[Attraction of gibberellin by indoleacetic acid as a factor in apical dominance]

Experiments with 20 cm long segments of etiolated pea epicotyls treated in the middle with 0,5% gibberellin paste (GA3) in the form of a ring and also with a 0,5% indoleacetic acid (IAA) paste either near the apical or near the basal pole showed that in all cases after 24 hours there was a stronger transport of GA3 to the IAA treated pole without regard to the polarity. Because the root participates significantly in the biosynthesis of gibberellin, the acropetal transport of gibberellin from this organ in an intact plant is probably connected with the attractive force of auxin activated in the shoot apex. This factor may be responsible for the more intensive growth of the apical part of shoot and therewith also for the apical dominance.