Which one of the following pairs of plant structures has haploid number of chromosomes?

Options

A. Megaspore mother cells and antipodal cells
B. Egg cell and antipodal cells
C. Nucellus and antipodal cells
D. Egg nucleus and secondary nucleus

Explanation

To solve the question "Which one of the following pairs of plant structures has haploid number of chromosomes?", we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Haploid and Diploid**:
- Haploid (n): A cell that contains one complete set of chromosomes.
- Diploid (2n): A cell that contains two complete sets of chromosomes, one from each parent.

2. **Identifying Plant Structures**:
- We are given pairs of plant structures to evaluate. Common structures include megaspore mother cells, egg cells, antipodal cells, and nucellus.

3. **Evaluating Each Pair**:
- **Pair 1: Megaspore Mother Cell and Antipodal Cells**:
- Megaspore mother cell: Diploid (2n).
- Antipodal cells: Haploid (n).
- Conclusion: This pair is not correct as one is diploid.

- **Pair 2: Egg Cell and Antipodal Cells**:
- Egg cell: Haploid (n).
- Antipodal cells: Haploid (n).
- Conclusion: This pair is correct as both structures are haploid.

- **Pair 3: Nucellus and Antipodal Cells**:
- Nucellus: Diploid (2n).
- Antipodal cells: Haploid (n).
- Conclusion: This pair is not correct as one is diploid.

- **Pair 4: Egg Nucleus and Secondary Nucleus**:
- Egg nucleus: Haploid (n).
- Secondary nucleus: Diploid (2n) (formed by the fusion of two haploid nuclei).
- Conclusion: This pair is not correct as one is diploid.

4. **Final Conclusion**:
- The only pair that consists entirely of haploid structures is the **Egg Cell and Antipodal Cells**.

### Answer:
The correct answer is **Egg Cell and Antipodal Cells**.