Radiation intensity and transpiration.

Abstract

Stomatal aperture quickly increased with light intensity to a maximum and then decreased until the stomata closed. Transpiration was optimal at a weak light intensity and then the curve fell quite sharply, increasing again rectilinearly at higher intensities, the latter increase being due to cuticular transpiration. Analysis of the curved part representing stomatal transpiration suggested that the relative humidity within the leaf was <100% at points represented by the ascending part of the curve. It appeared that, whatever the stomatal apertures, the transpiration rate was proportional to the light intensity, but the gradient increment of the curves obtained decreased as the stomatal apertures increased. If in agricultural practice the transpiration is found to be proportional to radiant energy, it has to be assumed that, in the different observational periods, equal mean stomatal apertures have occurred. (Abstract retrieved from CAB Abstracts by CABI’s permission)