The influence of acclimatization treatment and plantlet morphology on early greenhouse-performance of tissue-cultured Douglas fir [Pseudotsuga menziesii (Mirb.) Franco

Abstract

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.