Colleters in Chamaecrista (L.) Moench sect. Chamaecrista and sect. Caliciopsis (Leguminosae-Caesalpinioideae): anatomy and taxonomic implications

Abstract

The genus Chamaecrista contains ca. 330 species organized into six sections, of which section Chamaecrista is the second largest (ca.75 species) distributed among six series, while the section Caliciopsis contains only two species. Colleters have been described in the genus Chamaecrista and they show potential taxonomic and phylogenetic significance. They are associated with lubrication, desiccation prevention and protection from microbial attacks of young developing organs. Although six types of colleters have been described for the genus Chamaecrista, there have been no studies focusing on the diversity of colleters in the sections Chamaecrista and Caliciopsis. Samples from developing leaves and flowers of both sections were obtained from herbarium and field collections and subjected to standard methodologies for both light and scanning electron microscopy. Histochemical tests were also performed to determine the nature of the exudates. Five types of non-vascularized colleters were found: short digitiform, long digitiform, club-shaped, pyriform and short bottle-shaped. Polysaccharides, pectins, lipids and proteins were detected in the exudates of all types of colleters. Among the five types of colleters observed, pyriform is a novelty for Chamaecrista, reinforcing the significant morphological diversity of these secretory structures in this genus.