Under natural conditions, the inhibitory rate(IR)of aqueous extracts from different parts of allelopathic rice accession PI312777(planted in paddy soil)in different life stage(3~6 leaf)to the root growth of barnyardgrass were studied. The IR of root exudates at 6 leaf stage of rice planted in paddy soil and in hydroponics and treated by polar resin ADS 21 and nonpolar resin ADS-5 respectively, were tested in the bioassay,too. The results show that the IR of the aqueous extracts in same rice parts at 5 leaf ...