The Influences Of N,P On Growth And Physiology Of Submerged Macrophytes In Eutrophic Waters

It is universal for the decline and the disappering of aquatic vegetation, especially submerged macrophytes, with the development of eutrophication in water today. Submerged macrophytes is an important makeup in Lake Ecosystem. 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 macrophytes and the adaption of submerged macrophytes to eutrophication. The paper starting with the water body closely related to submerged macrophytes, adopted ecology model and experiment, studied on the effect of diffetent N,P concentration on the branches,roots and biomass of Elodea nuttallii and M.spicatum l. Investigate on the effect of different N,P concentration on the content of chlorophyll,soluble sugar,soluble protein and MDA, enzyme activity of POD,CAT and SOD of Elodea nuttallii. The results are those:1. The N,P have an important effect on the growth of the submerged macrophytes of Elodea nuttallii and M.spicatum l. In definite limit concentration, submerged macrophytes grow better with the increase of N,P. However, when the N,P were too high, which will have a bad effect on the growth of submerged macrophytes. When Elodea nuttallii in C1 concentration, its branches,roots and biomass were the best. Whereas, when M.spicatum l. in CK concentration, its branches,roots and biomass were the best.2. with the increase of N> P stress and the time going on, the chlorophyll contents, the soluble sugar contents and the soluble protein contents of Elodea nuttallii decreased obviously. And MDA contents increased, but decreased in the 8th day. POD activity of Elodea nuttallii rised at first and lower later. Whereas, CAT activity of Elodea nuttallii increased first, decreased later and increased in the end. Furthermore, increased N,P in media resulted in continuous increase of SOD activity. POD activity is sensitive to N,P concentration than CAT activity and SOD activity.All these results demonstrated that under high N,P concentration, the activity of reactive oxygen species scavenging enzymes were interrupted in Elodea nuttallii, which resulted in enhanced oxidative stress in plant and even serious membrane damage of cells.