In coleoptile tissue, auxin -

Options

A. is not transported, because auxin is used where it is made
B. is transported by diffusion, with no preferred direction
C. Is transported from base to tip
D. Is produced by the growing apices of the stem and roots, from where they migrate to the regions of their action

Answer

**Step-by-Step Solution:**

1. **Understanding Auxin**: Auxin is a type of plant hormone that plays a crucial role in regulating plant growth and development. It is classified as a plant growth regulator (PGR) and is involved in various processes such as cell division, elongation, and differentiation.

2. **Location of Auxin Production**: Auxin is primarily produced in the growing tips of the plant, specifically in the shoot tips (apical meristems) and root tips. This is where the plant actively grows and develops.

3. **Transport Mechanism**: Auxin is transported from the base of the plant to the tip. This polar transport occurs in a specific direction, which is crucial for the plant's growth response to environmental stimuli, such as light.

4. **Phototropism Experiment**: The discovery of auxin's role in plant growth was significantly advanced by the experiments conducted by Charles Darwin and his son, Francis. They observed that when the coleoptile (the protective sheath covering the emerging shoot) of canary grass was illuminated from one side, it bent towards the light. This bending is known as phototropism.

5. **Conclusion**: Based on the understanding of auxin's production and transport, the correct statement regarding auxin in coleoptile tissue is that it is produced by the growing tips of the stem and roots, from where it migrates to regions of action. Therefore, the correct answer is option 4.

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