Allelopathic effects of aqueous extracts from different parts and root exudates of rice on barnyardgrass

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.The results show that the IR of the aqueous extracts in same rice parts at 5 leaf stage is the highest among 3～6 leaf stages,and the IR of the aqueous extracts from leaves at 5 leaf stage is the strongest.The IR of the root exudates of the rice which are planted in paddy soil to 6 leaf stage is 47.06%,and the IR increases to 64.71% after treated by ADS-21 and decreases to 26.47% after treated by ADS-5;the IR of the root exudates of the rice which are grown in hydroponics to 6 leaf stage is 38.24%,and the IR increases to 58.82% after treated by ADS-21 and decreases to 20.59% after treated by ADS-5.The results implies that the allelopathic effects of the rice root exudates might be mainly resulted from the nonpolar(or weak polar)components,and could be weaken by the polar components.