Article,
Cavitation in plants at low temperature: is sap transport limited by the tensile strength of water as expected from Briggs Z-tube experiment?
New Phytologist, (2007)
Abstract
Xylem cavitation in plants is thought to be caused by a loss of adhesion at the conduit wall surface because a rupture in the body of the water column was implicitly ruled out by an experiment by Lyman J. Briggs with Z-tube capillaries. However, Briggs reported a drastic increase in cavitation pressure of water below 5C which, if it were also true in xylem conduits, would suggest that water transport in plants could be limited by water cohesion at low temperature. In this study we have repeated Briggs experiment using stem segments. Xylem vulnerability curves were obtained with a centrifuge technique at 1, 25 and 50C on yew (Taxus baccata). Contrary to Briggs finding, vulnerability to cavitation, measured as per cent loss conductance, did not increase sharply at 1C and was even less than at 25C and 50C. Moreover, the onset of cavitation in yew at 1C was measured at a much more negative pressure than Briggs value. This points out an artefact in Briggs experiment at low temperature possibly related to imperfections in the tube walls which act as cavitation nuclei.
