Corolla traits and their osmophores in three neotropical Malpighiaceae: the putative impacts on plant-pollinator interactions

This study presents the comparative, function-oriented analysis of petal structure and osmophore distribution in three Malpighiaceae species, complementing the established role of calyx elaiophores. Integrating light and electron microscopy with floral biology observations and visitor records, the authors document interspecific variation across core floral traits: anthesis timing; corolla senescence, color, and dimensions; petal micromorphology; and the spatial organization of scent-emitting areas. Byrsonima coccolobifolia possesses flat, textured petal surfaces without glands; scent is emitted from a lobed, striated basal outer region whose cells accumulate starch prior to anthesis, indicating metabolic provisioning. In contrast, Banisteriopsis variabilis and Peixotoa reticulata share rough petal surfaces but differ in epidermal cell shape—cone-shaped in B. variabilis versus rounded in P. reticulata. Both species display enlarged intercellular spaces and minute, vascularized scent glands along fimbriate petal margins that exhibit subcellular traits diagnostic of osmophores, supporting their role in volatile biosynthesis and release. Across the three focal taxa, the findings resolve two principal scent-emission strategies: a diffuse basal emission zone (B. coccolobifolia) versus discrete marginal osmophores (B. variabilis, P. reticulata). Functionally, petal surface architecture and mesophyll organization likely enhance visual signaling, while osmophores are central to attracting oil-collecting bees. Under an evolutionary framework, the evidence indicates ongoing specialization of floral tissues for scent production, with probable effects on pollinator attraction and specificity. The study thus refines our understanding of multimodal floral signaling in Malpighiaceae and suggests that diversification in petal anatomy and osmophore placement may shape plant–pollinator interactions and the evolution of pollination systems within the family.