Abstract

Shoot branching in plants is a highly plastic trait, enabling them to adjust to changing environmental conditions. While growth of the primary axis occurs through activity of the shoot apical meristem at the primary shoot apex, secondary axes arise through outgrowth of axillary buds. This in turn depends on the activity of axillary shoot apical meristems. In many plants, including Arabidopsis thaliana, the primary shoot apex is able to impose dormancy on axillary buds, an effect that has long been attributed to the plant hormone auxin, exported from the primary apex and transported down the main stem. The transport of auxin is facilitated through specialised efflux carriers, called PIN -FORMED (PIN) proteins, allowing polar movement of auxin throughout the plant. Auxin positively regulates its own transport through these transporters and movement from an auxin source to an auxin sink results in a progressive narrowing of its transport stream, a process called canalisation. For buds to activate, we hypothesise that they need to be able to export their auxin and that this export is dependent on canalisation of auxin transport from the bud to the main stem. Here I present several experiments aimed at investigating how auxin transport canalisation between the axillary shoot apex and the main stem may play a role in bud activation.