Figure 7.31 Spatial distribution of (a) elongation rates and (b) turgor pressures along apical zones of maize roots grown either in hydrated (Ψ = -0.02 MPa; filled circles) or rather dry ($\Psi$ = -1.6 MPa; open circles) vermiculite. Note that water deficit only depressed growth at positions more than 2 mm from the apex but $P$ was lower at all positions in water deficient roots. (WG Spollen and RE Sharp, Plant Physiol 19: 565-576, 1991)