Study On The Response Of Ammonium Nitrogen Stress In Water By The Myriophyllum Verticillatum Of Submerged Plant

Submerged plants are an important part of the ecosystem of rivers and lakes.In the world,especially in China,more and more people are paying attention to the pollution and eutrophication of rivers and lakes caused by human activities.In the process of water treatment,the reconstruction of submerged vegetation is an important link in preventing and controlling lake eutrophication.In the process of water eutrophication,Myriophyllum verticillatum is widely used as a pioneer species to reduce the total nitrogen level in water.In the early stage of governance,the content of nitrogen in water was reduced mainly by planting and salvaging.In the later prevention and treatment,it was found that the level of ammonium nitrogen in water body had a significant influence on the long-term water colonization process of foetail.Ammonium nitrogen is an essential nutrient for plant growth,and excessive ammonium nitrogen will also produce toxic effects on plant growth.Chloroplasts are the most sensitive organelles in response to environmental changes.In the process of chloroplast responding to ammonium nitrogen stress,chloroplast membrane structure of chloroplast was seriously damaged,and the accumulation of thylakoid membrane protein was also seriously affected,and a large amount of starch was accumulated in chloroplastsr.Ammonium chloride was used to simulate ammonium nitrogen stress in water,chloroplast leaves of Myriophyllum verticillatum under high concentration of ammonium nitrogen were chlorinated,and their growth was inhibited.The chloroplast structure also showed similar thylakoid membrane damage and starch accumulation.The change of reactive oxygen species(ROS)in leaf was the direct cause of chloroplast structure change caused by ammonium nitrogen stress.ROS generation in leaf was reduced by decreasing chlorophyll level and increasing non-photochemical quenching(NPQ).At the same time,there were significant differences in the enzyme activities of the antioxidant enzyme system of Myriophyllum verticillatum under the stress of different ammonium nitrogen levels,and the enzyme activities of peroxidase(POD)and catalase(CAT)in Myriophyllum verticillatum under the condition of high concentration of ammonium nitrogen were higher.Together,they constitute the anti-oxidation mechanism of Myriophyllum verticillatum against ammonium nitrogen stress.The behavior of model plant arabidopsis thaliana in the ammonium nitrogen gradient concentration was similar to that of Myriophyllum verticillatum,which laid a foundation for further study on the mechanism of plant response to ammonium nitrogen stress.At the same time,the results of this study have guiding significance for the further use of Myriophyllum verticillatum in the prevention and control of water eutrophication,and promote the understanding of the process of submerged plant reconstruction.