Convergence point formation in a single layer of cells.

(A) This image is to be considered as a shoot apical meristem viewed from above. Regions of high cell auxin concentration and PIN polarization appear. White arrows make the local direction of PIN polarization more easily visible. There is a strong tendency for PIN proteins to be allocated on membrane elements with small areas (a few examples are pointed by red arrows). This produces an unrealistic pattern of PIN convergence. For explanation of graphical conventions, see Fig 1B. (B) Same simulation, but with lateral diffusion of membrane-bound PINs. The exaggerated role played by membranes with a small area has disappeared and the PIN pattern is more realistic.