Inhibition Of Potamogeton Crispus On Algae And Its Resistance Mechanism To The Stress Of Eutrophicaiton

Frequent outbreaks of cyanobacteria bloom caused by water eutrophicationhas been an extremely important global environment issue. To inhibit the growth ofalgae by allelopathy of higher aquatic plant has become one of the research focusesin the prevention and treatment of water bloom at home and aboard.In order to find higher aquatic plant which can both inhibit the growth ofalgae effectively and has tolerance of the stress of eutrophication, through wideinvestigation and analysis, this study firstly systematically discussed the toleranceand its mechanism of submerged macrophyte Potamogeton crispus which isdistributed widely on the stress of eutrophication, compared the mutual allelophyand its mechanism of Potamogeton crispus with algaes of different densities mixedwith Microcystis aeruginosa and Scenedesmus obliquus, further separated andidentified the allelochemicals from Potamogeton crispus. The results are asfollows:1. study on the stress of eutrophication on Potamogeton crispus The resultsindicated that Potamogeton crispus had a rather high tolerance on the stress ofeutrophication, especially in the middle eutrophication, the biomass ofPotamogeton crispus increased10.58%more than that of control group, whichhad an obviously statistical significance; however, the biomass of Potamogetoncrispus decreased evidently in the high eutrophication which was rich in nitrogen,phosphorus, nitrogen and phosphorus; they respectively reduced7.58%,8.18%and9.93%less than that of control group. The activities of antioxidant enzymes CATand POD and the content of MDA indicated that Potamogeton crispus could resistthe stress of eutrophication by enhancing the express of antioxidant enzymes in themiddle eutrophication to have the best growing condition; nevertheless, in the higheutrophication, the activites of CAT and POD declined substantially, the content ofMDA raised obviously, which indicated that the stress of high eutrophication mightexceed the resistance of Potamogeton crispus and lead to the decline of biomass.Therefore, Potamogeton crispus has extremely important research significance forbioremediation in the middle eutrophication water. 2. study on mutual allelopathy and its mechanism of Potamogeton crispus andcompounded algaes The resuls showed that Potamogeton crispus and algae hadmutual allelopathy in the middle eutrophication. For the compounded algaes of105cells mL-1initiative density of, Potamogeton crispus strongly inhibit the growth ofalgaes by excreting allelochemicals, eapecially on Microcystis aeruginosa; For thealgaes of103cells mL-1initiative density which might not reach the threshold valueto stimulate allelochemicals to excrete, both Potamogeton crispus and algaes couldgrow normally which did not have significant difference compared with respectivecontrol group; For algaes of the107cells mL-1initiative density, inhibition declinedsubstantially, the biomass of Potamogeton crispus decreased, which representedthat Potamogeton crispus had allelopathic inhibition on algae (excluding thecompetition of light and nutrition). The activites of antioxidant enzymes CAT andPOD and the content of MDA indicated: for the algaes of105cells mL-1initiativedensity, Potamogeton crispus caused obvious oxidative damage on algaes;However, For the algaes of107cells mL-1initiative density, algaes gave rise to theoxidative stress of Potamogeton crispus. Hence, only the treatment of water bloomalgaes started at prevention in the early stage, could we get better effect.3. separation and identification of allelochemicals from Potamogeton crispusAfter the fraction was extracted by organic solvent and absorbed by macroporousresin XAD1180and eluted by eluent and then detected by gas chromatographequipped with a mass selective detector(GC-MS), the results showed that the mainallelochemicals from Potamogeton crispus were Methyl isobutenyl ketone,Diacetonealcohol,4-Methyl-1-pentanoylbenzenes, β-Methylnaphthalene andGlyceryl Monostearate and so on. These substances are inclusive of unsaturateddouble bonds, liable to cause the chain reaction of free radicals and a series ofoxidative damage in the cells. Thus, identification of allelochemicals providesstrong proof for the the algae inhibition and allelopathy of Potamogeton crispus.In conclusion, Potamogeton crispus not only can grow exuberantly in themiddle eutrophication but also has favorable inhibition on algaes of certain density.Potamogeton crispus is distributed widely in the water in our country, so theprevention and treatment of algal bloom by Potamogeton crispus has a goodapplication prospect.