Mechanism of Cell Wall Formation

As an outgrowth of x-ray studies on the molecular structure of cellulose walls of plant fibers (12, 13, 14), several steps in the process by which the cell wall grows in thickness, seem to have become evident. They are associated with the regularity of molecular arrangement in the wall and with the forces which produce that regularity of structure. As the x-ray data, during the progress of the investigations, made it more and more certain that the structural units are glucose residues, and that they are arranged with the regularity of the molecules in a crystal, the concept became clearer and more convincing that the mechanism of cell wall growth in thickness was associated intimately with the forces which are active in causing that regular arrangement of the residues, that is, with forces similar to those which produce crystallization. The mechanism which is described in the following pages is concerned with only one phase of cell wall growth ; that is, with the increase in thickness of the cell wall. While it may be associated also with the increase in surface area as the cell becomes enlarged and even with the formation of the original wall, those two phases are not included in the present discussion. The problem then becomes restricted to a consideration of the mechanism by which new cell wall material is deposited upon older previously formed cell wall.