Name the scientist who discovered that decapitated coleoptile would resume photo-sensitivity and growth if severed tip is reattached through a gelatin disc.

Options

A. Darwin
B. Van Overbeek
C. Boyson Jensen
D. Paal.

Answer

To answer the question regarding the scientist who discovered that a decapitated coleoptile would resume photosensitivity and growth if the severed tip is reattached through a gelatin disc, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components**:
- The coleoptile is the protective sheath covering the emerging shoot in monocotyledonous plants. It plays a crucial role in directing the growth of the plant towards light (phototropism).

2. **Identify the Experiment**:
- The experiment involved severing the tip of the coleoptile and then reattaching it using a gelatin disc. This setup was used to study the effects on growth and photosensitivity.

3. **Recognize the Key Observations**:
- After reattaching the severed tip through a gelatin disc, it was observed that the coleoptile resumed normal growth and photosensitivity (phototropism).

4. **Link the Experiment to the Scientist**:
- The scientist who conducted this experiment and made these observations was **Boysen Jensen**. He demonstrated that the growth response could be restored even after severing the coleoptile, which indicated the presence of growth substances.

5. **Eliminate Other Options**:
- Darwin is known for his theory of evolution, not for this specific experiment. Van Overbeek is associated with cytokinins and plant regeneration, while Pahl is not directly related to this discovery. Hence, they are not the correct answers.

6. **Conclude the Answer**:
- Therefore, the correct answer to the question is **Boysen Jensen**.

### Final Answer:
**Boysen Jensen**