The ladder like thickenings in tracheids and vessels are called

Options

A. annular
B. spiral
C. scalariform
D. reticulate

Answer

**Step-by-Step Solution:**

1. **Identify the Components**: Understand that tracheids and vessels are types of tracheary elements found in the xylem of plants.

2. **Describe Tracheids**: Recognize that tracheids are elongated cells pointed at both ends and are imperforate, meaning their primary wall is continuous without any openings.

3. **Describe Vessels**: Understand that vessel members are perforated at their ends, allowing them to connect and form a tube-like structure known as a vessel or trachea.

4. **Understand Perforation Plates**: Note that the parts of the cell wall that bear the perforations are called perforation plates, which can have different types of arrangements.

5. **Identify Types of Perforation Arrangements**: Learn that perforation plates can have simple or multiple perforations. The multiple arrangements can be in various forms.

6. **Focus on Ladder-like Thickenings**: Specifically, the question asks about the ladder-like thickenings. This arrangement is referred to as "scleriform" thickenings.

7. **Conclusion**: Therefore, the answer to the question is that the ladder-like thickenings in tracheids and vessels are called **scleriform thickenings**.

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