Allelopathic Effect Of The Rice Straw Aqueous Extract On The Growth Of Microcystis Aeruginosa

Harmful algae blooms(HABs)as a result of eutrophication have been an urgent problem in the area of water resources protection.In China,the eutrophication of freshwater lakes such as taihu lake and dianchi lake has not been well controlled until now.Allelopathic algicides are regarded as potential natural resources to constrain HABs for their exclusive and efficient characteristics.Previously,the allelopathic effect of rice straw has received great attention,but most of them are focused on herbicides to inhibit barnyard grass.In this dissertation,the basic concept and pollution status of eutrophication in China has been described,and summarized the treatment means of landscape water eutrophication.Applications and mechanisms of allelopathic algae,especially by the plant allelopathic were reviewed.Based on the widely reported validity of algal inhibition effects by occidental type of barley,effects and action modes of the most important crop in our country,rice straw were studied.The oberservations in this work will provide a theoretical gist and technology guide for the use of rice straw methods in algal control filed.The main experimental results are as follows:(1)The results revealed that a dosage of 4.0–10.0 g L-1 of rice straw aqueous extract could markdely constrain the growth of M.aeruginosa(Microcystis aeruginosa).(2)In contrast to the control group,the algal biomass of M.aeruginosa at all high concentration tested concentrations were observably reduced during the whole experiment period and exhibited a concentration-dependent trend.When the dosage of the rice straw aqueous extract was 10.0 g/L,the largest inhibition rate could be up to 98%,almost no algae growth was observed.(3)The results showed that Chl-a as one of primary photosynthetic pigment in cells was damaged by rice straw aqueous extract.The oxidative enzyme activity including MDA content,SOD activity,CAT activity,and GSH content showed a trend which firstly increasing and then decreasing.Rice straw could release allelochemicals to inhibit activity of antioxidant enzyme system in M.aeruginosa,and thus the algal could not scavenge intracellular free radicals,leading to that highly reactive an d toxic free radicals could react with M.aeruginosa cells,terminating the algal growth.