Responses To Atrazine Stress Of Iris Pseudacorus And Its Removal Potential Of Atrazine-contaminated Water

Abstract:Atrazine is a selective systemic herbicide that is commonly used for the control of annual grass weeds and broadleaf weeds.Atrazine has a strong water solubility,a long residual period,a large application range and a wide range of uses,resulting in increasingly prominent environmental problems,and its ecotoxicological effects have attracted widespread attention.In order to explore the effects of atrazine on plant growth and physiology,and to explore the mechanism of plant response to atrazine stress,Iris pseudacorus was selected as the test plant in this experiment.Hydroponics was used to set up bacteriostatic and non-bacteriostatic treatment,studying the growth physiological characteristics of Iris pseudacorus under different concentrations of atrazine and the absorption characteristics of atrazine in different parts of the plant,in order to reveal the response mechanism of Iris pseudacorus to Atrazine stress,and evaluate the potential and feasibility of Iris pseudacorus for phytoremediation.The research results were as follows:1.Iris pseudacorus had a certain tolerance to atrazine.With the increase of stress concentration,plant height,root length,biomass,root-shoot ratio,chlorophyll content,Fv/Fm,qP and ETR showed a downward trend,while the plant chlorophyll a/b value,fixed fluorescence Fo and qN of plants increased,indicating that low concentration(0.1～0.5 mg·L^-1)stress promoted plant growth.When the stress concentration reached 8 mg·L^-1,the stress had a certain destructive effect on the PSII reaction center of Iris pseudacorus.The damage to the chloroplast can be reduced by adjusting the value of chlorophyll a/b and increasing the dissipation of heat.2.Plants can alleviate the toxicity of atrazine through their own antioxidant system.Malondialdehyde content（MDA）,superoxide dismutase（SOD）,peroxidase（POD）,polyphenol oxidase（PPO）and glutathione S-transferase（GSTs）all increased first and then decreased,indicating that Iris pseudacorus can activate its own antioxidant system to regulate external resistance under certain concentrations of atrazine stress,but when the stress concentration reaches 8 mg·L^-1,the plant’s ability to regulate was weakened,and 8 mg·L^-1 was the safety threshold for resistance to atrazine.3.Microorganisms can significantly alleviate the toxicity of atrazine to Iris pseudacorus.In this experiment,the stress damage of plants treated in short time and low concentration was small;when the stress time was longer(1～8 mg·L^-1),the physiological indexes of non-bacterial treatment were significantly better than the inhibition.Bacterial treatment indicates that the plant needs microbial assistance to jointly resist the stress of atrazine.Under the bacteriostatic conditions,the safety threshold of plant resistance stress decreased to 1 mg·L^-1,which further proved that the presence of microorganisms can alleviate the toxicity of atrazine stress to some extent,and expand the tolerance of Iris pseudacorus to Atrazine stress.4.In this test,when the concentration of atrazine was 0.1 mg·L^-1,the removal of atrazine by Iris pseudacorus was the best.When the concentration of atrazine was not higher than 4 mg·L^-1,the repair effect of Iris pseudacorus was stable,but when the concentration of atrazine reached 8 mg·L^-1,the degradation rate of atrazine was slowed down.Compared with bacteriostatic treatment,non-bacteriostatic treatment can significantly improve the efficiency of degradation of atrazine in Iris pseudacorus.The difference in degradation rate between the two treatments increases first and then decreases with increasing concentration of atrazine.When the concentration of atrazine is low,the plants transport more atrazine from the underground part to the aerial part;when the stress concentration is larger,the root absorption and degradation of atrazine is dominant.The main metabolic pathway of atrazine is the hydroxylation metabolic pathway.Deisopropylatrazine（DIA）appeared at the latest,and it began to appear after 4 days.Iris pseudacorus has a high rate of degradation of atrazine,and it is a practical method to repair atrazine contamination in water with Iris pseudacorus.