A specialized pale cell in blue green algae which is impermeable to oxygen is

Options

A. akinete
B. hormogonia
C. heterocyst
D. spore

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a specialized pale cell in blue-green algae (cyanobacteria) that is impermeable to oxygen.

2. **Analyzing the Options**:
- **Acinet**: This is a thick-walled, non-motile form of cyanobacteria, but it does not specifically refer to a cell type that is impermeable to oxygen.
- **Hormogonia**: These are motile filaments formed during vegetative reproduction in some cyanobacteria. They are not specialized cells that are impermeable to oxygen.
- **Heterocyst**: These are specialized cells in some cyanobacteria that function as sites for nitrogen fixation. They create an anaerobic environment to protect the nitrogenase enzyme from oxygen, making them impermeable to oxygen.
- **Spore**: Spores are reproductive cells that can develop into new individuals. They are not specifically related to nitrogen fixation or impermeability to oxygen.

3. **Identifying the Correct Answer**: Based on the analysis, the specialized pale cell in blue-green algae that is impermeable to oxygen is the **heterocyst**. Heterocysts facilitate nitrogen fixation by creating a micro anaerobic environment, which protects the nitrogenase enzyme from being inactivated by oxygen.

4. **Conclusion**: The correct answer to the question is **heterocyst**.