Atividade alelopática de substâncias químicas isoladas da Acacia mangium e suas variações em função do PH

Abstract

RESUMO -Os objetivos deste trabalho foram isolar, identificar e caracterizar a atividade alelopática de substâncias químicas produzidas por Acacia mangium, além de determinar as variações na atividade das substâncias em função da variação do pH da solução. A atividade alelopática foi avaliada em bioensaios de germinação (25 o C de temperatura e fotoperíodo de 12 horas) e crescimento de radícula e hipocótilo (25 o C de temperatura e fotoperíodo de 24 horas) das plantas daninhas malícia (Mimosa pudica) e mata-pasto (Senna obtusifolia). Avaliou-se a interferência do pH (3,0 e 9,0) da solução na atividade alelopática das substâncias sobre a germinação das sementes da espécie malícia. Os triterpenoides lupenona (3-oxolup-20(29)-eno) e lupeol (3β-hidroxilup-20(29)-eno), obtidos das folhas caídas da planta doadora, isolados e em par, evidenciaram baixo efeito alelopático inibitório da germinação de sementes e do crescimento do hipocótilo, especialmente do primeiro, cujos efeitos não ultrapassaram o valor de 2,0%. Os efeitos promovidos sobre o crescimento da radícula foram de maior magnitude, atingindo valores superiores a 40%, com destaque para as inibições promovidas pela substância lupenona. Isoladamente, as substâncias promoveram efeitos superiores aos efetivados pelas substâncias analisadas em pares, indicando a existência de antagonismo. O pH da solução influenciou a atividade alelopática das substâncias; para lupenona os efeitos foram mais intensos em pH ácido, enquanto para lupeol os melhores resultados foram verificados em condições alcalinas, mostrando que este fator é ponto importante a ser considerado em trabalhos de campo.Palavras-chave: alelopatia, Leguminosae, lupenona, lupeol.ABSTRACT -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 o C and under 12-12 h light-dark cycle) and radicle and hypocotyl development (at 25 o C and under 24-24 h light-dark cycle) of the weed species malicia (Mimosa pudica) and matapasto (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 effe...

Contribution of legume tree residues and macrofauna to the improvement of abiotic soil properties in the eastern Amazon

“…In addition to the lower residue quality, substances such as phenolic acid and lupenone (which is a triterpenoid), which are present at very high concentrations in A. mangium, could have contributed to allelopathic effects and inhibited soil-specific invertebrates (Zhang et al, 2010;Luz et al, 2010). Compared to other leguminous species, Acacias strongly promote Isoptera abundance, which results in less fauna diversity (Shannon) and evenness (Pielou).…”

Weeds occurrence and importance under distinct intercropping systems

“…This means that (1) the straw resulting from plants desiccation was not homogeneously distributed at the soil surface, (2) the amount of straw present (t ha -1 ) was not enough to promote physical inhibition of emergence of these species, or (3) the density of these weed species was too high and the prevention of access to light was not enough for its occurrence at considerable density. Besides the physical effect, allelopathic effect by the decomposing straw of forage species after desiccation is proved to suppress the development of some important weed species (Luz et al, 2010).…”

Identification of phenolic compounds and their relationship to the natural resistance of wood from Dipteryx polyphylla Huber and Acacia mangium Willd

“…Racosperma mangium (Willd.) Pedley] (Tropicos, 2020) originates from Australia and Malaysia, and has easily adapted to the tropical Brazilian soil and climatic conditions (Luz et al, 2010). The commercial plantations of this species in Brazil extract tannins obtained from bark, which are used in the tannery industries, and the wood is used by the cellulose industry, as well as for generating energy and the production of wood panels (Attias et al, 2013).…”