Other tools for weed management should be considered in addition to the use of herbicides. In this context, the identification and use of allelopathic compounds deserves attention. Question: To quantify phenolic compounds and evaluate the allelopathic potential of extracts of Conyza sumatrensis on the germination of Bidens pilosa. Studied species: Conyza sumatrensis (Retz.) E.Walker, Bidens pilosa L. (Asteraceae) Study site: Palotina, state of Paraná, Brazil. Methods: The aqueous extracts were

more »

... repared with shoot and root portions of C. sumatrensis in concentrations: 0, 1, 5 and 10 %. Germination and germination speed index were evaluated. The total flavonoids and phenols of the tested extracts were also quantified. Results: With increasing concentrations of the extracts there was an increased inhibition of germination of B. pilosa and delays in the germination process. The extracts from the shoot of C. sumatrensis had a more expressive effect on seed germination when compared to the extracts obtained from the root. At concentration of 10 %, the extract from the shoot reduced in 83 % the percentage of germination. This may be related to the higher concentration of total flavonoids and phenols found. Conclusion: The allelopathic potential of C. sumatrensis plants can be considered since both shoot and root extracts inhibited and/or reduced the germination of B. pilosa.