Two extracts of Magnolia grandiflora linn,hexane extract and butanol extract,were found having strong inhibitory effects on Microcystis aeruginosa by our previous studies.In order to probe the anti-algal mechanism of these two extracts,the content of chlorophyll-a,superoxide dismutase(SOD),membrane permeability and ultrastructure of Microcystis aeruginosa that treated by this two extracts were investigated.The results showed that content of chlorophyll-a was declined rapidly,the SOD activity of algal cell w...