Temperature Profiles for Germination of Bluebunch and Beardless Wheatgrasses

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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 [USA] 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 mo. after harvest were 84% with a mean of 62%. The germination response of 1-mo. 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.degree. C through a constant 25.degree. C. This range of germination temperatures is much wider than that exhibited by squirreltail [Sitanion hystrix] and Sandberg bluebunch [Poa sandbergii]. The bluebunch wheatgrass material has the inherent potential to germinate and to be highly germinable at a wide range of temperatures.