Allelopathic effect of organic acids from Canna indica on Microcystis aeruginosa

The organic acids were obtained from aqueous leachates of Canna indica leaves by liquid-liquid extraction. The allelopathy effects of the organic acids were studied, the results showed that organic acids could promote the physiological metabolism at low concentrations and inhibit the metabolism at high concentrations. The average inhibitory rates reached 98.57% and 99.37% after six days with the addition of 13.3 g/L and 20.0 g/L organic acids from Canna indica leaves, respectively. The content of chlorophyll decreased, whereas T-SOD and CAT activities increased initially and decreased gradually, suggesting that the growth of Microcystis aeruginosa was inhibited probably by the damage of antioxidant systems and decrease in the content of chlorophyll. The organic acids were further analyzed by gas chromatograph-mass spectrometry (GC-MS)and a total of 32 organic acids were identified, including 18 saturated fatty acids, 7 unsaturated fatty acids, 5 aromatic acids and 2 phenolic acids.