Oscillatory Transpiration and Water Uptake of Avena Plants

The action of D₂O on oscillatory transpiration of Avena plants was investigated. D₂O affects the amplitude and the period of the oscillations when given as a root medium to intact plants. The period is then dependent on the amplitude. From such experiments it is not possible to conclude whether the period change is simply due to the changed amplitude or to a change in the stomatal parameters. When given to xylem compressed, excised plants without roots, the D₂O hardly affects the amplitude of the oscillations but the period is increased. Thus, the period of the self-sustained transpiratory oscillations is lengthened by D₂O action on the stomatal parameters. Phase and amplitude changes of the oscillatory transpiration caused by short D₂O pulses given both to intact and excised plants, are discussed. The following conclusion is emphasized: a substance which affects the root system can also cause profound changes in the stomatal water regulation.