Simulations of the model showing computed time courses of osmotic and hydrostatic pressures, cell growth rate, and cell wall thickness in response to changes in the wall hardening factor <i>α</i>.

<p><b>A-C</b>: The effect of dropping <i>α</i> to zero, the equivalent of removing external calcium, (so the wall strength has the value for pectin without cross linking): hydrostatic and osmotic pressure gradients fall to zero as the cell bursts, growth rate becomes unstable and the cell wall bursts as its thickness falls to zero. <b>D-F</b>: Hardening is increased twenty fold, the equivalent of raising the external calcium concentration from 0.1 to 2 mM: turgor pressure rises to equal the osmotic pressure gradient, growth rate falls to zero as the wall thickness rises. <b>H-I</b>: Hardening is lowered to 50% of the steady state value; turgor pressure falls abruptly, growth rate rises and tip thickness remains stable.