Anatomy of the extrafloral nectaries in species of Chamaecrista section Absus subsection Baseophyllum (Leguminosae, Caesalpinioideae)

Abstract

In this paper the ontogenesis and histochemistry of the petiolar glands found on the petiole/rachis of theeight Chamaecrista species of the section Absus, subsection Baseophyllum (Leguminosae, Caesalpinioideae)are studied by using light microscopy techniques, aiming to characterise these structures and to providetaxonomic characters which may be useful in phylogenetic approaches. Strips for glucose identificationreacted positively with the exudates of the glands, confirming the presence of nectar in the secretion,characterising these glands as extrafloral nectaries (EFN). Histochemical tests also detected the presenceof neutral and acid muco-polysaccharides, pectins, mucilages, total proteins, and phenolic compounds inthe EFNs. The EFNs arise from a group of meristem cells (protodermis, ground meristem and procambium)in the petiole/rachis. All EFNs of the investigated taxa share some morpho-anatomical characters, sothat their peculiarities are too weak to be used alone in the identification of particular species. Rathertheir similarities may be used to include these species into a single group, supporting the hypothesis ofmonophyly of the subsection Baseophyllum