During daylight, a leaf from a well-watered plant is kept at 25 °C. Its stomata remain open.
A sensor measures the water-vapour concentration inside the leaf air spaces and in the air immediately outside the stomata. Measurements are taken before and after air starts moving across the leaf.
| Condition | Inside leaf air spaces (g/m³) | Air outside stomata (g/m³) |
|---|---|---|
| Before air movement | 22 | 10 |
| After air movement | 22 | 4 |
Use the data to explain how the change outside the stomata affects the diffusion of water vapour and the evaporation of water from mesophyll cell surfaces.
Explain how the movement of air is expected to affect the rate of water uptake by the roots.
80 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.