Apical dominance in higher plants is due to

Options

A. C/N ratio
B. Photoperiodism
C. Phototropism
D. Auxin-cytokinin balance.

Answer

**Step-by-Step Solution:**

1. **Understanding Apical Dominance**:
- Apical dominance is a phenomenon in higher plants where the main stem (apex) grows more vigorously than the lateral branches. This results in the suppression of lateral branch growth.

2. **Role of Hormones**:
- The primary hormone responsible for apical dominance is **auxin**. Auxins are produced at the tip of the shoot and promote the growth of the main stem while inhibiting the growth of lateral buds.

3. **Mechanism of Suppression**:
- The auxin produced in the apical bud travels down the stem and suppresses the growth of lateral buds. This is why the lateral branches grow slower compared to the main stem.

4. **Counteracting Hormones**:
- While auxin promotes apical dominance, another hormone called **cytokinin** is responsible for breaking this dominance. Cytokinins promote the growth of lateral buds and can counteract the effects of auxin.

5. **Conclusion**:
- Therefore, apical dominance in higher plants is due to the balance between auxin and cytokinin. Auxin maintains the dominance, while cytokinin can promote the growth of lateral branches when its levels are higher.

**Final Answer**: Apical dominance in higher plants is due to the balance of auxin and cytokinin, with auxin being the primary hormone that promotes dominance.

---