Identification of volatile organic compounds (VOC) emitted from three European orchid species with different pollination strategies: two deceptive orchids (Himantoglossum robertianum and Ophrys apifera) and a rewarding orchid (Gymnadenia conopsea)

Volatile organic compounds (VOC) emission was evaluated in the inflorescences of three species of the family Orchidaceae: Himantoglossum robertianum, Ophrys apifera and Gymnadenia conopsea, that comprise three different pollination strategies: non-rewarding food deceptive, non-rewarding sexually deceptive and nectar rewarding, respectively. VOC were dynamically sampled in custom packed glass multi-sorbent cartridge tubes (Carbotrap, Carbopack X and Carboxen 569). A modified Tedlar® gas sampling bag was placed in vivo covering the inflorescence of the studied orchid, a design that prevents the dilution of the VOC mixture emitted by the flower. Multi-sorbent bed tubes were analysed through automatic thermal desorption coupled with a capillary gas chromatography/mass spectrometry detector. A total of 106 different VOC were found in the scents emitted by the three different studied orchids. A 54% of these compounds had already been identified in floral scents. Generally, only 3 compounds were highly abundant in each species: α-pinene, β-pinene and limonene in Himantoglossum robertianum; 1-butanol, butyl ether and caryophyllene in Ophrys apifera; and phenethyl acetate, eugenol and benzaldehyde in Gymnadenia conopsea. The employment of the presented methodology for the retention of emitted VOC has proven to be suitable for the identification of a wide range of floral released compounds.