Allelopathy of oats. I. Assessment of allelopathic potential of extract of oat shoots and identification of an allelochemical

The allelopathic potential of oat (Avena sativa L.) extracts was investigated under laboratory conditions. The ethyl ether-, acetone-, and water-soluble fractions obtained from the extract of oat shoots inhibited the germination and growth of roots and hypocotyls of lettuce (Lactuca sativa L.). The inhibitory activity of the water-soluble fraction was maximum, followed by that of ethyl ether-soluble and acetone-soluble fraction. An active principle of the water-soluble fraction was isolated and its structure was determined by spectral data as l-tryptophan. l-Tryptophan inhibited the growth of hypocotyls and roots of lettuce seedlings at concentrations greater than 0.03 and 0.1 mM, respectively. These results suggested that l-tryptophan may be an allelochemical which affects the growth or germination of different plant species.