A gardener grows a tomato plant. During summer, the leaves produce large amounts of sucrose through photosynthesis. By autumn, the developing tomato fruits are the main regions receiving sucrose. Explain how sucrose moves from the leaves to the developing fruits in the tomato plant.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Sucrose is transported through the phloem.
The leaves act as a source, where sucrose is produced by photosynthesis.
The developing fruits act as a sink, where sucrose is stored or used.
Translocation requires energy, supplied by the pressure‑flow mechanism.
The leaves act as a source, where sucrose is produced by photosynthesis.
The developing fruits act as a sink, where sucrose is stored or used.
Translocation requires energy, supplied by the pressure‑flow mechanism.
Examiner tips
- Use the terms ‘source’ and ‘sink’ explicitly. Mention the phloem as the transport tissue. Show that translocation is an active process requiring energy. Keep each point short and to the point.
Common mistakes
- Confusing xylem with phloem. Forgetting to identify the fruits as a sink. Saying translocation is passive instead of energy‑dependent.
Mark scheme (4 marks)
- Sucrose is transported through the phloem
- The leaves act as a source (where sucrose is produced)
- The developing fruits act as a sink (where sucrose is stored or used)
- Translocation requires / uses energy
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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