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.

Ultrastructural changes during nectar secretion from extrafloral nectaries of Pithecellobium dulce Benth

“…This type of vasculature pattern in P. dulce is an indicator of specialized EFN (Sharma and Pillai 1982;Dave and Menon 1987). A similar pattern of the vascular system comprised of the main vascular system of the petiole along with accessory bundles ensuring the exclusive supply of photoassimilates towards EFNs has been reported in Chamaecrista species (Coutinho et al 2012(Coutinho et al , 2022.…”

“…Single-layered non-secretory epidermal cells are characteristic features of EFNs from other reported species of the Leguminosae family (Pascal et al 2000 ; Coutinho et al 2012 ) and could be a taxonomic character for this family (Coutinho et al 2022 ). Multilayered nectariferous parenchyma surrounded by a few layers of highly vacuolated cells where vascular tissues end is a common feature reported in the EFNs of Leguminosae (Durkee et al 1999 ; Melo et al 2010 ; Marazzi et al 2013 ; Coutinho et al 2022 ). The presence of two abaxial veins on either side of nectariferous cells making a continuous rim throughout the secondary rachis constitutes the vascular connection between EFNs and petiole in P. dulce .…”

“…The typical structural EFNs are characterized by the presence of parenchymatous nectariferous tissue composed of densely packed, thin-walled cells with dense cytoplasm and a glandular epidermal tissue through which exudation of nectar occurs (Marazzi et al 2019). Single-layered nonsecretory epidermal cells are characteristic features of EFNs from other reported species of the Leguminosae family (Pascal et al 2000;Coutinho et al 2012) and could be a taxonomic character for this family (Coutinho et al 2022). Multilayered nectariferous parenchyma surrounded by a few layers of highly vacuolated cells where vascular tissues end is a common feature reported in the EFNs of Leguminosae (Durkee et al 1999;Melo et al 2010;Marazzi et al 2013;Coutinho et al 2022).…”

“…According to the topography, the nectaries associated with floral parts are referred to as floral nectaries, while the glands associated with vegetative portions of plants and which secretes primarily sugars are called extrafloral nectaries (EFNs) (Durkee 1982;Coutinho et al 2012). EFNs proved to have importance in taxonomic studies and the establishment of phylogenetic relationships within taxonomic groups (Marazzi et al 2019, Dalvi et al 2013, 2020Souza et al 2021;Coutinho et al, 2022). Furthermore, the chemical nature of the secretion of EFNs has been considered to be an ecologically significant indicator for understanding the relationship between visiting ants and plants (Coutinho et al 2022).…”

“…EFNs proved to have importance in taxonomic studies and the establishment of phylogenetic relationships within taxonomic groups (Marazzi et al 2019, Dalvi et al 2013, 2020Souza et al 2021;Coutinho et al, 2022). Furthermore, the chemical nature of the secretion of EFNs has been considered to be an ecologically significant indicator for understanding the relationship between visiting ants and plants (Coutinho et al 2022). The functional significance of the ontogeny of EFNs is attributed to the support of the mutualists of plants such as ants in Acacia drepanolobium (Young et al 1997) and Opuntia imbricata (Miller 2007).…”