INFLUENCES OF CROWN SIZE AND MATURATION ON FLOWER PRODUCTION AND SEX EXPRESSION IN PICEA-GLAUCA TREATED WITH GIBBERELLIN A(4 7)/

We evaluated the effects of exogenous gibberellin A(4/7) (GA(4/7)) on the production of seed and pollen cones in four stock types of Picea g lauca (Moench) Voss. From 1987 to 1991, a combined treatment that incl uded GA(4/7), root pruning and heat stress was applied to 5- to 10-yea r-old container-grown grafts, representing over 90 clones and originat ing from 17- to 27-year-old ortets. Hormonal treatments were applied t o pruned field-grown grafts in 1991 and 1992, and to unpruned field-gr own grafts from the same set of clones in 1990, 1991 and 1992. In 1992 , 26-year-old mature trees in a progeny test were treated with GA(4/7) The GA(4/7) treatment was effective in promoting seed-cone production in all four stock types, whereas it promoted pollen-cone production o nly in unpruned field-grown grafts and mature trees. The older and tal ler a tree, the less the response to the GA(4/7) treatment was influen ced by the climatic conditions prevailing during the differentiation p hase.