To further knowledge on cell wall composition in early land plants, we localized cell wall constituents in placental cells of the liverwort Marchantia polymorpha L. using monoclonal antibodies (MAbs) in the transmission electron microscope and histochemical staining. The placenta of M. polymorpha is similar to the majority of bryophytes in that both generations contain transfer cells with extensive wall ingrowths. Although the four major cell wall polymers, i.e., cellulose, pectins, hemicelluloses, and arabinogalactan proteins, are present, there are variations in the richness and specificity across generations. An abundance of homogalacturonan pectins in all placental cell walls is consistent with maintaining cell wall permeability and an acidic apoplastic pH necessary for solute transport. Although similar in ultrastructure, transfer cell walls on the sporophyte side in M. polymorpha are enriched with xyloglucans and diverse AGPs not detected on the gametophyte side of the placenta. Gametophyte wall ingrowths are more uniform in polymer composition. Lastly, extensins and callose are not components of transfer cell walls of M. polymorpha, which deviates from studies on transfer cells in other plants. The difference in polymer localizations in transfer cell walls between generations is consistent with directional movement from gametophyte to sporophyte in this liverwort.

为了进一步了解早期陆地植物的细胞壁组成，我们在 透射电子显微镜和组织化学染色中使用单克隆抗体（MAb）定位了地钱地钱胎盘细胞中的细胞壁成分。地钱的胎盘  与大多数苔藓植物相似，两代都含有具有广泛壁向内生长的转移细胞。 尽管存在四种主要的细胞壁聚合物，即纤维素、果胶、半纤维素和阿拉伯半乳聚糖蛋白，但不同世代的丰富度和特异性存在差异。所有胎盘细胞壁中丰富的同型半乳糖醛酸果胶与维持细胞壁通透性和溶质运输所需的酸性质外体 pH 一致。尽管超微结构相似，但地精孢子体侧的转移细胞壁富含木葡聚糖和胎盘配子体侧未检测到的多种 AGP。配子体壁向内生长的聚合物成分更加均匀。最后，延伸蛋白和胼胝质不是地钱花转移细胞壁的成分， 这与对其他植物转移细胞的研究不同。代际间转移细胞壁中聚合物定位的差异与该苔类植物中从配子体到孢子体的定向运动一致。