Fig. 1

Dynamics of DS induced auxin accumulation. a Layout of auxin efflux carriers (PIN proteins) as used in the simulations, shown on 1/2 of the root. Starting levels of PIN (effective efflux permeability P _{e f f} ) of individual cell faces are one of three: high (red; 20 μm/s), low (cyan; 5 μm/s) or background (bg; no colour; 1 μm/s), following [21]. These layouts result in a rootward auxin flux in the vascular tissue (to the right in these figures) and a less strong shootward counterflux in the cortex. The cartoon plant on top illustrates the orientation of the root segments. b Simulation setup: from the start of the simulation, DS is produced continuously in a single epidermal cell and diffuses outward through the root segment. c–f Auxin accumulation in response to DS signal produced in a single epidermal cell after 1, 10 and 60 minutes from the start of the simulation. White contours occur at 5 C _v and 25 C _v (bold). C _v is the average vascular auxin concentration before induction. g Corresponding concentration profiles of the DS. This is the same for all simulations, regardless of response parameters. Contour lines are plotted at 0.3, 0.1, 0.03, 0.01, 0.003 and 0.0001 a.u. (DS concentration in arbitrary concentration units). All simulations have an overall sensitivity of h=100/a.u.. The response steepness is varied from p = 1 (c), 2 (d), 3 (e) to 5 (f). Movies of C-F are available as Additional files 1, 2, 3 and 4