Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700, Fribourg, Switzerland.
Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
New Phytol. 2018 Aug;219(3):1124-1133. doi: 10.1111/nph.15229. Epub 2018 Jun 1.
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.
加利福尼亚罂粟（California poppy）的花瓣坚韧、柔韧，通常呈现出强烈的橙色或黄色，这是由于类胡萝卜素色素的存在；在某些角度下，它们还具有高度的反射性，产生出丝质般的效果。为了了解加利福尼亚罂粟中增强颜色和反射率的机制，这种植物是早期分化的真双子叶植物中的模式物种之一，我们使用光学显微镜和电子显微镜结合分光光度法和折射角测量法，研究了花瓣的发育、超微结构、色素组成和光学特性。狭长的花瓣表皮细胞各具有一个密集增厚的棱柱状脊，主要由细胞壁组成。表面脊强烈地将入射光聚焦到位于细胞基部质体中的色素上。我们的结果表明，这种非常不寻常的、深脊状的表面结构不仅增强了这种沙漠物种的深颜色响应，而且还导致强烈的角度依赖性“丝质”反射率，这种反射率具有各向异性且主要是定向的。
