Ecological anatomy of Bacopa species (Gratioleae-Plantaginaceae): aquatic macrophytes of the Iberá Macrosystem

Abstract

Most Bacopa species (Gratioleae-Plantaginaceae) are macrophyte plants with a series of morphological, anatomical, and eco-physiological adaptations in their vegetative organs. We studied the vegetative anatomy of five Bacopa species present in the Iberá Macrosystem, and one species of Paraguay wetland. To study leaf and cauline anatomy, paradermal and transverse sections were made with freehand and rotating microtome from previously fixed material. The anatomical studies showed differences between the Bacopa species analyzed concerning the leaf: types of trichomes; types, distribution, and the density of stomata; and mesophyll type. In terms of the stem, two patterns of cortical aerenchyma were characterized, which are related to the environments inhabited by the species and their adaptations. As a conclusion, a dichotomous key was elaborated with vegetative anatomical characters of the Bacopa species that grow in wetlands.