Some evidence of stomatal restriction of evaporation from well‐watered plant canopies

Various aspects of stomatal control of evaporation and their practical significance have been considered in a recent exchange of opinions in this journal. The present paper describes some considerable departures from potential evaporation rates observed under conditions of generous soil water supply. These departures occurred on days of high potential rates and represented reductions of up to about 20% from levels that might otherwise have been expected under the prevailing atmospheric conditions. However, the reductions represented only a few percent of the seasonal or annual evaporation. Accompanying symptoms of plant moisture stress are discussed.