Physiological Response Study On Plateau Submerged Macrophytes Of Ammonium

Nitrogen is an important element for plant growth and development.Changes in nitrogen concentration have a major impact on the composition and distribution of vegetation in water bodies.When the concentration of ammonium in the water body is low(NH₄⁺<3mg/L),it can promote plant growth.When the concentration of ammonium increases until it exceeds the nutrient requirement for plant growth,the excessively high ammonium will have a toxic effect on plants,thereby affecting the health of the ecosystem.Submerged macrophytes are the main producer in the aquatic ecosystems.They can use nitrogen and other nutrients for their growth and metabolism,thereby alleviating excessive nitrogen and other nutrients in the water body,and promoting the nitrogen cycle of the aquatic ecosystem.The role of submerged macrophytes in the ecosystem has aroused great interest among researchers.The interaction between submerged macrophytes and nutrients in water bodies have been extensively studied.Using submerged macrophytes to restore water in aquatic ecosystems is an economical and environmentally friendly method.Sensitivity to the nitrogen content in the water body varies between aquatic plants species.The stems and leaves of most submerged macrophytes can absorb nitrogen from the water body.In this study,submerged macrophytes species sensitive to ammonium were screened as water indicator species,and submerged macrophytes that were not sensitive to ammonium were selected as pioneer species for water quality restoration,and their response mechanisms were compared.Classification can provide technical reference and species selection for water quality restoration.We collected nineteen common submerged macrophytes in the wild.Subsequently,the nineteen species of plants were cultivated for four days under the lab conditions of 0,0.1,3,15 and 50 mg/L ammonium concentration.We performed the following seven assays:chlorophyll fluorescence(Fv/Fm),chlorophyll content,water quality parameters,ammonium,total plant nitrogen,plant free amino acids(FAA)and the soluble protein content of plants.Three types of plants can be distinguished based on our results.Have strong resistance to high concentrations of ammonium:Elodea canadensis,Ceratophyllum demersum,Myriophyllum spicatum and Stuckenia pectinata.Vallisneria natans,Vallisneria spinulosa,Najas minor,Najas marina,Ottelia acuminata and Ottelia alismoides shows sensitivity to high concentrations of ammonium.Potamogeton maackianus,Egeria densa,Hydrilla verticillata,Cabomba caroliniana,Potamogeton wrightii,Potamogeton crispus,Potamogeton intortifolius,Potamogeton lucens,and Potamogeton perfoliatus are not tolerant to high ammonium but their The sensitivity is weaker than Vallisneria natans,Vallisneria spinulosa,Najas minor,Najas marina,Ottelia acuminata and Ottelia alismoides.The study on the absorption ratio of ammonium by submerged plants found that as the concentration of ammonium nitrogen in the culture solution increases,submerged plants have a certain limit on the consumption of ammonium in the water.In this experiment,most of the submerged macrophytes are 0.1mg/L or 3mg/L ammonium concentration solution can carry out relatively complete physiological activities,the degradation effect of ammonium in the water body is the most obvious,and the consumption ratio is higher.Research on the response of ammonium-sensitive submerged macrophytes to ammonium has found that submerged macrophytes release the toxicity of high concentrations of ammonium to submerged plants by producing free amino acids.The ability of the photosynthetic cells of submerged macrophytes leaves to produce free amino acids and their protein content are related to the ammonium purification of submerged macrophytes leaves and the sensitivity of submerged macrophytes to ammonium.The leaves can produce more free amino acids,the higher protein content,the more effective the leaves are for purifying ammonium in water.When the concentration of ammonium is too high,the photosynthetic system of submerged macrophytes is destroyed,photosynthetic capacity is severely disturbed,the content of free amino acids and protein that can be synthesized in plant cells also drop sharply,which seriously affects the mechanism of detoxification of ammonium by submerged plants.Physiological activity makes submerged plants lose their activity and gradually fade away.