Which of the following statements is not true for class phaeophyceae?

Options

A. Vegetative reproduction takes place by fragmentation
B. The protoplast contains, in addition to plastids, a centrally located vacuole and nucleus.
C. Sexual reproduction may be isogamous, anisogamous or oogamous.
D. Asexual reproductive by uniflagellate zoospores

Answer

To determine which statement is not true for the class Phaeophyceae, we will analyze each of the provided statements one by one.

### Step-by-Step Solution:

1. **Understanding Phaeophyceae**:
- Phaeophyceae, commonly known as brown algae, are a class of algae characterized by their brown color due to the presence of the pigment fucoxanthin. They are primarily found in marine environments and are known for their photosynthetic capabilities.

2. **Analyzing the First Statement**:
- **Statement**: "Vegetative reproduction takes place by fragmentation."
- **Analysis**: This statement is true. In Phaeophyceae, vegetative reproduction often occurs through fragmentation, where parts of the algae break off and develop into new individuals.

3. **Analyzing the Second Statement**:
- **Statement**: "The protoplast contains in addition to plastids."
- **Analysis**: This statement is also true. The protoplast of Phaeophyceae contains various organelles, including plastids, vacuoles, and the nucleus.

4. **Analyzing the Third Statement**:
- **Statement**: "Saxonal reproduction may be isogamous and isogamous-pneumogamous."
- **Analysis**: This statement is true. Phaeophyceae can reproduce sexually through isogamous (gametes of similar size and shape), anisogamous (gametes of different sizes), and oogamous (one gamete is motile, usually male) methods.

5. **Analyzing the Fourth Statement**:
- **Statement**: "A saxonal reproduction by uniflagellate zoospores."
- **Analysis**: This statement is false. In Phaeophyceae, sexual reproduction occurs through biflagellate zoospores, which have two flagella, not uniflagellate (one flagellum).

### Conclusion:
The statement that is not true for class Phaeophyceae is the fourth statement: "A saxonal reproduction by uniflagellate zoospores."

### Final Answer:
The answer is the fourth statement.

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