ALLELOPATHIC POTENTIAL OF 3 FORAGE LEGUME S ON 3 PASTURE WEEDS

Bioassays were carried out to identify and characterize the allelopath ic potential effects of forage legumes ''leucena'' (Leucaena leucoceph ala), ''mineirao'' (Stylosanthes guianensis cv. Mineirao) and ''calopo ganio'' (Calopogonium mucunoides) on germination and radicle elongatio n of the pasture weeds ''desmodio'' (Desmodium adscendens), ''guanxuma '' (Sida rhombifolia) and ''assa-peixe'' (Vernonia polyanthes). Aqueou s seeds and shoot extracts were prepared in a concentration of 10% (w/ v). The pH and osmotic potential were measured in each extract. The ef fects of the osmotic potential on the results were calculated consider ing the regression equations adjusted to the variations of osmotic pot ential in each parameter and the osmotic potential of the extracts. Th e results showed that the pH did not constitute in a source of variati on of the results. The donor species indicated allelopathic potential that varied in function of donor and receiver species and part of the donor plant. The aqueous shoot extract of ''mineirao'' and ''calopogon io'' showed inhibition potential higher than the extract from seeds, w hile for leucena the effects more evident were obtained with the extra ct from seeds. Comparatively, the radicle elongation was a more sensit ive indicator than germination to the effects of the extracts. The rec eiver species ''assa-peixe'' was the less sensitive to the effects of the extract.