Separate And Combined Effects Of Glyphosate And Copper On Growth And Antioxidative Enzymes In Salvinia Natans

The coexistence of glyphosate and copper are widely found in water bodies and terrestrial ecosystems due to the large number applications of herbicides and copper algicide.However,their joint ecotoxicological risks in aquatic remains unknown.The experiment investigated separate and combined effects of glyphosate and copper on growth and physiological response in Salvinia natans.Cu²⁺concentrations were set at0,0.2,1,5,8,10 mg l^-1;glyphosate at 0,1,5,25,50,75 mg l^-1,and Cu²⁺+glyphosate mixtures were set at 0+0,0.2+1,1+5,5+25,8+50,10+75 mg l^-1,respectively.The results showed that their joint toxicity is related to concentration.Antagonistic effects of two poisons were induced when the plants were expoesd to low concentrations of glyphosate and copper(?1+0.2 mg l^-1).Synergistic effects were elicited at higher doses(?5+1 mg l^-1).50 and 75 mg l^-11 were between the half-lethal concentration and the lethal concentration of glyphosate against S.natans.The chlorophyll a,b and total chlorophyll of the plant significantly decreased under individual or the combined stress of glyphosate and copper.Increased hydrogen peroxide indicated the occurrence of oxidative stress at individual and combined exposures.To deal with oxidative stress,S.natans can activate antioxidant defense systems,such as increased superoxide dismutase and changes in peroxidase,ascorbate peroxidase and catalase.High concentrations combined pollution exceeds the oxidative defense capabilities of plants.Therefore,Malonaldehyde content increased significantly.Our results indicated that ecotoxicity of glyphosate or copper may be exacerbated in aquatic and caused evident damage to S.natans.