(A) Confocal microscope images of BOR1-GFP and GFP-NIP5;1 localisation in A. thaliana roots, revealing polar localisation of both transporters, facing inwards and outwards, respectively. Cell file identities are shown in the top-left with numbers representing, in increasing order, cell files from the outermost to the innermost cells, such as ep, epidermis; co, cortex; en, endodermis; va, vasculature. (B) Detailed view along a transversal section of the tissue at the proximal meristem. lrc, lateral root cap. (C) Schematic diagram of the NIP-BOR boron transport model, consisting of a transversal root cross-section composed of cells between the medium and the xylem. For a simplified A. thaliana model, we consider . Depicted is a generic root model consisting of cell files, not showing all cells and cell walls in between and for illustration purposes. The model includes intracellular and apoplastic compartments, as well as membrane-based properties such as transporter activity and background permeability rates. : cell wall width; : cell width; : cell height. For a full description of the parameters, see Table 1.