Abstract
When measuring plant water potential in conditions of fluctuating temperature, commercial psychrometers exhibit large errors which are caused by a temperature difference between the reference junctions and the chamber air. A novel psychrometer capable of field use is described which incorporates an electronic device for controlling reference junction temperatures. It consists of a chamber with a thermocouple mounted in it for measuring dewpoints and another thermocouple for sensing the temperature gradients. A thermo-electric heat-pump keeps the temperature of the reference junctions the same as that of the chamber air. Good agreement was found between measurements made with this psychrometer and independent measurements made with the destructive pressure chamber method in the glasshouse and in the field under conditions of widely fluctuating temperature. Corresponding measurements with a commercial psychrometer without temperature control failed to show such agreement. Heavy thermal insulation is necessary, despite the temperature control, which can restrict the psychrometers used. Possibilities for further improvements are discussed.
Similar content being viewed by others
References
Baughn L W and Tanner C B 1976 Leaf water potential: Comparison of pressure chamber andin situ hygrometer on five herbaceous species. Crop Sci. 16, 181–184.
Campbell E C, Campbell G S and Barlow W K 1973 A dewpoint hygrometer for water potential measurement. Agr. Meteorol. 12, 113–121.
Campbell G S and Campbell M D 1974 Evaluation of a thermocouple hygrometer for measuring leaf water potentialin situ. Agron. J. 66, 24–27.
Dixon M A and Tyree M T 1984 A new stem hygrometer, corrected for temperature gradients and calibrated against the pressure bomb. Plant, Cell and Environ. 6, 693–697.
McBurney T and Costigan P A 1982 Measurement of stem water potential of young plants using a hygrometer attached to the plant stem. J. Exp. Bot. 33, 426–431.
McBurney T and Costigan P A 1984 Rapid Oscillations in plant water potentials measured with a stem psychrometer. Ann. Bot. 54, 851–853.
McBurney T and Costigan P A 1986 Plant water potential measured continuously in the field. Plant and Soil 97, 145–149.
McBurney T and Johnson D C 1987 Method and apparatus for making fine-wire thermocouples. J. Physics E: Sci. Instr. (In press).
Michel B E 1977 A miniature stem thermocouple hygrometer. a Pl. Physiol. Lancaster, 60, 645–7.
Neumann H H and Thurtell G W 1972 A Peltier-cooled thermocouple dewpoint hygrometer forin situ measurements of water potentials.In Psychrometery in Water Relations Research. Eds. R W Brown and B P Van Haveren. pp 103–112. Utah Agric. Exp. Sta., Utah State University, Logan, Utah.
Neumann H H, Stevenson K R and Beadle C L 1974 Leaf water content and potential in corn, sorghum, soybean and sunflower. Can. J. Plant Sci. 54, 185–95.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
McBurney, T. A temperature-controlled plant psychrometer. Plant Soil 109, 271–275 (1988). https://doi.org/10.1007/BF02202094
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02202094