Microspores of Pinus are shed at:

Options

A. 3-cell stage
B. 2-cell stage
C. 1-cell stage
D. 4-cell stage

Answer

To solve the question regarding when microspores of Pinus are shed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Microspores in Pinus**:
- Microspores in Pinus are also referred to as pollen grains. They are crucial for reproduction in gymnosperms.

2. **Stages of Microspore Development**:
- Microspores can develop through various stages: one cell stage, two cell stage, three cell stage, and four cell stage.

3. **Identifying the Correct Stage for Pinus**:
- In the case of Pinus, the microspores are shed when they reach the four-cell stage. This means that by the time they are released into the environment, they have developed into a structure consisting of four cells.

4. **Characteristics of Pinus Pollen**:
- The pollen grains of Pinus consist of two prothallial cells and do not have an antheridium. Instead, they produce sperm directly.
- Additionally, the pollen grains have two larger air sacs that help them float in the wind, facilitating their dispersal.

5. **Conclusion**:
- Therefore, the correct answer to the question is that microspores of Pinus are shed at the four-cell stage.

### Final Answer:
Microspores of Pinus are shed at the four-cell stage.

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