ALLELOPATHIC EFFECTS OF AQUEOUS EXTRACTS FROM SIX HYGROPHYTE SPECIES ON ACTIVITIES OF P. JAPONICA

Little has been reported on ecological characteristics of Phragmites japonica Steud. (Poaceae), perhaps due to its narrow distribution in the Far East. In this study, therefore, allelopathic effects of aqueous extracts (5.0 g L-1) from leaves or stems of six hygrophytes, Typha latifolia L., Phragmites australis (Cav.) Trin., Lythrum salicaria L., Phalaris arundinacea L., Phragmites japonica Steud. and Scrirpus tabernaemontani Gmel., on the activities of P. japonica seed and epigeal stolon were assayed under laboratory conditions, and growth after transplanting was also evaluated. All aqueous extracts from six hygrophytes produced no inhibition on seed germination. The radicle length of the seedlings, however, was inhibited by treatment with aqueous extracts from leaves of P. australis, L. salicaria and P. arundinacea (35.5-57.2% of untreated control). Further, these inhibitory effects on the radicle length of the seedlings are likely caused by some kind of allelochemicals, based on the lack of effect with preparations of the aqueous extracts on a polymeric absorbent (Amberlite XAD-4 resin). For epigeal stolon activity, no negative effects were observed for aqueous extracts of any of the hygrophytes. Dry weights of the above-and below-ground organs formed from epigeal stolon also reached 7.3 times of those of seedlings after the transplanting.