The Effect Of Physiological Response And Nitrogen Acts For Sediment In The Myriophyllum Spicatum L. On Nitrogen Nutrition

Submerged macrophytes, an important component of the aquatic-ecosystems system and the major primary producers, between the interface of water-soil, water-air and land-water, plays an important role in material cycle, algae control, water stability and water quality improvement of the aquatic-ecosystems system. At present, the mechanism of submerged macrophytes'decay in eutrophicated lakes decay is still not clear, this is also a hot question for domestic and international experts. In fact, the level of nitrogen and phosphorus nutrition constraints is an important factor in submerged macrophytes growth, however, the mechanism about nutrients for plant growth and physiological characteristics, and the impact of add organic carbon sink for sediment is still not very clear. What has been done in this paper is one part of a key project financed by the government of our country, and the serial number of this project is 2002CB412304. Cultivate the use of greenhouse, Studied at different nutritional condition, submerged plants on water purification and its own mechanism of the changes in antioxidant enzyme system, the impact of nitrogen ratio for selective absorption and its own physiological response in submerged macrophyte Myriophyllum Spicatum L., and add organic carbon sink for sediment, the effects of ammonium sorption and ammonium release for sediment. The main findings are as follows:In this paper, we selected three submerged macrophytes, Myriophyllum Spicatum L., Hydrilla Verticillata L., Ceratophyllum Demersum L., in greenhouse, designed two different nutritional condition, the study found that Myriophyllum Spicatum L. has a good removal efficiency of TN, NH₄⁺-N, NO₃^-- N than the other two types of submerged macrophytes in the two different nutritional condition, removal efficiency have reached stability,during the trial of the 14 days, NO₃^-- N removal rate is 100%, and submerged macrophytes have better aerobics effect; During the experimental conditions, the activitys of SOD, POD and MDA of Ceratophyllum Demersum L changed greatly, and raised rapidly in the late of experiment, which indicated that those two submerged macrophytes got more nutrient stress than Myriophyllum Spicatum L, and the nutritional stress-resistant ability of Myriophyllum Spicatum L was higher than those two submerged macrophytes in the medium nutritional condition.Seconad, research the impact of nitrogen ratio for selective absorption and its own physiological response in submerged macrophytes Myriophyllum Spicatum L.,the study found that biological nitrogen fixation and denitrification of nitrogen assimilation significantly, the higher of the NO₃^--N content in water , the nitrogen assimilation was more strongly, NO₃^--N content has been reduced to 0.52mg?L-1 following,on the first five days of the trial in water, the NH₄⁺-N's change in water does not significantly, NH₄⁺-N is dominant stress for Myriophyllum Spicatum.L. Because of plant leaves and stems has different roles, the growth of plant height is strong, and plant fresh weight and protein content of the water body is lagging behind some of the reaction when Myriophyllum Spicatum.L absorbed of nutrients in water. The changes of SOD activity and changes in free proline content was negatively correlated of Myriophyllum Spicatum.L, the POD activity and NR activity significantly correlated. Overall, Myriophyllum Spicatum.L has a certain degree of tolerance for test environment, but the tolerance was been weakening when the extension of time.At the same time, the sediments play an imponant role for the submerged macrophytes growth and have a greater impact on physical, this paper studied that add organic carbon sink for sediment, the effects of ammonium sorption and ammonium release for sediment. The study found that cultivation of submerged macrophytes Myriophyllum Spicatum.L for sediments did not change the distribution of nitrogen, different forms of nitrogen in sediments is still the DONt> NH₄⁺-N > NO₃^--N, but deal with different nutrients in the sediment nitrogen content is the slight difference, the NH₄⁺-N and DON content higher throughout the trial period about add 1% glucose group, were 0.094mg·g^-1 and 0.20mg·g^-1, the NO₃^--N content higher about add 1% organic matter group, were 0.024mg·g^-1. In the period of rapid growth of plants, Myriophyllum Spicatum.L has not changed the trend of the nitrogen adsorption and release of sediment, but it changed the strength of the NH₄⁺-N adsorption/release, Myriophyllum Spicatum.L cultivation reduced the strength of the NH₄⁺-N release,and enhanced the quality of the NH₄⁺-N adsorption, the planting of submerged macrophytes, it increased the potential of release of NH₄⁺-N from sediment to water when the cases of add organic matter 1%, and it caused the possibility of increased lake eutrophication.