Apical dominance
Overview
Apical dominance is a growth control mechanism in plants that regulates the outgrowth of lateral buds along the plant stem. This phenomenon is characterized by the main, central stem of the plant being dominant over (i.e., growing more strongly than) the other side stems; on a branch the main stem of the branch is further dominant over its own side branchlets Learn more.
Mechanism of Apical Dominance
The mechanism of apical dominance is complex and involves a balance of plant hormones, primarily auxins, cytokinins, and strigolactones. The apical bud produces the plant hormone auxin, which is transported down the stem and suppresses the growth of lateral buds. This suppression prevents the outgrowth of lateral buds and the formation of branches, thus maintaining the dominance of the apical bud Learn more.
Role of Auxin in Apical Dominance
Auxin is produced in the apical bud and is transported down the stem in a process known as polar auxin transport. This hormone has a suppressive effect on the growth of lateral buds, thus maintaining the dominance of the apical bud. The concentration of auxin is highest in the apical bud and decreases down the stem, which is why the upper lateral buds are more suppressed than the lower ones Learn more.
Role of Cytokinins and Strigolactones
While auxin is the primary hormone involved in apical dominance, cytokinins and strigolactones also play important roles. Cytokinins are produced in the roots and transported up the stem, promoting the outgrowth of lateral buds. Strigolactones, on the other hand, are produced in the roots and stems and transported to the buds, where they suppress bud outgrowth. The balance of these hormones determines whether a lateral bud will grow or remain dormant Learn more Learn more.
Release of Apical Dominance
The release of apical dominance, also known as de-dominance, occurs when the apical bud is removed or damaged. This removal disrupts the auxin flow down the stem, which relieves the suppression on the lateral buds and allows them to grow. This process is often used in horticulture to promote branching and bushiness in plants Learn more.
Apical Dominance in Agriculture and Horticulture
Understanding and manipulating apical dominance is important in agriculture and horticulture. For example, the practice of pruning involves the removal of apical buds to promote the outgrowth of lateral buds and increase branching. This can lead to increased fruit production in fruit trees or increased flower production in ornamental plants. Similarly, the control of apical dominance can be used to shape plants and control their growth Learn more.