Separate and combined effects of cadmium(Cd) and nonylphenol(NP) on growth and antioxidative enzymes in Hydrocharis dubia (Bl.) Backer

Abstract

\n Cadmium (Cd) is listed as a priority pollutant, and nonylphenol(NP) is a common organic pollutant in water environment. However, the ecological risks of combined pollution of Cd and NP have not been fully elucidated. In this study, the effects of Cd (0.01, 0.1, 0.5, 1, 5 mg/L), NP (0.1, 0.5, 1, 5, 10 mg/L) and Cd-NP (0.01\u2009+\u20090.1, 0.01\u2009+\u20091.0, 0.5\u2009+\u20090.1, 0.5\u2009+\u20091.0, 5\u2009+\u20090.1, 5\u2009+\u20091.0 mg/L) on growth and physiology of Hydrocharis Dubia (Bl.) Backer were studied. The results showed that the toxicity of H. dubia showed a dose-dependent effect. Growth level and chlorophyll contents of H. dubia induced by NP stress alone showed a certain toxicant excitatory effect. It meant that low concentrations of toxins promote plants growth, high concentrations of toxins inhibit plants growth. The increase of H2O2 content and the decrease of soluble protein content in the plant indicated that both Cd and NP caused oxidative damage to H. dubia. Under the stress, the antioxidant defense systems were activated, the activity of superoxide dismutase (SOD) was significantly decreased. The activity of catalase (CAT) reacted negatively under stress alone, but increased significantly under combined stress. The activity of peroxidase (POD) increased, which was used to alleviate the damage caused by toxics stress. The joint toxicity evaluation showed that the joint toxicity of Cd and NP to H. dubia was antagonistic when the concentrations of Cd\u2009+\u2009NP were 0.01\u2009+\u20090.1 mg/L and 0.01\u2009+\u20091 mg/L. At 0.5\u2009+\u20090.1 mg/L and 0.5\u2009+\u20091 mg/L, Cd and NP had a strong synergistic effect on H. dubia.