Phloem and xylem are the two main transport vessels found in plants. Describe how the structure of xylem vessels is adapted to transport water efficiently through a plant.

Eduqas A-Level Biology — 2.4 Adaptations for nutrition · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

Xylem vessels are made from hollowed‑out, dead cells, so they contain no cytoplasm and can be very long.
The end walls of adjacent cells are removed, forming a continuous tube.
The cell walls are impermeable to water, preventing leakage.
They are strengthened with lignin, giving rigidity and resistance to collapse.
The long, narrow lumen creates a continuous column of water that can move efficiently from roots to leaves.

Examiner tips

  • Use the exact terms: "hollowed‑out, dead cells", "end walls removed", "impermeable", "lignin", "continuous column".
  • Show the sequence of adaptations and link each to efficient transport.

Common mistakes

  • Confusing xylem with phloem or describing living cells.
  • Omitting the role of lignin or the continuous tube.

Mark scheme (5 marks)

  1. Xylem vessels are made from hollowed-out / dead cells
  2. The end walls of the cells are removed / broken down to form a continuous tube
  3. The walls of xylem vessels are impermeable to water / waterproof
  4. Xylem vessels are strengthened with lignin
  5. The long, narrow tube / small lumen formed provides a continuous column of water from roots to leaves

Key terms in this question

xylem

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