Ferns exhibit a strong pattern of dominance in the areas in which they grow, forming almost pure associations, where only a few species coexist. Ethanol extractions of five species of Pteridaceae, in concentrations of 250, 500 and 1,000mg.L-1, were evaluated using germination and growth bioassays under laboratory conditions, to verify the potential for allelopathic activity against Lactuca sativa (L.) strain Grand rapids (lettuce) and Allium cepa (L.) strain Baia periforme (onion). Adiantopsis radiata (L.) Feé, Adiantum serratodentatum Willd. and Pteris denticulata Sw. var. denticulata were collected at the Fazenda Azulão, situated in the municipality of Dourados, MS, Brazil, while the species Adiantum tetraphyllum Willd. and Pityrogramma calomelanos (L.) Link var. calomelanos were collected at the Fazenda Curupi, situated in Ponta Porã, MS, Brazil. The bioassays carried out revealed the following: 1) the five vegetal extracts did not significantly interfere with the germination of the lettuce or onion; 2) the extracts of Adiantum serratodentatum, Adiantum tetraphyllum, Adiantopsis radiata, and Pityrogramma calomelanos inhibited the radicular growth of the lettuce seedlings; 3) Adiantum serratodentatum, Adiantum tetraphyllum, and Pteris denticulata inhibited the growth of the hypocotyls of lettuce; 4) Adiantopsis radiata, Adiantum serratodentatum, and Pteris denticulata inhibited both the growth of the radicles and the coleoptiles of the onion seedlings. The results obtained so far permit the conclusion that the ethanol extracts of the species studied contain substances that modify the growth of lettuce and onion seedlings.
allelochemicals; germination; growth; fern; lettuce; onion