FROST HARDINESS AND COLD-STORAGE TOLERANCE OF THE ROOT-SYSTEM OF PICEA-SITCHENSIS, PSEUDOTSUGA-MENZIESII, LARIX-KAEMPFERI AND PINUS-SYLVESTRIS BARE-ROOT SEEDLINGS

During the winter of 1990-91, fine roots of 2-year-old, undercut and wrenched Pseudotsuga menziesii, Larix kaempferi, Pinus sylvestris, and Picea sitchensis (Alaskan, Queen Charlotte Islands, and Oregon) were tested using electrolyte leakage for frost hardiness and tolerance to storage at +1-degrees-C for 30 and 90 days as excised roots. Pseudotsuga menziesii and P. sylvestris showed only minor changes in root frost hardiness with a maximum of -4-degrees-C and -7-degrees-C respectively. Larix kaempferi and P. sitchensis developed much greater root frost hardiness, L. kaempferi had a maximum hardiness of -12-degrees-C while P. sitchensis (Queen Charlotte Islands) reached -13-degrees-C during the winter. The root frost hardiness of P. sitchensis increased with the provenance's latitude. There were clear species and provenance differences in the level of long-term cold-storage tolerance attained, increasing in the order P. menziesii, P. sylvestris and P. sitchensis (Oregon), L. kaempferi, P. sitchensis (Queen Charlotte Islands), and P. sitchensis (Alaskan). In spite of highly significant correlations (p = 0.0001) between root electrolyte leakage after cold-storage and frosting tests, root frost hardiness did not accurately indicate all aspects of long-term cold tolerance and has limitations as a means of determining safe cold-storage dates.