Extrafloral nectary development, characterization and secretion in Chamaecrista debilis and Chamaecrista desvauxii var. langsdorfii (Leguminosae, Caesalpinioideae)

Abstract

Although the petiole glands in Chamaecrista are usually termed extrafloral nectaries (EFNs), additional studies on the morphoanatomy and chemical nature of the exudates are necessary to properly classify a plant secretory structure. The correct classification of such structures is also important in taxonomic and phylogenetic studies. Based on standard anatomical procedures for light microscopy our study aims to broaden our current understanding of the EFNs in Chamaecrista. We describe and compare the ontogenesis and the morphoanatomy of the petiole EFNs in C. debilis and C. desvauxii var. langsdorfii, species that belong to two distinct sections in Chamaecrista. The morphoanatomy along with the presence of sugars in exudates supports the classification of the petiole glands in both species as EFNs. The EFN development is rapid, and their secretory activity starts before the young leaves complete their expansion. The major difference among the EFNs of both species is their outer morphology which is useful on the taxonomy. Both EFNs are anatomically similar and composed of a secretory epidermis, a nectariferous parenchyma and vascular tissue more abundant in phloem in comparison to xylem.