GROWTH AND FREEZING TOLERANCE OF WINTERFAT SEEDLINGS

Tolerance to freezing temperatures may be an important factor in the r egeneration ecology of winterfat (Ceratoides lanata (Pursh) J.T. Howel l). Therefore, growth and freezing tolerance of winterfat seedlings we re determined after being grown under different controlled temperature s for 7, 14, 21, or 28 days, Growth of seedlings was greater under day temperatures of 15 and 20 degrees C relative to 5 and 10 degrees C. F reezing tolerance of seedlings was dependent on seedling age and growt h conditions, Younger seedlings were more freezing tolerant than older ones grown under the same environmental conditions, Seedlings grown u nder lower temperatures were more freezing tolerant than those grown u nder higher temperatures, The lowest observed lethal temperature for 5 0% mortality (LT(50)) was -11.8 degrees C for 7-day old seedlings grow n under 10/0 degrees C alternating temperatures, and the highest LT(50 ) Was about SOC for seedlings 28 days of age when grown under 29/1 deg rees C. Based on seedbed temperatures in the field, the results sugges t that freezing temperatures may indeed limit the establishment of win terfat seedlings on Northern Mixed Prairie, Seedbeds with litter accum ulations or standing dead plant material may ameliorate low temperatur e extremes and reduce mortality of winterfat seedlings.