Abstract: Two common macrophytes Nymphoides peltatum and Hydrilla verticillata were chosen to construct three types of aquatic microphyte communities, i.e., N. peltatum community (floating-leaved), H. verticillata community submerged), and N. peltatum + H. verticillata compound community, which were respectively cultivated in a simulated eutrophic aquatic environment with the blue-green algae introduced from natural water body, aimed to study the inhibitory effects of these macrophyte communities on algal growth. All the test communities showed an evident inhibitory effect, with the sequence of N. peltatum community > compound community > H. verticillata community. By the end of the experiment, the chl-a concentration was decreased by 63.1%, 44.7% and 3.3%, respectively. N. peltatum community had an intensive inhibitory effect on Cyanophyta, whose total cell density was decreased by 99.5%, but the total cell density of Chlorophyta was increased by 31.6%. H. verticillata community showed more inhibition on Chlorophyta, but less impact on Cyanophyta. In N. peltatum + H. verticillata compound community, the total cell density of Cyanophyta decreased by 95.9%, and that of Chlorophyta remained at a lower level. The composition of algae varied with macrophyte communities. In N. peltatum community, the dominant algae changed gradually from Cyanophyta such as Microcystis and Chroococcoid to Chlorophyta such as Chlorella, Tetraedron, and Scenedesmus; in H. verticillata community, Cyanophyta remained dominant, and companied with less species such as Chlorella, Tetraedron, and Cryptomonas; and in the compound community, the variation of algal composition was similar to that in N. peltatum community. During the experiment, the total cell density of Cyanophyta decreased gradually, while Chlorophyta increased. Macrophyte biomass increased markedly, with the wet weight of N. peltatum and H. verticillata in their single and compound communities increased by 129.8% and 63.6%, and 108.8% and 66.5%, respectively. The macrophyte growth showed a distinct influence on the aquatic environment factors such as illumination, temperature and pH. In N. peltatum community, the reduction rate of illumination at water depth 20 cm had a significant correlation with the chl-a concentration in water body, suggesting that N. peltatum’s shading effect was the main cause of algal inhibition.

Key words: Glycine soja, Glycine max, Salt stress, Polyamines(PAs), Polyamine oxidase(PAO) activity, Salt tolerance