An important finding in Went's experiment was

Options

A. Unequal distribution of elongation promoting substance in Avena coleoptile
B. Presence of elongation factor in all cells of root
C. Curvature of coleoptile is proportional to auxin concentration
D. Curvature occurred due to irregular elongation of cells.

Answer

### Step-by-Step Solution:

1. **Understanding Went's Experiment**: Went conducted an experiment to study the effects of auxins, which are plant hormones that promote cell elongation. He used a bioassay known as the Avena curvature test to demonstrate this.

2. **The Concept of Curvature**: In the context of plant growth, curvature refers to the bending of the plant towards a light source. This bending occurs due to the unequal distribution of auxins.

3. **Mechanism of Auxin Action**: When a plant is exposed to light, auxins accumulate on the side of the plant that is away from the light (the darker side). This accumulation leads to increased cell elongation on that side compared to the side facing the light.

4. **Result of Auxin Distribution**: The result of this unequal distribution of auxins is that the cells on the darker side elongate more than those on the lighter side, causing the plant to bend towards the light source.

5. **Identifying the Correct Answer**: Based on the findings of Went's experiment, the important conclusion is that the unequal distribution of elongation-promoting substances (auxins) leads to the curvature of the plant. Therefore, the correct answer to the question is the option stating "unequal distribution of elongation promoting substance."

6. **Eliminating Incorrect Options**:
- The presence of elongation factors in all cells of the root is incorrect because auxins are produced at the shoot tip and affect the shoot rather than the root.
- The curvature of the coleoptile being proportional to auxin concentration is misleading as it does not directly address the mechanism of unequal distribution.
- The idea that curvature occurs due to irregular elongation of cells is also incorrect; it is specifically due to the differential elongation caused by auxin distribution.

### Final Answer:
The important finding in Went's experiment was the **unequal distribution of elongation promoting substance (auxin)**.

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