Bias in pressure chamber measurements of leaf water potential

Abstract

A new technique is described for preventing loss of tissue water from excised leaves during pressure-chamber determinations of leaf water potential. Unless such loss is prevented, from excision through to conclusion of measurement, results will be biased. For field-grown wheat and barley in southern England, bias varies diurnally and with soil water status, and can be as large as 0.6 MPa (6 bar). Neither humidification of the chamber, nor storage of leaves in foil-lined bags after excision nullifies the bias, although storage in moist bags — a common practice — does lessen it, but to a variable extent. A technique involving the wrapping of leaves in plastic clingfilm prior to excision and throughout measurement which is both reliable and convenient to use is described.