Velamen or uniseriate epidermis? Root apices in Bromeliaceae Juss

Abstract

The anatomy of Bromeliaceae roots has attracted the attention of researchers for a long time. Several authors have described them by highlighting characters associated with mechanisms of water uptake, water retention and adaptation to the environment. In this context, the dermal tissue is frequently mentioned, being described by different authors as uniseriate or pluriestratified epidermis, or even as velamen. In the present study we analyzed the apical meristem region of adventitious roots of nine species belonging to the Pitcairnioideae, Bromelioideae and Tillandsioideae subfamilies. The goal of this study was to elucidate the ontogenetic origin of the tissue referred by several authors as velamen. The root anatomy of analyzed species showed characteristics shared by all taxa, such as the presence of uniseriate epidermis, parenchymal cortex, idioblasts and air channels, as well as a polyarch vascular cylinder. The ontogenetic analysis of the root epidermis carried out in this study enabled us to clarify issues related to the anatomy of this organ that were previously unknown. Our analysis revealed the presence of a uniseriate epidermis in all analyzed taxa in this study, thus increasing the knowledge about the root anatomy of the family.