Effect of relative hormone concentration on auxin-gibberellin interaction in correlative inhibition of axillary buds

Summary Indole-3-acetic acid (IAA) applied to the fully elongated second internode of decapitated Phaseolus multiflorus plants always inhibited axillary bud elongation at concentrations down to 100 g/g lanolin, whereas gibberellic acid (GA₃) enhanced bud elongation at concentrations down to 1000 g/g lanolin. Lower concentrations than these of either IAA or GA₃ were without significant effect. All possible combinations of IAA and GA₃ within the concentration range 10¹ to 10⁵ g/g lanolin were antagonistic; IAA tending to inhibit, and GA₃ promote, axillary bud elongation growth. Treatment of an elongating internode with the hormones resulted in an increase in inhibition of bud growth by IAA in the presence of GA₃.