Floral elaiophores of Vitekorchis, Cyrtochilum and Oncidium

Molecular approaches have been used to investigate the phylogeny of subtribe Oncidiinae, resulting in the recent re-alignment of several of its genera. Davies et al. compare the floral elaiophores (oil glands) of four species formerly assigned to Oncidium (Oncidiinae), namely Gomesa longipes, Vitekorchis excavata, Cyrtochilum meirax and florally dimorphic Oncidium heteranthum. They find that, except for C. meirax, which lacks obvious elaiophores, this structure occurs on the labellar callus, has glabrous and trichomatous regions, and comprises a single-layered, secretory epidermis lacking palisade cells, the oil being produced either by smooth endoplasmic reticulum or as plastoglobuli within elaioplasts. Subsequent stages of secretion differ little between species, with the oil traversing the cell wall and accumulating beneath the distended cuticle. Floral dimorphism has little effect on elaiophore structure.