Fig. 2

Gradients of GlnLux output of leaves of maize seedlings using the GlnLux leaf disk assay. Leaves 1, 2 and 3 were sampled (a). Leaf 3 was assayed at positions 1 (b), 2 (c), 3 (d), and 4 (e), extending from the leaf base to leaf tip. Leaf 2 was assayed at positions 1 (f), 2 (g), 3 (h), 4 (i), and 5 (j). Leaf 1 was assayed at positions 1 (k), 2 (l), and 3 (m). Plants had not been provided with N from germination for a period of 12 days, at which time modified Hoagland’s solution containing 0, 2, 5, 10, 15 or 20 mM N (n) was applied. Plants were allowed different durations (1, 6, 12, 18 or 24 h) of N uptake/assimilation, after which tissue disks were harvested. Means of 3–4 replicates +/− SEM are shown. RLU, relative light units intercepted by the luminometer in a one second interval per well. Asterisks indicate significant differences between the 0 mM (black lines) and 20 mM (red lines) N treatments, based on the Holm-Šídák test at P < 0.05. The data is displayed to highlight the N-uptake/assimilation gradient. The N rate response gradient is highlighted in Additional file 1: Figure S1. The two datasets are the same. Shown is Trial 1. For Trial 2, see Additional file 2: Figure S2 and Additional file 3: Figure S3