Eurotia lanata (pursh) moq. (winterfat) is a boreal cold-desert subshrub, seldom more than 2ft. tall, and thrives in dry climates at cooler temperatures. Stem, leaves, and dispersal units called diaspores are covered with a dense mix of short and long white hairs that aid in water retention. It is excellent forage for both wildlife and domestic cattle. Diaspore collections were soaked in a tween solution, and then in dilute sodium hypochlorite and were next placed on moistened filter paper in petri dishes and germinated at room temperature. At the time of radicle emergence (ca.3mm), seeds were placed in ampules in a microcalorimeter. Heat-rate (q) was measured at a given temperature, and then a vial containing NaOH was added to measure the rate of CO2 evolution (RCO2) for the same tissue at the same temperature. This procedure was repeated for each of the populations at temperatures ranging from 10 to 20 degrees Celsius. From these measurements efficiency and predicted specific growth rates were calculated. Optimum temperature for germination, metabolism, and early seedling growth is about 10 degrees Celsius. Stress is noted near 20 degrees Celsius and 5 degrees Celsius. Acclimation during germination had no effect. Differences between the three populations correlated with altitude rather than latitude.

Key words: Eurotia lanata, growth rate, metabolism, temperature, winterfat