a and b. Maximum intensity Z-stack projection images of 5 DAG old roots expressing the R2D2 auxin signaling reporter 12 HAT to ammonium (a) or nitrate (b) supplemented media. White arrows mark the position of the 10th and 20th cells from QC; "e" and "c" mark epidermis and cortex, respectively. Scale bar=50 µm. Graphs denote normalized relative auxin levels at the respective positions. Lines represent polynomial regression fit with 95% confidence band. Data are derived from 5 roots per condition from 3 biological replicates. 