Apical dominance

Definition

Apical dominance is the phenomenon where the main central stem of a plant grows more strongly than the other side stems, primarily due to the influence of plant hormones. This growth pattern allows plants to focus their energy on upward growth towards light, optimizing photosynthesis and resource acquisition while suppressing the growth of lateral buds.

5 Must Know Facts For Your Next Test

1. Apical dominance ensures that plants grow taller and can outcompete neighboring plants for sunlight, which is critical for their survival.
2. The balance between auxins and cytokinins is essential for regulating apical dominance; high levels of auxins promote dominance while cytokinins can help release lateral buds from dormancy.
3. Removal or damage to the apex (top) of a plant often results in the release of lateral buds from apical dominance, allowing them to grow.
4. Apical dominance can vary among different plant species and is influenced by environmental factors such as light availability and nutrients.
5. Understanding apical dominance has practical applications in agriculture and horticulture, including pruning techniques that can enhance plant growth and yield.

Review Questions

• How do auxins contribute to the phenomenon of apical dominance in plants?
  • Auxins are key hormones in promoting apical dominance by inhibiting the growth of lateral buds while stimulating cell elongation in the main stem. When auxins are concentrated at the tip of the plant, they prevent nearby lateral buds from developing into branches. This creates a direct pathway for energy and resources towards upward growth, allowing the plant to maximize exposure to sunlight.
• What role do cytokinins play in modifying apical dominance, and how can this knowledge be applied in horticulture?
  • Cytokinins counteract the effects of auxin by promoting cell division and stimulating lateral bud growth. When their levels increase relative to auxins, they can effectively break apical dominance, allowing side branches to develop. In horticulture, understanding this relationship helps gardeners manage plant shape and productivity through techniques such as selective pruning or applying hormones.
• Evaluate how environmental factors influence apical dominance and plant growth patterns in different ecosystems.
  • Environmental factors such as light availability, nutrient levels, and competition with neighboring plants significantly impact apical dominance. In low-light conditions, plants may reduce auxin production, leading to less dominant central stems and more lateral bud growth. Conversely, in competitive environments with ample light, stronger apical dominance ensures maximum height and resource acquisition. This adaptability allows plants to optimize their growth strategies according to specific ecological contexts.

Related terms

Auxin: A class of plant hormones that promote cell elongation, especially in stems, and play a key role in apical dominance by inhibiting the growth of lateral buds.

Lateral Bud: A bud that arises from the axil of a leaf, which has the potential to grow into a new branch; its growth is inhibited by the presence of apical dominance.

Cytokinins:

Plant hormones that promote cell division and can stimulate the growth of lateral buds, counteracting the effects of auxin in apical dominance.