Fig. 8.

(Color figure online) Schematic illustrating the geometry used for root hair length quantification with distance from the initiating surface. For both cylindrical (a) and Cartesian (b) geometries, the hair length ($L_{\mathrm{r},\mathrm{tot}}$) enclosed within each of n annular sub-volumes is recorded. The fluid-coincident hair length ($L_{\mathrm{r},\mathrm{wet}}$) under explicit growth conditions (c) is calculated by neglecting the gaseous pore-coincident fraction of $L_{\mathrm{r},\mathrm{tot}}$ (d). For the homogenous controls in which fluid is not explicitly considered (e), an approximation of the wetted length is given by multiplying $L_{\mathrm{r},\mathrm{tot}}$ by the volume fraction of hydrated textural phase (j) in the non-primary mineral domain (f)