Which part of a leaf carries on most of the photosynthesis of a plant ?

Options

A. Mesophyll
B. Epidermal layer
C. Stoma
D. Guard cells

Explanation

To answer the question "Which part of a leaf carries on most of the photosynthesis of a plant?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand Photosynthesis**: Photosynthesis is the process by which plants convert light energy into chemical energy, primarily in the form of glucose. This process occurs mainly in the leaves of the plant.

2. **Identify Leaf Structures**: The leaf consists of several parts, including:
- **Epidermal Layer**: The outer protective layer of the leaf.
- **Mesophyll**: The inner tissue of the leaf where most photosynthesis occurs.
- **Stoma**: Pores in the leaf that allow for gas exchange (CO2 in, O2 out).
- **Guard Cells**: Specialized cells that surround the stoma and regulate its opening and closing.

3. **Focus on Mesophyll**: The mesophyll is composed of two types of cells:
- **Palisade Mesophyll**: Located just beneath the upper epidermis, these cells are tightly packed and contain a high number of chloroplasts, making them the primary site for photosynthesis.
- **Spongy Mesophyll**: Located below the palisade layer, these cells have air spaces that facilitate gas exchange but are not as densely packed with chloroplasts.

4. **Conclusion**: Given that the mesophyll contains the highest concentration of chloroplasts, it is the part of the leaf that carries out most of the photosynthesis.

### Final Answer:
The part of a leaf that carries on most of the photosynthesis of a plant is the **mesophyll**.

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