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| Physical mechanism | Visual appearance | Examples | Function |
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| Thin film interference | Iridescent blue. Interference within the peridium, a 200 nm transparent layer in fungi. | Slime mold Diachea leucopodia | Photoprotection |
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Multilayer interference | Iridescent blue leaves.
Various layers on the surface, each layer less than 100 nm thick. | Peacock fern Selaginella willdenowii,
S. uncinata, Diplazium crenatoserratum (Figure 4),
D. tomentosum, Lindsaea lucida, Danaea nodosa,and Trichomanes elegans | Photoprotection |
| Iridescent blue leaves. Modified chloroplast structures (iridoplasts) with many layers and each layer less than 100 nm thick. | Peacock begonia Begonia pavonina, Phyllagathis rotundifolia (Figure 4), and P. griffithii | Photoprotection |
| Iridescent red. Multilayer system with 17 electron opaque and translucent layers between ten and a few hundred nanometers thick. | Algae Iridaea | Byproduct of wear-protection mechanism |
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| Diffraction gratings | Petals iridescence. Diffractive optics. Surface striated one micrometer apart. | Hibiscus trionum, Tulipa kolpakowskiana | Blue, green, and yellow structural colouration in hibiscus: structural colouration in tulips in the UV part of the spectrum (not visible to people, visible for bees). |
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| Scattering | Microscopic air spaces in surface hairs (trichomes) that reflect the light. Epicuticular wax structures. | Blue spruce Picea pungens | Preferential scattering of short wavelengths and enhanced reflectance of UV. |
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| Photonic crystals | Iridescence in fruits. Iridosomes (secreted by epidermis cells of fruits, partly cellulosic situated inside cell wall), multilayer system arranged in 3D structure.
Internal structure of hollow hairs acts as a 2D photonic crystal (optical fiber with photonic crystal cladding). | Blue quandong Elaeocarpus angustifolius syn. E. grandis
Edelweiss Leontopodium nivale subsp. alpinum | Absorption of UV light, photoprotection, display and defence. |
| Iridescent blue fruit. Multilayers in cell walls of epicarp [11]. | Pollia condensata | Curved micro-Bragg reflector, used for display and defence. |
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| Cholesteric liquid crystals | Modified chloroplasts with helicoidal structures. | Fern Danaea nodosa | |
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