(Transmission electron microscopy on ultrathin section of a high-pressure frozen, freeze-substituted and resine-embedded 5-day-old Arabidopsis root)

In the centre of the micrograph the elongated tracheary elements (xylem) of Arabidopsis thaliana show classic secondary wall thickenings at the edges and cavities in the central part. Tracheids are surrounded by perycle, endodermis and cortex cells.