Influence of temperature regimes and water stress on the germination of three range grasses and its possible ecological significance to a shortgrass priarie

Abstract

To evaluate the influence of temperature and water stress on germination of three range grasses, viz. [Bouteloua gracilis (H.B.K.) Lag. ex Steud], [Agropyron smithii Rydb.], and [Buchloe dactyloides (Nutt.) Engelm.], a germination response study using mannitol was conducted in environment-controlled growth chambers. The highest rate of germination in western wheatgrass was obtained at 24/13° C (day/night temperature regime) while in blue grama and buffalo grass the same was recorded at 29.5/18° C. Seed germination in buffalo grass, western wheatgrass, and blue grama was delayed at water stress greater than −3, −7 and −11 bars respectively under the two temperature regimes. The germination response of blue grama and buffalo grass at high temperature and at greater water stress conditions was greater than western wheatgrass. Results of this study are discussed in the light of the temperature and water stress conditions operative in a shortgrass prairie. A 9-day sequence with water stress less than or equal to −1 bar under a temperature range of 13° C to 29.5° C was found to be the most suitable period for germination of these species, under field conditions.