Richard K. Hermann

Spring shoot growth in douglas-fir may be initiated by gibberellins exported from the roots.

Trials conducted under controlled environments demonstrated that the delay of bud activity of Douglas-fir (Pseudotsuga menziesii) seedlings occasioned by low temperature of the soil could be eliminated by application of gibberellic acid. Analyses of field-grown plants showed a parallel increase in bud activity, level of gibberellin-like compounds in xylem sap, and soil temperature during February and March.

Effect of Environment on the Development of Dormancy and Growth of Douglas-Fir Seedlings

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.