Figure 7.

Optics of mature petal of Eschscholzia californica. (a) Imaging scatterometry of the epoxy cast corresponding to the adaxial surface. The circles indicate scattering angles of 5°, 30°, 60° and 90°. Light scattering by the cast's surface is highly anisotropic, as shown by the appearance of a line in space – a mirror would, for instance, only reflect a single spot (cf. van der Kooi et al., 2017). (b) Goniometry spectra for a fixed angle of incidence of 135° of a fresh petal from the adaxial epidermis. (c) Polar plot of average reflectance in the wavelength range 550–650 nm for a fresh petal from the adaxial (green) and abaxial (red) epidermis. (d) Goniometry of an epoxy replica of the adaxial epidermis for angles of incidence of 30° (blue), 40° (red) and 50° (black). Goniometry results confirm the directional and anisotropic light scattering by the petal.