Allelopathic Effection By Three Kinds Of Aquatic Plants Root Water Extract On Pseudanabaena Sp.

In recent years,water eutrophication,a global environmental issue was increasingly severity by human activities.Eutrophication could cause an explosion in growth of phytoplankton and form algal blooms with multiple dangers,such as contaminated water,injured human and animals healthy by releasing algal toxins,etc.Therefore,seeking economical,effective and ecologically-safe ways to control algae has become a hot spot in the water environment and using allelochemical released by plants to control harmful algal blooms has great applicative prospect.Pseudanabaena sp.has been a preponderant algae specie in a cascade reservoir group in South China and has been proved to be 2-methylisoborneol?2-MIB?producer.But research about its effectives control method is very limited.The research compared the inhibitory effects of different concentrations of three kinds of aquatic plants root water extract on the Pseudanabaena sp..The root water extract were extracted from the roots of the Hydrocotyle vulgaris,Spathiphyllum kochii and Anthurium andraeanum.The allelopathic effects of root water extract from three kinds of aquatic plants on algae growth and different initial concentrations of algae were introduced.The optimal concentration of root water extract to control algae was established through comparing algal growth inhibition rates.We analyze the effects of three kinds of aquatic plants root water extract on photosynthesis and the mechanism of algae inhibition in physiological.The photosynthetic activities of Pseudanabaena sp.in three kinds of plants root extract were investigated by determining photosynthetic parameters,namely the maximal quantum yield?Fv/Fm?,the relative electron transport rate?r ETR?,semi-saturated light intensity?Ik?,the light energy utilization efficiency???.The effects of allelochemicals on the physiology of Pseudanabaena sp.were studied by measuring the activities of SOD,POD and the concentrations of MDA in the algae.?1?We studied the allelopathic effects of Spathiphyllum kochii,Hydrocotyle vulgaris and Anthurium andraeanum on Pseudanabaena sp with 5 levels of root water extract concentrations,finding that they can promote the growth of Pseudanabaena sp.when exposed to 2 and 4 g·L^-1 root water extract.The concentrations of root water extract had inhibitory effect on algal growth started from 6g·L^-1 and the allelopathic inhibition was positively correlated with the concentrations of root water extract.The Spathiphyllum kochii root water extract has strongest inhibitory effect on algal growth followed by Anthurium andraeanum root water extract and the weakest is Hydrocotyle vulgarisroot water extract.The highest inhibition rate of Pseudanabaena sp.is 99.95% under 10g·L^-1 Spathiphyllum kochii root water extract on the 22 nd day.?2?Studies on the photosynthesis of algae showed that aquatic plants root water extract could inhibit the chlorophyll fluorescence parameters.When the concentrations of water extract were 6 g·L^-1,8 g·L^-1 and 10 g·L^-1,obvious allelopathic inhibition on Pseudanabaena sp.was observed.Values of Fv/Fm,r ETR and Ik were all significantly lower than the control group,indicating that the photosynthesis of algae were impaired.?3?Studies on the physiological activities of algae showed that the enzyme system of Pseudanabaena sp.was affected.The amount of reactive oxygen species in algae increased substantially,and the SOD,POD activities of Pseudanabaena sp.were significantly lower than the control group,the c?MDA?of Pseudanabaena sp.was significantly higher than the control group on the 20 th day.That means the allelopathic effects may lead to the lipid peroxidation of the algae cells and algae cells were injured seriously.?4?The initial concentrations of algae have significantly effect on allelopathic inhibition.The inhibition rates were extremely high at low inoculation concentrations of algae.The inhibition rate of algae reached 100% with the inoculation concentration was 30 ?g·L^-1.The Hydrocotyle vulgaris root water extract can effectively reduce the concentration of 2-MIB,when the Pseudanabaena sp.initial concentration is 30?g·L^-1,Hydrocotyle vulgaris root water extract dosage is 8 g·L^-1,the remove efficiency of 2-MIB could reach 77%.