What is Apical Dominance?
In the context of
plant biology and
histology, apical dominance refers to the phenomenon where the main, central stem of the plant is dominant over other side stems; this growth pattern is primarily regulated by the plant hormone
auxin. The apical meristem, located at the tip of the plant, actively inhibits the growth of lateral buds to ensure vertical growth.
Histological Features of Apical Dominance
The histological examination of apical dominance involves studying the
tissues and
cell types involved in this process. The apical meristem is composed of actively dividing cells, which are small, with dense cytoplasm and a prominent nucleus. The cells in the lateral buds are relatively dormant, having larger vacuoles and less dense cytoplasm.
Role of Auxin in Apical Dominance
Auxin, primarily indole-3-acetic acid (
IAA), is synthesized in the apical meristem and transported downwards through the plant. This hormone inhibits the growth of lateral buds, maintaining apical dominance. Histological studies often show high concentrations of auxin in the apical meristem and lower concentrations in the lateral buds.
Interaction with Other Hormones
While auxin plays a central role, other
plant hormones such as cytokinins, gibberellins, and abscisic acid also interact to modulate apical dominance. Cytokinins promote cell division and bud growth, often counteracting the effects of auxin. Gibberellins generally promote stem elongation, and abscisic acid can inhibit growth under stress conditions.
Histological Changes Upon Removal of Apical Meristem
When the apical meristem is removed, a phenomenon known as
decapitation, the inhibition on lateral buds is lifted, leading to their growth. Histologically, this is marked by the reactivation of cell division in the lateral buds, which can be observed as an increase in mitotic figures and a reduction in vacuole size.
Importance in Agriculture and Horticulture
Understanding apical dominance is crucial for
pruning and
training plants to achieve desired shapes and sizes. By manipulating apical dominance, horticulturists can encourage the growth of lateral branches, leading to bushier plants and potentially more fruit production.
Conclusion
Apical dominance is a key concept in plant histology, involving a complex interplay of hormones and cellular changes. Histological studies provide detailed insights into the cellular and tissue-level changes that underpin this phenomenon, offering valuable knowledge for both basic plant science and practical applications in agriculture and horticulture.
