Growth substance that stimulates nodule formation in leguminous plants is

Options

A. NAA
B. IAA
C. IBA
D. ABA.

Answer

To determine the growth substance that stimulates nodule formation in leguminous plants, we can analyze the options provided:

1. **NAA (Naphthalene Acetic Acid)**:
- NAA is a synthetic growth regulator known to affect various physiological and biochemical processes in plants. However, it does not play a role in nodule formation.
- **Conclusion**: NAA is not the correct answer.

2. **IAA (Indole Acetic Acid)**:
- IAA is a naturally occurring auxin, which is a type of plant hormone. It is known to stimulate cell elongation and division. Importantly, IAA induces nodule formation in the roots of leguminous plants.
- **Conclusion**: IAA is the correct answer as it stimulates nodule formation.

3. **IBA (Indole Butyric Acid)**:
- IBA is another auxin, specifically a synthetic one, which is primarily used to induce adventitious rooting in stem cuttings. It does not contribute to nodule formation.
- **Conclusion**: IBA is not the correct answer.

4. **ABA (Abscisic Acid)**:
- ABA is a plant hormone that plays a role in various developmental processes, including seed and bud dormancy and stomatal closure. It does not stimulate nodule formation.
- **Conclusion**: ABA is not the correct answer.

**Final Answer**: The growth substance that stimulates nodule formation in leguminous plants is **IAA (Indole Acetic Acid)**.

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