Water Deficit Development in Old and New Soybean Cultivars

Abstract

Abstract Crop productivity depends to some degree on a cultivar's capacity to maintain a high plant water status over a range of soil water conditions. We conducted this 2‐yr study to examine whether newer soybean [ Glycine max (L.) Merr.] cultivars have more favorable leaf turgor potentials than older cultivars during the pod elongation and seed enlargement stages of crop development, and to determine whether the older and newer cultivars differ in leaf water potential components and stomatal resistances when grown under drought stress. Two older (‘Manchu’ and ‘Dunfield’) and two more recent (‘Clark 63’ and ‘Williams 82’) cultivars were field grown under irrigated (I) and nonirrigated (NI) conditions at Urbana, IL. Although large differences in soil water potential were found between the water treatments, afternoon leaf water potentials of the cultivars were decreased only an average of 0.14 MPa and afternoon leaf turgor potentials were not reduced as a result of the NI treatment. In both the NI and I plots, Manchu and Dunfield generally had lower and similar leaf turgor potentials, respectively, as did the modern cultivars during the day. Under NI conditions, greater stomatal closure occurred for the older cultivars than for the newer cultivars, indicating that the older cultivars are more efficient in conserving water under drought stress.