Chemical characterization and phytotoxicity of the essential oil from the invasive Hedychium coronarium on seeds of Brazilian riparian trees

The release of allelochemical compounds by some plants may directly affect the development of other plant species and is considered one of the mechanisms that facilitate plant invasions. However, little is known about the role phytotoxicity plays in plant invasions in the neotropics, especially regarding to the response of different native species to the phytotoxic compounds of invasive plants. In this study, we assessed the effect of oil extracted from the rhizomes of Hedychium coronarium J. Konig, an important invasive plant in Brazilian riparian habitats, on the germination speed index (GSI) and germination percentage (GP) of four tree species native from Brazilian riparian forests (Anadenanthera macrocarpa, Peltophorum dubium, Mimosa bimucronata and Sesbania virgata). We also measured the radicle growth of S. virgata. The essential oil was extracted, chemically characterized, and germination bioassays were performed using oil concentrations of 0.01%, 0.1% and 1%, distilled water and Tween 80 (1%) as controls. The concentration 1% of the essential oil inhibited the GP and the GSI of all tested species (except the GP of S. virgata) and the radicle growth of S. virgata. The oil concentration 0.1% also reduced the GSI and GP of M. bimucronata. Our results revealed that some phytotoxic compounds of the invasive H. coronarium negatively affect the germination of native tree species, which may enhance its dominance in riparian forests.