| Bioremediation of eutrophic waters has been considered as a low cost, simple operation and management, good combined effects and repair effect, and widely used technology. Currently, many researches have focused on aquatic plants, herbaceous plants, microbes, aquatic animals, and the composite type of these biologies. But little is available on the studies on using woody plants for purifying eutrophic waters, and endopytic microbes has been fewly used to enhance eutrophic water purification. In this study simulation experiment, solution culture experiment and greenhouse static experiments were conducted, in order to test the effects of willow-endophytic bacteria interaction on purification of eutrophic waters, by means of screening efficient willow genotype and effective endophytic bacteria derived from Sedum alfredii H. The main research results were summarized as follows:1. Through simulation experiment, this study compared the growth and nitrogen and phosphorus absorption of 20 local energy willows genotypes in natural eutrophic waters and in Waston solution, to select efficient purification genotypes suitable for different eutropic water load. After 45 days growth in hydroponic experiment, significant differences in biomass were noted among the willow genotypes.In nutrient solution willow genotypes J799, J795 had larger biomass (1.97 g·plant-1,1.56 g·plant-1), nitrogen accumulation (65.4 mg·plant-1,53.0 mg·plant-1) and phosphorus accumulation (10.8 mg·plant-1,8.8 mg·plant-1) than others. While in natural eutrophication water, willow genotypes SM24, SB 11 were grew better and had higher biomass (0.71 g plant-1, 0.85 g·plant-1), nitrogen accumulation (9.4 mg·plant-1,9.4 mg·plant-1) and phosphorus accumulation (3.4 mg·plant-1,1.8 mg·plant-1) than others. It indicated that willow genotypes of J799 and J795 seemed to be suitable foe for remediate heavier eutrophic water bodies, whereas genotypes of SM24 and SB 11 seems more suitable for remediate moderately eutrophication of water bodies.2. Solution culture experiment was conducted to study effects of inoculated 8 different endophytes separated from the hyperaccumulation Sedum alfredii H. on growth, nitrogen and phosphorus uptake by willow plant. The results obtained showed that chlorophyll content of the willow plant was significantly increased by 15% and 14% with inoculation of SaMR12 and SaMR10 endophytic strains, as compared with the control. The whole plant biomass of willow was increased by 234%,43% and 54% after inoculation with LM02, SaNRl and SaMR12, respectively. The root morphology was significantly improved after inoculation with LM02, SaNRl and SaMR12, with total root length of the willow plant being increased by 163%,136%, 66%, root surface area increased by 54%,12%,17%, and the number of root tips increased by 54%,44%,48%, respectively. The accumulation of nitrogen and phosphorus was significantly higher with inoculation of LM02, SaMR12 and SaMR10, as compared with the control. Shoot nitrogen accumulation was increased by 176%,26%,41%, and phosphorus accumulation raised by 109%,12%,30% after inoculation with LM02, SaMR12 and SaMR10, respectively, as compared with the control. The accumulation of nitrogen in root was increased by 8.3 times,2.4 times and 3.4 times, and the accumulation of phosphorus was increased by 4.8 times,2.1 times and 2.8 times, respectively, after inoculation of LM02, SaMR12 and SaMR10, as compared with the control. These results showed that the endophytic bacteria from the hyperaccumulation Sedum alfredii Hance could effectively promote the growth of willow, and used to enhance the phytoremediation of eutrophication water by willow. And LM02, SaMR12 and SaMR10 showed to be more effective endophytic strains.3. Through the greenhouse static experiment, we studied the effects of willow-endophytic bacteria interaction on purification of eutrophic water. The willow genotypes used was SM24 and the endophytic microbe strains selected were LM02 and SaMR10. The results showed that inoculation of endophtic bacteria significantly increased the removal rate of TN, TP, NH4+-N and IMn index by the willow plant from the eutrophic water. The TN and TP removal rate by the endophyte-inoculated willow plant increased by 10% and 20%, respectively, as compared with the controls. And after inoculation, the willow biomass and N/P accumulation increased significantly. Further study found that plant leaf SPAD value, root morphology, organic acid content and root exudates, pH value were changed with inoculation of endophytic bacteria. The rusults indicated that endophytic bacteria strains of LM02 and SaMR10 could promote the growth of willow and improve the removal efficiency of nitrogen and phosphorus from eutrophication water. |
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