Identification and Quantification of Physiologically Active Substances Contained in Water Immersion of Fresh and Incinerated Barley Straw

Abstract

As part of a study to clarify the mechanism of the allelopathic activities in barley straw on the early development of paddy weeds in northern Kyushu, we examined the effect of water immersion taken from fresh straw and incinerated straw (ash) on seed germination of mustard spinach (Brassica rapa var.perviridis) seeds. Water immersion from fresh straw inhibited the germination of mustard spinach, while that from the ash did not. Since a similar trend was observed with or without addition of soil to the water immersion, the inhibitory effect of mustard spinach on seed germination was considered to have derived directly from the fresh straw or its ash rather than from a degradation metabolite of the straw by soil microorganisms. The water immersions from fresh straw and their ash were examined for phenolic substances using liquid chromatography/TOF-mass spectroscopy. As a result, five active substances were identified, and (±)-2-phenylpropionic acid at a concentration of 2 ppm was found to markedly inhibit the seed germination of mustard spinach.