The anterior end of pollen tube burst by the process of in embryosac-

Options

A. lmbibition
B. Exosmosis
C. Enzymatic action
D. Endosomosis

Answer

### Step-by-Step Solution:

1. **Understanding the Pollen Tube**:
- The pollen tube is a structure that develops from the pollen grain after it lands on the stigma of a flower. It is responsible for delivering male gametes (sperm cells) to the ovule for fertilization.

2. **Structure of the Pollen Tube**:
- The pollen grain consists of a vegetative cell and a generative cell. The vegetative cell develops into the pollen tube, while the generative cell divides to form two male gametes.

3. **Pathway of the Pollen Tube**:
- After the pollen grain germinates on the stigma, the pollen tube grows down through the style and into the ovary, where the ovule is located.

4. **Bursting of the Pollen Tube**:
- The question specifically asks about the process by which the anterior end of the pollen tube bursts in the embryo sac. This is crucial for the release of the male gametes for fertilization.

5. **Evaluating the Options**:
- **Option A: Imbibition**: This is the process of absorption of water by dry substances, but it does not apply to the bursting of the pollen tube.
- **Option B: Osmosis**: This is the movement of water across a semi-permeable membrane, but it does not directly cause the pollen tube to burst.
- **Option C: Enzymatic Action**: While enzymes play roles in various biological processes, they are not responsible for the bursting of the pollen tube in this context.
- **Option D: Endosmosis**: This is the correct answer. Endosmosis refers to the movement of water into the pollen tube, causing it to swell and eventually burst, releasing the male gametes.

6. **Conclusion**:
- The anterior end of the pollen tube bursts by the process of **endosmosis** in the embryo sac. Therefore, the correct answer is **Option D: Endosmosis**.