| Water eutrophication caused by the rapid development of society has become one of the hot issues in water environment protection.Eutrophication often leads to the abnormal proliferation of algae in water,such as filamentous algae.The decomposition of dead algae will cause declined water quality,moreover,the harmful substances will be enriched in human body through the food chain,which will cause huge damage to human health.The existing methods of removing filamentous algal blooms in water mainly include physical method,chemical method,and biological method.The practical application of physical and chemical methods are limited because the two methods have visible disadvantages.Therefore,the biological method is considered as the most economical and safest one in algae control.Recent years,researchers have founded that the allelopathy between plants will release plant-derived active substance,which can be used as algae suppressant.With good research and application value,the research and development of this algae suppressant becomes the key breakthrough in biological algal control.This article chooses Cladophora sp.as research subject and adopts the progressive method to deeply research the inhibition effect and mechanism of plant extracts and monomer active substances,and explore the potential of practical application of this active substance.The main results of the article can be summarized as follows:(1)The selection and optimization of plant-derived inhibitors for Cladophora sp.First,compared and analyzed the inhibitory effects of three different defoliation extracts on Cladophora sp..The results showed that the inhibitory effect of Ginkgo-leaf extract on the growth and photosynthetic fluorescence parameters of Cladophora sp.was higher than that of Willow-leaf extract and that of compounded extract with Ginkgo leaf and Willow leaf.Second,compared the inhibitory effects of Ginkgo-leaf extract with different extractants on Cladophora sp..The results showed that the inhibitory effects of Ginkgo-leaf extracts with different extractants on the biomass of Cladophora sp.were as follows:acetone>ethanol>chloroform>water;the inhibitory effects on fluorescence parameters of Cladophora sp.were as follows:ethanol>chloroform>acetone>water.Comprehensively,ethanol extract of Ginkgo biloba leaves had the highest algae inhibition effect.Third,compared the algal inhibition effects of different concentrations l of Ginkgo-leaf ethano extract.The results showed that in the range of 0.75 g/L-6.00 g/L,the inhibitory effect of the Ginkgo-leaf ethanol extract on photosynthetic fluorescence parameters of Cladophora sp.improved as the increase of concentration,The inhibition rate of all fluorescence parameters in Ginkgo-leaf ethanol extract with concentration of 6.00 g/L was close to 100%in 96 hours.(2)Inhibition of physiological and fluorescence parameters of different active monomers on Cladophora sp.This part compared and analyzed the inhibitory effect of four monomeric flavonoids active substances with high content in Ginkgo-leaf on Cladophora sp..The results showed that the inhibitory effects of different flavonoids on the biomass of Cladophora sp.were as follows:quercetin>kaempferol>catechin>luteolin;The inhibitory effects of different flavonoids on photosynthetic fluorescence parameters of Cladophora sp.were as follows:quercetin>kaempferol,catechin and luteolin.Comprehensively,quercetin has the highest inhibitory effect on Cladophora sp..(3)The research on the optimization of dosing times of quercetin and its inhibition mechanism for Cladophora sp.First,compared the inhibitory effects of quercetin at different concentrations on Cladophora sp..The results showed that in the range of 100 mg/L-400 mg/L,the inhibitory effect of quercetin on the biomass and photosynthetic fluorescence parameters of Cladophora sp.improved with the increase of quercetin concentration.The quercetin with the concentration of 400 mg/L had the highest algae inhibition effect.Second,compared the effects of different dosing times on algae inhibition.The results showed that the inhibitory effects of different dosage frequencies on the biomass of Cladophora sp.were as follows:four-times dosing>two-times dosing>single dosing;the inhibitory effect on photosynthetic fluorescence parameters of Cladophora sp.were as follows:two-times dosing>four-times dosing>single dosing;the destruction of cell membrane permeability were as follows:two-times dosing>single dosing>four-times dosing.Comprehensively,two-times dosing of quercetin had the highest algae inhibition effect.Third,researched the effects of two-times dosing of quercetin on the enzyme activity system of Cladophora sp..The results showed that quercetin made significant inhibit impact on SOD,ATPase and total protein of Cladophora sp..(4)The toxicological experiment on the safety of quercetinThe experiment chose Vallisneria natans as the representative of non targeted organisms and researched the effects of quercetin on Vallisneria natans and water quality.The results showed that the photosynthetic fluorescence parameter F_v/F_m decreased temporarily for a short time,and no significant difference between the concentration group and the control group after 96 hours.But the photosynthetic fluorescence parameter F_v’/F_m’decreased and then increased under the impact of quercetin of different concentration,showing that Vallisneria natans can adapt to the impact of quercetin under experimental conditions.Comprehensively,quercetin within 500 mg/L would not cause significant damage to the photosynthetic system of Vallisneria natans.After the dosing of quercetin,DO in the water of each experimental group decreased in varying degrees,but increased in the later stage of the experiment,showing that the self purification regulation of water can restore the level of DO in the water to a certain extent.There was no visible effect on p H in each experimental group.TN and TP in 500 mg/L experimental group increased,while in 300 mg/L and 400 mg/L experimental group decreased,Comprehensively,quercetin within 400 mg/L will not cause visible pollution to the water quality. |
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