A : Endosperm in Cycas is haploid in nature.
R : Cycas roots shows association with oxyphoto - bacteria.

Options

A. If the Assertion & Reason are true and the reason is the correct. Explanation of the assertion.
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion.
C. If Assertion is true statement but Reason is false.
D. If both Assertion and Reason are false statements.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Endosperm in Cycas is haploid in nature."
- Cycas is a genus of plants that belongs to the group Gymnosperms.

2. **Explanation of Endosperm**:
- Endosperm is a tissue that provides nutrition to the developing embryo within the seed.
- In Gymnosperms, the endosperm is formed from the female gametophyte, which is haploid.

3. **Haploid Nature of Endosperm**:
- Since the endosperm in Cycas is derived from the haploid female gametophyte and does not undergo fertilization, it remains haploid.
- Therefore, the assertion is correct.

4. **Understanding the Reason**:
- The reason states that "Cycas roots show association with oxyphoto-bacteria."
- Oxyphoto-bacteria refers to cyanobacteria, which can perform photosynthesis and fix nitrogen.

5. **Role of Corolloid Roots**:
- Cycas has specialized roots known as corolloid roots that associate with nitrogen-fixing bacteria, including cyanobacteria.
- These roots help in nitrogen fixation and are involved in the photosynthetic process.

6. **Evaluating the Reason**:
- While the reason is true (Cycas roots do associate with cyanobacteria), it does not explain why the endosperm is haploid.
- The reason does not directly relate to the assertion about the nature of the endosperm.

7. **Conclusion**:
- Both the assertion and reason are true, but the reason does not correctly explain the assertion.
- Therefore, the correct answer is that the assertion is true, and the reason is true but does not explain the assertion.

### Final Answer:
- Assertion (A) is true: Endosperm in Cycas is haploid in nature.
- Reason (R) is true: Cycas roots show association with oxyphoto-bacteria.
- The correct option is B: Both assertion and reason are true, but the reason is not the correct explanation of the assertion.