BACKGROUND AND AIMS Development and architecture of plant roots are regulated by phytohormones. Cytokinin (CK), synthesized in the root cap, promotes cytokinesis, vascular cambium sensitivity, vascular differentiation and root apical dominance. Auxin (indole-3-acetic acid, IAA), produced in young shoot organs, promotes root development and induces vascular differentiation. Both IAA and CK regul...

Tree architecture develops over time through the collective activity of apical and axillary meristems. Although the capacity of both meristems to form buds is crucial for perennial life, a comparative analysis is lacking. As shown here for hybrid aspen, axillary meristems engage in an elaborate process of axillary bud (AXB) formation, while apical dominance prevents outgrowth of branches. Devel...

In many plant species only a small proportion of buds yield branches. Both the timing and extent of bud activation are tightly regulated to produce specific branching architectures. For example, the primary shoot apex can inhibit the activation of lateral buds. This process is termed apical dominance and is dependent on the plant hormone auxin moving down the main stem in the polar auxin transp...

Indoleacetic acid and gibberellic acid were added to decapitated lightgrown 'Alaska' pea seedlings as substitutes for the intact apex in the control of apical dotiinance. Of various concentrations and combinations tried, a conrbintation of 1 % indoleacetic acid 1 % gibberellic acid was the most inihibiting to side bud growth. The greatest degree of hormonally induced side bud inhibition was ach...

An important aspect of plant development is the order in which lateral buds are activated to produce branches. This order may manifest itself, for example, in the gradient of branch lengths, or in the flowering sequence. One progression type is acropetal, with the lateral buds activated from the bottom up. Other plants exhibit a basipetal sequence of bud activation, with a downward progression ...