| Abstract: | Summary An in situ thermocouple psychrometer was tested to determine its capability for tracking the changing leaf water potentials of aspen (Populus tremuloides Michx.) under controlled conditions and in the field. The results agreed with theoretical expectations — a sharp decline in leaf water potential during the photoperiods and recovery during the dark periods, each to progressively lower levels during a soil drying cycle. In the field, a mid-day pause in the declining leaf water potentials was noted and attributed to transient stomatal closure. Details of the construction and use of the assembly are given.The authors are plant physiologists, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401, stationed in Logan, Utah, at the Forestry Sciences Laboratory. |
