Derivation of Plant Cell Wall Water Content by Examination of the Water-Holding Capacity of Membrane-Disrupted Tissues10

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Abstract
Plant cell lumina are several orders of magnitude larger than cell wall pores. If the membranes of the plant sample are disrupted and the tissue dried out, a ψ value should be reached at which the cell lumina have drained but the cell walls remain relatively hydrated. The water content of membrane-disrupted tissues at low ψ may, therefore, serve as a good approximation of plant cell wall water content (CW). The relationship between ψ and water content of membrane-disrupted tissues was measured for four grass spaces over the ψ range of 0 to −40 MPa. It was found that most water loss occurred above a ψ of − 10 MPa. CW was estimated from the water content of membrane-disrupted tissues at lower ψ and it was found that there was very little intra-or intraspecific variability in CW estimates when water content was expressed as a percentage dry weight of the tissue. This is in contrast to the high variability in CW estimated from the analysis of inverse water potential—water content (IP—WC) curves measured with the thermocouple psychrometer. Applications of the membrane-disruption method of estimating CW of plant tissue are discussed.