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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #126643


item Hardegree, Stuart
item Van Vactor, Steve

Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2001
Publication Date: 12/20/2002
Citation: Hardegree, Stuart P., Jones, Thomas A., Van Vactor, Steven S., Variability in Thermal Response of Primed and Non-primed Seeds of Squirreltail {Elymus elymoides (Raf.) Swezey and Elymus multisetus (J.G. Smith) M.E. Jones}. Annals of Botany 2002, v. 89, p. 311-319.

Interpretive Summary: Current methods for evaluating seeds used in rangeland plantings rely on simple tests of total germination at a single, arbitrary, temperature in the laboratory. This approach is overly simplistic in at least three ways: germination rate is often more important than total germination in assessing field performance; the seedbed environment is extremely variable among and between years; and environmental conditions in the field can alter inherent germinability of any given seedlot. Seed priming is a method by which maximum germination rate can be induced by allowing the seeds to begin the germination process before being planted. In this study, we evaluated potential field performance of primed and nonprimed seeds of 11 squirreltail seedlots under field- variable temperature conditions. Current tests of germination response in the laboratory only rank seedlots relative to each other. Our study allowed us to ask the question: what would have happened to these seedlots had they been planted on any day between March 1 and May 15 in any of the previous 6 years? This study gave more realistic information about how seeds potentially respond in the environment. Studies of this type may lead to improved seeding technologies that take advantage of enhanced knowledge of potential environmental response.

Technical Abstract: Bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey = Sitanion hystrix (Nutt.) J.G. Smith] and big squirreltail [Elymus multisetus (J.G. Smith) M.E. Jones = Sitanion jubatum (J.G. Smith)] have a broad geographic distribution and have been identified as a high priority species for restoration of degraded rangelands in the western United States. These rangelands exhibit high annual and seasonal variability in seedbed microclimate. The objective of this study was to examine variability in thermal response of both primed and non-primed seeds of these species in the context of field-variable temperature regimes. Primed and non-primed seeds were evaluated for laboratory germination response under 12 constant-temperature treatments between 3 and 36 degrees C. Thermal-time and base temperature were estimated by regression analysis of germination rate as a function of temperature in the sub-optimal temperature range. The thermal-germination model and 6 years of field-temperature data were used to simulate potential germination response under alternative field planting scenarios. Seed priming increased germination rate (lowered days to 50 percent germination) by 3.8 to 8.4 days at 6 degrees C with a mean germination advancement of 6.9 days. Maximum germination advancement in the model simulations was 5-10 days for planting dates between March 1 and May 15. Model simulations can be used to expand germination analysis beyond simple treatment comparisons, to include a probabilistic description of potential germination response under historical or potential future conditions of seedbed microclimate.