Figure 4.

A, Spatial mapping of [¹¹C]IAA biosynthesis from [¹¹C]IAN across three nodal root zones, including the upper proximal region (zone 1), the midroot region including the elongation zone (zone 2), and the root tip (zone 3; n = 5, control; n = 6, root herbivory). Higher levels of [¹¹C]IAN metabolism are indicated in zone 1. Root herbivore treatment significantly increased tracer metabolism in this zone but had no effect in zones 2 and 3. B, Ln-fold change in NIT1 and NIT2 gene expression measured across the same three root zones as a function of root herbivore treatment. No change in NIT1 gene expression was noted across any of the zones or as a function of treatment (n = 3). On the other hand, NIT2 gene expression was significantly down-regulated with herbivore treatment in zones 2 and 3 but exhibited a slight up-regulation of expression in zone 1 (n = 4), though not statistically significant (P = 0.062). Where appropriate, statistical significance was denoted as *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001.