Use of the pressure chamber and thermocouple psychrometer to determine the water relations of plant tissues

Advantages, disadvantages and precautions of using the pressure chamber and thermocouple psychrometers for determinations of plant water potential. and osmotic and turgor pressures are discussed. Comparison of results obtained with both instruments will be influenced by the sampling technique, consistency in both sampling and measurement procedures, and errors inherent to the method itself. In-situ readings of either plant or soil water potential with thermocouple psychrometers are perhaps worthless, or worse (they may even be misleading). Use of thermocouple psychrometers is strictly limited to the laboratory where isothermal conditions can be obtained. The method to determine the water relations of plant tissues should be chosen according to the plant material and the research objectives.