Phenolic Compounds Influence Seed Dormancy of Palicourea rigida H.B.K. (Rubiaceae), a Medicinal Species of the Brazilian Savannah

Palicourea rigida H.B.K. (Rubiaceae), a medicinal species commonly known as douradinha, has wide distribution across ecosystems in Central and South America. This species exhibits seed dormancy delaying germination until optimal conditions for seedling growth and development are in place. As dormancy ensures species survival, it also presents a technical problem for developing P. rigida's plant production program. Thus, the objective of this study was to investigate if secondary metabolites present in seeds influence the seed dormancy of P. rigida. Mature fruits were harvested from the native habitat, in the savanna region of the State of Minas Gerais during February 2009, 2010 and 2011. The contents of loganin and phenolic compounds in the seed of P. rigida were measured, and the allelopathic effects were assessed using the germination of lettuces as model to detect phytotoxicity. The P. rigida seeds geminated at rates varying between 16 and 23% with a Seed Germination Index (SGI) of 0.05. Data suggest that the phenolic compounds present in the seeds may be responsible for seed dormancy. Acknowledgements: Fapesp proc. 2007/58503 – 7