The Effect Of Nutrient Salts On Growth Indicators And Antioxidant System Of Submerged Plant

Lake eutrophication is one of the most important environmental problems in China. The nutrients as an important restricting factor of lake eutrophication, in particular the concentration of ammonia nitrogen and phosphorus concentration is a serious stress on the submerged plant growth, has seriously affected the normal physiological activities of submerged plant.This study was based on the sub-project"Mechanism of Degenerates and Restores of the Aquatic Vegetation (2002CB412307)"of the"973"Project"Research of Lake Eutrophication Process and Blue-Green Alga Eruption Mechanism".Two submerged cultivars, Hydrilla verticillata and Myriophyllum spicatum,was used to do an experiment material, applied relatively ecology theory and method to study the effect of different ammonia-Nitrogen and phosphorus concentrations on growth indicators and antioxidant system of submerged plant.The results mainly showed:1 When the ammonia-nitrogen concentration was 0.2mg·L^-1 the growth of Hydrilla verticillata was normal, the growth indicators such as plant height, plant roots, fresh weight increased amount and enzyme indicators such as the protein content, chlorophyll content were significantly higher than other groups and reached the largest, SOD and POD activity changed relatively flat and showed the normal dismutation capacity; And ammonia-nitrogen concentration from 1.5mg·L^-1 began to induce the antioxidant enzymes SOD, POD activity, and the Hydrilla verticillata normal growth was stressed which showed that the Hydrilla verticillata prefers low ammonia-nitrogen concentration.2 Myriophyllum spicatum could grow normally when concentration of ammonia-nitrogen from 1.5 to 4.0mg·L^-1, but low ammonia-nitrogen (0,0.2mg·L^-1) and high ammonia-nitrogen (8.0mg·L^-1) concentrations both had an impact on the normal metabolism of Myriophyllum spicatum.The suitable ammonia-nitrogen concentration for Myriophyllum spicatum growth was far higher than Hydrilla verticillata, it showed that Myriophyllum spicatum was more tolerance of high-quality concentration of ammonia-nitrogen.3 When the phosphorus concentration was 0.2mg·L^-1, the chlorophyll and protein content of Hydrilla verticillata and Myriophyllum spicatum were significantly higher than all other treatment groups, and SOD, POD, CAT activity changed relatively flat and maintained normal metabolic balance, plants grew normally. From submerged aquatic plant enzyme indicators can see that when phosphorus concentration was 0.2mg·L^-1,it was optimum concentration for Hydrilla verticillata and Myriophyllum spicatum.4 From the observation of growth indicators, the phosphorus concentration of 0.2mg·L^-1 was optimum concentration for Hydrilla verticillata and performed that the number of branches, plant t height, plant roots and fresh weight increased amount was significantly increased than Myriophyllum spicatum. So from the point of view a plant growth potential and plant community, Hydrilla verticillata better than Myriophyllum spicatum.5 Under the conditions of the experiment, the ammonia-nitrogen and phosphorus concentration that is suit for growth of Myriophyllum spicatum and Hydrilla Verticillata is more high than ammonia-nitrogen and phosphorus concentration of the eutrophic water bodies. So the single ammonia-nitrogen or the single phosphorus concentration is not directly cause for the degradation of submersed macrophyte in eutrophic water bodies.