The forgotten component of plant water potential

Abstract

Experts in plant water relations are challenged to explain why the standard expression for the water potential of an intact, transpiring leaf omits one of the pressure components, namely the tissue pressure of the living leaf cells. Two questions are posed: A) Is there a reason for omitting this component? B) If not, what evidence exists that it may be ignored? When this component contributes significantly, the water potential cannot be interpreted in the accustomed way as measuring tension in the xylem sap.