| As the main research direction in the paper,the eutrophication of landscape water was studied.The paper described the basic concept and pollution status of eutrophication,and summarized the treatment means of landscape water eutrophication including the physical,chemical and biological technology.The comparative analysis focuses on using ecological bioremediation technology to treat the urban landscape water eutrophication and its influence mechanism were also discussed.Based on the principle of ecological bioremediation technology to renovate landscape water eutrophication,we selected two common emergent plants Sagittaria trifolia Linn and Eleocharis dulcis,which were widely used in urban landscape water landscape design.Three cultural mode on the growth of Microcystis aeruginosa including planting water,plant maceration extract and co-culture were investigated.Then we selected the Eleocharis dulcis to extract the allelochemicals which has a better inhibitory effect on Microcystis aeruginosa,and investigated the inhibitory effect of Eleocharis dulcis allelochemicals on Microcystis aeruginosa and algal-inhibition mechanism.The main experimental results are as follows:1.Both Sagittaria trifolia Linn planting water and Sagittaria trifolia Linn tuber aqueous extract,Eleocharis dulcis planting water and Eleocharis dulcis tuber aqueous extract could inhibit the growth of Microcystis aeruginosa.The highest inhibition rate reached 57.04%under Eleocharis dulcis planting water,while the highest inhibition rate reached 55.45%under Sagittaria trifolia planting water.The highest inhibition rate reached 89.30%under Sagittaria triblia Linn tuber aqueous extract,while the highest inhibition rate reached 91.40%under Eleocharis dulcis tuber aqueous extract.Both the two plants tuber aqueous extract showed the similar trend on the inhibitory of Microcystis aeruginosa,which inhibition rate increased with the increase of tuber aqueous extract concentration.When put it into practical application,the pattern of tuber aqueous extract is more effective than the planting water.We observed that Eleocharis dulcis tuber aqueous extract has a stronger inhibiting effect than Sagittaria trifolia Linn,which could give priority to Eleocharis dulcis tuber aqueous extract on inhibiting Microcystis aeruginosa.2.When Sagittaria trifolia Linn was co-cultured with Microcystis aeruginosa,the chlorophyll a of Microcystis aeruginosa was obviously inhibited,the algal chlorophyll a content of control group increased from 331.11?g·L-1 to 531.85?g·L-1 in 6 days(60.62%of increase);while the algal chlorophyll a content of the Sagittaria trifolia Linn group decreased from 327.14?g·L-1 to 263.1 ?g·L-1 in 6 days(19.55%of decrease).The results revealed that the MDA content of the algae increased significantly,the content of MDA in the experimental group reached the highest value(up to 6.89?g protein-1),which was 5 times of that in the control group.The oxidative enzyme activity including SOD activity,CAT activity,and GSH content firstly increased and then decreased,and the pH value of the culture medium increased continuously during the culture period.The experimental data revealed that the excessive accumulation of ROS damaged the antioxidant enzyme system of algal cells,which was an important reason for the death of the cells.This study demonstrated that the oxidative damage caused by Sagittaria trifolia Linn was the main mechanism for inhibiting the growth of Microcystis aeruginosa under co-culture with Microcystis aeruginosa.3.When Eleocharis dulcis was co-cultured with Microcystis aeruginosa,the chlorophyll a of Microcystis aeruginosa was obviously inhibited,the algal chlorophyll a content of control group increased from 331.11?g·L-1 to 531.85?g·L-1 in 6 days(60.62%of increase);while the algal chlorophyll a content of Eleocharis dulcis group decreased from 365.04?g·L-1 to 282.15?g·L-1 in 6 days(22.70%of decrease).The results revealed that the MDA content of the algae increased significantly,the content of MDA in the experimental group reached the highest value(up to 5.88?g protein-1),which was 3.23 times of that in the control group.The antioxidative enzyme activity including SOD activity,CAT activity,and GSH content firstly increased and then decreased,and the pH value of the culture medium increased continuously during the culture period.The experimental data revealed that the excessive accumulation of ROS damaged the antioxidative enzyme system of algal cells,which was an important reason for the death of the cells.This study demonstrated that the oxidative damage caused by Eleocharis dulcis was the main mechanism for inhibiting the growth of Microcystis aeruginosa under co-culture with Microcystis aeruginosa.4.The qualitative analysis of Eleocharis dulcis peel on the chemical composition revealed that Eleocharis dulcis peel contained saponins,alkaloids,steroids,terpenoids,flavonoids and their glycosides,strong heart glucoside,coumarins,saccharides and glycosides,tannins,organic acids,and phenols.According to the extraction separation experiments of Eleocharis dulcis peel with different solvent,and compared the algal inhibition ability of ethyl acetate extract,n-butanol extract,chloroform extract and petroleum ether extract with algal inhibiting ring method,the ethyl acetate extract was the most effective chemical for inhibiting algae.The experiment of separating and purificating the extract of Eleocharis dulcis peel revealed that the chloroform,ethyl acetate,and methanol mixture was the most effective solvent for separating extract of Eleocharis dulcis peel by thin layer chromatography.Therefore,the mixed solvent with different volume and proportion were used as eluent for column chromatography.The algae were separated and purified twice by silica gel column chromatography,and component 7 with the strongest inhibitory effect was obtained.Then the GC-MS was used to identify the component 7 for exploring the chemical structure of algae inhibiting substance,and the 4 kinds of active substances,such as the flavonoids,flavonoids,organic acids and esters were obtained.5.The corresponding exogenous compounds eriodictyol of the detected active substance C15H12O6 could inhibit the growth of Microcystis aeruginosa,which demonstrated that C15H12O6 was one of the allelopathic constituents of Eleocharis dulcis.The half effective concentration of flavonoids is 1.12×10-7mg·cell-1.When flavonoid content was 8 mg·L-1,the inhibition rate of Microcystis aeruginosa reached 96.76%,which could almost kill Microcystis aeruginosa in medium.Therefore,the addtion of 8 mg·L-1 flavonoids was chosen as the experimental group.According to the measurement of Microcystis aeruginosa cell antioxidant enzyme system of SOD and CAT,malondialdehyde(MDA),glutathione(GSH)and other growth indexes,stress response was activated on antioxidant enzyme system of algal cells.SOD activity decreased,the O2·-processing capacity continued to decline.The determination of CAT data revealed that the increase of CAT activity caused by the decrease of SOD activity could led to a great damage on the algal cells,which can be reflected by the MDA and GSH data.It can be concluded that the damage to the antioxidant enzyme system of flavonoids is the main reason for the decrease of the number of algal cells and even the death. |
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