Xylem as the tissue that transports water in the stem and leaves of plants. The cohesion-tension theory of water transport in the xylem.

Phloem as the tissue that transports organic substances in plants. The mass flow hypothesis for the mechanism of translocation in plants. The use of tracers and ringing experiments to investigate transport in plants.

Students should be able to:

- recognise correlations and causal relationships
- interpret evidence from tracer and ringing experiments and to evaluate the evidence for and against the mass flow hypothesis.