WINDING THREADS AROUND PLANT-CELLS - A GEOMETRICAL MODEL FOR MICROFIBRIL DEPOSITION

In this paper, a geometrical model is put forward to account for the d eposition orientation of plant cell wall microfibrils (CMFs). The mode l presupposes the insertion in the plasma membrane of CMF initiation c omplexes, which, once inserted, are moved through the fluid plane of t he plasma membrane by the kinetic force of CMF synthesis, leaving CMFs in their wake. Deposition occurs in a limited space and the CMFs are linked to wall matrix molecules. CMF orientation is governed by the la ws of geometry and, taking space-limiting conditions into account, the refore depends on (1) cell geometry, (2) the other wall molecules link ed to the CMFs, and (3) the number of CMF initiation complexes inserte d into the plasma membrane, The model does not exclude the idea that c ortical microtubules may determine initial CMF orientation after cell division by determining the cell elongation direction.