A technique for measuring xylem hydraulic conductance under high negative pressures
A technique for measuring hydraulic conductances of excised xylem segments exposed to high negative pressures is described. A centrifugal force is used to generate negative pressures ( P ) in the sample and to create a positive hydrostatic pressure difference ( ∆ P ) between its two ends. ∆ ∆ ∆ P forces water through the sample at a flow rate ( F ) determined optically during centrifugation. The sample hydraulic conductance k is derived from F and ∆ P . The sample vulnerability curve is given by the dependence of k on P . Results for Cedrus atlantica Manetti and Laurus nobilis L. shoots are given. The technique is appropriate for the analysis of xylem refilling under negative pressure.