, protein and malondialdehyde (MDA) content, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity were measured. After the experiment; the roots and leaves cultivated in the 0 mg·L^-1 of Cu²⁺ group showed chlorophyll and protein content reduced while the MDA content, POD and SOD activity were increased notoriously. Compared with the 0 mg·L ^-1 of Cu²⁺ group, the 5 mg·L^-1 of Cu²⁺ group showed chlorophyll and protein content increase, SOD and POD activity showed also a slight increase, while MDA content decreased. However, for the 10 mg·L^-1 of Cu²⁺ group, the decrease of chlorophyll and protein content and the increase of MDA content were observed. Also a sharp increase of SOD and CAT activity compared with the 5 mg·L^-1 group were found; for over 10 mg·L^-1 of Cu²⁺ concentration, chlorophyll content and protein content fell off, whereas increase of MDA became considerable, CAT raised up steadily and POD showed a decrease trend. The results showed that, both insufficiency and overabundance of Cu²⁺ in water environment can affect the anti-oxidation function of Vallisneria asiatica, which can be observed by the value of SOD, CAT and POD activity. Therefore, the measurement of anti-oxidation activity, protein content and MDA as a forecast and judgment indicator of Cu²⁺ contaminations in the water environment can be considered in the future.