Proposed dates for lifting Sitka spruce planting stock for fresh planting or cold storage, based on physiological indicators
2000
O'Reilly, C. | McCarthy, N. | Keane, M. | Harper, C.P.
The relationship between physiological status and theability to withstand the stresses of lifting, cold storing and planting was evaluated from 1992–1995 in Sitka spruce (Picea sitchensis (Bong.) Carr.)2 + 1 transplants of Washington/northern Oregon origins growing in Ireland. Needle primordium initiation continued until later and cold hardiness developed more slowly in the mild lifting season of 1994/95. The seasonal decline in shoot mitotic activity was generally similar each year, with apices becoming inactive in December. Cell divisions in roots ceased in November or December. Shoots began to deharden in early February each year, but the rates of dehardening were slow until March. Cell divisions in root apices resumed in February each year, compared with March for shoot apices. The vitality of the seedlings following cold storage was high for most lift dates except the October and April dates. The period of highest stress resistance (as indicated by cold hardiness levels) for lifting for immediate planting was from about late November/early December to early March; shoots were cold hardy to about −20 °C (LT50) at this time. Seedlings could be lifted and cold stored (1–2 °C)until May/June when shoots were cold hardy to about −30 °C or lower, which coincided with the period from mid- to late December until March.
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