Dormancy induction in container-grown Abies seedlings: Effects of environmental cues and seedling age

Abstract

Twelve-week-old container-grown seedlings of noble fir (Abies procera Rehd.) and Shasta red fir (A. magnifica A. Murr. var. shastensis Lemm.), both high-elevation species, were grown under controlled environments in a study of induction of terminal-bud dormancy. Eight treatment combinations of “long” (15 h) or “short” (11 h) photoperiods, “warm” (25°/20°C) or “cool” (18°/12°C) thermoperiods, and “dry” (−1.2 MPa) or “wet” (−0.6 MPa) moisture regimes were imposed upon seedlings for 12 weeks. Treatment factors significantly affecting the induction of dormancy in terminal buds of seedlings were identified over time. The results suggest that seedlings responded dynamically to dormancy cues. The “warm/dry” and “cool/wet” combinations induced dormancy in the first 2 weeks in noble fir and in the first week in Shasta red fir. “Short-day/warm” and “long-day/cool” combinations enhanced dormancy induction in weeks 3 to 4 in noble fir and in weeks 1 to 7 in Shasta red fir. “Short” days and “cool” thermoperiods independently hastened dormancy induction in noble fir in weeks 5 through 12.