Tracheids and Vessels - Practice Questions & MCQ

Elements of Xylem - Tracheids and Vessels

Tracheids:

• Tracheids can originate from procambium or vascular cambium.
• These are elongated cells.
• They have thick and lignified cells. 
• Their lumen is wider than that of fibers.
• Their end walls are tapering.
• The perforation (pits) are seen on the face walls.
• At maturity, these are dead and devoid of protoplasm.
• These are primitive and fundamental types of xylem cells.
• These are present in all the plants of Tracheophyta. 
• Ancient vascular plants only have tracheids in their xylem.
• In the metaxylem of gymnosperms, the bordered pits are very common.

Functions of Tracheids:

1. Conduction of water and minerals from the roots to leaves
2. Providing mechanical strength to the plant
3. Main conducting elements in pteridophytes and gymnosperms.
    

Vessels:

• These arise from procambium during the primary growth and from vascular cambium during secondary growth.
• The pattern of secondary wall deposition is determined by the microfibrils.
• Vessels are made up of vessel elements placed one over the other.
• Vessel elements have perforated end walls. 
• Hence, vessels are multicellular pipe-like structures.
• They have comparatively a wider lumen than tracheids.
• At maturity, they are devoid of protoplasm and are dead.
• In pteridophytes and gymnosperms, the vessels are absent. Their wood is called the non-porous wood.
• In angiosperms, the vessels are present. Their wood is called porous wood.

TIP: 
Ephedra and Gnetum are the gymnosperms that have vessels. Selaginella and  Pteridium are the pteridophytes that have vessels.
Winteraceae, Trochodendraceae, and Tetracentraceae of Angiosperms do not have vessels.