Sesbania virgata (Cav.) Pers. is a pioneer species native to South America able to release allelochemicals that affect germination and development of other plant species. The aim of this work was to evaluate the allelopathic effect of S. virgata on the germination and development of co-occurring species from gallery forest and on agronomic species. Two forest native species, Enterolobium contortisiliquum (Vell.) Morong and Sapindus saponaria L., and two agronomic species (these as control), Oryza sativa L. and Solanum lycopersicum L. were used in the lab and greenhouse assays with seeds and leaf extracts of S. virgata. Agronomic species were more affected than native species when co-germinated with seeds of S. virgata. The germination percentage and speed germination index of the agronomic species were reduced in both in vitro and greenhouse assays. In the same assays, the seeds of native species showed no significant differences in the parameters mentioned. However, the initial growth of the four species assayed was affected, with reduction in plant length and shoot diameter followed by significant reduction in plantlet shoot and root weights. In the assays with irrigation of S. virgata leaf extracts, no significant inhibitory effects on germination were observed for all species. Height and shoot diameter of the native species were not affected by the leaf extracts, nor were fresh and dry weights. However, these parameters increased in the agronomic species as they were irrigated with leaf extracts. Based on our data we conclude that seed leachates of S. virgata affect germination and seedling development of other species, suggesting that its invasive behavior is due mainly to seed allelochemicals. Although with less pronounced effects on native species, allelopathy of S. virgata might also influence Interspecific competition in its natural environment.
Seed exudates of Sesbania virgata (Cav.) Pers. stimulate the asymbiotic phase of the arbuscular mycorrhizal fungus Gigaspora albida Becker & Hall). Sesbania virgata is a legume used in the restoration of degraded areas and forms a symbiosis with arbuscular mycorrhizal fungi (AMF). Its seeds exude secondary metabolites that may influence the colonization by AMF. In this work, we studied the effects of seed (SE) and root exudates (RE) of S. virgata on the asymbiotic phase of Gigaspora albida. Spores of G. albida were germinated in medium supplemented with different concentrations of SE or RE. After seven days, spore germination was stimulated (46.6%) in the medium supplemented with the highest concentration of SE, while the mycelial growth was stimulated with the lowest SE concentration. In turn, RE had no effect on the fungal asymbiotic phase. We concluded that SE exert a positive effect on the asymbiotic phase of G. albida and that the different effects between SE and RE of S. virgata can be explained by their distinct content of secondary metabolites.RESUMO -(Exsudatos de sementes de Sesbania virgata (Cav.) Pers. estimulam a fase assimbiótica do fungo micorrízico arbuscular Gigaspora albida Becker & Hall). Sesbania virgata é uma leguminosa utilizada na restauração de áreas degradadas e que forma simbiose com fungos micorrízicos arbusculares (AMF). Suas sementes exudam metabólitos secundários que podem influenciar a colonização pelos AMF. Neste trabalho, estudamos os efeitos de exsudatos de sementes (SE) e radiculares (RE) de S. virgata na fase assimbiótica de Gigaspora albida. Esporos de G. albida foram germinados em meio suplementado com diferentes concentrações de SE ou RE. Após sete dias, a germinação dos esporos foi estimulada (46,6%) com a maior concentração de SE, enquanto o crescimento micelial foi estimulado com a menor concentração de SE. Por sua vez, RE não teve efeito na fase assimbiótica de G. albida. Conluiu-se que SE exercem efeitos positivos na fase assimbiótica de G. albida e que os efeitos diferenciais entre SE e RE de S. virgata na fase de assimbiótica fúngica podem ser explicados pelo seu conteúdo distinto de metabólitos secundários. Palavras-chave: crescimento micelial, exudação de plantas, germinação, Glomeromycota
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