Comparative leaf and root anatomy of seven species of Catasetum Rich. ex Kunth (Orchidaceae: Catasetinae)

Abstract

The genus Catasetum is a complex group, and little is known about the anatomical composition of its leaves and roots. The present study aimed to describe and anatomically compare the leaf and root structure of seven species and contribute to the anatomical and taxonomic knowledge of the species included in the Catasetinae subtribe. The samples were fixed in FAA70 and preserved in 70% ethanol. The sections were performed freehand, clarified in 50% sodium hypochlorite, and later stained with basic fuchsin and 0.05% Astra blue. The slides were mounted with glycerin gelatin and matched with colorless enamel. The specimens studied are structurally similar to each other, with unistratified epidermal sheets, thin and smooth cuticle on both sides, angular collenchyma, sclerenchyma surrounding the vascular bundle of the main vein and homogeneous mesophyll and roots with distinguishable epivelamis, multistratified canopy with secondary thickening, unistratified exoderm with the presence of tylossomes, multistratified parenchymal cortex, unistratified endoderm and pericycle, and polyarc vascular cylinder. These data are found in accordance with the literature for the genus. Records of amphistomatic leaves are described here for the first time for the anatomy of Catasetum. However, no useful anatomical markers were found to differentiate the species studied or that would contribute to taxonomic purposes or to the systematics of this genus.