Arimoclomol

A phenomenon in plant biology

Apical dominance is a phenomenon in plant biology where the main, central stem of the plant is dominant over other side stems. This dominance is primarily due to the presence of the apical bud at the tip of the plant, which suppresses the growth of lateral buds along the sides of the stem. The apical bud produces auxins, a class of plant hormones that inhibit the growth of lateral buds, thereby maintaining the plant's vertical growth pattern.

Mechanism

The mechanism of apical dominance involves the production and distribution of plant hormones, particularly auxins. Auxins are synthesized in the apical bud and transported down the stem, where they inhibit the growth of lateral buds. This hormonal control ensures that the plant grows taller rather than wider, which can be advantageous in environments where light is a limiting factor.

In addition to auxins, other hormones such as cytokinins and gibberellins also play roles in modulating apical dominance. Cytokinins, which are produced in the roots and transported upward, can promote lateral bud growth. The balance between auxins and cytokinins is crucial in determining the degree of apical dominance.

Ecological Significance

Apical dominance is ecologically significant as it allows plants to optimize their growth for light capture. By prioritizing vertical growth, plants can outcompete neighbors for sunlight, which is essential for photosynthesis. This growth pattern is particularly beneficial in dense forests or crowded plant communities.

Manipulation in Horticulture

Horticulturists often manipulate apical dominance to achieve desired plant shapes and sizes. By removing the apical bud, a process known as "pinching" or "topping," the suppression of lateral buds is lifted, allowing them to grow and create a bushier plant. This technique is commonly used in the cultivation of ornamental plants and in bonsai to control plant architecture.

Examples

Several plant species exhibit strong apical dominance, including many conifers and deciduous trees. For instance, the Norfolk Island pine (Araucaria heterophylla) is known for its pronounced apical dominance, which gives it a characteristic symmetrical shape.

Gallery

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  Araucaria heterophylla exhibiting strong apical dominance.
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  A weeping larch tree showing apical dominance in its growth pattern.
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  Topiary garden where apical dominance is manipulated for aesthetic purposes.

Related pages

• Auxin
• Cytokinin
• Gibberellin
• Plant hormone