Temperature Profiles for Germination of Bluebunch and Beardless Wheatgrasses

Abstract

The germination of seeds of beardless and bluebunch wheatgrasses was investigated over a wide range of constant and alternating temperatures. Seeds of 'Whitmar' beardless wheatgrass, a collection from Nevada, and numbered accessions of bluebunch wheatgrass were used. Seeds of 'Whitmar' beardless wheatgrass germinated at 87% of the 55 temperature regimes tested with a mean germination of 52%. Germination at 42% of the temperature regimes was optimum [defined as not significantly (P = 0.01) different from maximum], with a mean of 84%. Freshly harvested seeds of the Nevada source of bluebunch wheatgrass germinated at 78% of the temperature regimes with a mean of 40%. Comparable figures for fully ripened seeds 5 months after harvest were 84% with a mean of 62%. The germination response of 1-month old bluebunch wheatgrass seeds indicated that germination could occur at the high seedbed temperatures encountered in a late summer moisture event. The temperature-germination profiles for the numbered accessions of bluebunch wheatgrass had the same general pattern as the Nevada source. Generally, seeds were highly germinable at a number of temperatures. Optimum germination of all the sources of seed occurred at 37 temperature regimes at least once and always occurred at 15 temperatures ranging from an alternating 5/15 degrees C through a constant 25 degrees C. This range of germination temperatures is much wider than that exhibited by squirreltail and Sandberg bluebunch. The bluebunch wheatgrass material has the inherent potential to germinate and to be highly germinable at a wide range of temperatures.