The cell wall and control of cell growth

Abstract

The growth of plant cells depends on the interaction between the turgor pressure, which presses the protoplast outwards against the wall, and the mechanical strength of the wall, which tends to prevent any rapid increase in volume (Fig. 4.1). In multicellular organisms, the pressure exerted by neighbouring cells may be important, but in the tissue as a whole the interaction between turgor pressure and wall strength controls growth. In most plant cells, the outward pressure produced by turgor is approximately equalled by the inward force exerted by the wall. As turgor increases, the wall stretches only slightly before the additional forces set up within it serve to counterbalance the increased turgor and to prevent rapid changes in volume. Only in a few cases (such as stored growth — see Section 4.3 — and in the thigmonastic response of Mimosa) do such rapid changes in volume occur.