Thermocouple psychrometer for measurements of water potential in plant tissues by isopiestic method
ABSTRACT The paper describes a thermocouple psychrometer for measurements of water potential (ψw) and its components—osmotic potential (ψs + m) and turgor pressure (ψp)—in biological objects. The isopiestic method applied in this work does not require preliminary scarification of plant material
for eliminating cuticular resistance to diffusion of water vapors. The device is reliable and simple in operation owing to
an original design of replaceable plungers carrying the thermocouples. A modified construction of the lid for a thermocouple
chamber and the application of a cryoholder excluded the necessity of removing the sample from the chamber after ψw measurements prior to its freezing in liquid nitrogen and subsequent thawing for determination of ψs +m. This feature improves the accuracy of determining ψp, which is calculated as ψw − ψs + m. The device can operate with minimal quantities of plant material and allows determination of all three components (ψw, ψs + m, ψp) for the same sample.
Key wordsplants-isopiestic method-thermocouple-psychrometer-water potential-osmotic potential-turgor pressure
- SourceAvailable from: Hiroshi Nonami[show abstract] [hide abstract]
ABSTRACT: Turgor measured with a miniature pressure probe was compared to that measured with an isopiestic thermocouple psychrometer in mature regions of soybean (Glycine max [L.] Merr.) stems. The probe measured turgor directly in cells of intact stems whereas the psychrometer measured the water potential and osmotic potential of excised stem segments and turgor was calculated by difference. When care was taken to prevent dehydration when working with the pressure probe, and diffusive resistance and dilution errors with the psychrometer, both methods gave similar values of turgor whether the plants were dehydrating or rehydrating. This finding, together with the previously demonstrated similarity in turgor measured with the isopiestic psychrometer and a pressure chamber, indicates that the pressure probe provides accurate measurements of turgor despite the need to penetrate the cell. On the other hand, it suggests that as long as precautions are taken to obtain accurate values for the water potential and osmotic potential, turgor can be determined by isopiestic psychrometry in tissues not accessible to the pressure probe for physical reasons.Plant physiology 04/1987; 83(3):592-5. · 6.56 Impact Factor
- Science 11/1958; 128(3331):1089-90. · 31.03 Impact Factor
- Unsteady Heat Exchange in Peltier Thermocouple Psychrometer, Chislennye issledovaniya v mekhanike sploshnykh sred, Sb. nauch. tr. Matematicheskie issledovaniya (Numerical Investigations in Entire Medium Mechanics..