Changes in competible IAA binding in relation to bud development in pea seedlings1

An insoluble (particulate) 3H-IAA-binding system similar to that reported by Hertel et al. (3) is described in buds from pea seedlings. The binding is competed by NAA as well as IAA. Auxin-competible binding is optimal at 25°C and pH6.5; Ca+2 increases binding as does a 1 hr preincubation at 4°C. Release of apical dominance produces outgrowth and a large decrease in the NAA-competible 3H-IAA-binding activity in the axillary buds; this correlates with a decreased ability of auxin to inhibit the buds. Both the antiauxin triiodobenzoic acid and the cytokinin benzyladenine also compete with the bound IAA.