Pits are unthickend areas that occur in

Options

A. Primary wall
B. Secondary wall
C. Middle lamellum
D. All of them

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where pits, which are unthickened areas, occur in plant cell walls. The options provided are primary wall, secondary wall, middle lamella, and all of these.

2. **Analyzing the Primary Wall**: The primary wall is the first layer formed during cell growth. It is primarily composed of cellulose and is thin and flexible. Importantly, pits are absent in the primary wall.

3. **Analyzing the Secondary Wall**: The secondary wall forms after the primary wall and is thicker, consisting of multiple layers. When the secondary wall forms, cell growth stops, and this wall can develop pits. Therefore, pits are present in the secondary wall.

4. **Analyzing the Middle Lamella**: The middle lamella is the layer that exists between two adjacent plant cell walls. It is primarily made of pectin and does not contain pits. Its role is to adhere cells together and facilitate cell division.

5. **Conclusion**: Since pits are not found in the primary wall or the middle lamella, but are present in the secondary wall, the correct answer to the question is that pits are found in the secondary wall.

**Final Answer**: Pits are unthickened areas that occur in the secondary wall.

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