Preliminary results on gibberellin induction of flowering of seedlings and cuttings of Norway spruce indicate some carry-over effects

Abstract

In 1983 and 1984 flower induction experiments where conducted on 12-year-old seedlings and 9-year-old cuttings of Norway spruce ( Picea abies (L.) Karst). Potted plants were moved into a greenhouse when the shoot elongation of lateral branches was around 50% completed. Treatments included stem injection or spraying of gibberellins ( GA 4 7 ) with or without girdling. In 1984 few seedlings produced female flowers in response to the 1983 GA treatments. In 1985 abundant flowering (up to 63 and 40% of trees respectively for female and male flowering) was observed on both seedlings and cuttings, exclusively on trees treated with GA in 1983. This demonstrates a strong carry-over effect of these treatments. After treatment in 1984 (only cuttings), male flowering was observed for all treatments, but especially on control trees in the greenhouse. Girdling and GA appeared to reduce male flowering. On the other hand, female flowering (up to 64% of the trees) was exclusively associated with GA treatments, indicating that, at the concentrations we used, GA 4 7 increases the female cone production. For both experiments, girdling alone had no positive effect on flowering.