A technique to measure root tip hydraulic conductivity and root water potential simultaneously

A procedure for the simultaneous measurement of hydraulic conductivity and xylem water potential of roots is presented. Roots remain intact and attached to the transpiring plant during measurement. The rate of water uptake by roots is measured at different water potential gradients along the root radial axis, obtained by placing them in solutions with different osmotic potentials. Hydraulic conductivity and xylem water potential are calculated by regression analysis of the relationship between water uptake rate and osmotic potential of the bathing solution, assuming that xylem water potential and reflection coefficient remain constant during measurement. Results for tomato plants experiencing drought are presented and discussed.