Wang Zi, Verboven Pieter, Nicolai Bart
Division MeBioS, Department of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium.
Flanders Centre of Postharvest Technology, Willem de Croylaan 42, 3001 Leuven, Belgium.
Plant Methods. 2017 Nov 28;13:105. doi: 10.1186/s13007-017-0256-5. eCollection 2017.
X-ray micro-CT has increasingly been used for 3D imaging of plant structures. At the micrometer resolution however, limitations in X-ray contrast often lead to datasets with poor qualitative and quantitative measures, especially within dense cell clusters of plant tissue specimens. The current study developed protocols for delivering a cesium based contrast enhancing solution to varying plant tissue specimens for the purpose of improving 3D tissue structure characterization within plant specimens, accompanied by new image processing workflows to extract the additional data generated by the contrast enhanced scans.
Following passive delivery of a 10% cesium iodide contrast solution, significant increases of 85.4 and 38.0% in analyzable cell volumes were observed in pear fruit hypanthium and tomato fruit outer mesocarp samples. A significant increase of 139.6% in the number of analyzable cells was observed in the pear fruit samples along the added ability to locate and isolate better brachysclereids and vasculature in the sample volume. Furthermore, contrast enhancement resulted in significant improvement in the definition of collenchyma and parenchyma in the petiolule of tomato leaflets, from which both qualitative and quantitative data can be extracted with respect to cell measures. However, contrast enhancement was not achieved in leaf vasculature and mesophyll tissue due to fundamental limitations. Active contrast delivery to apple fruit hypanthium samples did yield a small but insignificant increase in analyzable volume and cells, but data on vasculature can now be extracted better in correspondence to the pear hypanthium samples. Contrast delivery thus improved visualization and analysis the most in dense tissue types.
The cesium based contrast enhancing protocols and workflows can be utilized to obtain detailed 3D data on the internal microstructure of plant samples, and can be adapted to additional samples of interest with minimal effort. The resulting datasets can therefore be utilized for more accurate downstream studies that requires 3D data.
X射线显微计算机断层扫描（X-ray micro-CT）越来越多地用于植物结构的三维成像。然而，在微米分辨率下，X射线对比度的限制常常导致数据集的定性和定量测量结果不佳，尤其是在植物组织标本的密集细胞簇中。本研究开发了将基于铯的造影增强溶液输送到不同植物组织标本的方案，目的是改善植物标本内的三维组织结构表征，并伴有新的图像处理工作流程，以提取造影增强扫描产生的额外数据。
在被动输送10%碘化铯造影溶液后，梨果实托杯和番茄果实外中果皮样品中可分析细胞体积分别显著增加了85.4%和38.0%。在梨果实样品中，可分析细胞数量显著增加了139.6%，同时在样品体积中定位和分离更好的石细胞和维管束的能力也有所增强。此外，造影增强显著改善了番茄小叶叶柄中厚角组织和薄壁组织的清晰度，从中可以提取关于细胞测量的定性和定量数据。然而，由于基本限制，叶片维管束和叶肉组织未实现造影增强。向苹果果实托杯样品主动输送造影剂确实使可分析体积和细胞有小幅但不显著的增加，但现在可以更好地提取与梨托杯样品相对应的维管束数据。因此，造影剂输送在密集组织类型中对可视化和分析的改善最大。
基于铯的造影增强方案和工作流程可用于获取植物样品内部微观结构的详细三维数据，并且可以轻松地应用于其他感兴趣的样品。因此，所得数据集可用于需要三维数据的更准确的下游研究。
