A technique for the elucidation of corm microstructures of a cotton-sedge, Eriophorum vaginatum, using X-ray muCT imaging

X-ray computed tomography (CT) has recently been effectively applied to botanical research as a suite of non-destructive imaging methods. The application of Medical X-ray CT and X-ray muCT was investigated to digitally examine the tussock and corm of Eriophorum vaginatum, an ecologically important sedge species in arctic tussock-tundra and boreal peatlands. A Toshiba Aquilion 64 Medical X-ray CT scanner was successfully used to image the morphological components of the E. vaginatum tussock with details at the tissue-level being marginally apparent in the images. This result suggested that higher-resolution scans to study corm tissues may be possible. Thus, a novel technique was developed to scan isolated corms with a GE MS8X-130 X-ray muCT scanner. Optimal imaging parameters included scanning' corms at 80kVp and 100muA using an isotropic voxel size of 10mum. A Gaussian blur image filter was applied to the optimal dataset to improve tissue detection and visual contrast of images with minimal loss of feature boundaries. A blur radius (sigma) of 2 pixels reduced image noise by 99.2%. With this X-ray muCT technique, several undocumented anatomical characteristics of the corm were identified including the vascular connections between branching corms and the 3D shape and location of sclereid clusters. Sclereid clusters are lance shaped and their perimeter is greatly reinforced by sclereids with thicker secondary cell walls as compared to those of the interior of the cluster. This structure of sclereid clusters and their association with leaf traces in' groups suggests they may protect vascular tissues from physical damage by stabilizing the leaf-corm connection. In contrast, sclereid clusters were not located at the interface between corms and cormels which allows for them to be easily separated. Sclereid cluster stabilization of this interface may not be required either due to the ability of each corm to initiate tussock growth or due to the compact tussock morphology which may render such strengthening irrelevant for survival of this species. In conclusion, X-ray muCT is an excellent tool to determine the 3D structure of E. vaginatum corms, while the use of lower resolution Medical X-ray CT scanning supports the investigation of the branching architecture of the tussock. Medical X-ray CT and X-ray muCT scans may be used in future to detect alterations in tussock and tissue structure or chemistry in response to environmental changes within E. vaginatum and in similar species.;Keywords: Medical X-ray CT, X-ray muCT, microtomography, Eriophorum vaginatum, cotton-sedge, sclereid clusters, tussock architecture, 3D image...