What does the term apical dominance mean ?

Options

A. Suppression of growth of apical bud by axillary buds in the presence of hormone
B. Suppression of growth of axillary buds by the presence of apical buds under the effect of hormone auxins.
C. Suppression of growth of axillary buds by the presence of apical buds under the effect of hormone cytokinins.
D. Suppression of growth of apical buds by the presence of axillary buds under the effect of hormone cytokinins.

Answer

### Step-by-Step Solution:

1. **Definition of Apical Dominance**:
- Apical dominance refers to the phenomenon where the growth of the main or central stem of a plant is prioritized over the growth of lateral or axillary buds. This is primarily due to the presence of hormones, particularly auxins.

2. **Role of Auxins**:
- Auxins are plant hormones that are crucial for the regulation of growth. They are produced at the tips of shoots and roots. The main type of auxin involved in apical dominance is Indole-3-Acetic Acid (IAA).

3. **Mechanism of Apical Dominance**:
- The auxins produced in the apical bud suppress the growth of axillary buds. This means that when the apical bud is present, it inhibits the development of lateral buds, ensuring that the plant grows taller rather than bushier.

4. **Examples of Auxins**:
- Besides IAA, other examples of natural auxins include Indole-3-butyric acid. These hormones are essential for maintaining the apical dominance.

5. **Effects of Apical Dominance**:
- Apical dominance not only influences the growth pattern of the plant but also plays a role in flowering and processes like parthenocarpy, which is the development of fruits without fertilization.

6. **Cytokinins and Apical Dominance**:
- Cytokinins are another class of plant hormones that can counteract apical dominance. When cytokinins are present, they can promote the growth of axillary buds, thus reducing the dominance of the apical bud.

7. **Conclusion**:
- In summary, apical dominance is the suppression of axillary bud growth by the apical bud due to the action of auxins, which promotes vertical growth of the plant.