Comparative survey of secretory structures and floral anatomy of Cohniella cepula and Cohniella jonesiana (Orchidaceae: Oncidiinae). New evidences of nectaries and osmophores in the genus

Abstract

The morpho-anatomical structure of nectaries, osmophores, and elaiophores, and the anatomical and micromorphological features of floral pieces of Cohniella cepula Hoffmans. and Cohniella jonesiana Rchb.f. were comparatively analyzed. In both species, bracteal and sepal nectaries are structured, i.e., they present a secretory epidermis, secretory parenchyma, and vascular bundles. Nectar secretion is released through stomata. The anatomical and micromorphological traits are similar in both nectaries, which can be detected only if the nectar drops are secreted. Considering the location of these nectaries, the secreted nectar would not be a reward to pollinators. Osmophores are located at the base of both callus and laterals lobes, and consist of a layer of secretory epidermis composed of quadrangular cells and papillae. Elaiophores are found on the callus of the labellum and are of the epithelial type. The anatomical features of floral pieces are similar in both species. The anatomical analysis of sepals and petals showed a few differences, which could be of potential taxonomic value. Our results contribute valuable and novel information for the knowledge of these species and the genus, which will be useful in future taxonomic evaluations.