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Ringing Experiments

A ring of cells is removed from the outer layer of a tree. This outer layer contains the protective bark and also contains phloem.When the phloem is removed, the region above the ring swells as sugars accumulate above the ring and there is death of tissue below the ring.This shows that phloem rather than xylem is responsible for translocating sugars in plants.

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Specification: AQA Biology (7401), AS-level, 3.3.4.2 Mass transport in plants. Topic: Mass Transport in Plants.

Key terms in this lesson

xylem
Plant vascular tissue, made of dead, lignified tubular cells, that transports water and mineral ions from the roots to the leaves.
phloem
Plant vascular tissue, made of sieve tube elements and companion cells, that transports organic solutes such as sucrose around the plant.

More in Mass Transport in Plants

All 15 lessons in Mass Transport in Plants · All AQA AS-level Biology topics