Colleters, osmophores, and nectaries in the species Ceropegia lenewtonii: a sapromyiophilous stapeliad (Asclepiadoideae, Apocynaceae)

Abstract

Ceropegia lenewtonii (Plowes) Bruyns (=Huernia keniensis), currently belonging to the Huernia section of the genus Ceropegia, is a stapeliad species distributed in Africa and the Arabian Peninsula; but it is widely cultivated as ornamental in most parts of the world. This species of stapeliad presents “carrion flowers” associated with a sapromyophilous pollination syndrome since the flowers emit an unpleasant odor. In this work, we describe the floral morphology and anatomy of the calyx, corolla, and corona of this species based on bright-field and scanning electron microscope techniques. We detected the presence of diverse floral secretor tissues, and based on different histochemical tests, the principal component of the secreted substance was identified. We interpret the functions of the glands and compare with other related species of stapeliads. Our results indicate that flowers of C. lenewtonii present colleters in sepals, osmophores in corolla, and primary and secondary nectaries in corona. All these floral glands have specific functions that involve the processes of pollination and reproduction of this species, as well as protection and defense mechanisms.