During double fertilization , the pollen tube enters the embryo sac through

Options

A. Egg cell
B. Persistent synergid
C. Degenerating synergid
D. Central cell

Answer

To solve the question regarding where the pollen tube enters the embryo sac during double fertilization, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Double Fertilization**:
- Double fertilization is a unique process in angiosperms (flowering plants) where one sperm fertilizes the egg cell to form the zygote, and the other sperm fuses with two polar nuclei to form the triploid endosperm.

2. **Structure of the Embryo Sac**:
- The embryo sac is a structure within the ovule that contains several types of cells: the egg cell, two synergids, three antipodal cells, and two polar nuclei.

3. **Role of Synergids**:
- The synergids are located at the micropylar end of the embryo sac, adjacent to the egg cell. They play a crucial role in guiding the pollen tube to the egg cell.

4. **Pollen Tube Entry**:
- As the pollen tube approaches the embryo sac, it is directed by the synergids. The synergids secrete chemical signals (chemotaxis) that attract the pollen tube, allowing it to enter the embryo sac.

5. **Degeneration of Synergids**:
- After the pollen tube penetrates the embryo sac and releases the sperm cells, the synergids begin to degenerate as they have fulfilled their role in guiding the pollen tube.

6. **Conclusion**:
- Therefore, during double fertilization, the pollen tube enters the embryo sac through the synergids, specifically the degenerating synergids.

### Final Answer:
The pollen tube enters the embryo sac through the **degenerating synergids**.

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