A grower tests the position of humid-air outlets in a glasshouse. Similar pepper plants are kept under the same conditions. The outlets produce a layer of humid air beside the nearest surface of each leaf. Air beside the other surface remains at the usual glasshouse humidity.
The table shows the mean water loss from each plant over six hours.
| Position of humid-air outlets | Mean water loss in g\text{g}g |
|---|---|
| above the leaves | 46 |
| below the leaves | 28 |
Explain why the plants supplied with humid air below the leaves lost less water than the plants supplied with humid air above the leaves.
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.