Marine plants control the accumulation of biofouling organisms (epibionts) on their surfaces by various chemical and physical means. Ascophyllum nodosum is a perennial multicellular brown alga known to shed patches of epidermal material, thus removing epibionts and exposing unfouled surfaces to another cycle of colonization. While surface shedding is documented in multiple marine macroalgae, the cell and developmental biology of the phenomenon is almost unexplored. A previous investigation of Ascophyllum not only revealed regular cycles of epibiont accumulation and epidermal shedding but also stimulated the development of methods to detect the corresponding changes in epidermal (meristoderm) cells that are reported here. Confocal laser scanning microscopy of cell walls and cytoplasm fluorescently stained with Solophenyl Flavine 7GFE (Direct Yellow 96) and the lipophilic dye Rhodamine B (respectively) was combined with light and electron microscopy of chemically fixed or freeze-substituted tissues. As epibionts accumulated, epidermal cells generated thick, apical cell walls in which differentially stained central layers subsequently developed, marking the site of future cell wall separation. During cell wall separation, the outermost part of the cell wall and its epibionts plus the upper parts of the anticlinal walls between neighboring cells detached in a layer from multiple epidermal cells, exposing the remaining inner part of the cell wall to new colonizing organisms. These findings highlight the dynamic nature of apical cell wall structure and composition in response to colonizing organisms and lay a foundation for further investigations on the periodic removal of biofouling epibionts from the surface of Ascophyllum fronds.

中文翻译：

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细胞壁结构变化导致褐藻 Ascophyllum nodosum 分离和脱落生物污染的表皮细胞壁层

海洋植物通过各种化学和物理手段控制其表面上生物污垢生物（表皮生物）的积累。Ascophyllum nodosum 是一种多年生多细胞褐藻，已知会脱落表皮物质，从而去除表皮生物并将未污染的表面暴露于另一个定植周期。虽然在多种海洋大型藻类中记录了表面脱落，但这种现象的细胞和发育生物学几乎没有被探索过。先前对 Ascophyllum 的研究不仅揭示了表皮细胞积累和表皮脱落的规律循环，而且还刺激了检测此处报告的表皮（分生组织）细胞相应变化的方法的发展。用 Solophenyl Flavine 7GFE（直接黄 96）和亲脂性染料罗丹明 B（分别）荧光染色的细胞壁和细胞质的共聚焦激光扫描显微镜与化学固定或冷冻替代组织的光学和电子显微镜相结合。随着表皮细胞的积累，表皮细胞产生厚厚的顶端细胞壁，其中随后形成了差异染色的中央层，标志着未来细胞壁分离的部位。在细胞壁分离过程中，细胞壁的最外面部分及其表皮生物体加上相邻细胞之间的背斜壁的上部与多个表皮细胞分离成一层，使细胞壁的剩余内部部分暴露于新的定殖生物。