In summer, a mature leaf supplies sucrose to a fruit above it and a root below it. In spring, the root supplies sucrose to a new shoot.
Which conclusion follows from these observations?
Phloem transport only occurs downwards even when sources and sinks change.
Xylem transport only carries sucrose upwards even when storage needs change.
Xylem transport can carry sucrose upwards or downwards as storage needs change.
Phloem transport can occur upwards or downwards as sources and sinks change.
43 exam-style questions on Edexcel GCSE Biology 6.2 Transport in plants, covering 6.2.1 Root hair cell adaptations, 6.2.2 Structure of xylem and phloem, 6.2.3 Transpiration and stomata, 6.2.4 Translocation of sucrose, 6.2.5 Leaf structure for photosynthesis, 6.2.6 Environmental factors on water uptake, 6.2.7 Rate calculations for transpiration, and 6.2.8 Plant adaptations to extreme environments. Each one has a worked solution and a mark scheme showing where the marks go.