Fitotoxicidade de extratos foliares de barbatimão [Stryphnodendron adstringens (Mart.) Coville] em bioensaio com alface

Abstract

Chemical substances can modulate the growth and development of adjacent plants, phenomenon known as allelopathy. The aim of this work was to evaluate the phytotoxic action of barbatimão leaf extracts in lettuce bioassay. We obtained the aqueous, acetonic and water fraction extract of barbatimão leaves. To develop the bioassay parameters were used: germinability (G%), germination speed index and mitotic index were studied. Seeds of lettuce (Lactuca sativa L.) were exposed to concentrations of 5, 10, 25 and 50mg mL-1 of the extract and distilled water was used as control. All extracts reduced the G(%), delayed germination and affected cell division. The aqueous and acetone extracts inhibited germination even at lower concentrations, which was not observed for the aqueous fraction. Although the root protrusion occurred in 70% of the seeds, on average, meristematic root region proved to be oxidized and, after 72 hours, no longer increased, due to degradation of its tissues, indicating phytotoxic action of the extracts. The results obtained indicate the presence of chemical inhibitors in the extracts, indicating an allelopathic potential of the extracts evaluated.