PARENT SESSION
Poster Session #45: Gas Exchange.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Physiological and metabolic evaluation of Poa secunda Presl. populations of the Intermountain West.
Monsen, Stephen 1, Monaco, Thomas2, Smith, Bruce3, Hansen, Lee3, 1 2 3
ABSTRACT- We initiated two experiments to identify the potential physiological mechanisms responsible for the persistence of Poa secunda Presl. in the Intermountain west. Respiration and metabolic heat rates as a function of temperature were inventoried for eleven populations of Poa secunda in the laboratory and from field grown plants using infra-red gas analysis and calorimetry techniques, respectively. We hypothesized that physiological and metabolic activity of low and high elevation populations will be closely related to periods of active growth and environmental conditions at specific sites of origin. Low elevation populations generally had higher laboratory respiration rates than high elevation populations. Values of metabolic heat rate and respiration rate linearly decreased during the growing season with greatest variation at 20°C. Consequently we were unable to reject the hypothesis. We used these data to model the relative specific growth rate (RSG) and substrate carbon conversion efficiency (e) of three low and high elevation populations as a function of temperature. The model indicated that RSG and e increased with temperature in low elevation populations and decreased with high elevation populations early in the season. Our results suggest that performance in the field may be best selected by late season high temperature tolerance. Application of these techniques can be used to rapidly determine if populations of perennial species have the appropriate physiological and metabolic potential to establish and develop optimally under specific environmental conditions.
KEY WORDS: Intermountain west, plant calorimetry, respiration rate, heat rate