Question

Match the type of xylem cell to its characteristic feature.

• A. Thin walled
• B. Obliterated lumen
• C. Perforation plates
• D. Tapering ends

Answer 1

Xylem vessels have four types of cells, tracheids, vessels, xylem fibres and xylem parenchyma. Tracheids are elongated or tube like cells with thick and lignified walls and tapering ends. These are dead and are without protoplasm. The inner layers of the cell walls have thickenings which vary in form. Vessel is a long cylindrical tube-like structure made up of many cells called vessel members, each with lignified walls and a large central cavity. The vessel cells are also devoid of protoplasm. Vessel members are interconnected through perforations in their common walls. Xylem fibres have highly thickened walls and obliterated central lumens. These may either be septate or aseptate. Xylem parenchyma cells are living and thin-walled, and their cell walls are made up of cellulose.