Cell wall water dilution: an explanation of apparent negative turgor potentials

Abstract

Errors in psychrometric determinations of osmotic potential (Ψs) due to dilution of the cytoplasm by cell wall water are investigated. Model systems using filter paper to represent the cell wall and sucrose solution and distilled water to represent protoplasm and cell wall water, respectively, show significant dilution of the sucrose solution at cell wall to protoplast ratios typical of plant tissue. Mathematical simulation of error in Ψs determination as a function of percent cell wall and cell wall hydration indicate that wall water dilution can be a significant problem and could explain reported apparent negative turgor potentials.