Apical dominance

Definition

Apical dominance is a phenomenon in plants where the growth of the main central stem is prioritized over the growth of lateral branches. This process ensures that a plant can efficiently compete for light and space by directing its resources toward vertical growth, allowing it to reach higher and capture more sunlight for photosynthesis. Apical dominance is regulated by hormonal signals, primarily auxins, which are produced at the tips of the shoots and inhibit the growth of nearby lateral buds.

5 Must Know Facts For Your Next Test

1. Apical dominance allows plants to optimize their height for better access to sunlight, which is essential for photosynthesis.
2. The suppression of lateral bud growth is primarily due to the high concentration of auxins at the shoot tip, which inhibits the growth of nearby buds.
3. When the apical bud is removed or damaged, lateral buds are released from inhibition and can begin to grow, resulting in a bushier plant.
4. Other factors, such as environmental conditions and interactions with other hormones like cytokinins, can modify the degree of apical dominance.
5. Apical dominance is a critical factor in plant architecture, affecting how plants respond to their environment and compete for resources.

Review Questions

• How does apical dominance influence plant structure and growth in relation to competition for light?
  • Apical dominance plays a significant role in shaping plant structure by prioritizing vertical growth over lateral branching. This adaptation allows plants to grow taller and better compete for light, which is crucial for photosynthesis. By directing resources towards the main stem, plants can outgrow neighboring plants, ensuring they have optimal access to sunlight and increasing their overall survival chances.
• Discuss the role of auxins in regulating apical dominance and how their concentration affects lateral bud growth.
  • Auxins are key hormones involved in apical dominance, as they are produced at the shoot tip and transported downward to inhibit the growth of lateral buds. When auxin concentrations are high near the apex, they suppress lateral bud development. Conversely, if the apical bud is removed or damaged, auxin levels decrease in the surrounding areas, allowing lateral buds to break dormancy and grow, leading to a bushier appearance in plants.
• Evaluate how environmental factors might alter apical dominance and influence plant adaptation strategies.
  • Environmental factors such as light availability, competition from neighboring plants, and nutrient levels can significantly impact apical dominance. For instance, if a plant is shaded by others, it may respond by increasing lateral bud growth to compete for sunlight more effectively. Additionally, if water or nutrients are scarce, hormonal balances may shift to favor horizontal growth instead of vertical dominance. This adaptability illustrates how plants strategically respond to their environment while managing resources for survival.

Related terms

Auxins: Plant hormones that play a crucial role in regulating growth and development, particularly in promoting stem elongation and influencing apical dominance.

Lateral Buds: Buds located along the sides of a plant stem that can develop into branches or flowers; their growth is often suppressed by apical dominance.

Ethylene: A plant hormone involved in various processes, including fruit ripening and senescence, which can interact with auxins to influence apical dominance.