A student used young bean plants in growth cabinets to investigate how light intensity affects photosynthesis. The volume of oxygen released by each plant in 5 minutes was measured. The plants had the same leaf area, and carbon dioxide concentration was kept constant.
| Condition | Light intensity (lx) | Temperature (°C) | Oxygen produced in 5 minutes (cm³) |
|---|---|---|---|
| P | 12 000 | 20 | 20 |
| Q | 3 000 | 20 | 10 |
| R | 3 000 | 25 | 15 |
Explain what the results show about the effect of light intensity on photosynthesis, and why temperature must be controlled when investigating this effect.
Use data from the table in your answer.
87 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.