Hydroalcoholic extracts from shoot, roots and seeds and seed raw extracts from Canavalia ensiformis were prepared to identify and characterize their potential allelopathic effects on seed germination and radicle elongation of the weeds Mimosa pudica, Urena lobata, Senna obtusifolia, and Senna occidentalis. The germination bioassay was carried out at 25 ºC and a 12-hour photoperiod, and the radicle elongation bioassay at 25 ºC and a 24-hour photoperiod. Distilled water was used as the control treatment. The effects varied according to the receiving species, concentration and part of the donor plant. Germination and radicle elongation inhibition were directly proportional to the concentration of the extract, with the most active inhibition being observed at the concentration of 4.0%. Regardless of the receiving species, seeds and roots were the main source of compounds with allelopathic activities. The analysis of different raw extracts showed that the compounds with potential allelopathic activity have polarity between ethyl acetate and methanol. For the raw methanol extract, concentration higher than 0.4% had a completely inhibitory effect on the seed germination of the receiving species, with 0.6 and 0.8 concentrations being also inhibitory for M. pudica and S. occidentalis germination. The sensitivity of the receiving species varied in the following decreasing order: M. pudica > S. occidentalis > S. obtusifolia > U. lobata.
allelopathy; germination; inhibition; weed; radicle; seed
