Fig. 3.

Simulation models of basipetal and convergent patterns of bud activation controlled by auxin transport. Schematic representations are as in Figs. 1 and 2. (A–E) Selected stages of basipetal bud activation. During vegetative growth beginning with the initial structure (A), the main apex creates a sequence of metamers with associated lateral buds (B). The flow of auxin from the apex inhibits the outgrowth of lateral apices. Upon transition to flowering (C), the supply of auxin to the topmost metamer decreases, resulting in the activation of its lateral bud (transition from state D to C in Fig. 1). Auxin produced by these buds is exported into the main stem, inhibiting the bud below. After transition of the topmost bud to the flowering state, the next lateral bud becomes activated (D). The resulting relay process continues until it is stopped by the residual supply of auxin from the floral apices (E). (F) Convergent activation pattern resulting from a combination of this process with acropetal activation (Fig. 2 D–F).