Two varieties of grass, P and Q, are grown in the same nutrient solution. The concentration of nitrate ions in the solution around the roots is 0.30 mmol dm⁻³.
Scientists collect data from root hair cells of each variety.
| Grass variety | Nitrate ion concentration inside root hair cells (mmol dm⁻³) | Mean number of mitochondria in a standard area of cytoplasm | Rate of nitrate ion uptake (μmol g⁻¹ h⁻¹) |
|---|---|---|---|
| P | 2.4 | 24 | 12.0 |
| Q | 1.8 | 8 | 4.0 |
Use the data to explain how nitrate ions are taken up by the root hair cells and why the rate of uptake differs between varieties P and Q.
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.