Magnolia denudata(M. denudata) leaf litter extract(MDLLE) was tested on the response of Microcystis aeruginosa(M. aeruginosa). The inhibition of M. aeruginosa increased from 7.6% to 49.8% at 0.4 g·L^(-1) dosage while it increased from 15.7% to 77.4 % at 2.0 g·L^(-1) dosage during 15 days of incubation. The parameter variation of relative electron transport rate(rETR), maximal quantum yield(Fv/Fm ), and electron transport rates(rERTmax) indicated that photosynthesis was an important target impaired by MDLLE, including the photosynthetic center photosystem II(PSII) of M. aeruginosa which demonstrated from the rapid light curves(RLCs). The results of Chlorophyll-a(Chl-a) fluorescence, RLCs, and fluorescein diacetate(FDA) staining assays were consistent with those of growth inhibition tests. The results demonstrated that the application of MDLLE offered great potential on cyanobacterial blooms control especially at the initial stage of development. Furthermore, several kinds of volatile chemicals had been isolated in MDLLE, and the role on suppression of growth for M. aeruginosa should be further studied separately.
