Question

The most primitive tracheary elements are

• A. Tracheids with annular thickenings
• B. Tracheids with scalariform thickenings
• C. Pitted tracheids
• D. Pitted tracheids and vessels.

Answer 1

Answer: (A)

Tracheids with annular thickenings

Tracheids are the more ancient tracheary elements, the main water conductive cells of the pteridophytes and the gymnosperms. They are elongate cells with tapering ends. Their cell walls characteristically bear annular or ring-like thickenings: The deposition of lignin takes place in the form of rings on the inner surface of the cell wall.

So, the correct answer is 'Tracheids with annular thickenings.'