EVALUATION OF ALLELOPATHIC ACTIVITY OF RICE PLANTS THROUGH HYDROPONIC CULTURE

摘要

To investigate the differential allelopathic activity of rice plants, the inhibitory activity of water extract of the shoot and root of three rice cultivars, Taichung natine I(TN1) and IAC165(allelopathic rice) and AUS196(non-allelopathic rice), grown in hydroponic culture was evaluated. The release of germination inhibitors by allelopathic rice plants into hydroponic solution was also determined with freshly collected solution and XAD-4 resin desorbate. The degree of the inhibition was quantified in terms of root growth in Echinocloa colona, E. crus-galli, E. crus-galli var. oryzicola, Triantema portulacastrum and Lactuca sativa. The allelopathic activity of rice plants was species specific, and depended on source and concentration. Root length of all test species was inhibited by the different concentrations of shoot extract of allelopathic and non-allelopathic rices. However, of the three cultivars, TN1 showed higher inhibition than the IAC165 and AUS196 in all test species. Water extracts of shoot and roots significantly inhibited root growth in E. crus-galli but the shoot extract gave the greater inhibitory effect on E. crus-galli than the root extract. Root exudate of TN1 inhibited root elongation of E. crus-galli from 2 weeks after transplanting (WAT) and the inhibition was prolonged for 4 WAT. The results confirmed the previous finding of laboratory bioassay that the TN1 had allelopathic activity and produced allelochemicals that inhibit growth of weed species.