Comparative anatomy of the floral elaiophore in representatives of the newly re-circumscribed Gomesa and Oncidium clades (Orchidaceae: Oncidiinae)

Abstract

In terms of location, morphology, anatomy and ultrastructure, the floral elaiophores of both Gomesa and Oncidium species examined are very similar, and distinction between these genera is not possible based on elaiophore features alone. Furthermore, many of these elaiophore characters are shared with representatives of other clades of Oncidiinae, including the Ornithocephalus clade. Consequently, elaiophores are considered homoplasious and of limited value in investigating the phylogeny of this subtribe.

Elaiophores: their taxonomic distribution, morphology and functions

“…The epithelial elaiophores are generally constituted by one layer of cuboid (Singer & Cocucci 1999;Pacek & Stpiczyńska 2007;Pacek et al 2012;Gomiz et al 2013;Davies et al 2014) or palisade-like , Stpiczyńska & Davies 2008Davies & Stpiczyńska 2009;Gomiz et al 2013;Stpiczyńska et al 2013) epithelial cells which are covered by a cuticle. Sometimes the elaiophore presents a wrinkled surface as in Oncidium cheirophorum (Pacek & Stpiczyńska 2007).…”

“…Sometimes the elaiophore presents a wrinkled surface as in Oncidium cheirophorum (Pacek & Stpiczyńska 2007). Below the secretory epithelium can have a few layers (1-3) of subepithelial parenchyma (Pacek & Stpiczyńska 2007;Stpiczyńska et al 2007;Stpiczyńska & Davies 2008;Aliscioni et al 2009;Davies & Stpiczyńska 2009;Pacek et al 2012;Gomiz et al 2013;Stpiczyńska et al 2013) and also a ground vascularized parenchyma (Pacek & Stpiczyńska 2007;Aliscioni et al 2009;Davies & Stpiczyńska 2009;Pacek et al 2012;Stpiczyńska et al 2013). In Oncidium ornithorhynchum the subepithelial parenchyma is unusual, since it shows well-developed intercellular spaces, where a flocculent material accumulates in the pre-secretory stage (Davies & Stpiczyńska 2009).…”

“…Most of species have well-defined epithelial elaiophores (Pacek & Stpiczyńska 2007;Stpiczyńska et al 2007;Stpiczyńska & Davies 2008;Aliscioni et al 2009;Davies & Stpiczyńska 2009;Pacek et al 2012;Gomiz et al 2013;Stpiczyńska et al 2013) but some, such as Gomesa recurva and Cyrtochilum meirax (Davies et al 2014) have morphologically undifferentiated, constituted by oval or cuboid epithelial cells, lacking secretory features such as a dense and abundant cytoplasm.…”

“…In most plant species the lipidic secretion accumulates beneath the cuticle before its release (Singer & Cocucci 1999;Pacek & Stpiczyńska 2007;Stpiczyńska et al 2007;Stpiczyńska & Davies 2008;Pacek et al 2012;Stpiczyńska et al 2013). Generally the secretions are released after cuticle rupture, sometimes triggered only by floral visitors Stpiczyńska & Davies 2008;Pacek et al 2012;Stpiczyńska et al 2013).…”

“…In most plant species the lipidic secretion accumulates beneath the cuticle before its release (Singer & Cocucci 1999;Pacek & Stpiczyńska 2007;Stpiczyńska et al 2007;Stpiczyńska & Davies 2008;Pacek et al 2012;Stpiczyńska et al 2013). Generally the secretions are released after cuticle rupture, sometimes triggered only by floral visitors Stpiczyńska & Davies 2008;Pacek et al 2012;Stpiczyńska et al 2013). However, in some species the authors did not observe the detachment or disruption of the cuticle, suggesting that the secretion passes through the cell wall and cuticle (Aliscioni et al 2009;Pansarin & Pansarin 2011;Davies et al 2014).…”