Potencial alelopático de macrófitas aquáticas de um estuário cego

Abstract

Potencial alelopático de macrófi tas aquáticas de um estuário cego 1 RESUMO (Potencial alelopático de macrófi tas aquáticas de um estuário cego). Macrófi tas aquáticas representam uma das comunidades mais produtivas e através de sua atividade metabólica são capazes de produzir grandes interferências no ambiente. As interações alelopáticas são aparentemente aumentadas sob condições de estresse biótico e abiótico e podem existir em estuários devido à competição, variações de salinidade e outros fatores. O objetivo desse trabalho foi avaliar as propriedades alelopáticas de extratos aquosos foliares de 25 espécies de macrófi tas aquáticas de um estuário cego. Testamos os efeitos dos extratos foliares em quatro concentrações sobre a germinação de alface. Ordenamos e comparamos as espécies doadoras de acordo com a dose reposta sobre a variedade de tratamentos a partir de valores únicos de índices alelopáticos. Onze das 25 espécies diminuíram a porcentagem de germinação, todas diminuíram a velocidade de germinação e aumentaram a entropia informacional de germinação das sementes da espécie alvo em pelo menos uma das concentrações testadas. ABSTRACT(Allelopathic potential of aquatic macrophytes from a blind estuary). Aquatic macrophytes represent one of the most productive communities and through metabolic activity are capable of producing great interference in the environment. Allelopathic interactions are apparently increased under biotic and abiotic stress and may exist in estuaries due to competition, salinity variation and other factors. Th e aim of this study was to evaluate the allelopathic properties of leaf extracts of 25 aquatic macrophyte species from a blind estuary. We tested leaf extract eff ects in four concentrations on the germination of lettuce. We ranked and compared the donor species according to the dose-response over the variety of treatments through unique values of allelopathic indexes. Eleven of 25 species decreased the germination percentage, all of them decreased the speed of germination and increased the germination informational entropy of the target species seeds in at least one of the tested concentrations. Crinum americanum L., Sagittaria montevidensis Cham. & Schl. and Ipomoea cairica (L.) Sweet presented the highest allelopathic index values. In general, the lowest germination percentages concurred with the lowest germination speed and highest germination informational entropies of lettuce seeds, showing an assemblage of alterations occurring simultaneously with the increase of extract concentrations.

The effect of competition on Bacopa monnieri zonation in an temporarily open/closed tropical estuary

“…Ant herbivory was also observed in another experiment conducted at the study site, in which Crinum americanum L. were preyed upon when transplanted out of the water. Both B. monnieri and C. americanum are soft-tissue plants with no physical defence mechanisms but with strong allelopathic properties (Takao et al, 2011), suggesting they rely on chemical defences to avoid herbivory. This interpretation is consistent with the findings of Morrison and Hay (2011) that indicate high investment in chemical defences among tropical macrophytes.…”