In vitro studies, soil was incubated with 5,7,40-trihydroxy-30,50-dimethoxyflavone or root exudates of allelopathic PI312777 and non-allelopathic Liaojing-9 under flooded and non-flooded conditions, respectively. Both root exudates and the flavone
increased dehydrogenase activities under both flooded and nonflooded conditions.