The innermost wall layer of microsporangia which provides nutrition to the developing pollen grain is

Options

A. Epidermis
B. Endothelium
C. Middle layer
D. Tapetum

Answer

To solve the question regarding the innermost wall layer of microsporangia that provides nutrition to the developing pollen grain, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Microsporangia Structure**: Microsporangia, which are found in the anthers of flowering plants, have a wall composed of four distinct layers.

2. **Identify the Layers**: The four layers of the microsporangial wall are:
- **Epidermis**: The outermost layer, which serves a protective function.
- **Endothecium**: The layer beneath the epidermis, which develops fibrous thickening and is hygroscopic, aiding in the dehiscence of the anther.
- **Middle Layer**: This layer consists of 2 to 3 layers and primarily serves as a storage for reserved food material.
- **Tapetum**: The innermost layer of the microsporangial wall.

3. **Determine the Function of Each Layer**:
- The **Epidermis** protects the microsporangia.
- The **Endothecium** aids in the release of pollen grains.
- The **Middle Layer** stores nutrients but does not directly nourish the pollen grains.
- The **Tapetum** is crucial as it provides nutrition to the developing pollen grains.

4. **Identify the Correct Answer**: Based on the functions of these layers, the tapetum is identified as the innermost layer that provides essential nutrients to the developing pollen grains.

5. **Conclusion**: Therefore, the correct answer to the question is **Tapetum**.

### Final Answer:
The innermost wall layer of microsporangia which provides nutrition to the developing pollen grain is the **Tapetum**.