Allelopathic Effect of Water Extracts from Two Submerged Macrophytes on Growth of Scenedesmus obliquus

Elodea canadensis and Potamogeton pectinatus L.are submerged plants used for phytoremediation on eutrophic lakes, and Scenedesmus obliquus is one of the pollution indicator species in fresh water.This paper studied the allelopathic effect of water extracts from two submerged macrophytes Elodea canadensis and Potamogeton pectinatus L.on growth of Scenedesmus obliquus.The plants were immersed respectively in distilled water to collect allelochemicals.The results indicated that the water extracts from the two submerged macrophytes had allelopathy on Scenedesmus obliquus and performed by ‘low concentration promoted, high inhibited'.During 7 days of the experiment, the growth of Scenedesmus obliquus was stimulated in the treatment groups with 20% of the water extracts from Elodea canadensis and Potamogeton pectinatus L., while, the experimental groups with 50%~90% of the water extracts had different inhibition on Scenedesmus obliquus, and the allelopathic inhibitory effects increased with the increasing concentrations of the water extracts.The cell concentrations of Elodea canadensis and Potamogeton pectinatus L.in experimental group with 90% of the water extracts were 38% and 32% of those in the control, respectively.These two submerged macrophytes might be a potential candidate for algae control.The EC50(6 d)of Elodea Canadensis and Potamogeton pectinatus L.on Scenedesmus obliquus were 70% and 55%, respectively.From the allelopathic inhibition of algae, the water extracts from Potamogeton pectinatus L.had more inhibitory effects on Scenedesmus obliquus than Elodea canadensis.