Phyllotaxy is the mode of arrangement of leaves and the principle underlying it is :

Options

A. to minimize the number of leaves on a branch
B. to increase the number of leaves on a branch
C. to hide leaves against sunlight
D. to expose leaves equally to sunlight

Explanation

### Step-by-Step Solution:

1. **Understanding Phyllotaxy**: Phyllotaxy refers to the arrangement of leaves on a stem or branch. This arrangement can significantly affect how well the leaves can capture sunlight for photosynthesis.

2. **Analyzing the Options**: The question provides four options regarding the principle underlying phyllotaxy:
- A) To minimize the number of leaves on a branch
- B) To increase the number of leaves on a branch
- C) To hide leaves against sunlight
- D) To expose leaves equally to sunlight

3. **Evaluating Each Option**:
- **Option A**: Minimizing the number of leaves does not align with the purpose of phyllotaxy, which is to optimize light capture.
- **Option B**: Increasing the number of leaves might seem beneficial, but it does not directly relate to the arrangement principle.
- **Option C**: Hiding leaves against sunlight would hinder photosynthesis, which is not the goal of leaf arrangement.
- **Option D**: Exposing leaves equally to sunlight is crucial for maximizing photosynthesis efficiency, as it ensures that all leaves receive adequate light.

4. **Conclusion**: After evaluating all options, the correct principle underlying phyllotaxy is to expose leaves equally to sunlight. This arrangement facilitates optimal photosynthesis.

### Final Answer:
**The principle underlying phyllotaxy is to expose leaves equally to sunlight.**

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