c and d. Representation and quantification of cell length in epidermal (e) and cortical (c) cell files. Optical, longitudinal sections of 5 DAG old Col-0 roots 12 HAT to ammonium (C) or nitrate (D) supplemented media. The first 20 epidermal (e) and cortex (c) cells (from quiescent center (QC)) are highlighted in grey and in red on ammonium (C), and in blue and green on nitrate (D), respectively. Scale bar=30 µm. Column bars denote the geometric mean of the cell lengths at the respective positions. Lines represent a polynomial regression fit, with calculated slopes between cells 10 and 20 of 3.32639+0.17172 (ammonium, epidermis), 1.22033+0.08754 (ammonium, cortex) and 1.70502+0.09532 (nitrate, epidermis), 0.82342+0.06973 (nitrate, cortex). Data are derived from 3 biological replicates, n=18 roots in each case. 