Study On Biological Effects Of Sediments And Water Nutrition Condition To Submerged Plant

It is universal for the decline and the disappearing of aquatic vegetation, especially submerged plant, with the development of eutrophication in water body. Submerged plant is an important makeup in Lake Ecosystem. Species, biomass, mulch area, spatial distribution, fashion and degree used of submerged plant are directly related to the environmental quality of the lake. The restoration and maintaining of submerged vegetation are internationally attached importance in polluted lake. At present, it is not clear for the mechanism of eutrophication on submerged plant and the adaptation of submerged plant to eutrophication. The paper starting with the sediment and water body closely related to submerged plant, adopted ecology model and experiment culture, studied physiological effects of medium nutrition on submerged plant, in order to accumulating data in adapted mechanism and providing reference in restoration of submerged plant. The study investigated the effects of sediment nutrition on growth and physiology of Hydrilla verticillata, the effects of nitrogen concentration, phosphor concentration and nitrogen form in water body on photosynthesis of Hydrilla verticillata and the effects of nitrogen concentration in water body on the adsorbing in total nitrogen and phosphor of Hydrilla verticillata. The results showed (1) sediment nutrition significantly affected the growth of Hydrilla verticillata. The sediment (HH) with the highest nutrient could accelerate the growth and the photosynthesis of Hydrilla verticillata in early growing stage, but at high temperature season it could decrease root vigor and chlorophyll content of Hydrilla verticillata, and affect later growth of Hydrilla verticillata;The TR sediment with lower nutrition level inhibited the biomass accumulation of Hydrilla verticillata;The HK sediment could provide enough nutrition for Hydrilla verticillata, and it was favorable for the growth and the photosynthesis of Hydrilla verticillata at high temperature season. (2) the photosynthesis of submerged plant was affected by nitrogen concentration, phosphor concentration and nitrogen form. It was favorable for the photosynthesis of Myriophyllam verticillatum with the addition of nitrogen concentration in water body, when nitrogen concentration was ≤ 3 mg/L;It was favorable for the photosynthesis of Hydrilla verticillata with the addition of nitrogen concentration in water body, when nitrogen concentration was ≤ 4 mg/L;Myriophyllam verticillatum was more sensitive to high nitrogen in water body than Hydrilla verticillata;the increase of NH₄⁺-N ratio in water body could inhibited the photosynthesis of Myriophyllam verticillatum and Hydrilla verticillata to some extent. Net photosynthetic rate and maximum photosynthetic rate of Myriophyllam verticillatum and Hydrilla verticillata reduced with the increase of NH₄⁺-N ratio in water body, whereas light compensation point dark respiration rate enhanced. (3)the absorption of total nitrogen and phosphor in Hydrilla verticillata was affected by nitrogen concentration in water body. The absorption of total nitrogen and phosphor increased with the addition of nitrogen concentration (< 2.0 mg/L) in water body, but the absorption would reduced when nitrogen concentration was more that 2.0 mg/L;the three absorption kinetic parameters of total phosphor in Hydrilla verticillata all first increased, then reduced and were the maximum in 2.0 mg/L of nitrogen concentration. The absorption kinetic parameter (Imax) of total nitrogen in Hydrilla verticillata reduced with the addition of nitrogen concentration, Km and Cmin increased with the addition of nitrogen concentration in culture solution.