Anatomical interpretations of the taxonomy of Chamaecrista (L.) Moench sect. Absus (Leguminosae–Caesalpinioideae)

Abstract

Chamaecrista (L.) Moench (Caesalpinioideae-Leguminosae) with 330 species is organized into six sections: Apoucouita, Absus, Grimaldia, Chamaecrista, Caliciopsis and Xerocalyx. Section Absus is the largest section of the Chamaecrista and is organized into four subsections, viz., subsect. Adenophyllum, subsect. Baseophyllum, subsect. Otophyllum and subsect. Absus. This section is not monophyletic and has a complex taxonomy. This study aims to anatomically characterize 60 taxa of Chamaecrista, identifying meaningful morphoanatomical characters that may shed light on the evaluations of the taxonomic and phylogenetic framework of Chamaecrista, especially C. sect. Absus. Standard light microscopy techniques were used to anatomically characterize the leaves. The anatomical data were subjected to a multivariate analysis (Jaccard index). Epidermal papillae on the abaxial side, the distribution and types of secretory and tector trichomes, variations in the arrangement of the vascular system of the midvein and the type of arrangement of the vascular system of the petiole are useful for separating species or groups of species. The presence and type of secretory structure, the type and position of stomata and the venation pattern are important in establishing the affinities between sections and subsections. The phenetic analysis demonstrates that the anatomical data contribute to the establishment of affinities between sections and subsections, supporting the elevation of the taxonomic status of the clade Baseophyllum to section and the insertion of C. absus (C. sect. Grimaldia) into C. sect. Absus, corroborating molecular studies.

Morphoanatomy of nectaries of Chamaecrista (L.) Moench sections Chamaecrista , Caliciopsis and Xerocalyx (Leguminosae: Caesalpinioideae)

“…Although morphologically different, our study found anatomical similarities among the extrareproductive nectaries of Chamaecrista in that all of them comprise a single layered epidermis, several layers of nectary parenchyma with underlying layers of subnectary parenchyma and vascularization. Such anatomical similarity is also shared with other species of Chamaecrista that bear extra-reproductive nectaries (Coutinho et al 2012;Francino et al 2015).…”

“…Coriaceae and in C. desvauxii var. langsdorfii (section Xerocalyx) (Francino et al 2015). Verruciform and urceolate nectaries were uncommon.…”

“…Baseophyllum (Coutinho et al 2012) and subsect. Otophyllum (Francino et al 2015). These studies have demonstrated how different extra-reprodutive nectaries can be even among species of the same genus, since the chemical nature of the secretion of extra-reproductive nectaries in Chamaecrista can differ and some species develop a wound-healing periderm during senescence.…”

“…These studies have demonstrated how different extra-reprodutive nectaries can be even among species of the same genus, since the chemical nature of the secretion of extra-reproductive nectaries in Chamaecrista can differ and some species develop a wound-healing periderm during senescence. The extra-reproductive nectaries of the species of Chamaecrista may be stalked or sessile, and are anatomically composed of four distinct regions (Coutinho et al 2012;Francino et al 2015).…”

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

“…Different secretory structures with high potential for taxonomic and phylogenetic relevance have been described in Chamaecrista, including: nectaries (on leaves and/or racemes), mucilage idioblasts in the mesophyll and/or epidermis, sticky glandular hairs and colleters (Irwin & Barneby 1982;Coutinho et al 2012;Meira et al 2014;Francino et al 2015). Colleters are secretory structures that are usually found on the adaxial side of vegetative and/or reproductive structures such as stipules, bracts, sepals and petals (Fahn 1979;Thomas 1991;Mayer et al 2013;Coutinho et al 2015).…”