Aqueous extracts from leaves and bark of "Acapu" plants were prepared in concentration levels of 0, 1, 2, 3 and 5% to identify and characterize potential allelopathic activity of such plants. The extract effects on seed germination and primary root elongation of pasture weeds, such as Mimosa pudica and Urena lobata, were analyzed. The germination bioassays were developed under 25 ºC and a photoperiod of 12 hours. For the primary root elongation, the bioassay conditions were 25 ºC and photoperiod of 24 hours. The results indicated a variation in response, according to the source of aqueous extract, the analyzed parameter and the extract concentration. The reductions observed both in germination and primary root elongation increased with the increase of extract concentration. The most intense effects were observed at an extract concentration level of 5%. Regardless of the receiving species and the analyzed parameter, the extract prepared from the bark showed greater inhibiting allelopathic activity. The parameter primary root elongation was more sensitive to the potential allelopathic effects than seed germination. Comparatively, bark and leaves showed differences in relation to the chemical compound classes. Cumarins were identified in the bark but not in the leaves, while steroids and triterpenoids were observed in the leaves but not in the bark.
allelopathy; germination; Cumarins; steroids; triterpenoids
