Growth and freezing tolerance of winterfat seedlings.

Abstract

Tolerance to freezing temperatures may be an important factor in the regeneration ecology of winterfat (Ceratoides lanata (Pursh) J.T. Howell). Therefore, growth and freezing tolerance of winterfat seedlings were determined after being grown under different controlled temperatures 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. Freezing tolerance of seedlings was dependent on seedling age and growth conditions. Younger seedlings were more freezing tolerant than older ones grown under the same environmental conditions. Seedlings grown under lower temperatures were more freezing tolerant than those grown under higher temperatures. The lowest observed lethal temperature for 50% mortality (LT50) was -11.8 degrees C for 7-day old seedlings grown under 10/0 degrees C alternating temperatures, and the highest LT50 was about -5 degrees C for seedlings 28 days of age when grown under 29/1 degrees C. Based on seedbed temperatures in the field, the results suggest that freezing temperatures may indeed limit the establishment of winterfat seedlings on Northern Mixed Prairie. Seedbeds with litter accumulations or standing dead plant material may ameliorate low temperature extremes and reduce mortality of winterfat seedlings.