• Bitterbrush Germination with Constant and Alternating Temperatures

      Evans, R. A.; Young, J. A. (Society for Range Management, 1977-01-01)
      The germination of bitterbrush (Purshia tridentata) seeds in relation to constant and alternating temperature regimes was investigated. The germination of untreated, stratified, and thiourea-treated seeds was compared. Germination of untreated seeds was greatest with cold (night) temperatures in the optimum range (2 degrees to 5 degrees C) for stratification. Warm (day) temperatures of 10 degrees to 40 degrees C gave relatively high germination when the night temperatures were in the stratification range. Thiourea treatment greatly expanded the number of temperature regimes that gave maximum germination. Thiourea treatment also increased the amount of germination, both in the optimum temperature range and at suboptimal or superoptimal ranges. Stratification enhanced germination of bitterbrush seeds, but the magnitude of response in relation to temperature regimes was not identical to enhancement with thiourea treatment.
    • Squirreltail Seed Germination

      Young, J. A.; Evans, R. A. (Society for Range Management, 1977-01-01)
      Germination tests on squirreltail seed showed that three temperature regimes always produced optimum germination of 76 to 100%. We defined optimum as not statistically (p = 0.01) different from maximum. The always optimum temperature regimes were: (1) a constant 15 degrees C, (2) alternating 10/15 degrees C (16 hours cold/8 hours warm each day), and (3) 10/20 degrees C. When seed was produced in a year with good growing conditions, optimum germination extended over a wide range of temperatures. At optimum temperatures, the rate of germination was very rapid with a high percentage of total germination occurring within a week. The lack of inherent germination requirements that restrict germination, high germinability, and a rapid rate of germination help to explain the colonizing ability of this species.