Transient heat and mass transfer from a leaf undergoing stomatal closure in a low pressure environment.

Stomatal control of water loss was studied in a low pressure environment by using detached leaves of Crassula argentea Thunb., Peperomia obtusifolia (L.) A. Dietr., and Setcreasea pallida Rose cv. ;Purple Heart.' The transient behavior of temperature and rate of mass loss were determined. A model based on free molecule gas flow was developed and used to predict mass loss to within the same order of magnitude of experimentally obtained results. By utilizing this model, the transient behavior of stomatal aperture was determined. The "nonphysiological" experimental conditions do not inhibit the closing process; therefore, this new experimental technique is a valid method of studying stomatal closure.