Résumé
Descriptions of root internal structure are often limited to 2D cross-sections, with little information about three dimensions, and the evolution of xylem vessels along root axis has not been clearly presented. A computer-aided 3D-reconstruction method was developed based on paraffin serial slices techniques. The image processing protocol involved slice images alignment, registration, and 3D reconstruction. The stability of this approach was quantified and proven to be satisfactory. The 3D reconstruction conducted on wheat nodal roots illustrated that metaxylem vessel number decreased along root axis. Most vessels connected to the existent or new-formed vessels by lateral cell walls before disappearing. Thus metaxylem vessels in longitudinal profiles were not straightforward. The proposed imaging technique was low cost. It allowed various visualizations and quantitative comparisons of root structures. In the ongoing work, the technique is used to illustrate the spatial coordination of the radial pathway (passage cells, lateral roots), and longitudinal conduits (xylem vessels) of water and nutrient transport.