Abstract: Submerged macrophytes and microalgae are important components of the aquatic ecosystem. There may be a competition between them, and submerged plants can often take advantage by allelopathic effects. In order to explore the allelopathic inhibition effect of submerged plants on freshwater microalgae, Scenedesmus obliquus was selected as the test organism, the growth and physiology properties were detected under the Potamogeton Malaianus, Ceratophyllum demersum and their mixed culture condition. The results showed that under the condition of co-culture with submerged plants, the growth of S. obliquus was significantly inhibited, and the chlorophyll content decreased, the chlorophyll autofluorescence changed, which probed the damage of microalgal photosynthetic system, and the increase of malondialdehyde and antioxidant enzymes activities could illustrate the damage of the antioxidant system. All the results proved that both submerged plants and their mixed cultures had strong algae-inhibiting effects, which could lead to a series of damage to algae cells. The above research results would provide a scientific basis for the investigation of the mechanism of allelopathic inhibition, the analysis of related phenotypes, and the ecological relationship between submerged plants and microalgae.

Key words: submerged macrophytes, Scenedesmus obliquus, growth inhibition, physiology properties