Temperature Requirements for Mountain Rye, Hycrest Crested Wheatgrass, and Downy Brome Germination

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Abstract
In this study we determined that mountain rye (Secale montanum), and crested wheatgrass (Agropyron cristatum .times. desertorum ''Hycrest''), and downy brome (Bromus tectorum) have similar germination temperature requirements and thus have the potential to germinate under similar soil temperature regimes, a feature which could be advantageous for subsequent seedling competition of mountain rye or crested wheatgrass against downy brome. Germination temperature profiles were compared using a thermogradient germination plate. Fifty-six different day/night temperature regimes were utilized for the comparisons. The bivariate spline model was found to be the best model for predicting germination-temperature response of the 3 species. Mountain rye and downy brome produced high germination under widely fluctuating (20-30.degree. C, 16 hr day/5-10.degree. C, 8 hr night) temperature regimes with crested wheatgrass demonstrating an optimum germination temperature over a 10-20.degree. C day/25.degree. C night regime. One of the 2 downy brome sources evaluated exhibited a much broader optimum germination temperature range. However, the differences in germination temperature profiles obtained were not of a magnitude likely to be biologically or ecologically significant due to the relatively high germination obtained over a wide range of fluctuating day/-/night temperatures for all 3 species.