mark the incorrect statement w.r.t symbiotic `N_(2)` fixation

Options

A. Root hairs curl by the action of nod factors secreted by bacteria
B. Rapid division of cortical cell is due to secretion of auxins and cytokinins
C. Small component of nitrogenase has Fe-Cu moiety
D. Reducing agents are required

Answer

To solve the question regarding the incorrect statement with respect to symbiotic nitrogen fixation, we will analyze each of the provided statements one by one.

### Step-by-Step Solution:

1. **Understanding Symbiotic Nitrogen Fixation**:
- Symbiotic nitrogen fixation is a process where certain bacteria, such as Rhizobium, form a symbiotic relationship with leguminous plants to convert atmospheric nitrogen (N₂) into a form that plants can use (ammonia).

2. **Analyzing the Statements**:
- **Statement 1**: "Root hairs curl due to the action of nod factors secreted by the bacterium."
- This statement is **correct**. Rhizobium bacteria secrete nod factors that induce the curling of root hairs, allowing the bacteria to infect the plant roots.

- **Statement 2**: "Infected root hairs form an infectious thread that carries the bacteria to the inner cortex."
- This statement is also **correct**. Once the root hairs are infected, they form an infectious thread that transports the bacteria deeper into the plant's root system.

- **Statement 3**: "Prokaryotes are able to fix nitrogen because of the presence of the enzyme nitrogenase, which is a molybdenum iron protein."
- This statement is **correct**. Nitrogenase is indeed a molybdenum-iron protein that plays a crucial role in nitrogen fixation.

- **Statement 4**: "Iron and copper are required for the nitrogenase enzyme."
- This statement is **incorrect**. While iron is essential for nitrogenase activity, copper is not required for nitrogenase function. The presence of copper in this context is misleading.

3. **Conclusion**:
- The incorrect statement regarding symbiotic nitrogen fixation is **Statement 4**: "Iron and copper are required for the nitrogenase enzyme."

### Final Answer:
The incorrect statement with respect to symbiotic nitrogen fixation is **Statement 4**.

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