Ação alelopática de óleos essenciais de alecrim-pimenta e capimsanto na germinação de aquênios de alface

Abstract

The alecrim-pimenta and the lemongrass produce secondary compounds that can be used in alternative management of weed. The objective of this work was to evaluate the allelopathic effect of the essential oils of alecrim-pimenta and lemongrass in germination of lettuce achenes. It was used mature leaves of both species, and extracted the essential oil by distillation method of drag by water vapor. The bioessay was performed using achenes of crisp-leaf lettuce for summer and arranged in factorial scheme 5 x 2, being five concentrations of 0, 0.25, 0.5, 0.75 and 1.0% and two species of medicinal plants. It was used four replicates of 50 achenes. The oil of lemongrass was more detrimental to the germination of lettuce achenes when compared with the oil of alecrim-pimenta, being this effect dependent of the concentration. Germination of lettuce achenes treated with lemongrass oil declined by 34%, 12% and 75% for concentrations of 0.25%, 0.75% and 1.0%, respectively when compared with alecrim-pimenta oil. The germination speed index, the length and dry weight of hypocotyl and radicle of lettuce seedlings was compromised by the contact of alecrim-pimenta and lemongrass oils. Although there were lettuce achenes germination treated with alecrim-pimenta oil, the percentage of abnormal seedlings was high, which compromises their survival.