Tolerance of conifer fine roots to cold storage

Fine-root electrolyte leakage from 2-year-old planting stock of three conifer species was measured on 13 dates between October 1989 and April 1990. The three species (Picea sitchensis (Bong.) Carr., Pseudotsuga menziesii (Mirb.) Franco, and Larix leptolepis (Sieb. & Zucc.) Gord.) were raised using either transplanting or undercutting and wrenching regimes. On each lifting date, excised fine roots were stored at 1 degree C for 30 and 90 days. The deterioration of the fine roots was assessed by comparing electrolyte leakage values before and after storage. As the lifting date progressed from October to mid-December all three species became less adversely affected by storage, indicating that roots undergo physiological changes that increase their tolerance to prolonged cold storage. The interaction between lifting date and storage duration on fine-root quality differed in the three species. For example, Picea sitchensis could tolerate 90 days' storage commencing at any time from mid-December till early April with negligible root damage. Pseudotsuga menziesii could not tolerate 90 days' storage at any time of year, and tolerance to 30 days' storage was limited and could be substantially reversed. Fine roots of Larix leptolepis were only slightly damaged after 90 days' storage beginning from mid-November to the end of December.