Pollen tube enters the embryo sac usually

Options

A. by penetrating egg cell
B. through one degenerated synergid
C. by destroying antipodal cells
D. between persistent synergid and central cell

Answer

### Step-by-Step Solution

1. **Understanding the Question**: The question asks where the pollen tube enters the embryo sac during fertilization. Specifically, it seeks to identify the correct entry point among the provided options.

2. **Analyzing the Options**:
- **Option A**: "By penetrating the egg cell."
- This option is incorrect because the pollen tube does not directly penetrate the egg cell. The egg cell is situated above the synergids, making this pathway impossible.

- **Option B**: "Through one degenerated synergid."
- This option is correct. The pollen tube typically enters the embryo sac through one of the synergids, which degenerate to allow the pollen tube to pass through. This process facilitates the release of the male gametes.

- **Option C**: "By destroying the antipodal cells."
- This option is incorrect. The antipodal cells are located at the chalazal end of the embryo sac and are covered by integuments, making it difficult for the pollen tube to penetrate this area.

- **Option D**: "Between the persistent synergid and the central cell."
- This option is also incorrect. If the pollen tube were to enter between the synergid and the central cell, it would not be able to fertilize the egg cell, which is essential for embryo formation.

3. **Conclusion**: Based on the analysis of the options, the correct answer is that the pollen tube enters the embryo sac through one degenerated synergid.

### Final Answer
The pollen tube enters the embryo sac usually through one degenerated synergid.

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