IGCSE Biology glossary
Xylem
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Definition
A plant transport tissue that carries water and dissolved mineral ions from the roots to the leaves and stems. Xylem vessels are made of dead, hollow cells joined end to end with no end walls, and their walls are strengthened with lignin.
What to include in an exam answer
Xylem transports water ONE WAY (upwards only). Key features for exams: dead cells, no end walls (continuous tubes), lignin for support. Transport in xylem is driven by transpiration pull, not active transport.
Example in context
Describe how xylem is adapted for its function (3 marks): Xylem vessels are hollow with no end walls, forming continuous tubes for easy water flow. Walls are strengthened with lignin for support. The cells are dead, so there is no cytoplasm to obstruct water movement.
Related syllabus topic
Transport in plants