Effect Of Water Nutrient On The Growth Of Potamageton Crispus

Water eutrophication is a worldwide environmental problem mainly caused by the increasing dense of nutrients, which affects the structure and functions of aquatic ecosystem, as well as the use of water resource, and endangers human beings directly. In our country, water pollution becomes more severe, and restricts the suxtainable development of economy considerably. Thus, controlling pollution, improving water quality and restoring degenerative ecosystem become urgent. Hydrophyte, especially submerged plant, is the crucial functional group in hydrophily ecosystem.On the one hand they can purify contamination effectively and maintain superior water quality, on the other hand they are able to adjust and control the structure and function of ecosystem. Unfortunately, hydrophyte sometimes degenerates and even disappears. It becomes inevitably vital to study on the effect of water nutrient on the hydrophyte which can restore degenerative ecosystem and improve water quality.In this paper, we take Potamageton crispus as an example, to study on the effect of nutrient on the gemmation and growth of Potamageton crispus and its endurance of eutrophication water. The findings include these:(1) Within design concentration range of nutrient (NH₄⁺-N:0.5～10.0mg·L^-1, TN:1.0～16.0 mg·L^-1, TP:0.2～1.0 mg·L^-1), nutrient have no obviously effect on the gemmation of Potamageton crispus. Germination rates are all 100% in each experimental water. In the range of NH₄⁺-N≤3 mg·L^-1, TN≤4 mg·L^-1, TN≤0.6 mg·L^-1, nutrient could accelerate the growth of plantlets. Light energy absorbed by plantlets were mostly used to drive photochemical reaction. Whereas, as the concentration of nutrient go up higher, the growth of plantlets would be restrained. More energy were dissipated as heat to protect the photosynthetic apparatus PSII temporality.(2) High nutrient is able to breed floating algae in the resting water. Algae reproducing largely could lower underwater illumination which had influence on the photosynthesis. This would damage the photosynthetic apparatus PSII. In the water of NH₄⁺-N≤1.5 mg·L^-1,TN≤2.0 mg·L^-1,TP≤0.4 mg·L^-1, although floating algae had effect on the growth of Potamageton crispus in the early time, when Potamageton crispus grow higher and biomass increases constantly, thus can control the growth of algae. Nevertheless, in the water of NH₄⁺-N > 3.0 mg·L^-1,TN > 4.0 mg·L^-1,TP > 0.6 mg·L^-1, on the one hand nutrient stressed Potamageton crispus, on the other hand floating algae restrained Potamageton crispus. the photosynthetic and physiological apparatus would be damaged. So Potamageton crispus couldn't survival.(3) Potamageton crispus is a submerged macrophtye which could endure heavy eutrophication water. In the eutrophication water of NH₄⁺-N≤1.5 mg·L^-1,TN≤2.0 mg·L^-1,TP≤0.4 mg·L^-1,Chla≤118.51 mg·m^-3, we were able to introduce Potamageton crispus immediately. However, in the eutrophication water of NH₄⁺-N > 3.0 mg·L^-1,TN > 4.0 mg·L^-1,TP > 0.6 mg·L^-1,Chla > 195.99 mg·m^-3, we should first use such as ecology float-island or snails,mussels to improve water environment then we can introduce Potamageton crispus.