However, inhibitory activities of rice seedlings incubated in 0.01 N medium against barnyard grass root and shoot growth, respectively, were still 1.9- and 1.7-fold less than those of rice seedlings incubated with barnyard grass (Fig. 1A). Themomilactone B concentration in rice seedlings incubated with 0.01 N medium was 2.7-fold less than in rice seedlings incubated with barnyard grass (Fig. 1B). Therefore, there may be some other mechanism by which allelopathic activity and momilactone B concentration are increased in rice seedlings by mixed-incubation of rice with barnyard grass, other than potential nutrient competition between two species.