Stomatal Behaviour of Kenaf and Sorghum in a Semiarid Tropical Environment. II. During the Day

Abstract

The influence of leaf water potential (Ψl), saturation deficit (δe), and temperature on stornatal conductance (gs) of kenaf and sorghum was determined at non-limiting quantum fluxes both at high and low soil water status in the field, and under controlled environment conditions. Sorghum stomata closed in response to Ψl in a manner consistent with the classical feedback control, while kenaf stomata responded directly to δe, independently of Ψl. The rate of decrease of gs of kenaf with increasing δe was greater at higher temperatures. Also the stomata of stressed kenaf were less sensitive to δe than those of the well-watered crop due to the limitation in degree of stomatal opening imposed by water stress. The degree of stomatal adjustment in kenaf was also assessed. In the stressed kenaf, the Ψl at half the maximum gs was c. 0.17 MPa lower and gs was more sensitive to decreases in Ψl, than in the well watered control. However, there was little difference in the Ψl at 95% stomatal closure.