A Comparison of Thermocouple Psychrometer and Pressure Chamber Measurements of Leaf Water Potential in Peanuts

Abstract

SUMMARYThe pressure chamber method for measuring leaf water potential in peanuts was compared with the thermocouple psychrometer technique. The pressure chamber over-estimated leaf water potential by an average of 0.4 MPa over the range −0.5 to −5.0 MPa. It is suggested that the pressure chamber technique may be appropriate in comparative studies of peanut water stress. However, where absolute measurements are required, as in the calculation of leaf turgor potential, either a correction factor should be applied or, preferably, the thermocouple psychrometer technique used. If no account is taken of the discrepancy between techniques, erroneously large negative turgor potentials will result.