Role of phenolic compounds in the antialgal activity of barley straw.

Barley straw decomposing in well-aerated water releases a substance(s) that inhibits algal growth. Phenolic compounds are toxic to algae but are unlikely to be present in sufficient quantities to account for the extended antialgal action of straw. However, straw is antialgal under conditions that may promote oxidation of phenolic hydroxyl groups to quinones; tannins are antialgal under similar conditions. The toxicity of authentic quinones towardsMicrocystis is confirmed; the quinones are some 10(3) times more antialgal than phenolic acids. The possibility that oxidized lignin derivatives may be involved in straw toxicity towards algae is discussed.