Sexual zonation in the crown of Piceaglauca and the flowering response to exogenous GA4/7

Strobili distribution on crowns of 8- and 9-year-old white spruce (Piceaglauca (Moench) Voss) was evaluated and modified by gibberellin A4/7 (GA4/7) applied as a foliar spray to branches in the transitional (female → male) zone and strictly male zone. Treatment with GA4/7 increased female strobili production 6.2-fold and male strobili production 2.4-fold on branches in the transitional zone. On male zone branches treated with GA4/7, female strobili were induced and male strobili production increased sixfold.