Joint Ecotoxicological Effects Of Chlorimuron-ethy And Heavy Metals And Their Molecular Diagnosis

The residual of chlorimuron-ethyl has adverse effects on sensitive crops and other plant species all around even long after spraying. So its prolonged and wide use will lead to territorially agroecological pollution and eventually cause the loss of agroecological integrity. Meanwhile, the use of fertilizers and pestcides will input heavy metals such as Cd, Cu, Pb and Zn, which will lead to the combined pollution of chlorimuron-ethyl and heavy metals. The results of this study could be considered as the base for the ecological risk assessment of combined pollution of chlorimuron-ethyl and heavy metals. And sensitive biomarkers have been screened in this work for the diagnosis of the joint stress of chlorimuron-ethyl and heavy metals.When chlorimuron-ethyl and heavy metals are combined with low concentrations, chlorimuron-ethyl and heavy metals have antagonistic effect on the root elongation of wheat seedlings. However, when the concentrations of chlorimuron-ethyl and heavy metals are high, chlorimuron-ethyl and heavy metals have significantly synergistic effects on the shoot and root elongation of wheat seedlings. Meanwhile, the joint effects were more depended on the effects of heavy metals than on those of chlorimuron-ethyl.As one of the visible symptoms, the obvious decrease of chlorophyll content in wheat seedlings only was detected under single stress of chlorimuron-ethyl and Cd. With combined stresses of chlorimuron-ethyl and heavy metals, the toxic effects of the two chemicals on chlorophyll content were alleviated by the antagonistic action of chlorimuron-ethyl and heavy metals. The change of antioxidant enzyme activities was correlated with the change of soluble protein content. However, the alteration of soluble protein content was caused mainly by the toxic chemicals due to their inhibition of protein biosynthesis. The chemical property of pollutants determined the toxic mechanisms to plants and the joint effects of the combined pollution. There were significant difference in the toxic mechanisms between chlorimuron-ethyl and heavy metals as well as between single stress of chlorimuron-ethyl and heavy metals and combined stress of chlorimuron-ethyl-heavy metal. However, there existed common toxic mechanisms between combined treatments of chlorimuron-ethyl-Cd and chlorimuron-ethyl-Cu as well as between single stress of Cd and Cu. And the join effects of chlorimuron-ethyl and heavy metals on wheat seedlings at the biochemical level altered among different concentration combination of the two chemicals as well as among different action tissues of plants. The decrease of POD and SOD activities and SP content in wheat roots could be considered biomarkers indicating the stress of chlorimuron-ethyl and heavy metal.Single stress of Cd had more toxicity to DNA than single stress of chlorimuron-ethyl and joint stress of chlorimuron-ethyl and Cd. When treated with special concentration combination of chlorimuron-ethyl and Cd, chlorimuron-ethyl would decrease the toxicity of Cd to DNA. The sensivity to pollutants would alter with different sequence of primers. The damage caused by chlorimuron-ethyl and Cd might be taken place at the special sites of DNA sequence. There were different appearance frequency of new bands between single and joint stress of Cd and chlorimuron-ethyl, which might be due to the decrease of the change rate in DNA sequence at the primer S1156 site caused by the transaction of chlorimuron-ethyl and Cd.