Relation of Soil Water Potential to Stomatal Resistance of Soybean¹

Abstract

Abstract This research was undertaken to establish a meaningful relationship between stomatal resistance of soybeans and soil water potential. The main objectives were to establish this relationship and examine some of the factors affecting measurements of stomatal resistance of soybeans. Stomatal resistance in the soybean leaves was measured with a stomata porometer and plotted against soil water potential. A definite relationship was determined in two consecutive growing seasons between the soil water potential and stomatal resistance. Adaxial stomatal resistance increased rapidly when soil water potentials decrease to near −4 bars. It was found that stomatal resistance of upper canopy leaves were not affected by the physiological stage of growth of the whole plant. The difference in stomatal resistance of well‐irrigated and nonirrigated soybeans was distinct, and stomatal resistance showed promise in determining irrigation schedules.