BACKGROUND:Biological materials have a complex, hierarchical structure, with vital structural features present at all size scales, from the nanoscale to the macroscale. A method that can connect information at multiple length scales has great potential to reveal novel information. This article presents one such method with an application to the bamboo culm wall. Moso (Phyllostachys edulis) bamboo is a commercially important bamboo species. At the cellular level, bamboo culm wall consists of vascular bundles embedded in a parenchyma cell tissue matrix. The microfibril angle (MFA) in the bamboo cell wall is related to its macroscopic longitudinal stiffness and strength and can be determined at the nanoscale with wide-angle X-ray scattering (WAXS). Combining WAXS with X-ray microtomography (XMT) allows tissue-specific study of the bamboo culm without invasive chemical treatment. RESULTS:The scattering contribution of the fiber and parenchyma cells were separated with spatially-localized WAXS. The fiber component was dominated by a high degree of orientation corresponding to small MFAs (mean MFA 11°). The parenchyma component showed significantly lower degree of orientation with a maximum at larger angles (mean MFA 65°). The fiber ratio, the volume of cell wall in the fibers relative to the overall volume of cell wall, was determined by fitting the scattering intensities with these two components. The fiber ratio was also determined from the XMT data and similar fiber ratios were obtained from the two methods, one connected to the cellular level and one to the nanoscale. X-ray diffraction tomography was also done to study the differences in microfibril orientation between fibers and the parenchyma and further connect the microscale to the nanoscale. CONCLUSIONS:The spatially-localized WAXS yields biologically relevant, tissue-specific information. With the custom-made bench-top set-up presented, diffraction contrast information can be obtained from plant tissue (1) from regions-of-interest, (2) as a function of distance (line scan), or (3) with two-dimensional or three-dimensional tomography. This nanoscale information is connected to the cellular level features.

译文

背景:生物材料具有复杂的层次结构,在从纳米到宏观的所有尺寸尺度上都具有重要的结构特征。一种可以在多个长度尺度上连接信息的方法具有揭示新颖信息的巨大潜力。本文介绍了一种这样的方法,并将其应用于竹茎壁。毛竹(Phyllostachys edulis)竹是商业上重要的竹种。在细胞水平上,竹茎壁由嵌入实质细胞组织基质中的血管束组成。竹细胞壁中的微纤丝角(MFA)与它的宏观纵向刚度和强度有关,并且可以通过广角X射线散射(WAXS)在纳米尺度上确定。将WAXS与X射线显微断层扫描(XMT)结合使用,可以对竹茎进行组织特异性研究,而无需进行侵入性化学治疗。
结果:通过空间定位的WAXS分离了纤维和实质细胞的散射贡献。纤维组分主要由较高的取向度决定,该取向度对应于较小的MFA(平均MFA 11°)。薄壁组织的方向性明显降低,在较大角度时最大(平均MFA 65°)。纤维比率,即纤维中细胞壁的体积相对于细胞壁的总体积,是通过使散射强度与这两种成分相匹配来确定的。还从XMT数据确定了纤维比例,并且从两种方法获得了相似的纤维比例,一种方法连接到细胞水平,另一种方法连接到纳米级。还进行了X射线衍射断层扫描,以研究纤维与薄壁组织之间微纤维取向的差异,并进一步将微尺度连接到纳米尺度。
结论:空间定位的WAXS产生生物学相关的组织特异性信息。通过提供定制的台式设备,可以从植物组织(1)的感兴趣区域,(2)作为距离的函数(线扫描)或(3)从植物组织获得衍射对比度信息。二维或三维断层扫描。该纳米级信息连接到细胞水平的特征。

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