Nees-Institut für Biodiversität der Pflanzen, Rheinische Friedrich-Wilhelms-Universität Bonn, Meckenheimer Allee 170, D-53115, Bonn, Germany.
Am J Bot. 2018 Jul;105(7):1109-1122. doi: 10.1002/ajb2.1136. Epub 2018 Aug 6.
Stinging hairs are striking examples of plant microengineering-the plant equivalent of the hypodermic syringe. The requisite mechanical properties are mostly achieved by cell wall mineralization. Stinging hairs of Urtica dioica (Urticaceae) are known to be mineralized with silica and calcium carbonate and those of Loasaceae also with calcium phosphate, but no comparative study has been provided across different taxa with stinging hairs.
Light microscopy and scanning electron microscopy (SEM) with cryo-SEM and energy-dispersive x-ray spectroscopy were used to analyze morphology and biomineralization of stinging hairs of 43 species from the families Caricaceae, Euphorbiaceae, Loasaceae, Namaceae, and Urticaceae.
Stinging hair morphology is similar across the taxa studied, in striking contrast to the divergent patterns of biomineralization. Trichome bases are mostly calcified, sometimes silicified, the shafts are mostly calcified, and the apices silicified (Urticaceae), and contain calcium phosphate (Caricaceae, Namaceae), both silica and calcium phosphate (some Loasaceae), or no minerals (Cnidoscolus, Euphorbiaceae). Some stinging hairs are superficially thinly coated with silica over a cell wall otherwise mineralized with calcium carbonate or calcium phosphate.
Mineralization patterns are surprisingly diverse and involve three different biominerals deposited in different parts of individual trichomes with calcium phosphate a common component. The physical properties of different wall regions of the stinging trichomes are thus fine-tuned to optimize their function via modulation of wall thickness and differential element deposition. Similar function is apparently achieved through divergent wall compositions.
蛰刺毛是植物微观工程学的典型范例——植物界的皮下注射器。必要的机械性能主要通过细胞壁矿化来实现。已知荨麻科（Urticaceae）的蛰刺毛被矿化为硅和碳酸钙，萝藦科（Loasaceae）的蛰刺毛还被矿化为磷酸钙，但尚未在具有蛰刺毛的不同分类群中进行过比较研究。
使用光学显微镜和扫描电子显微镜（SEM）以及冷冻扫描电子显微镜（cryo-SEM）和能量色散 X 射线光谱法来分析来自 Caricaceae、Euphorbiaceae、Loasaceae、Namaceae 和 Urticaceae 科的 43 种物种的蛰刺毛的形态和生物矿化。
蛰刺毛形态在研究的分类群中相似，与生物矿化的发散模式形成鲜明对比。毛根基部大多钙化，有时硅化，毛干大多钙化，顶端硅化（荨麻科），并含有磷酸钙（Caricaceae、Namaceae），同时含有硅和磷酸钙（一些萝藦科），或不含矿物质（Cnidoscolus、大戟科）。一些蛰刺毛的细胞壁表面薄薄地涂有一层硅，而细胞壁其他部分则矿化为碳酸钙或磷酸钙。
矿化模式出人意料地多样化，涉及三种不同的生物矿物质，沉积在单个蛰刺毛的不同部位，磷酸钙是常见成分。因此，通过调节细胞壁厚度和差异元素沉积，蛰刺毛不同细胞壁区域的物理性质被精细调整，以优化其功能。显然，类似的功能是通过不同的细胞壁成分实现的。
