Institute of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany.
Institute of Inorganic Chemisty, University of Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany.
Planta. 2022 Sep 10;256(4):75. doi: 10.1007/s00425-022-03976-2.
TEM and AFM imaging reveal radial orientations and whorl-like arrangements of cellulose microfibrils near the S1/S2 interface. These are explained by wrinkling during lamellar cell growth. In the most widely accepted model of the ultrastructure of wood cell walls, the cellulose microfibrils are arranged in helical patterns on concentric layers. However, this model is contradicted by a number of transmission electron microscopy (TEM) studies which reveal a radial component to the microfibril orientations in the cell wall. The idea of a radial component of the microfibril directions is not widely accepted, since it cannot easily be explained within the current understanding of lamellar cell growth. To help clarify the microfibril arrangements in wood cell walls, we have investigated various wood cell wall sections using both transmission electron microscopy and atomic force microscopy, and using various imaging and specimen preparation methods. Our investigations confirm that the microfibrils have a radial component near the interface between the S1 and S2 cell wall layers, and also reveal a whorl-like microfibril arrangement at the S1/S2 interface. These whorl-like structures are consistent with cell wall wrinkling during growth, allowing the radial microfibril component to be reconciled with the established models for lamellar cell growth.
TEM 和 AFM 成像揭示了 S1/S2 界面附近纤维素微纤维的放射状取向和螺旋状排列。这可以通过层状细胞生长过程中的褶皱来解释。在最广泛接受的细胞壁超微结构模型中，纤维素微纤维在同心层上呈螺旋状排列。然而，这一模型与许多透射电子显微镜（TEM）研究相矛盾，这些研究揭示了细胞壁中微纤维取向的径向成分。微纤维方向的径向成分的想法并没有被广泛接受，因为它不能很容易地用目前对层状细胞生长的理解来解释。为了帮助澄清细胞壁中微纤维的排列，我们使用透射电子显微镜和原子力显微镜以及各种成像和标本制备方法研究了各种细胞壁部分。我们的研究证实，微纤维在 S1 和 S2 细胞壁层之间的界面附近具有径向成分，并且在 S1/S2 界面处也显示出螺旋状微纤维排列。这些螺旋状结构与生长过程中的细胞壁褶皱一致，使得径向微纤维成分与层状细胞生长的既定模型相协调。
