A biosynthesis/inactivation model for enzymatic WLFs or non-enzymatically mediated cell evolution.

We perform the analysis of influence of a 'wall-loosening factor' (hereafter: WLF) activity in cases of isotropic or anisotropic growth of a plant cell/organ. We further explore a generalized form of the Lockhart/Ortega type of equation and make the 'extensibility' Φ (and the yield stress Y) a time and space dependent parameter, able to report on changing (location-dependent) viscoelastic cell wall properties. This procedure results in scalar and tensor equations, which model WLF-mediated isotropic/anisotropic loosening of polymers composing plant cell walls, thereby allowing pressure-driven polymer creep and plant cell expansion growth. An application to six empirical situations, which temporally and spatially vary the amount of WLFs in the cell wall, is anticipated. Combining the resulting explicit formulae with a curve fitting routine provides a new analytical tool that may relate to physiology and biochemistry of the growth process. It is shown, that the regression lines calculated for the derived growth functions perfectly fit (R(2)~/=0.99998) the experimental data.