Scientists supplied one leaf on a plant with carbon dioxide containing radioactive carbon.
After 2 hours, they found radioactive sucrose in the phloem above the leaf, in the shoot tip, and in the phloem below the leaf, in the roots. No radioactive sucrose was found in the xylem.
Name the process that transports sucrose in the phloem.
Use the results to explain one difference between transport in the phloem and transport in the xylem.
Explain how the structure of phloem is adapted to transport sucrose.
The scientists then treated the stem with a poison that stops respiration. Translocation stopped, but water still moved up the xylem.
Suggest why.
114 exam-style questions on OCR GCSE Biology 2.2 The challenges of size, covering 2.2.1 Exchange surfaces and surface area : volume ratio, 2.2.2 Substances transported in organisms, 2.2.3 The human circulatory system, 2.2.4 The heart and blood vessels, 2.2.5 Red blood cells and plasma, 2.2.6 Uptake of water and mineral ions by plants, 2.2.7 Transpiration and translocation, 2.2.8 Xylem and phloem, 2.2.9 Environmental factors and water uptake, and 2.2.10 Using a potometer. Each one has a worked solution and a mark scheme showing where the marks go.