Pits occur in or pitted thickning occurs in

Options

A. sec. phloem
B. protoxylem
C. Metaxylem
D. bark

Answer

To answer the question about where pits occur or where pitted thickening occurs, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Context**: Understand that the question is asking about the occurrence of pits and pitted thickening in plants. This is related to the anatomy of flowering plants, specifically in the xylem.

2. **Understand Xylem Structure**: Recognize that xylem is composed of different types of cells, primarily tracheids and vessels. These cells are responsible for the conduction of water and minerals.

3. **Types of Thickening**: Familiarize yourself with the types of thickening that can occur in xylem cells. The video mentions various types including annular, spiral, scleriform, reticulate, pitted, and bordered pitted thickening.

4. **Differentiate Between Protoxylem and Metaxylem**: Know that xylem can be categorized into two types: protoxylem (primary xylem) and metaxylem (secondary xylem). Protoxylem is typically smaller and found in younger parts of the plant, while metaxylem is larger and found in older parts.

5. **Identify Where Pitted Thickening Occurs**: According to the transcript, pitted and reticulated cells are specifically present in metaxylem. Therefore, pitted thickening occurs in the metaxylem due to the larger size of the cells.

6. **Conclusion**: Based on the information gathered, we can conclude that pits or pitted thickening occurs in the metaxylem of xylem tissue.

### Final Answer:
Pits occur in or pitted thickening occurs in **metaxylem**.