Foliar application of GA3 during terminal long-shoot bud development stimulates shoot apical meristem activity in Pinus sylvestris seedlings

Abstract

The effect of exogenous gibberellin (GA3) on shoot apical meristem activity in conifer vegetative buds was investigated by spraying 0 or 0.1% GA3 on the foliage of first-year Scots pine (Pinus sylvestris L.) seedlings twice weekly for 9 weeks during development of the terminal long-shoot bud. Exogenous GA3 promoted mitotic activity in the apical zone, thereby increasing both the rate and duration of cataphyll formation and giving rise to a higher and wider apical meristem. The increase in number of cataphylls increased the number of axillary meristems, which developed as short-shoot buds.