Estudos do potencial herbicida dos extratos metanólicos do caule e de folhas de Myracrodruon urundeüva Fr. A1L (aroeira preta) sobre a atividade da clorofila e sobre a germinação de sementes

Abstract

The leaves and stalk extracts of the Myracrodruon plant urundeuva Fr All. (black aroeira) were studied with regard its action on the chlorophyll activity and germination of damage plants and cultures. The studies on the germinations had been carried through the cultures Oriza sativa L. (rice), Phaseolus vulgaris L. (beans), Glycine max L. (soybean) and with weed plants Portulaca oleracea L. (beldroega) and Brachiaria brizantha (braquiária). The leaf extract of Myracrodruon urundeúva Fr All. inhibits the germination of the braquiária in the concentration of 1,0 pg.mL'1 without affecting the germination of the cultures, being able to be used in this concentration for the combat of the germination of the braquiária in the crops of soy, bean and rice. The extract of stalk inhibited the germination of soy and stimulated the germination of beans. Therefore, the stalk extract cannot be used for inhibit the germination of damage plants, once it didn't present effect on the same ones. The chlorophyll activity was studied observing chlorophyll fluorescence of extracted chloroplasts of spinach leaves(Sp inacea oleracea L.) and the 2,6-dichlorophenolindophenol (DCPIP) photoreduction. The results on the fluorescence show that, the leaves and stalk extracts promote an alteration in the quantum yield of chlorophyll fluorescence.The deactivation of the electrons acceptor can be following, by two ways, to know: Io) suppression for deactivation of excited States, where the energy, for example, can be wasted in the heat form (extract of the leaf), 2o) light emission increasing the quantum yield (extract of the stalk). DCPIP photoreduction show clearly that the leves extracts and stalk block the electron transference of chlorophyll for the DCPIP, in all the tested concentrations of the leaf extract, reduzing the chlorophyll activity more than 50%. The stalk extract also inhibits this transference of electrons, but in smaller proportion that of leaves, not reaching the value of 50% in none of the used concentrations. The leaf and stalk extracts of the Myracrodruon urundeuva Fr All. (black aroeira) can act as a potential herbicide acting on photosystem 11.