Internodal elongation is stimulated by

Options

A. auxin
B. ABA
C. cytokinin
D. gibberellin

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which hormone stimulates internodal elongation in plants. Internodal elongation refers to the growth of the sections of the stem between the nodes (the points where leaves are attached).

2. **Identifying Plant Hormones**: The options given are auxin, abscisic acid (ABA), cytokinin, and gibberellin. Each of these hormones has different roles in plant growth and development.

3. **Role of Gibberellin**: Gibberellin is a plant hormone known for promoting stem elongation, including internodal elongation. It facilitates growth by stimulating cell division and elongation, particularly in the stem and roots.

4. **Role of Auxin**: Auxin is primarily involved in the elongation of plant cells and is concentrated at the tips of shoots. It helps in the directional growth of plants towards light (phototropism) but is not specifically responsible for internodal elongation.

5. **Role of Cytokinin**: Cytokinins are involved in promoting cell division and differentiation. They play a role in shoot and root development but do not directly stimulate internodal elongation.

6. **Role of Abscisic Acid (ABA)**: ABA generally acts as a growth inhibitor and is involved in processes such as stress responses and dormancy. It counteracts the effects of gibberellin and can inhibit growth, leading to conditions like dwarfism.

7. **Conclusion**: Based on the roles of these hormones, gibberellin is the hormone that stimulates internodal elongation. Therefore, the answer to the question is gibberellin.

**Final Answer**: Internodal elongation is stimulated by gibberellin.

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