Efeitos potencialmente alelopáticos dos óleos essenciais de Piper hispidinervium C. DC. e Pogostemon heyneanus Benth sobre plantas daninhas

This study aimed to characterize the potential allelopathic activity of essential oils of pimenta longa (Piper hispidinervium C. DC.) and oriza (Pogostemon heyneanus Benth), and to examine, comparatively, their allelopathic effects. Essential oils obtained were prepared at concentrations of 0.25%, 0.5% and 1.0%, with ether methanol as eluent, and tested upon the germination of seeds and the development of the radicle and the hypocotyl of the weeds of cultivated grassland areas, malicia (Mimosa pudica) and mata-pasto (Senna obtusifolia). Depending on their concentrations, oils of the two species showed intensities of allelopathic activity on the donor species, on the receptor plant and on the examined plant factor. The germination of seeds was the factor most strongly inhibited by the oils. The intensities of inhibitions were positively related to the concentration, with the maximum inhibitions verified at 1%. Mimosa pudica was the receptor species most sensitive to the effects of oil. In comparison, the essential oil of Piper hispidinervium showed a higher potential for inhibiting the germination and development of the two receptor plants, notably in relation to the germination of seeds, when the differences were more striking. The results were attributed to the chemical composition of oils, especially in relation to the presence of monoterpenes, oxygenated monoterpenes and sesquiterpenes.