An octaploid male plant crossed with diploid female plant, then find the ploidy level of secondary nucleus and embryo respectively :

Options

A. 2n and 5n
B. 8n and 5n
C. 6n and 8n
D. 6n and 3n

Answer

To solve the problem of determining the ploidy level of the secondary nucleus and the embryo resulting from the cross of an octaploid male plant with a diploid female plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ploidy Levels of the Parent Plants:**
- The male plant is octaploid (8n).
- The female plant is diploid (2n).

2. **Determine the Ploidy of Male Gametes:**
- Male gametes are produced through meiosis. Since the male plant is octaploid (8n), the gametes will be haploid (n).
- Therefore, the male gametes will have a ploidy level of \( n = 4n \) (since 8n divided by 2 gives 4n).

3. **Determine the Ploidy of Female Gametes:**
- The female plant is diploid (2n), so the female gametes will be haploid (n).
- Therefore, the female gametes will have a ploidy level of \( n = 1n \).

4. **Determine the Ploidy of the Secondary Nucleus:**
- The secondary nucleus is formed by the fusion of two female gametes in the embryo sac.
- Since the female plant is diploid (2n), the secondary nucleus will also be diploid (2n).

5. **Determine the Ploidy of the Embryo:**
- The embryo is formed by the fusion of a male gamete with the egg cell.
- The male gamete has a ploidy level of \( 4n \) and the egg cell is haploid (n).
- Therefore, the ploidy level of the embryo will be \( 4n + n = 5n \).

### Final Results:
- The ploidy level of the secondary nucleus is **2n**.
- The ploidy level of the embryo is **5n**.

### Summary:
The correct answer is:
- Secondary nucleus: **2n**
- Embryo: **5n**