Morphology, anatomy and ultrastructure of petals in Alicia anisopetala and Callaeum psilophyllum (Malpighiaceae): implications for pollinator attraction

Abstract

In Malpighiaceae species, the corolla consists of five petals, with the posterior petal, or flag petal, being distinct in shapeand size. This differentiation facilitates the proper orientation and positioning of pollinators, allowing them to access floraloils while simultaneously contacting the anthers and the stigma, thereby enabling pollen transfer. To better understand therole of the corolla in pollinator attraction, a study was conducted on the morphology, anatomy and ultrastructure of allpetals of Alicia anisopetala and Callaeum psilophyllum. Flowers at anthesis were collected and fixed for subsequent analy-sis. Light microscopy, scanning electron microscopy and transmission electron microscopy techniques were employed.The results revealed morphological and anatomical differences between the posterior and lateral petals of both species.Hairs, druse crystals, and fimbriae were identified along the petal margins. Ultrastructural analysis revealed metabolicallyactive and secretory epidermal cells, associated to scent secretion, with distinctive characteristics observed in the emergentstructures of the posterior petal of C. psilophyllum. In summary, this study provides detailed information on petal structurein these Malpighiaceae species, suggesting adaptations for pollinator attraction through specific morphological featuresand fragrance secretion. These findings contribute to a deeper understanding of the fundamental role of the corolla in thepollination of A. anisopetala and C. psilophyllum.