Ecologists raise native salt-marsh grass plants before transplanting them into a damaged coastal habitat. They investigate how nursery conditions affect photosynthesis.
A sensor measures the volume of carbon dioxide taken in each minute by equal areas of leaf from the plants.
| condition | light intensity in W m⁻² | carbon dioxide concentration in % | temperature in °C | carbon dioxide uptake in cm³ min⁻¹ |
|---|---|---|---|---|
| A | 40 | 0.04 | 24 | 0.8 |
| B | 40 | 0.10 | 24 | 0.8 |
| C | 160 | 0.04 | 24 | 2.0 |
| D | 160 | 0.10 | 24 | 3.2 |
| E | 240 | 0.10 | 24 | 3.2 |
| F | 240 | 0.10 | 42 | 0.7 |
Explain why increasing the light intensity from condition D to condition E is unlikely to increase the biomass of plants available for transplantation.
The ecologists could increase the carbon dioxide concentration from 0.04% to 0.10% while raising the plants.
Explain the effect this would have on the biomass produced at a light intensity of 40 W m⁻² and at a light intensity of 160 W m⁻². Use the results in the table.
Explain the difference in carbon dioxide uptake between conditions E and F.
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.