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Studies On The Nutrient Ecology Of Water Hyacinth (Eichhornia Crassipes), An Exotic Invasive Species

Posted on:2004-06-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y H XieFull Text:PDF
GTID:1100360125455707Subject:Botany
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In recent years, water hyacinth (Eichhornia crassipes (Mart.) Solms), an exotic species, covers many lakes and rivers in China due to deterioration in ecological environment and eutrophication in surface water. Water hyacinth is recognized as an aquatic nuisance in that submersed plants are died for changed environments, living space of floating and free-floating plants is minished, food chain of freshwater ecosystem is destroyed, biodiversity is largely reduced, and thus the value of wetland protection is directly affected. The detrimental effects of water hyacinth are closely linked to its capacity of multiplying and spreading very rapidly. Performed studies showed that water hyacinth is a C3 plant, but its growth rate is higher than C4 plants. So it is difficult to explain this phenomenon just from photosynthetic efficiency. However, the actual photosynthetic efficiency of plants depends on whether other resources (such as nutrient) supply amply or not. In this study, we choosed macro-element N (nitrogen) and P (phosphorus) for subjects, and performed a series of outdoor and field experiments to investigate the effects and the mechanisms of nutrient on growth and clonal propagation of water hyacinth, the nutrient eco-physiological mechanisms of high growth and propagation rate and the strategies to adapt to low-nutrient environments. The results showed that:The impacts of nutrient-availability in the environments on growth and clonal propagation were significant. Total ramet number, different-order ramet number and biomass in different tissues increased with the level of nutrient supply. The biomass allcation pattern of this plant was affected by nutrient-availability in the habitats. The plant allocated more biomass to leaf in high nutrient environments, and more biomass was allocated to root in low nutrientwater-body. ANCOVA's analysis showed that the shifts in biomass allocation pattern as a response to nutrient was a plastic response. This variation improves the ability of water hyacinth to adapt to different environments. Gradually increasing level of nutrient supply in the environments stimulated the growth and clonal propagation of water hyacinth significantly. Noted worthily, the ratio of below-/ above-ground continuously decreased with increasing nutrient level during the experimental period, and this variation was a plastic response. In addition, resources (biomass, N, P) allocation analysis showed that relative allocation of biomass and N to different tissues was not affected by experimental treatments, but the P allocation pattern different, suggesting that P may be a limiting resource in this experiment.At the same nutrient level, the relative growth rate (RGR) and phosphorus absorption rate (PAR) per unit root weight (fresh weight) of water hyacinth were significantly higher than that of Hydrocharis dubia, but different tissue and total plant P concentration were lower. Further studies showed that the total surface area, active surface area and specific surface area per unit root weight (fresh weight) of water hyacinth were higher than that of H. dubia, but active surface area percentage were lower. Bigger root surface area of water hyacinth assured higher nutrient absorption rate, and higher growth and propagation rate were based on higher nutrient absorption rate and lower plant nutrient concentration. The relative biomass allocation to root of water hyacinth was higher than that of H, dubia, and the later mainly to shoot. These two species showed difference in resource use strategies. Strengthening in nutrient absorption is favorable for water hyacinth to adapt to water environments and to assure higher growth rate. The impacts of P-availability on phosphorus absorption efficiency (PAE) and phosphorus use efficiency (PUE) were significant, and decreased with increasing nutrient level.Compared with H. dubia, PAE and PUE of water hyacinth were higher, suggesting that water hyacinth can make the best of the nutrients in the environments and transform them into biological production effici...
Keywords/Search Tags:Eichhornia crassipes, ecological invasion, growth and propogation, nutrient
PDF Full Text Request
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