Temperature requirements for mountain rye, Hycrest crested wheatgrass, and downy brome germination

Abstract

In this study we determined that mountain rye (Secale montanum), crested wheatgrass (Agropyron cristatum × 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 degrees C, 16 hr day/5-10 degrees C, 8 hr night) temperature regimes with crested wheatgrass demonstrating an optimum germination temperature over a 10-20 degrees C day/25 degrees 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.