Study On Antifungal And Mechanism Of Plant Allelochemicals

Recent years,cyanobacteria bloomed frequently,causing ecological disasters with rivers and lakes,harm to water ecosystems,threatening human health,and leading to enormous energy and finance to study formation mechanism and controlling technologies of algal blooms.Without effective method of cyanobacteria blooms prevention,emergency management has become the last insurance.There are a series of methods such as chemical methods,physical methods,and ecological methods to treat cyanobacteria blooms.However,there are a large number of problems and defects with each method,and it is urgently to develop one method for treating algal blooms that without secondary pollution.Allelochemical technology is a new type of algal bloom treatment technology between biological and chemical methods,which Itutilizing the secondary metabolites or extracts of plants or microorganisms for algal bloom treatment,it has injected new vitality with the emergency treatment of algal blooms.The method has the advantages of ecological safety,environmental affinity and selectivity.However,how toget effective allelopathic material and reveal the mechanism of algae suppression has become the focus.This study identified the community structure of phytoplankton in Tianjin River,and analyzed the species composition of phytoplankton both time dimension and spatial dimension.The results show that the growth of algae in Tianjin River is mainly concentrated in July,August and September.They are evenly distributed throughout Haihe River Basin.Among them,the total number of Cyanophytas is highest,followed by Chlorophyta and Diatomophyta,and Cryptophyta has the longest growth time.Traditional Chinese medicine was conducted as a source of allelochemicals,four different Chinese herbs,Rhubarb,Polygonum multiflorum,Cassia and Polygonum cuspidatum were used for algal inhibition tests.The results showed that the crude extracts of Cassia obtusifolia,Polygonum multiflorum,Polygonum cuspidatum,and rhubarb behaved inhibitory effects on the growth of cyanobacteria.The algal inhibition rates were 5.44%,11.1%,22.2%and 60.0%,respectively.Rhubarb extract showed significant inhibitory effect on M.aeruginosa.During study of inhibitory effect,rhubarb organic extracts inhibited the growth of M.aeruginosa.After 16 days,the inhibition rate of n-hexane phase was 5.93%,the inhibition rate of ethyl acetate phase was 68.0%,ethyl acetate was opposite to M.aeruginosa.It is indicating that the ethyl acetate phase contains a large number of effective allelochemicals.Further experiments showed that the inhibition rates of ethyl acetate relative to chlorophyll a and carotenoid were 68.1%and 38.8%,respectively.Ethyl acetate showed significant inhibitory effects on phycobiliproteins of cyanobacteria.The inhibition rates of phycocyanin,algae protein,and phycoerythrin were 95.3%,74.6%.and 42.4%,respectively.Ethyl acetate had a significant inhibitory effect on algal toxins.After four days running,the content of algal toxins gradually declined to detection limit,and the inhibition rate was near to 100%.This means thubarb organic extracts can be used as an effective allelochemical source.Furthermore,the inhibition and mechanisms of the four extractions of rhubarb organic extracts against the growth of Microcystis aeruginosa,including chlorophyll a,carotenoids,phycobiliproteins,soluble proteins,MDA and the the concentration of algal toxins were studied.The results showed that the ethyl acetate phase,n-butanol phase and water phase had significant inhibitory effects on algae,leading to hollow with the surface of the cyanobacterial cells,and the algae cells were deformed as surface shrinks.Algal toxins decreased obviously.After four days treatment,the alginate was reduced to detection limit with ethyl acetate phase.After 16 days treatment,the content of algae toxin in the n-butanol phase and the aqueous phase decreased to detection limit as well.The inhibition rate of algal toxins was close to 100%.Lastly,infrared spectra analysis,nuclear magnetic resonance spectroscopy and LC-MC analysis were conducted with four extractants of rhubarb.Results showed that four kinds of organic extracts all contained free glycosides of emodin,chrysophanol,rhein,and emodin.Substances with significant inhibitory effects in the ethyl acetate phase,n-butanol phase,and water phase were all contained free alum compounds of aloe-emodin,emodin,chrysophanol,rhein,and emodin.It provides a basis for further study of key allelochemicals components.