Floral glands in myophilous and sapromyophilous species of Pleurothallidinae (Epidendroideae, Orchidaceae)—osmophores, nectaries, and a unique sticky gland
- 22 February 2021
- journal article
- research article
- Published by Springer Science and Business Media LLC in Protoplasma
- Vol. 258 (5), 1061-1076
- https://doi.org/10.1007/s00709-021-01624-2
Abstract
Pleurothallidinae orchids have been the focus of many multidisciplinary studies due to their challenging systematics and taxonomy. The synapomorphies already recognized in the group are mostly related to floral characters, the last proposed being the occurrence of alkanes in the floral fragrance. The composition of the floral bouquet varied significantly among the studied species, leading us to hypothesize that the variations in volatiles emitted could be linked to the structure of osmophores, especially when comparing the myophilous and sapromyophilous pollination syndromes. Sepals and labellum at different developmental stages of seven Brazilian Pleurothallidinae species were examined using light, scanning, and transmission electron microscopy. Nectar reabsorption was assessed by Lucifer Yellow CH tracer and imaged under confocal microscopy. Nectaries were restricted to the labellum of the myophilous species, whereas osmophores occurred in the dorsal and/or lateral sepals, varying according to species. In the sapromyophilous species, floral nectaries were not detected and osmophores were restricted to the labellum. Osmophore structure was correlated with the volatiles emitted, being the trichome osmophores notably present on the sepals of both myophilous species that possess nectaries. For the first time, we demonstrated reabsorption of the released nectar in Pleurothallidinae and the occurrence of a unique gland named sticky-exudate glands, which occurred in the lateral sepals and labellum of Echinosepala aspasicensis, a sapromyophilous species, that released a heterogeneous exudate composed of polysaccharides and lipids. Similar glands have been reported in Bulbophyllum, highlighting the convergence between both groups.Keywords
Funding Information
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (0588/12-1)
- Science Without Borders (0469-13-0)
This publication has 66 references indexed in Scilit:
- A light in the shadow: the use of Lucifer Yellow technique to demonstrate nectar reabsorptionPlant Methods, 2013
- Histopathology of postbloom fruit drop caused by Colletotrichum acutatum in citrus flowersEuropean Journal of Plant Pathology, 2012
- The family of terpene synthases in plants: a mid‐size family of genes for specialized metabolism that is highly diversified throughout the kingdomThe Plant Journal, 2011
- Morphological and histological characterization of the osmophores and nectaries of four species of Acianthera (Orchidaceae: Pleurothallidinae)Österreichische botanische Zeitschrift, 2010
- Self-incompatibility and myophily in Octomeria (Orchidaceae, Pleurothallidinae) speciesÖsterreichische botanische Zeitschrift, 2009
- Labellar Micromorphology of Two Euglossine-pollinated Orchid Genera; Scuticaria Lindl. and Dichaea Lindl.Annals of Botany, 2008
- A Trafficking Pathway for Anthocyanins Overlaps with the Endoplasmic Reticulum-to-Vacuole Protein-Sorting Route in Arabidopsis and Contributes to the Formation of Vacuolar InclusionsPlant Physiology, 2007
- Pollination mechanism in southern Brazilian orchids which are exclusively or mainly pollinated by halictid beesÖsterreichische botanische Zeitschrift, 1999
- Simultaneous Demonstration of Lipids and Starch in Plant TissuesStain Technology, 1975
- N,N-Dimethyl- p -phenylenediamine Oxidation by Serum from Schizophrenic ChildrenScience, 1958