Measurement of water potential in the trunks of citrus trees using screen-caged thermocouple psychrometers

Abstract

Screen-caged thermocouple Psychrometers were used to non-destructively measure the water potential (ψ) in the trunks of mature citrus trees (Citrus sinensis L. Osbeck), and the values compared with the ψ of covered, exposed, and shaded leaves of the same tree. The installation and thermal insulation of the trunk Psychrometers is described. Adequate thermal insulation of the trunk and enclosed Psychrometers was difficult despite a covering of polyurethane foam and reflective aluminium foil, and relatively large temperature gradients were indicated. The measured ψ’s were, however, similar to covered leaf ψ and within the expected range when compared to the leaf and soil values as well as with other published values. Possible methods of further reducing the thermal gradients are discussed. © 1988 Taylor & Francis Group, LLC.