Apical dominance is one of the fundamental developmental phenomena in plant biology, which determines the overall architecture of aerial plant parts. Here we show apex decapitation activated competition for dominance in adjacent upper and lower axillary buds. A two-nodal-bud pea (Pisum sativum L.) was used as a model system to monitor and assess auxin flow, auxin transport channels, and dormancy and initiation status of axillary buds. Auxin flow was manipulated by lateral stem wounds or chemically by auxin efflux inhibitors 2,3,5-triiodobenzoic acid (TIBA), 1-N-naphtylphtalamic acid (NPA), or protein synthesis inhibitor cycloheximide (CHX) treatments, which served to interfere with axillary bud competition. Redirecting auxin flow to different points influenced which bud formed the outgrowing and dominant shoot. The obtained results proved that competition between upper and lower axillary buds as secondary auxin sources is based on the same auxin canalization principle that operates between the shoot apex and axillary bud.

CEITEC Central European Institute of Technology Mendel University in Brno Zemedelska 1 613 00 Brno Czech Republic

Department of Molecular Biology and Radiobiology Mendel University in Brno Zemedelska 1 613 00 Brno Czech Republic

Department of Plant Biology Mendel University in Brno Zemedelska 1 613 00 Brno Czech Republic

Institute of Science and Technology Austria 3400 Klosterneuburg Austria

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