Fig. 1. Model scheme of inputs and outputs alongside one representative radial file (shown during the growing season when all cell types are present).

CAM cambium or proliferation zone, ENL enlargement-only zone, THK secondary wall-thickening zone, MAT mature zone with dead cells. The zones are delineated by zone widths (coloured vertical lines). Cells within each zone can only undergo certain processes (e.g. division in the proliferation zone, secondary wall thickening in the thickening zone). Temperature (thermometer icon) acts on all living cell types. A sugar-gradient (dot-dash line) emerges as a function of phloem sugar concentration and the requirements for primary wall growth of enlarging cells and secondary wall thickening of thickening cells. Derived variables are calculated from the model outputs.