Navegando por Assunto "Mata-pasto"

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Acesso aberto (Open Access)
Aleloquímico produzido pela gramínea forrageira Brachiaria humidicola
(2005-03) SOUZA FILHO, Antonio Pedro da Silva; PEREIRA, Angela Albertina Gaspar; BAYMA, Joaquim de Carvalho
The traditional methods of weed control in cultivated pasture do not meet society's present and future needs of protecting natural resources and life quality. An alternative to this problem could be the use of secondary metabolites produced by plants. These products present few risks to the environment and meet society interests. Therefore, this research was carried out to isolate, identify and characterize the allelopathic activity of chemical compounds produced by the forage grass Brachiaria humidicola. The allelopathic effects of the extracts, fractions and compound were tested on seed germination and root elongation of the weeds Mimosa pudica, Senna obtusifolia and Senna occidentalis. Germination bioassays were developed under 25 ºC and a photoperiod of 12 hours. For root elongation, the bioassay conditions were 25 ºC and photoperiod of 24 hours. Hydromethanolic extract was used as a source for isolating and identifying p-coumaric acid. The allelopathic effects were positively related to p-coumaric acid concentration, weed species and the evaluated parameter. Comparatively, S. occidentalis and M. pudica showed the greatest sensitivity to the allelopathic effects. For S. obtusifolia no allelopathic effects promoted by p-coumaric acid on seed germination or on root elongation could be detected under the concentration of 1.0 and 8.0 mg L-1. Root elongation was more sensitive to p-coumaric acid allelophatic effects than seed germination.
Acesso aberto (Open Access)
Atividade alelopática de substâncias químicas isoladas da Acacia mangium e suas variações em função do PH
(2010) LUZ, Sylmara de Melo; SOUZA FILHO, Antonio Pedro da Silva; GUILHON, Giselle Maria Skelding Pinheiro; VILHENA, Karyme do Socorro de Souza
The aim of this study was to isolate, identify and characterize the allelopathic activity of the substances produced by Acacia mangium and to determine the variations of this activity according to the pH variation of the solution. The allelopathic activity was evaluated in germination bioassays (at 25 oC and under 12-12 h light-dark cycle) and radicle and hypocotyl development (at 25 oC and under 24-24 h light-dark cycle) of the weed species malicia (Mimosa pudica) and mata-pasto (Senna obtusifolia). The influence of the pH (3.0 and 9.0) of the solution in the allelopathic activity of the substances on seed germination of the same species was evaluated. The triterpenoids Lupenone (3 oxolup-20(29)-ene) and Lupeol (3β-hydroxylup-20(29)-ene), obtained from fallen leaves of the donor plant, separately and in pair, showed low allelopathic effects on seed germination and hypocotyl growth, especially on the former, with effects showing values lower than 2%. The effects on radicle growth were higher than the other two, reaching values above 40%, especially inhibition promoted by the substance Lupenone. Separately, each substance showed higher effects than those observed when tested in pair, indicating the existence of antagonism. The pH of the solution influenced the allelopathic activity of the substances; for Lupenone, the effects were more intense at acidic pH, while for Lupeol, best results were observed under alkaline conditions, showing that this is an important factor to be considered in field works.