STOMATAL‐DIFFUSION RESISTANCE AND WATER POTENTIAL OF SOYBEAN AND SORGHUM LEAVES

Abstract

Hourly trends in stomatal resistance and water potential of the upper leaves of sorghum and of soybean canopies (measured with diffusion porometer and thermocouple psychrometer) tended to parallel each other. Vertical profiles (both canopies) indicated that the stomatal resistance of the lower leaves usually was greater than that of the upper leaves. The position of minimum resistance varied with time of day. The profiles of temperature and water‐vapour pressure were consistent with the profile of canopy transpiration resistance. The upper sorghum leaves had a lower water potential than the lower leaves. In the morning a strong gradient of water potential existed from lower to upper leaves in plants in both canopies; in the afternoon the gradients continued in sorghum but disappeared in soybean plants. Copyright © 1972, Wiley Blackwell. All rights reserved