Figure 1.

Model of a single file of cells. In the model, auxin molecules are initially in the source agar block, travel through the stem segment and are collected in the final agar block. We model the stem segment as a single two-dimensional line of N cells for simplicity, and suppose that efflux carriers are located on the downstream face of each cell membrane. We solve for the auxin concentrations in the two agar blocks, the N cytoplasm compartments and the N + 1 apoplast compartments.