X-ray lCT imaging technique reveals corm microstructures of an arctic-boreal cotton-sedge, Eriophorum vaginatum

Thu

10 Jun 2010

X-ray lCT imaging technique reveals corm microstructures of an arctic-boreal cotton-sedge, Eriophorum vaginatum

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Authors: Sarah J. Bogart ^a , Graeme Spiers ^a , Ewa Cholewa ^{b, *}

^aCentre for Environmental Monitoring and Department of Biology, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ont., Canada P3E 2C6

^b Department of Biology, Nipissing University, 100 College Drive, North Bay, Ont., Canada P1B 8L7

X-ray computed tomography (CT), a non-destructive imaging technique, has recently been effectively applied to botanical research. In this study an X-ray lCT technique was developed to allow for anatomical study of the overwintering corms of Eriophorum vaginatum, an ecologically important sedge species in arctic tussock-tundra and boreal peatlands. Using a GE Medical MS8X-130 X-ray lCT scanner, optimal imaging parameters included scanning isolated corms at 80 kVp and 100 lA with a 3500 ms exposure time and an isotropic voxel size of 10 lm. A Gaussian blur image filter with a blur radius (r) of two pixels was applied to the optimal dataset to improve visual detection and contrast of tissues while removing 99.2% of image noise. Using the developed X-ray lCT technique several undocumented anatomical characteristics of the corm were identified including the vascular connection between a parent corm and branching cormel and the 3D shape of sclereid clusters. The 3D structure of sclereid clusters was determined whereby the perimeter of their lance shape is greatly reinforced by sclereids with thicker secondary cell walls as compared to those of the interior of the cluster. The structure of sclereid clusters and their association with leaf traces suggests they may be stabilizing the corm-leaf connection to protect vascular tissues from physical damage. The proposed X-ray lCT technique is an excellent tool for determination of the 3D structure of E. vaginatum corms and may be used to detect alterations in tissue structure and chemistry in response to environmental change in this and other Cyperaceous species.