Compare the structures of xylem vessels and phloem vessels in plants.

Cambridge International IGCSE Biology (0610) — 8.1 Xylem and phloem · Compare · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Xylem vessels are dead cells with no cytoplasm, whereas phloem sieve tubes are living cells.
Xylem vessels have thick, lignified walls; phloem cells have thinner, non‑lignified walls.
Xylem vessels lack cross‑walls, forming continuous tubes; phloem sieve tubes have cross‑walls called sieve plates.
Xylem transports water and mineral ions; phloem transports sugars (sucrose) and amino acids.

Examiner tips

Use the word ‘dead’ vs ‘living’ to show cell status.
Mention lignified vs non‑lignified walls.
State the presence/absence of cross‑walls and the transport function for each tissue.

Common mistakes

Confusing sieve plates with pit‑holes.
Forgetting that xylem cells are dead.
Mixing up the transport substances (e.g. saying phloem moves water).

Mark scheme (4 marks)

Xylem cells are dead / have no cell contents, whereas phloem cells are living
Xylem vessels have thick, lignified walls, whereas phloem walls are not lignified / are thinner
Xylem vessels have no cross walls / form a continuous tube, whereas phloem cells have cross walls / sieve plates between cells
Xylem transports water and mineral ions, whereas phloem transports sugars (sucrose) and amino acids

Key terms in this question

xylem · phloem