Bioatividade de extratos hidroalcoólicos de Cymbopogon citratus (DC.) Stapf. sobre picão-preto (Bidens pilosa L.) e alface (Lactuca sativa L.)

Abstract

RESUMO:Este trabalho visou avaliar a bioatividade de extratos hidroalcoólicos de capim-limão sobre germinação e crescimento inicial da planta daninha picão-preto (Bidens pilosa L.) e da planta teste alface (Lactuca sativa L.). A partir de maceração hidroalcoólica de folhas secas e rasuradas (127,46 g) de capim-limão em 1L de álcool de cereais (70%), foram preparados os tratamentos como extratos hidroalcoólicos (HA) pela diluição (v/v) do macerado filtrado em água deionizada na proporção 1:1 (HA1:1) e 1:2 (HA1:2); dos quais foram obtidos os respectivos extratos secos (ES), a partir da evaporação da fase líquida de duas alíquotas de 50 mL de cada extrato HA, que após re-suspendidas em igual volume de água, sendo uma autoclavada (1 atm por 15 minutos), resultando nos extratos secos de HA1:1 e HA1:2 autoclavados (ES1:1A e ES1:2A) e nos extratos secos não autoclavados (ES1:1 e ES1:2); e água (AG) como controle. No primeiro dia dos bioensaios, foram aplicados 2 mL dos tratamentos, em DIC, com cinco repetições. Avaliou-se a porcentagem de germinação (G%), Índice de Velocidade de Germinação (IVG), altura da parte aérea (AA) e comprimento de radícula (CR) de aquênios (25) de picão-preto e de alface distribuídos em placas de Petri e mantidos em câmara de germinação (B.O.D.) por duas semanas. Os extratos HA1:1 e HA1:2 inibiram a G%, AA e CR das duas espécies. Todos os extratos secos reduziram a G%, IVG e o CR da alface. Para o picão preto, apenas o extrato ES1:1 reduziu a G% e o IVG foi reduzido por todos os extratos, a exceção do ES1:1A, mas nenhum extrato influenciou o crescimento inicial desta espécie.Palavras-chave: alelopatia, extrato seco, planta daninha, planta medicinal ABSTRACT: Bioactivity of hydroalcoholic extracts of Cymbopogon citratus (DC.) Stapf. on germination and early growth of beggartick (Bidens pilosa L.) and lettuce (Lactuca sativa L.). This study aimed to evaluate the bioactivity of hydroalcoholic extract of lemongrass on the germination and early growth of the weed plant beggartick (Bidens pilosa L.) and the test plant lettuce (Lactuca sativa L.). From the hydroalcoholic maceration of dried and cut leaves of lemon grass (127.46 g) in 1 L grain alcohol (70%), the following treatments were prepared, hydro-alcoholic (HA) extracts by diluting (v/v) the macerate in deionized water at 1:1 (HA1:1) and 1:2 (HA1:2) proportions, obtaining the respective dried extracts (DE) from the evaporation of the liquid phase of two 50-mL aliquots of each HA extract; after resuspension in the same water volume, one aliquot was autoclaved (1 atm for 15 minutes) resulting in HA1:1 and HA1:2 dried autoclaved extracts (DE1:1A and DE1:2A) and in dried non-autoclaved extracts (ES1:1 and ES1:2), and water as control. On the first day of bioassays, 2mL of treatments were applied, in completely randomized design, with 5 replicates. Germination percentage (G%), Germination Speed Index (GSI), shoot height (SH) and radicle length (RL) of achenes (25) of beggartick and lettuce were evaluated after having been distributed in Petri dishe...

Phytotoxic activity of extracts obtained from cagaita (Eugenia dysenterica DC. - Myrtaceae) on the growth of black-jack (Bidens pilosa L.)

“…The effect promoted by ethanolic and aqueous extracts obtained from E. dysenterica leaves may be associated with the presence of several secondary compounds, including phenols, hydrolysable tannins, flavonols, flavanones, flavanones, xanthones, flavones, free steroids and saponins (Malheiros et al 2019). The most expressive results were promoted by hydroalcoholic extracts, agreeing with the study by Lousada et al (2012) which showed that the black-jack germination was also inhibited by lemongrass hydroalcoholic extracts. Allelopathic compounds alter seed germination through a multiplicity of effects on physiological and biochemical processes, since there are hundreds of different structures upon which they exhibit multiple phytotoxic effects (Imatomi et al 2013), as is the case with phenolic compounds which affect cell wall elasticity and block mitochondrial respiration (Weir et al 2004), and saponins which showed action on the cell membrane, modifying cell permeability (Alves & Santos, 2002).…”

Physiological and sanitary potential of peanut seed treated with cinnamon powder

“…The initial growth phase appears to be more sensitive to allelochemicals than germination, which may lead to abnormal seedlings, root necrosis, or alterations in the growth (Ferreira and Borghetti, 2004). The influence of natural extracts on the growth of seedlings shows the ability of compounds acting at this stage of development (Lousada et al, 2012). The potential of natural products to inhibit the growth of seedlings may be related to the chemical constituents present in the plant or the interaction of its components .…”

Fitotoxicidade de extratos etanólicos de frutos e folhas de Banisteriopsis oxyclada (A. Juss.) B. Gates sobre o crescimento de plantas daninhas

“…Esses biotestes são mais indicados devido à complexidade das inter-relações planta e ambiente que podem interferir na atividade dos metabólitos secundários. Embora não revelem os compostos ou fenômenos envolvidos, podem detectar a interferência no crescimento e no desenvolvimento das espécies testadas, contribuindo com a indicação de possíveis fontes de novos compostos com bioatividade potencial (MAIRESSE et al, 2007;LOUSADA et al, 2012).…”