Floral secretory structures and pollinator rewards in Amburana cearensis (Fabaceae, Papilionoideae)

Resumen

Amburana cearensis is an early-branching papilionoid legume whose flowers deviate from the typical papilionate pattern seen in most papilionoids. Its small, entomophilous flowers are nectariferous and fragrant, featuring a gamosepalous calyx, a corolla with a single adaxial petal, free heteromorphic stamens, and a long hypanthium. In addition to nectar and fragrance, a translucent exudate was observed on the floral organs’ surfaces. This study elucidates the secretory sites of nectar, odor, and the exudate in A. cearensis flowers and explores their potential functions. Flower buds and flowers were processed for surface, anatomical, and ultrastructural analyses. The exudate was identified as a terpenic gum resin, secreted by the epidermis in the anther, as well as the epidermis and subepidermal parenchyma in the sepals, filaments and carpel. These cells contain dictyosomes, rough endoplasmic reticulum, mitochondria, plastids, and electron-dense substances, confirming the chemical nature of the exudate. Release occurs through stomata on the petals and carpel. Nectar is produced by a nectary in the lower half of the long hypanthial tube and released through stomata. The floral fragrance is attributed to the secretion of terpenes. Both nectar and terpenic gum resin enhance the flower’s attractiveness during pollen presentation, serving as rewards for pollinating bees.

 Citation: Leite, V.G., Mansano, V.F. & Teixeira, S.P. 2025. Floral secretory structures and pollinator rewards in Amburana cearensis (Fabaceae, Papilionoideae). Revista Jard. Bot. Nac. Univ. Habana 46 (Número especial 1): 121.

Trabajo presentado en el XIII Congreso Latinoamericano de Botánica. Sesión Estructura, Fisiología y Desarrollo.