Morphoanatomy and ecology of the extrafloral nectaries in two species of Passiflora L. (Passifloraceae)

Abstract

• The number of layers of the secretory epidermis varies according to the subgenera. • The secretor phase is evident with the distention of the cuticle. • The glucose occurrence in the exudates of the EFN in the leaves, several genera of ants and fungi associated to those structures allowed to identify those structures as extrafloral nectaries. The foliar glands of Passiflora are generally known as extrafloral nectaries, which, unlike floral nectaries, are not related to pollination. The present study describes and analyzes the foliar glands found in Passiflora ceratocarpa and Passiflora quadrangularis , in order to confirm their identity as extrafloral nectaries and discuss the taxonomic and ecological implications of these structures. The study material was collected in the metropolitan region of Belém (Brazil) and submitted to standard protocols for the analysis of plant anatomy by light and scanning microscopy, as well as histochemical testing. The extrafloral nectaries of the two species are anatomically very similar, including a multiseriate palisade epidermis, a nectariferous parenchyma consisting of voluminous, thin-walled cells, and predominantly phloematic vascularization. Their chemical composition is also highly similar, and includes sugars, and lipids. Five ant genera were found visiting the two Passiflora species, of which Camponotus was the most abundant, being found on both the study species.