Inhibitory and promotive allelopathy in rice (Oryza sativa L.)

Studies on allelopathic rice, which inhibits the germination and development of weeds such as barnyardgrass ( Echinochloa spp.) and ducksalad Heteranthera limosa (Sw.) Wild.], have been strongly conducted in the USA, the Philippines, Japan, Korea, and other countries since the 1980s. Weed-suppressing rice plants can compete with weeds for light and mineral nutrients by their rapid and thick growth characteristics, and probably also by their allelopathic effects. It was suggested that allelopathic properties were inherited from parents. Different screening methods for finding allelopathic rice simply and rapidly have been proposed. In contrast, stimulative allelopathy in rice, which promotes germination of the dormant and dormancy-awakened seeds of Monochoria vaginalis (Burm. f.) Kunth var. vaginalis , has been investigated by the authors since the 1990s. Rice seeds promoted the germination in the dark and in light under submerged conditions. Our experiments suggested that rice seeds, hulls, plants and straw contain stimulative substance(s) that promote seed germination of M. vaginalis .