Nod factor released by Rhizobium:
(a) Are oligosaccharides
(b) Cause curling of root tips
(c) Are O 2 scavengers
(d) Sugars

Options

A. Are oligosaccharides
B. Cause curling of root tips
C. Are `O_(2)` seavengers
D. Sugars

Answer

To solve the question regarding the nod factor released by Rhizobium, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Nod Factors**:
- Nod factors are signaling molecules produced by Rhizobium bacteria during their interaction with leguminous plants. They play a crucial role in the formation of root nodules where nitrogen fixation occurs.

2. **Analyzing Option (a)**:
- **Statement**: "Are oligosaccharides"
- **Explanation**: Nod factors are indeed classified as oligosaccharides, specifically lipochitooligosaccharides. This statement is correct.

3. **Analyzing Option (b)**:
- **Statement**: "Cause curling of root tips"
- **Explanation**: While nod factors initiate the process that leads to curling of root hairs, they do not directly cause curling. Curling occurs after the interaction of Rhizobium with the plant roots. Thus, this statement is misleading.

4. **Analyzing Option (c)**:
- **Statement**: "Are O2 scavengers"
- **Explanation**: This statement is incorrect. Oxygen scavenging in the root nodules is primarily performed by leghemoglobin, not by nod factors. Therefore, this option is incorrect.

5. **Analyzing Option (d)**:
- **Statement**: "Sugars"
- **Explanation**: Nod factors are not classified as sugars. They are specific oligosaccharides, which means they have a more complex structure than simple sugars. Thus, this statement is also incorrect.

6. **Conclusion**:
- The only correct statement regarding the nod factor released by Rhizobium is option (a): "Are oligosaccharides".

### Final Answer:
(a) Are oligosaccharides