Structure of the Osmophore and Labellum Micromorphology in the Sexually Deceptive Orchids Ophrys Bombyliflora and Ophrys tenthredinifera (Orchidaceae)

Abstract

Premise of research. The insect-like flowers of the Ophrys orchids are adapted to sexually deceptive pollination through pseudocopulation, providing chemical, visual, and tactile stimuli for male insects. Although the chemical composition of the odor bouquet of several species has long been identified, the precise site of fragrance production in the labellum remains unknown for most species, and little attention has been given to the visual and tactile signals provided by the labellum for pollinators. Here, the occurrence of an osmophore is investigated and the labellum micromorphology is characterized in detail for Ophrys bombyliflora and Ophrys tenthredinifera, two closely related species pollinated by Eucera bees.Methodology. Labella of flowers before and at anthesis were studied with scanning electron microscopy, light microscopy, and histochemistry.Pivotal results. The labellum of O. bombyliflora presents a distinctive hidden apical appendix that forms a concavity with a multicellular protuberance an...