Ultrastructure and optics of the prism‐like petal epidermal cells of Eschscholzia californica (California poppy)

Abstract

Summary The petals of Eschscholzia californica (California poppy) are robust, pliable and typically coloured intensely orange or yellow owing to the presence of carotenoid pigments; they are also highly reflective at certain angles, producing a silky effect.To understand the mechanisms behind colour enhancement and reflectivity in California poppy, which represents a model species among early‐divergent eudicots, we explored the development, ultrastructure, pigment composition and optical properties of the petals using light microscopy and electron microscopy combined with both spectrophotometry and goniometry.The elongated petal epidermal cells each possess a densely thickened prism‐like ridge that is composed primarily of cell wall. The surface ridges strongly focus incident light onto the pigments, which are located in plastids at the cell base.Our results indicate that this highly unusual, deeply ridged surface structure not only enhances the deep colour response in this desert species, but also results in strongly angle‐dependent ‘silky’ reflectivity that is anisotropic and mostly directional.

Vividly coloured poppy flowers due to dense pigmentation and strong scattering in thin petals

“…5 ). Similar within-flower air cavities have previously been demonstrated to exist in flowers of Caltha palustris (Whatley 1984 ) and California poppy (Wilts et al 2018 ), and have been shown to enhance the brilliance of buttercup flowers (Vignolini et al 2012 ; van der Kooi et al 2017 ).…”

“…For example, the chemistry and vacuolar pH have been studied for blue-flowered Meconopsis species (Yoshida et al 2006 ). E. californica has been investigated because of its pigmentation via the specific pigment eschscholtzxanthin (e.g., Strain 1938 ) and because of its ultrastructure (Wilts et al 2018 ).…”

Signal or cue: the role of structural colors in flower pollination

“…Although optical and physiological properties of plants such as ultrastructure and heliotropism have been shown to significantly increase the temperature of internal flower parts, potentially increasing pollen growth and accelerate ovule fertilization in some species (van der Kooi et al. 2017; Wilts et al. 2018), its effect on pollinator attraction remains inconclusive (Totland 1996).…”

Elena M. Kramer

“…I particularly like Beverley Glover's work on the physics of pollinator attraction (e.g. Moyroud & Glover, ; Wilts et al ., ), which has revealed new and surprising aspects of flower–pollinator interactions. Of course, I love a good evo‐devo story, such as Mark Rausher's work on petal spots in Clarkia (Martins et al ., ) or Francois Parcy's study of LEAFY function in Welwitschia (Moyroud et al ., ).…”