Fig. 1.

Schematics of the tissue geometry used for numerical simulations. a Simple geometry considering only intracellular space and cell membrane, with auxin flux considered to occur directly between cells. Here $V_i$ represents the volume of cell i, and $S_{\mathit{ij}}^m$ represents the size of the portion of the membrane of cell i between cells i and j. b Schematics of a plant tissue where the domains representing the apoplast are equally divided between neighbouring cells, and passive auxin flux also occurs in the apoplast. Here $V_{i,j}$ represents the volume of apoplast compartment bordering cell i between cells i and j, and $S_i^{\mathit{jk}}$ represents the size of the border between apoplast compartments (i, j) and (i, k)