Abstract
Martin Canny's concepts of “tissue pressure” and its derivative “compensating pressure”
are reviewed. Tissue pressure arises when the volume change of some living cells exerts
a pressure on adjacent living or dead cells. Contrary to previous assertions, tissue
pressure cannot cause a permanent change in pressure potential or water potential
of adjacent cells. Tissue pressure induces only a transitory increase of pressure
and water potential. After equilibrium is reestablished, the same or a more negative
pressure or water potential results. The idea that tissue pressure can prevent or
repair xylem embolism is without merit.
Key words
Tissue pressure - water potential - xylem tension
