EFFECTS OF AQUEOUS EXTRACT OF RICE PLANTS (ORYZA-SATIVA L.) ON SEED-GERMINATION AND RADICLE ELONGATION OF MONOCHORIA-VAGINALIS VAR. PLANTAGINEA

Laboratory experiments were conducted to examine the allelopathic pote ntials of rice plants (Oryza saliva L.) on seed germination and radicl e elongation of Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laubat. To compare the relative allelopathic potentials of rice plants at different growth stages, aqueous extracts of dried tissues were obtained from the seeds, husks, and seedlings harvested 1 0, 20, 40 and 120 days after seeding. When M. vaginalis seeds were inc ubated in solutions containing aqueous extracts, significant increases in the germination rate were observed for all the aqueous extracts ex cept for the extract of 10 d-old shoots at higher dosages. When partit ioned with ethyl acetate, the germination-promoter(s) in the aqueous e xtracts remained in the aqueous phase while some inhibitors were extra cted with ethyl acetate. In contrast, aqueous shoot extracts added to the incubation media at the same dosage for promotion of seed germinat ion inhibited radicle elongation of M. vaginalis, indicating that the sensitivity of the weed varies between these two growth stages.