title: The mirror crack'd: both pigment and structure contribute to the glossy blue appearance of the mirror orchid, Ophrys speculum.
abstract: The Mediterranean orchid genus Ophrys is remarkable for its pseudocopulatory pollination mechanism; naïve male pollinators are attracted to the flowers by olfactory, visual and tactile cues. The most striking visual cue is a highly reflective, blue speculum region at the centre of the labellum, which mimics the corresponding female insect and reaches its strongest development in the mirror orchid, O. speculum. We explored the structure and properties of the much-discussed speculum by scanning and transmission electron microscopic examination of its ultrastructure, visible and ultraviolet (UV) angle-resolved spectrophotometry of the intact tissue, and mass spectrometry of extracted pigments. The speculum contrasts with the surrounding labellar epidermis in being flat-celled with a thick, smooth cuticle. The speculum is extremely glossy, reflecting intense white light in a specular direction, but at more oblique angles it predominantly reflects blue and UV light. Pigments in the speculum, dominantly the cyanidin 3-(3''-malonylglucoside), are less diverse than in the surrounding regions of the labellar epidermis and lack quercetin copigments. Several physical and biochemical processes interact to produce the striking and much-discussed optical effects in these flowers, but the blue colour is not produced by structural means and is not iridescent.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.|Department of Physics, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
authors.forename: Silvia
authors.initials: S
authors.lastname: Vignolini
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Davey
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Bateman
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Rudall
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
authors.forename: Edwige
authors.initials: E
authors.lastname: Moyroud
authors.affiliation: Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Tratt
authors.affiliation: Radagatan 8, SE 531-52, Lidköping, Sweden.
authors.forename: Svante
authors.initials: S
authors.lastname: Malmgren
authors.affiliation: Department of Physics, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
authors.forename: Ullrich
authors.initials: U
authors.lastname: Steiner
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK.
authors.forename: Beverley J
authors.initials: BJ
authors.lastname: Glover
mesh_terms: D000818:Animals; D000872:Anthocyanins / Q000737:chemistry; D002473:Cell Wall / Q000648:ultrastructure; D003116:Color; D005260:Female; D035264:Flowers / Q000502:physiology* / Q000648:ultrastructure*; D005960:Glucosides / Q000737:chemistry; D007313:Insecta / Q000502:physiology*; D008027:Light; D008297:Male; D008855:Microscopy, Electron, Scanning; D055620:Optical Phenomena; D029595:Orchidaceae / Q000502:physiology*; D010860:Pigments, Biological / Q000737:chemistry* / Q000502:physiology; D019441:Plant Epidermis / Q000737:chemistry; D054817:Pollination; D011794:Quercetin / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
chemical_list: D000872:Anthocyanins; D005960:Glucosides; D010860:Pigments, Biological; C580656:cyanidin 3-(3''-malonylglucoside); C017154:cyanidin; D011794:Quercetin; C017185:delphinidin