Figure 1.

Schematic organization of the primary root. (A) The different cell layers in a longitudinal section along the primary root in Arabidopsis, note that there is only one cell per root cell layer; (B) the different cell layers in a longitudinal section along the primary root of M. truncatula, showing several cortical cells (only three are represented whereas four to five layers are usually observed); (C) Longitudinal organization of the primary root in the younger region of the root (close to the root tip), showing the different zones of the LR specification steps. (A) and (B) are adapted from [50]; (C) is adapted from [49].