Effects Of Exogenous IAA On Antioxidant System And Copper Accumulation Of Two Wetland (Acquatic) Plants Under Cu Stress

Potamogeton Crispus L.and Eichhornia crassipes were domesticated by hydroponic culture,and then exposed.The culture medium was replaced every 3 days,and plant samples were collected every 2 days.The effects of exogenous IAA on the growth status,physiological characteristics and Cu²⁺content of Potamogeton crispus L.and Eichhornia crassipes under Cu stress were studied by hydroponic experiments.The mechanism of auxins in plant anti-Cu²⁺toxicity was preliminarily discussed.The following results were obtained:?1?Under the stress of Cu,IAA had significant effects on the growth of P.Crispus L.and E.crassipes.In leaf condition,78.68?mol/LCu treatment resulted in yellowish-brown spots on water hyacinth leaves,31.47?mol/LCu treatment resulted in obvious chlorosis of tobacco leaves,and while 10?mol/LIAA treatment could keep the leaves tender green.In root length,Cu stress significantly inhibited the root length of P.Crispus L.and E.crassipes?p<0.05?,which decreased by69.7%and94.0%times as compared with the control.The longest roots of P.Crispus L.and E.crassipes were obtained under 10?mol/L IAA treatment,which increased by 1.10 and 1.23 times compared with the control.?2?Under the stress of Cu,IAA had significant effects on the physiological characteristics of P.Crispus L.and E.Crassipes.The chlorophyll content of water hyacinth and Potamogeton crispus was the highest under 150?mol/L and 10?mol/L IAA treatments,which was 2.57 and 1.62 times higher than that of Cu treatments,respectively.However,the content of malondialdehyd?MDA?was significantly decreased under this treatment concentration?p<0.05?,which was75.5%and80.9%times lower than that of Cu treatments.Under the stress of Cu,IAA made superoxide dismutase of water hyacinth and P.Crispus L.Superoxide dismutase?SOD?and peroxidase?POD?activities were significantly increased?p<0.05?,but catalase?CAT?activity of P.Crispus L.was inhibited by 50?mol/L IAA,which was 64.5%times lower than that of the control.?3?Under copper stress,exogenous IAA significantly increased the Cu²⁺content in tissues of E.Crassipes and root of P.Crispus L.,but the Cu²⁺content in stems and leaves of Potamogeton crispus decreased significantly?p<0.05?and the lowest was81.2%times under high concentration of Cu+IAA?50?mol/L?;under 30?mol/LIAA concentration,the transport coefficient of P.Crispus L.was the lowest,which was62.7%times lower than that under Cu stress,while that of water hyacinth was the lowest under78.68?mol/L.Exogenous IAA alleviates the toxicity of copper stress to two plants by increasing soluble protein content,increasing antioxidant enzyme activity and reducing membrane lipid peroxide content,and enhances the tolerance of plants to copper.Moreover,E.Crassipes has stronger antioxidant capacity than tobacco.The results can provide a method and basis for further research on copper tolerance of exogenous auxins to wetland plants.