Floral nectary and osmophore of Epipactis helleborine (L.) Crantz (Orchidaceae)

The analysis of flowers collected at different stages of anthesis provides strong evidence to conclude that the shell-shaped hypochile and the knobs of epichile form a nectary. The scent comes from the aromatic constituents of nectar and the epichile tissue and the apices of all tepals (osmophores). The comparison between pollinated and unpollinated flowers revealed that the anthesis of unpollinated flowers lasted up to the 16th day. The nectariferous secretory cells formed single-layered epidermis and several layers of underlying parenchyma built by small, isodiametric cells with thin walls and dense cytoplasm, relatively large nuclei, supplied by collateral vascular bundles. During the floral lifespan, the residues of secreted material were higher on the hypochile cells. The lipoid-carbohydrate material and lipid globules in the cell walls and in the cytoplasm were localised. The abundance of starch grains was observed at the beginning of anthesis and their gradual reduction during the flower lifespan. At the end of anthesis in unpollinated flowers, the lipoid-carbohydrate-phenolic materials have been demonstrated. The phenolic material was the same as in plastoglobuli. The features such as irregular plasmalemma, the secretory vesicles that fuse with it, fully developed dictyosomes, numerous profiles of ER indicate vesicle-mediated process of secretion. The substances could be transported by vesicles to the periplasmic space via granulocrine secretion and then to the external surface. Both micro-channels and slightly developed periplasmic space were visible in the hypochile epidermis. This is the first time for anatomical survey of secretory tissue in pollinated and unpollinated flowers of E. helleborine.