Studies On The Morphological Characters Of Eichhornia Crassipes And Its Relationships Between Some Ecological Factors

As a kind of alien invasive species, Eichhornia crassipes has flooded in most of the areas in South China which has caused jam in the waters and damage to the local ecosystem. So far the researches about Eichhornia crassipes both at home and abroad have focused on its purification function and biological prevention about its over-growth. However, few have mentioned the relations between Eichhornia crassipes and its environmental factors. This thesis has done many researches on quotas about the plant morphology, quality factor, phytoplankton, and zooplankton in Xiema Reach of Longfeng Xi River In Beibei District of Chongqing, a water pool and two rearing ponds in the Southwest University, during the growing period of Eichhornia crassipes between October 2006 and September 2007. And experiments on the implantation of Eichhornia crassipes in the cultivated liquor with different density and different N/P ratios have been carried out as well in this study.1,Comparison of the morphological characters in different water areasThe changing scope within one year of the biomass is 2488¹2406g. Seasonal changing trend: Oct.>Jan.>July>Apr. Changing trend in different water areas: Pond>River>Pool.The morphological quotas from different water areas vary from each other greatly, but no difference has been found between the two rearing ponds. Among all these morphological quotas, distinctive difference lies in leaf-length quota and stem-length quota.There is positive correlation with all these morphological quotas. Along with the growth of the plant, all the organs grow simultaneously. The morphological quotas that have stronger correlation are stem-length quota and leaf-length quota, leaf-length quota and individual-weight.2,Relations between Eichhornia crassipes morphological quotas and water area quality quotasThe correlation of Eichhornia crassipes and quality factors is increased while the coverage expands. Eichhornia crassipes biomass has also mounted with the increase of the density of nutritious salt N and P, and it is in negative correlation with COD.P has dramatically affected the morphological quotas. Root-length quota is in salient negative correlation with HPO₄^2-, while leaf-length quota is in salient positive correlation with it.The increase in the quotas of stem-length, individual-weight and biomass has resulted in the decrease of DO.3,The impact of Eichhornia crassipes on the phytoplanktonThe kinds of phytoplankton in the water area Eichhornia crassipes grows are mostly chlorophyta, cyanophyta, and bacillariophyta, and the amount of chlorophyta is the most of all. The basic seasonal successive mode of the phytoplankton is: bacillariophyta, chlorophyta (autumn and winter)—cyanophyta, chlorophyta (spring and summer).The changing trend of the phytoplankton biomass: (autumn and winter) Pond >Pool>River, (spring and summer) Pond>River. The amount of phytoplankton in spring and summer is much more than it in autumn and winter.The diversity index of phytoplankton does not change much, but varies a lot in spring and summer: River>Pond. The phytoplankton diversity index drops with the growing of Eichhornia crassipes, i.e. the growth of Eichhornia crassipes compresses phytoplankton diversity.The diversity index of phytoplankton is in negative correlation with the Eichhornia crassipes biomass. With the accretion of the Eichhornia crassipes biomass, the phytoplankton diversity declines.Phytoplankton diversity index reduces when the root-length quota increases.Phytoplankton biomass is in positive correlation with the living quotas of Eichhornia crassipes in the way that the biomass has acquired an ascending trend with the up-growing of the root and stem quotas.4,The impact of Eichhornia crassipes on zooplanktonWhen the coverage of Eichhornia crassipes is 100%, the zooplankton biomass decreases with the biomass accretion of Eichhornia crassipes.Zooplankton biomass in the water area where Eichhornia crassipes grows is in negative correlation with the morphological quotas, that is, this biomass reduces with the increase of stem, leaf and weight of Eichhornia crassipes.5,The most adaptable N, P water condition for Eichhornia crassipes growingThe P content within the plant is relatively stable when the density of P is 0.1～0.5 mg/L in the water.The absorbability of N by Eichhornia crassipes is luxurious absorb. When the density of N in the water is 0.2～18 mg/L, N content within the plant rises with the increase of N content in the water, but to a lesser extent than in the water. When the density of N in the water is 18～30 mg/L, the growing of the plant is limited.When the N content in the water exceeds 1.5 mg/L, P content in the plant will decrease. The fittest ratio of N and P in the water area Eichhornia crassipes grows is 8:1, and the fittest N/P inside the plant is 2.8:1.