Responses Of Vallisneria Spiralis And Elodea Nuttallii To Ammonium Nitrogen And Phosphorus Concentrations In Water Environment

A static simulation study was conducted to investigate physiology and growth characteristics of two important pioneer plants in restoration of submerged vegetation (Vallisneria spiralis and Elodea nuttallii) under different nutrition levels in water environment. Different levels of ammonium nitrogen (NH4+-N) concentrations under a fixed phosphorus (P) concentration as limiting factor and different levels of P concentrations under a fixed NH4+-N concentration as limiting factor were applied in this study. Differences of adaptability between two submerged macrophytes were studied to obtain safe concentrations of NH4+-N and P for growth in restoration progress of submerged vegetation. It could provide a theoretical basis for exploring the mechanism of submerged macrophytes recession and data support and practical guidance for the research of restoring eutrophic water by submerged macrophytes. The main results are as follows.1. Both of Vallisneria spiralis and Elodea nuttallii had stronger resistance abilities under high NH4+-N and P concentrations, with the highest application in NH4+-N (1.2mg/L) and P (0.8mg/L) concentrations respectively.2. There were different resistance responses to NH4-N and P between Vallisneria spiralis and Elodea nuttallii: sensitive indexes of resistance response to NH4+-N in Vallisneria spiralis were biomass, soluble protein, superoxide dismutase (SOD), peroxidase (POD), reduced glutathione (GSH), ascorbate (ASA) and malondialdehyde (MDA), but in Elodea nuttallii were SOD, GSH and ASA. In response to P concentrations in water environment, sensitive indexes in Vallisneria spiralis were biomass, soluble sugar, soluble protein, SOD, POD, GSH, ASA and MDA, but in Elodea nuttallii were biomass, SOD, GSH, ASA and MDA.3. High levels of NH4+-N and P concentrations in water environment had different influences on organization structure in different organs with an order of root> stem> leaf.4. There was no significant effect on biomass of Vallisneria spiralis and Elodea nuttallii with NH4+-N concentrations less than0.3mg/L and P concentrations less than0.05mg/L in water environment. However, physiology and biochemistry indexes including SOD, POD, ASA, GSH, etc were influenced by different Nt4+-N and P concentrations. It meant that low concentrations of NH4+-N and P had a hysteretic effect on biomass of two submerged macrophytes. Therefore, the physiology and biochemistry indexes could be used to judge the level of stress intensity in Vallisneria spiralis and Elodea nuttallii under the conditions of low concentrations of NH4+-N and P.