Figure 4. The simple anatomy of A. thaliana roots.
Longitudinal (left) and transverse (right) confocal sections of A. thaliana roots. Green fluorescence highlights the plasma membrane of the pericycle cells of an A. thaliana hma2hma4 double mutant line (Sinclair et al., 2007) (accession Wassilewskija). Red fluorescence of propidium iodide (PI) as a stain is overlaid to visualize cell walls. The root cell layers (consecutive outward to inward) are: epidermis (e), cortex (c), endodermis (n) and pericycle (p). Note that the Casparian Strip surrounding the endodermis cells forms an apoplastic diffusion barrier (Roppolo et al., 2011) that blocks the movement of PI further inward. Image credit: Ute Krämer and Scott A. Sinclair.