Abstract: Using pure culturing Scenedesmus obliquus with different concentrations of Oenanthe javanica extracts, the effects of O.javanica on the growth, chlorophyll content and structure of S.obliquus were studied. The results showed that 10 g·L^-1 O.javanica extracts significantly promoted the growth of S.obliquus, and 20 g·L^-1 O.javanica extracts increased the algae chroma and chlorophyll content of S.obliquus till the third day, and then caused obvious inhibition. 30-50 g·L^-1 O.javanica extracts inhibited the algae chroma and chlorophyll content observably on the second day, and intensified with time extension and concentration increase. When the growth of S.obliquus was affected by 20 g·L^-1 O.javanica extracts, the cell wall broke and even disappeared, cells of chloroplast swelled and even disintegrated, the nuclear broke, and the nuclear mass exosmosed. The results indicated that O.javanica extracts had allelopathy on S.obliquus, and lower concentrations promoted the growth, while higher concentrations inhibited.

Key words: Oenanthe javanica, extracts, Scenedesmus obliquus, growth, chlorophyll, ultrastructure