Pit membrane consists of

Options

A. Secondary cell wall
B. Middle lamella
C. Primary cell wall
D. Plasma membrane

Answer

### Step-by-Step Solution

1. **Understanding Pit Membrane**: The pit membrane is a specialized structure found in the cell wall of plants, particularly in the xylem. It is a thinner region that allows for communication and fluid exchange between adjacent cells.

2. **Composition of Pit Membrane**: The pit membrane is primarily composed of the secondary cell wall. The secondary cell wall is thicker and provides structural support, while the pit area is a discontinuity that allows for the passage of materials.

3. **Types of Pits**: There are two main types of pits:
- **Simple Pits**: These have a uniform width throughout the cavity.
- **Bordered Pits**: These have a cavity that narrows towards the cell lumen, and the membrane is typically curved over by the secondary cell wall.

4. **Characteristics of Pit Membrane**: The pit membrane is a characteristic feature of cells with secondary cell walls. It facilitates the exchange of fluids and communication between cells.

5. **Conclusion**: Based on the characteristics and composition discussed, we conclude that the pit membrane consists of the secondary cell wall.

### Final Answer
The pit membrane consists of the secondary cell wall.