Relationship of Stem Electrical Impedance and Water Potential of Douglas-fir Seedlings to Survival After Cold Storage
In experiment 1, 2-year-old Douglas-fir (Pseudotsuga menziesii) seedlings were lifted at 14-day intervals during the fall. Electrical impedance of seedling stems was measured on subsamples at 4.5 K Hz, before and after freezing to -10°C, and the remainder were stored at 2°C for 12 weeks. Seedlings were grown for 6 weeks in a greenhouse after storage, and survival was significantly correlated (r = 0.93) with postfreezing electrical impedance. In experiments 2 and 3, 2-year-old seedlings and transplants of coastal and interior origin Douglas-fir were lifted in February, March, and May and stored at 2°C or -2°C. Stem electrical impedance and water potential measurements were made before and after storage. In experiment 2, seedlings from all lifting dates were planted out in the open in June, and in experiment 3 seedlings were planted in the greenhouse after a uniform 4-month storage. Survival and shoot length relative growth rate (RGR) decreased through the three lifting dates from February to May. Storage of May lifted stock at -2°C reduced survival and no evidence of any advantage to storing at -2°C on the other lifting dates was apparent. Interactions of origin and stock type with lifting date and storage temperature were nonexistent, or small. Survival of seedlings in experiments 2 and 3 was significantly correlated (r = 0.6-0.8) with impedance measured before and after storage for all stock. Further, a critical impedance of 20 K ohms measured before or after storage, separated most of the stock with 70 percent survival, or more, from the remainder of the stock. Measurements made in experiment 4 showed that stem impedance was influenced by stem diameter, but stem diameter did not account for all the variation in impedance measurements. Water potential measurements were unrelated to seedling survival in experiments 2 and 3. Stem impedance measurements offer a method for determining suitability of nursery stock for lifting, but water potential measurements do not. Forest Sci. 25:507-517.
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Keywords: Pseudotsuga menziesii
Document Type: Journal Article
Affiliations: Tree physiologist, Research Branch, Ministry of Forests, Parliament Buildings, Victoria, B.C., V8W 3E7, Canada
Publication date: 01 September 1979