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Under Eucalyptus plantations in the South Brazilian grassland region, few plants establish, and allelopathy may be involved in shaping this pattern. We aimed to assess the phytotoxicity of essential oil and aqueous extract of Eucalyptus saligna Sm. leaf litter on grassland species. We tested the effects of E. saligna pure oil and extract on germination, seedling growth, H2O2 levels and electrolyte leakage of seedling membranes of Paspalum notatum Flüggé, Eragrostis plana Ness (Poaceae), Trifolium repens L. and Lotus corniculatus L. (Fabaceae). Essential oil and aqueous extract of E. saligna affected all recipient species, even at the lowest amounts/concentrations, inhibiting germination and initial growth, and also increasing H2O2 levels and electrolyte leakage of seedling membranes. Essential oil consisted mainly of monoterpenes and presented α-pinene and 1,8-cineole as the major compounds. The extract contained phenolics, and lower levels of these compounds in the extract were associated with decreased phytotoxicity. We conclude that E. saligna contains phytotoxic compounds in leaf litter that generate oxidative stress and lead to membrane damage, affecting seeds and seedling growth. In addition, we relate E. saligna phytotoxicity to monoterpenes that may be released from leaf litter by volatilisation, and phenolics that may be leached by rainfall. Our study indicates that E. saligna has allelopathic potential on the tested grassland species.

Reference: Silva, E. R., D. C. Lazarotto, J. Schwambach, G. E. Overbeck and G. L. Soares (2017). “Phytotoxic effects of extract and essential oil of Eucalyptus saligna (Myrtaceae) leaf litter on grassland species.” Australian Journal of Botany.

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