On the taxonomic value of the anatomical structure of vegetative organs and inflorescence axis of Abolboda species (Xyridaceae – Poales)1

Abstract

The species of Xyridaceae are grouped into two subfamilies: Xyridoideae, which includes the genus Xyris, and Abolbodoideae, comprising the genera Abolboda, Achlyphila, Aratitiyopea and Orectanthe. Since the inter- and infra-familiar relationships in Xyridaceae are not yet well established, this study aimed to characterize the morphology and anatomy of vegetative organs and inflorescence axis of Abolboda species in order to assess characters with taxonomic value. Characteristics such as the length and width of leaves, length of inflorescence axes, length of bracts of the inflorescence axis node, number and type of vascular bundles in the mesophyll, presence or absence of bundle sheath extensions in the leaves and shape of the leaf margin are important to delimit the species. The presence of an epidermis with thin-walled cells in the adaxial side and slightly thickened walls on the abaxial side and a hypodermis facing the adaxial side of the leaves differentiates Abolboda from the other genera of Xyridaceae. Partially thickened epidermal cells and nodes on the inflorescence axes are also diagnostic characters of Abolboda. The species of Abolboda have anatomical characteristics that contrast with those of Xyris and others that are similar to those of other genera of Xyridaceae, supporting the division of the family into two subfamilies.