Canadian Forest Service Publications
Dehardening and second-year growth of white spruce provenances in response to duration of long-night treatments. 1997. Coursolle, C.; Bigras, F.J.; Margolis, H.A.; Hébert, C. Canadian Journal of Forest Research 27: 1168-1175.
Available from: Laurentian Forestry Centre
Catalog ID: 16759
Long-night treatments (16 h) of 0 (control), 4, 8, 12, and 16 days duration were applied, in August 1994, to four provenances of 10-week-old white spruce (Picea glauca (Moench) Voss) seedlings. This was to determine the shortest duration that would produce seedlings having acceptable morphological and physiological characteristics for reforestation. The effects of these treatments and of the latitude of origin of seedlings on the course of dehardening and second-year growth were studied. Terminal bud burst, shoot and root dry mass accumulation, and frost tolerance were followed during the spring, and terminal shoot growth was measured until August. Seedlings exposed to 0 (control) or 4 long nights exhibited significant amounts of damage in the spring. This damage had occurred the previous fall or winter. Seedlings receiving 4 to 16 days of long-night treatments did not differ in timing of bud burst the following spring, while the most northern provenance flushed first (May 18) and the most southern flushed last, 4 days later. Seedlings subjected to 8, 12, and 16 long nights exhibited similar amounts of terminal shoot growth, dry matter accumulation, and frost tolerance. Frost tolerance of the 8-, 12-, and 16-d treatments during dehardening was unaffected by the latitude of origin of seedlings. Our results suggest that under the experimental conditions used, an 8-d long-night treatment applied in the fall would produce seedlings with the same morphological and physiological characteristics in the spring as a 12- or 16-d treatment.