Pollen tube is covered by :

Options

A. pectocellulose
B. sporopollenin
C. cellulose
D. lingnocellulose

Answer

To solve the question "Pollen tube is covered by:", we need to analyze the components that make up the pollen tube and identify the correct option from the given choices: Pactocellulose, Sporopollenin, Cellulose, or Lignocellulose.

### Step-by-Step Solution:

1. **Understanding the Structure of the Pollen Tube**:
- The pollen tube is a structure that forms after pollen germinates. It is essential for the delivery of sperm cells to the ovule during fertilization in plants.

2. **Identifying the Layers of the Pollen Tube**:
- The pollen tube has two main layers:
- **Inner Membrane**: This is the inner layer, which is relatively soft and is primarily made of cellulose.
- **Outer Layer**: This is the outer layer, which is harder and provides protection.

3. **Composition of the Outer Layer**:
- The outer layer of the pollen tube is composed of a mixture of pectin and cellulose. This combination is referred to as "Pactocellulose."

4. **Evaluating the Options**:
- **Pactocellulose**: This is a combination of pectin and cellulose, which matches the composition of the outer layer of the pollen tube.
- **Sporopollenin**: This is a tough substance found in the outer walls of pollen grains but is not specifically the covering of the pollen tube itself.
- **Cellulose**: While cellulose is part of the composition, it does not fully describe the outer layer, which includes pectin as well.
- **Lignocellulose**: This is a complex of lignin and cellulose, typically found in woody plants, and is not relevant to the pollen tube.

5. **Conclusion**:
- Based on the analysis, the correct answer is **Pactocellulose**, as it accurately describes the material covering the pollen tube.

### Final Answer:
Pollen tube is covered by **Pactocellulose**.