Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) first-year seedlings from seeds collected from stands in central British Columbia and different altitudes in Oregon were grown under a series of artificial environments for 4 months in each of 3 years. Vegetative growth of seedlings from all seed sources was-stimulated by long (15 hr) photoperiods, high (21 C) night temperatures, and moist soil. Early dormancy was induced by short (9 hr) photoperiods, low (3 C) night temperatures, and dry soil.
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Lavender et al. (1968) studied this question.
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