Responses to Water Stress in Wheat and Related Wild Species¹

Abstract

Various indices of drought resistance were studied in wheat ( Triticum aestivum , ‘Chinese Spring’ and ‘Seeon’) and three related wild species ( T, longissimum , T. kotschyi , and Agropyrum junceum ) grown in containers in a glasshouse. A. gropyrum junceum (a halophytic perennial) maintained a constant CO 2 fixation rate (measured by a 14 CO 2 ‐pulse method) down to a leaf water potential of −3.0 MPa (measured by the pressure chamber method). Among the three Triticum species, T. kotschyi (a desert annual) ranked highest and wheat ranked lowest in: a) the ability to maintain high leaf water potential as the soil dried; and b) the ability to maintain high stomatal aperture (measured by means of air‐flow porometer), high CO 2 fixation rate, and high relative water content with decreasing leaf water potential. The recovery of stomatal aperture following a period of water stress and rewatering was fastest in T. longissimum (an annual of semiarid to subhumid habitats), somewhat slower in T. kotschyi and much slower in wheat.