THE INFLUENCE OF ACCLIMATIZATION TREATMENT AND PLANTLET MORPHOLOGY ON EARLY GREENHOUSE-PERFORMANCE OF TISSUE-CULTURED DOUGLAS-FIR [PSEUDOTSUGA-MENZIESII (MIRB) FRANCO]

The objective of this investigation was to test for the possible effects of plantlet morphology and environmental stress on survival and growth during the acclimatization of tissue-cultured Douglas fir [Pseudotsuga menziesii (Mirb.) Franco]. Under a high-stress environmental regime of 40-70% relative humidity and 22-28°C, survival was 33%, compared to 89% under a low-stress regime of 80-90% RH and 15-20°C. Shoot elongation under low stress was twice as great as that under high stress. Certain morphological features were associated with improved survival under high stress, and they included a large (10+) root number, tall (40 + mm) shoots, and upright needles. Plantlets with 10 + roots had 52% survival, compared to 25% or 31% for those with 1-3 or 4-10 roots, respectively. Also, plantlets with an initial shoot height of 41-60 mm had a 53% survival rate compared to 20% or 37% for those with 21-30 mm or 31-40 mm shoots. Tall plantlets and those with 10+ roots also underwent the greatest shoot elongation during the 7 week observation period. However, plagiotropism was frequent on tall shoots. © 1990 Kluwer Academic Publishers.