Which of the following is a vestigial structure and soon disintegrates?

Options

A. Pollen tube
B. Pollen cytoplasm
C. Generative nucleus
D. Tube nucleus

Answer

To determine which of the following is a vestigial structure that soon disintegrates, we need to analyze the options provided: pollen tube, pollen cytoplasm, generative nucleus, and tube nucleus.

### Step-by-Step Solution:

1. **Understanding Pollen Grain Structure**:
- Pollen grains are male gametophytes that contain two types of nuclei: the vegetative (or tube) nucleus and the generative nucleus.

2. **Identifying the Nuclei**:
- The **vegetative nucleus** (also known as the tube nucleus) is responsible for forming the pollen tube and supporting the development of the germ.
- The **generative nucleus** divides to form two male gametes.

3. **Function of the Tube Nucleus**:
- The tube nucleus plays a crucial role in the initial stages of fertilization by forming the pollen tube that delivers the male gametes to the ovule.
- However, after the pollen tube has formed and the fertilization process begins, the tube nucleus does not have a further role and soon disintegrates.

4. **Conclusion**:
- Among the options given, the **tube nucleus** is the structure that is considered vestigial because it degenerates after fulfilling its function in the fertilization process.

### Final Answer:
The correct answer is the **tube nucleus**.

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