Abstract：
CONCLUSIONS: Fiber-like cells with thickened cell walls of specific structure and polymer composition that includes (1 → 4)-β-galactans develop in the outer stem cortex of several moss species gametophytes. The early land plants evolved several specialized cell types and tissues that did not exist in their aquatic ancestors. Of these, water-conducting elements and reproductive organs have received most of the research attention. The evolution of tissues specialized to fulfill a mechanical function is by far less studied despite their wide distribution in land plants. For vascular plants following a homoiohydric trajectory, the evolutionary emergence of mechanical tissues is mainly discussed starting with the fern-like plants with their hypodermal sterome or sclerified fibers that have xylan and lignin-based cell walls. However, mechanical challenges were also faced by bryophytes, which lack lignified cell-walls. To characterize mechanical tissues in the bryophyte lineage, following a poikilohydric trajectory, we used six wild moss species (Polytrichum juniperinum, Dicranum sp., Rhodobryum roseum, Eurhynchiadelphus sp., Climacium dendroides, and Hylocomium splendens) and analyzed the structure and composition of their cell walls. In all of them, the outer stem cortex of the leafy gametophytic generation had fiber-like cells with a thickened but non-lignified cell wall. Such cells have a spindle-like shape with pointed tips. The additional thick cell wall layer in those fiber-like cells is composed of sublayers with structural evidence for different cellulose microfibril orientation, and with specific polymer composition that includes (1 → 4)-β-galactans. Thus, the basic cellular characters of the cells that provide mechanical support in vascular plant taxa (elongated cell shape, location at the periphery of a primary organ, the thickened cell wall and its peculiar composition and structure) also exist in mosses.
摘要：
结论：在几种苔藓种配子体的外茎皮层中发育出具有特定结构和聚合物组成的增厚细胞壁的纤维样细胞，其中包括（1→4）-β-半乳聚糖。早期的陆地植物进化出几种特殊的细胞类型和组织，这些细胞类型和组织在其水生祖先中不存在。其中,导水元素和生殖器官受到了大多数研究关注。尽管专门用于实现机械功能的组织的进化在陆地植物中分布广泛，但研究却很少。对于遵循同质轨迹的维管植物，主要讨论了机械组织的进化出现，主要是从具有基于木聚糖和木质素的细胞壁的皮下立体或硬化纤维的蕨类植物开始的。然而,苔藓植物也面临着机械挑战，缺乏木质化的细胞壁。为了表征苔藓植物谱系中的机械组织，沿着多元的轨迹，我们使用了六种野生苔藓（Polytrichumjuniperinum，Dicranumsp.,罗氏,Eurhynchiadelphussp.,爬虫，和Hylocombiumsplendens）并分析了其细胞壁的结构和组成。在他们所有人中，叶状配子体世代的外茎皮层具有纤维样细胞，细胞壁增厚但未木质化。这样的细胞具有带有尖头的纺锤形形状。这些纤维样细胞中额外的厚细胞壁层由具有不同纤维素微原纤取向的结构证据的亚层组成，并且具有包括(1→4)-β-半乳聚糖的特定聚合物组成。因此，在维管植物类群中提供机械支持的细胞的基本细胞特征(细长的细胞形状，位于主要器官的外围，增厚的细胞壁及其独特的组成和结构）也存在于苔藓中。
