Functional optics of glossy buttercup flowers

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Abstract

Buttercup (Ranunculus spp.) flowers are exceptional because they feature a distinct gloss (mirror-like reflection) in addition to their matte-yellow coloration. We investigated the optical properties of yellow petals of several Ranunculus and related species using (micro)spectrophotometry and anatomical methods. The contribution of different petal structures to the overall visual signal was quantified using a recently developed optical model. We show that the coloration of glossy buttercup flowers is due to a rare combination of structural and pigmentary coloration. A very flat, pigment- filled upper epidermis acts as a thin-film reflector yielding the gloss, and additionally serves as a filter for light backscattered by the strongly scattering starch and mesophyII layers, which yields the matte-yellow colour. We discuss the evolution of the gloss and its two likely functions: it provides a strong visual signal to insect pollinators and increases the reflection of sunlight to the centre of the flower in order to heat the reproductive organs.

Original languageEnglish
Article number20160933
Number of pages9
JournalJournal of the Royal Society Interface
Volume14
Issue number127
DOIs
Publication statusPublished - 1-Feb-2017

Keywords

  • flower colour
  • epidermis
  • structural coloration
  • thin-film interference
  • pigment
  • starch
  • STARCH LAYER
  • INSECT POLLINATORS
  • RANUNCULUS-ADONEUS
  • STRUCTURAL COLOR
  • SEED PRODUCTION
  • PLANT-TISSUE
  • HELIOTROPISM
  • LIGHT
  • LEAVES
  • PETALS

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