[Selective Inhibition of Rice Straw Extract on Growth of Cyanobacteria and Chlorophyta].

Rice straw is supposed to be an environment-friendly biomaterial for inhibiting the growth of harmful blooms of the cyanobacterium . The effects of rice straw extract(RSE) on algal growth, morphologic parameters(cell size), and physiological parameters( Chl-a fluorescence) were investigated using flow cytometry. We examined the selective inhibitory potential of rice straw on four cyanobacterial strains(toxic and non-toxic , toxic , and ), in comparison with inhibitory effects on three common freshwater green algae(, and ). Concentrations from 2.0 to 10.0 g·L of RSE were found to efficiently inhibit the growth of cyanobacteria in a dose-dependent manner, simultaneously modifying the Chl-a fluorescence and cell size. The 50% growth-inhibition concentration(7 d) of (toxic strain), (non-toxic strain) was 1.72, 2.21, 2.92 and 5.72 g·L, respectively. Interestingly, the growth and cell size of and increased with the addition of RSE and colony formation was observed. In the case of , the inhibitory effect of RSE on growth and Chl- fluorescence occurred at 1.0-4.0 g·L, while RSE induced a stimulatory effect on algal growth at 8.0-10.0 g·L. Taken together, the sensitivity of cyanobacteria to RSE was significantly higher than that of and . The higher sensitivity of PSⅡ reaction center of cyanobacteria and the ability to form colonies of green algae may have important implications for the species-specific allelopathic antialgal activity of rice straw.