© 1990 Heron Publishing—Victoria, Canada
Comparison of three cold hardiness tests for conifer seedlings
Karen E. Burr (1), Richard W. Tinus (1), Stephen J. Wallner (2, 3) and Rudy M. King (4)
1. Rocky Mountain Forest and Range Experiment Station, Flagstaff, AZ 86001, USA / 2. Department of Horticulture, Colorado State University, Fort Collins, CO 80523, USA / 3. Department of Horticulture, Pennsylvania State University, University Park, PA 16802, USA. / 4. Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO 80526, USA / Received November 6, 1989
Summary
Greenhouse-cultured, container-grown ponderosa pine (Pinus ponderosa var. scopulorum Engelm.), interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco), and Engelmann spruce (Picea engelmannii (Parry) Engelm.) were cold acclimated and deacclimated in growth chambers over 19 weeks. Cold hardiness was measured weekly
by a whole-plant freeze test and by two quick tissue tests: freeze-induced electrolyte leakage of needles, and differential
thermal analysis of buds. The whole-plant freeze test provided results in 7 days, and indicated differences in cold hardiness
among stems, buds, and needles. Although the whole-plant freeze test could accurately measure cold hardiness, it was not precise,
and it required destructive sampling. Results from freeze-induced electrolyte leakage and differential thermal analysis were
available in 2 days and 1 hour, respectively. The freeze-induced electrolyte leakage test was a precise, sensitive and objective
predictor of changes or differences in tissue cold hardiness. To determine actual cold hardiness, results could be calibrated
to the response of the same tissue in the whole-plant freeze test. The speed and objectivity of differential thermal analysis
made this test useful for rapid, general assessment of cold hardiness status, but calibration was difficult, and precision
varied.
