THYGERSON, TONYA1*, BRUCE N. SMITH1, D. TERRANCE BOOTH2, and LEE D. HANSEN3. 1Dept. of Botany and Range Science BYU, Provo, UT 84606; 2Dept. of Chemistry and Biochemistry, BYU, Provo, UT 84606; 3USDA-ARS, High Plains Grassland Research Stat., Cheyenne, WY 82009. - Microcalorimetric studies on winterfat, Eurotia lanata, metabolism in response to temperature.
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