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Knowledge about mechanisms of water stress tolerance, growth, and development of forages are important in development of management practices and in germplasm improvement. Plants of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] and western wheatgrass [Pascopyrum smithii (Rydb.) Gould] were field grown at 3 soil water levels (50, 100, and 150% of average rainfall and 2 N levels (10 and 110 kg N ha-1) and sampled to determine proline, water soluble carbohydrate, and abscisic acid concentration from about the 4-leaf through heading stages of development. Proline concentration increased in both species as wabr stress increased. Proline decreased in crested wheatgrass but increased in western wheatgrass as plant development advanced. Abscisic acid concentrations increased in both species as water stress increased. Western wheatgrass contained about 1.7 times higher abscisic acid concentration than crested wheatgrass. Carbohydrate concentrations increased with water stress and were higher in crested than western wheatgrass. Increasing proline and abscisic acid concentrations in western wheatgrass and the decreasing concentrations in crested wheatgrass at later stages of development suggest that the stress response mechanisms that enhance proline and abscisic acid may be more operative in western than crested wheatgrass. These results suggesting that western wheatgrass is more tolerant of water stress under field conditions than crested wheatgrass should be useful in developing sustainable management practices. Also, proline concentration changes with plant development suggesting that germplasm sampling should be performed over time. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020