Applied gibberellin A 4/7 increases ovulate strobili production in accelerated growth jack pine seedlings

Jack pine (Pinusbanksiana Lamb.) seeds were sown in October, January, and March, and the seedlings were cultured under accelerated growth conditions in a greenhouse. At biweekly intervals, from May 15 to August 15, they were transplanted to a nearby nursery and sprayed with GA 4/7 or GA 4/7 + NAA. The following spring a fourfold increase in flowering was noted in trees receiving either of the GA 4/7 treatments. Trees in the March sowing did not flower. The data suggest that the increased flowering was caused by GA 4/7 -mediated differentiation of lateral long-branch primordia into ovulate strobili.