Canadian Forest Service Publications
Hardening and dehardening of shoots and roots of containerized black spruce and white spruce seedlings under short and long days. 1992. Bigras, F.J.; D'aoust, A.L. Canadian Journal of Forest Research 22(3): 388-396.
Issued by: Laurentian Forestry Centre
Catalog ID: 16450
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Containerized black spruce (Picea mariana (Mill.) B.S.P.) and white spruce (Picea glauca (Moench) Voss) seedlings that were 120 days old were acclimated under short-day (8-h photoperiod) and long-day (16-h photoperiod) conditions at 10°C for 12 h and 5°C for 12 h for 28 days. Afterwards, they were exposed to 3°C (8-h photoperiod) for 21 days and to 0°C (without light) for 28 days. Finally, seedlings were dehardened at 10°C (14-h photoperiod) for 21 days. Hardening of needles, excised stem parts, and whole seedlings was increased by short-day treatment, whereas roots hardened only in response to lowering of temperature. Whole seedlings and needles exposed to the short-day treatment dehardened earlier, whereas roots dehardened only in response to temperature changes. Bud formation was not influenced by photoperiod treatment, but seedlings exposed to the short-day treatment had an earlier bud break. No significant difference was observed between photoperiod treatments for water, sugar, and mineral content of shoots and roots prior to or during dehardening.