ABSTRACT
Summary Objectives were to characterize development of water stress in the field and in controlled environments; to determine stress effects on transpiration (E), stomatal conductance (C), leaf water potential (LWP), leaf osmotic potential (LOP), and photosynthesis (P); and to relate measured changes to drought tolerance in crested wheatgrass (Agropyron desertorum [Fisch.] Schult.), slender wheatgrass (A. trachycaulum [Link] Malte.), pubescent wheatgrass (A. intermedium var. trichophorum [Link] Haloc), and western wheatgrass (A. smithii Rydb.). Both LWP and LOP decreased for all species as soil water potential decreased, but not in a 1:1 ratio indicative of maximum osmotic adjustment. The LWP at zero turgor potential ranged from -28 and -27 bars for crested and slender, respectively, to -24 bars for western and -23 bars for pubescent wheatgrasses. Results from field plants suggest a greater degree of osmotic adjustment in crested, slender, and pubescent wheatgrasses than in western wheatgrass. For growth-chamber plants, based on rate of P, E, and C, western was more sensitive to decreasing soil water potential, followed by pubescent and crested wheatgrasses. Data on species response to water stress are important to development of growth and water-use relationships required for predictive models and in management and cultivar development.
