When a tetraploid male plant is crossed with diploid female plant, the ploidy levels of fertilized egg, secondary nucleus, perisperm respectively formed to be

Options

A. 4n, 3n, 2n
B. 3n, 4n. , 2n
C. 3n, 2n, 2n
D. 2n, 3n, 2n

Answer

To solve the problem of determining the ploidy levels of the fertilized egg, secondary nucleus, and perisperm when a tetraploid male plant is crossed with a diploid female plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ploidy of Parents**:
- The male plant is tetraploid (4n), meaning it has four sets of chromosomes.
- The female plant is diploid (2n), meaning it has two sets of chromosomes.

2. **Gamete Formation**:
- During gametogenesis, the male tetraploid plant will undergo meiosis to produce gametes. Since it is tetraploid, the gametes produced will be diploid (2n).
- The female diploid plant will also undergo meiosis to produce haploid (n) gametes.

3. **Fertilization Process**:
- In flowering plants, fertilization involves the fusion of male and female gametes. In this case:
- The diploid male gamete (2n) from the tetraploid male plant fuses with the haploid female gamete (n) from the diploid female plant.
- This fusion results in a fertilized egg (zygote) with a ploidy of 3n (2n from the male gamete + n from the female gamete).

4. **Secondary Nucleus Formation**:
- The secondary nucleus is formed from the central cell of the embryo sac, which contains two polar nuclei. Since the male gamete does not contribute to the secondary nucleus, its ploidy remains unchanged.
- Therefore, the secondary nucleus retains its ploidy of 2n (the two polar nuclei).

5. **Perisperm Formation**:
- Perisperm is derived from the nucellus and is not affected by the male parent’s ploidy. It typically retains the ploidy of the female parent.
- Thus, the perisperm will also have a ploidy of 2n.

### Summary of Ploidy Levels:
- **Fertilized Egg (Zygote)**: 3n
- **Secondary Nucleus**: 2n
- **Perisperm**: 2n

### Final Answer:
- The ploidy levels of the fertilized egg, secondary nucleus, and perisperm are 3n, 2n, and 2n, respectively.

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