Concurrently Inhibitory and Allelopathic Effects of Allelochemicals Secreted by Myriophyllum Spicatum on Growth of Blue-green Algae

Abstract

The objectives of this study were to determine (i) the concurrent action of four polyphenols ; pyrogallic acid, gallic acid, (+)-catechin and ellagic acid secreted by Myriophyllum spicatum on their inhibitory effects on growth of blue-green algae (Microcyctis aeruginosa) and (ii) their contribution to allelopathy between M. spicatum and M. aeruginosa.
Comparing the inhibitory effects of a mixture of the four polyphenols with those expected by Colby's equation suggested that the mixture of the four polyphenols caused synergistic growth inhibition of M. aeruginosa. There was much difference between the EC₅₀ (the concentration inhibited normal growth of M. aeruginosa by 50 %) of each polyphenol and an apparent concentration detected in the culture solution of M. spicatum, because the four polyphenols were easily autoxidized in the culture solution of M. spicatum. Total amounts of the four polyphenols secreted from M. spicatum were estimated from their apparent concentrations and their autoxidation rates. The artificial solution was prepared based on the total amounts of the four secreted polyphenols. A comparison of the inhibitory effects of the culture solution of M. spicatum with those of the artificial culture solution prepared by using the four polyphenols was made on the basis of the equivalent M. spicatum concentrations of both culture solutions. The results showed that the four polyphenols could contribute to the allelopathic effects of M. spicatum at 10-100%.