High porosity with tiny pore constrictions and unbending pathways characterize the 3D structure of intervessel pit membranes in angiosperm xylem
High porosity with tiny pore constrictions and unbending pathways characterize the 3D structure of intervessel pit membranes in angiosperm xylem
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DOI：
10.1111/pce.13654
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发表时间：
2019-11-13
影响因子：
7.3
通讯作者：
Jansen, Steven
中科院分区：
文献类型：
--
作者：
Zhang, Ya;Carmesin, Cora;Jansen, Steven
木质部导管间的纹孔膜在被子植物水分运输中起着重要作用。然而，它们作为纤维多孔介质的三维（3D）结构仍然未知，主要是由于技术挑战和样品制备人工制品。在这里，我们采用了一种建模方法的基础上的厚度测量新鲜和完全萎缩的坑膜的七个物种。还通过用已知尺寸的胶体金颗粒灌注新鲜材料来目视研究孔收缩。根据收缩模型，新鲜的纹孔膜显示出微小的孔隙收缩约。20 nm，但具有平均0.81的非常高的孔隙率（即孔体积分数）。灌注实验表明，在新鲜样品中，远低于50 nm的透射电子显微镜的基础上，类似的孔收缩。干燥造成50%的收缩坑膜，导致更小的孔隙收缩。这些研究结果表明，坑膜代表一个介孔介质，具有多个收缩的孔隙空间的特点。收缩比先前假设的小得多，但孔隙体积大且高度互连。孔隙不会形成高度曲折、弯曲或弯曲的通道。这些见解提供了一个新的观点，坑膜，这是必不可少的发展机制，通过这种多孔介质的空气播种的三维理解。
Pit membranes between xylem vessels play a major role in angiosperm water transport. Yet, their three-dimensional (3D) structure as fibrous porous media remains unknown, largely due to technical challenges and sample preparation artefacts. Here, we applied a modelling approach based on thickness measurements of fresh and fully shrunken pit membranes of seven species. Pore constrictions were also investigated visually by perfusing fresh material with colloidal gold particles of known sizes. Based on a shrinkage model, fresh pit membranes showed tiny pore constrictions of ca. 20 nm, but a very high porosity (i.e. pore volume fraction) of on average 0.81. Perfusion experiments showed similar pore constrictions in fresh samples, well below 50 nm based on transmission electron microscopy. Drying caused a 50% shrinkage of pit membranes, resulting in much smaller pore constrictions. These findings suggest that pit membranes represent a mesoporous medium, with the pore space characterized by multiple constrictions. Constrictions are much smaller than previously assumed, but the pore volume is large and highly interconnected. Pores do not form highly tortuous, bent, or zigzagging pathways. These insights provide a novel view on pit membranes, which is essential to develop a mechanistic, 3D understanding of air-seeding through this porous medium.