The Forgotten Component of Plant Water Potential: A Reply - Tissue Pressures are not Additive in the Way M. J. Canny Suggests

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