| Water eutrophication is a serious environmental issue in China,it can lead to frequent outbreak of cyanobacteria bloom,resulting in a wide range of water quality deterioration and damaging water landscape and aquatic ecosystem functions,so that the aquaculture industry suffered economic losses,aggravate the water crisis and seriously affect human health.Therefore,effective control eutrophic algae and prevent blooms occurred has become the world's environmental problems to be resolved.Traditional methods of inhibiting algae include physical,chemical and biological methods.All of the above methods have obvious defects,and the allelopathic effect on algae control is a low-risk,long-lasting,environment-friendly method.In order to find a kind of aquatic plants that can not only effectively restain the growth of algal,but also be able to bear the stress of eutrophic waters.This study was systematically explored the tolerance of Typha orientalis to different levels of eutrophic salt,the inhibitroy effects on Microcystis aeruginosa and Anabaena sphenella were studied and the inhibitroy mechanism was discussed,meanwhile we made the allelochemicals isolated from Typha orientalis and identified them.The experimental results were as followed:1.Typha orientalis disposed by different levels of eutrophic salts to study the tolerance mechanism of Typha orientalis to eutrophication and its elimination of nitrogen and phosphorus in water.The results showed that Typha orientalis has good tolerance to eutrophic salt,and it can effectively eliminate nitrogen and phosphorus in eutrophic water.The removal rate of nitrogen reached the maximum up to 77.33% in the middle eutrophication,while the phosphorus maximum removal rate reach the highest-77.87% in the lightly eutrophication.Under the condition of high eutrophication,the chlorophyll content of Typha orientalis increased,and by increasing the activity of POD and SOD to remove more reactive oxygen,so as to resist the nutrient stress and make itself growing in best condition.Under the condition of super-rich nutrition,the chlorophyll content,SOD and POD activity of Typha orientalis were decreased compared with the control,the content of MDA increased significantly,indicating that the production of reactive oxygen beyond the scope of antioxidant enzyme eliminate ability and the growth of Typha orientalis has been severely stressed.Therefore,Typha orientalis has extremely important significance for water restoration and blooming prevention and control under the high eutrophication.2.Allelopathic effects of aqueous extract from the different organ of Typha orientalis on seed of four aquatic plants.Results showed that the root,leaf and pollen extract of Typha orientalis had significant effects on germination and seedling growth.The whole trend is promoting in low concentration and inhibiting in high concentration.The order of inhibiting of different parts extracts is leaf extract > pollen extract > root extract,and the effect on radicle greater than seedling.Under the condition of three aquatic extracts,the activity of MDA and SOD showed a trend of ‘up-down' pattern.Thus,the effects of T.orientalis aqueous extracts on seeds of aquatic plants caused membrane lipid peroxidation and destroyed antioxidant enzyme systems which eventually affected the germination and growth of seedlings;meanwhile,leaves were the main organcausing allelopathic effects.3.Through different initial algae density tests found that in the role of Typha orientalis' leaf extract,the growth of algae was not significantly affected when the initial density was 104 ind·L-1.And had a significant inhibitory effect on the microcystis aeruginosa with initial algal density of 106 ind·L-1 and 107 ind·L-1.The inhibition rates on the tenth day were 71.85% and 59.49%.For algaes of the 106 ind·L-1 initiative density,the anti-algae effect of Typha orientalis was the best.The algal inhibitory of different organization parts experiments showed that the inhibitory effects of different Typha orientalis parts were different,leaf extract >root extract>pollen extract.At the 10 th day,the inhibition rates of leaf,root and pollen extract on Microcystis aeruginosa were 72.35%,54.57%,30.7%.Leaves were the strongest algal inhibitory of Typha orientalis.Meanwhil,T.Orientalis extracts have stimulation effect on M.aeruginosa and A.flos-aquae at lower concentrations.With the increasing concentration,the inhibition increased.Meanwhile,the inibition effect on M.Aeruginosa is significantly greater than A.flos-aquae.At day 12 of incubation,the inhibition rate on M.aeruginosa and A.flos-aquae were 91.37% and 65.64% versus T.Orientalis' s concentration at 50 g·L-1.It demonstrates that the allelopathic effect of T.Orientalis' s on the two alga species has a certain selectivity.4.Through the changes of chlorophyll a content,cell membrane permeability,soluble protein content,antioxidant enzyme activity and MDA content in M.aeruginosa and A.flos-aquae,the Inhibitory Mechanism of Typha orientalis on M.aeruginosa and A.flos-aquae were studied.The results show that T.Orientalis extracts have stimulation effect on M.aeruginosa and A.flos-aquae at lower concentrations.With the increasing concentration,the inhibition increased.Meanwhile,the inibition effect on M.Aeruginosa is significantly greater than A.flos-aquae.At day 12 of incubation,the inhibition rate on M.aeruginosa and A.flos-aquae were 91.37% and 65.64% versus T.Orientalis' s concentration at 50 g·L-1.It demonstrates that the allelopathic effect of T.Orientalis' s on the two alga species has a certain selectivity.During the incubation period,the quantity of two alga species' s chlorophyll-a diminished gradully,SOD,CAT,POD activity and MDA content increased initially and dreacsed gradually thereafter.The study demonstrated that T.Orientalis could induce M.aeruginosa and A.flos-aquae's stress,cauing membrane lipid oxidation intensified and damage on cell structures,facilitate chlorophyll-a gedragation and interfere with cell metabolism,influence photosynthesis and eventually inhibit the growth of M.aeruginosa and A.flos-aquae.5.Separation and identification the allelochemicals isolated from Typha orientalis.The results showed that the main allelochemicals from Typha orientalis were phenolic acid,fatty acid,ester,ketone,amide and so on.The joint experiments shows that the combination of o-diphenol and benzoic acid has a significant synergistic effect,and palmitic acid and benzoic acid combination of synergistic effect is not obvious. |
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