title: Why do so many petals have conical epidermal cells?
abstract: BACKGROUND
  The conical epidermal cells found on the petals of most Angiosperm species are so widespread that they have been used as markers of petal identity, but their function has only been analysed in recent years. This review brings together diverse data on the role of these cells in pollination biology.
  
  
  METHODS
  The published effects of conical cells on petal colour, petal reflexing, scent production, petal wettability and pollinator grip on the flower surface are considered. Of these factors, pollinator grip has been shown to be of most significance in the well-studied Antirrhinum majus/bumble-bee system. Published data on the relationship between epidermal cell morphology and floral temperature were limited, so an analysis of the effects of cell shape on floral temperature in Antirrhinum is presented here. Statistically significant warming by conical cells was not detected, although insignificant trends towards faster warming at dawn were found, and it was also found that flat-celled flowers could be warmer on warm days. The warming observed is less significant than that achieved by varying pigment content. However, the possibility that the effect of conical cells on temperature might be biologically significant in certain specific instances such as marginal habitats or weather conditions cannot be ruled out.
  
  
  CONCLUSIONS
  Conical epidermal cells can influence a diverse set of petal properties. The fitness benefits they provide to plants are likely to vary with pollinator and habitat, and models are now required to understand how these different factors interact.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Whitney
authors.forename: K M Veronica
authors.initials: KM
authors.lastname: Bennett
authors.forename: Matthew
authors.initials: M
authors.lastname: Dorling
authors.forename: Lucy
authors.initials: L
authors.lastname: Sandbach
authors.forename: David
authors.initials: D
authors.lastname: Prince
authors.forename: Lars
authors.initials: L
authors.lastname: Chittka
authors.forename: Beverley J
authors.initials: BJ
authors.lastname: Glover
mesh_terms: D000818:Animals; D048430:Cell Shape; D035264:Flowers / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D059828:Plant Cells / Q000378:metabolism* / Q000648:ultrastructure; D019441:Plant Epidermis / Q000166:cytology* / Q000648:ultrastructure; D054817:Pollination / Q000502:physiology; D013696:Temperature