Allelopathic Inhibitory Effects Of The Crude Extracts Of Eichhornia Crassipes On Microcystis Aeruginosa

In recent years, the algal bloom caused by eutrophication breaks out frequently, and it causes serious threat to human society. There are many defects in the traditional physical, chemical and biological control methods, and the governance effect is limited. Using allelopathy is a lasting and effective means to control the algal bloom, and have been receiving more and more attention for the broad prospects.Microcystis aeruginosa is the most common algae type of water bloom, so its inhibition study is helpful to control water bloom. In the experiment, we examined the removal effects of the extracts from Eichhornia crassipes roots on Microcystis aeruginosa, and explored the inhibitory modes of allelochemicals on algae. The experimental results are summarized as below:(1)The chemical substances in water extracts from Eichhornia crassipes roots inhibited the growth and reproduction of Microcystis aeruginosa. The inhibitory effect was enhanced by the increasing concentration. We extracted the allelochemicals by using methyl alcohol. When the methyl alcohol extract was less than1.0mg/mL, it would promote the growth of algae. But if the methyl alcohol extract was more than1.5mg/mL, the growth of algae could be inhibited.(2) The allelochemicals of Eichhornia crassipes were extracted by the means of petroleum ether solvent, ethyl acetate solvent and n-butanol solvent. Petroleum ether fraction didn’t have the inhibition activities to the growth of Microcystis aeruginosa, but ethyl acetate and n-butanol fractions had, and ethyl acetate fraction was the best extract. After10d cultivation the inhibition rates of ethyl acetate extract were over70%against the growth of Microcystis aeruginosa. The active substances of Eichhornia crassipes mainly existed in ethyl acetate extract.(3)The results of anti-algal mechanism show that the allelochemicals extracted from Eichhornia crassipes roots can affect the physiological and biochemical reaction. When the ethyl acetate extract was added into cultural liquid, the rate of photosynthetic oxygen evolution and respiration oxygen consumption declined obviously; soluble protein content decreased; the SOD activity, POD activity and MDA content of algal cell were slightly increased first and then presented a urgent decline.(4)Using the high performance liquid chromatography (HPLC) to analyze the ethyl acetate extract, we found that the composition of extract is very complex and there are two kinds of algal inhibiting substances:N-phenyl-1-naphthylamine and N-phenyl-2-naphthylamine.