Potential Allelopathic Effect of Ipomoea aquatica to Microcystis aeruginosa Growth

The allelopathic effect of macrophytes to phytoplankton has been widely formalized and accepted, while, less attention has been paid to aquatic vegetable. Herein, we investigated the inhibitory ability of Ipomoea aquatica ( I. aquatica ) at different concentrations to Microcystis aeruginosa , and verified the inhibition effect of main allelopathic substances. Results showed that, I. aquatica root secretion solution could effectively inhibit the growth of Microcystis aeruginosa (95%), and exhibited a concentration dependent effect. Seven potential allelopathic substances was both detected in root exudates and secretion solution of I. aquatic, they were succinic acid, salicylic acid, cinnamic acid, 3-(4-hydroxyphenyl) propionic acid, trans-cinnamic aldehyde, coumarin, and isophorone. Exogenous addition experiment further verified the inhibition effect, and the inhibition level varied with the types. Succinic acid, salicylic acid and cinnamic acid showed the tendency of promotion in lower concentration and inhibition in high concentration, with the inhibition threshold of 0.8 mmol/L, which was positively correlated with its concentration. 3-(4-hydroxyphenyl) propionic acid, coumarin and isophorone showed strong inhibition on Microcystis aeruginosa when the concentration was higher than 0.2 mmol/L, which was positively correlated with its concentration and co-culture time. Ipomoea aquatica can continuously release allelopathic substances under natural conditions and is expected to contribute to the restoration of aquatic ecosystems.