A technician investigates photosynthesis in four equal areas of moss growing on damp tiles.
Each tile is supplied with air containing a set concentration of carbon dioxide. The light intensity and temperature are also controlled.
The table shows the conditions and the mean rate of carbon dioxide uptake for each tile.
| Tile | Light intensity in lux | Temperature in °C | Carbon dioxide concentration in % | Mean carbon dioxide uptake in mg min⁻¹ |
|---|---|---|---|---|
| M | 3 500 | 18 | 0.10 | 0.24 |
| N | 14 000 | 18 | 0.10 | 0.56 |
| O | 14 000 | 26 | 0.10 | 0.84 |
| P | 14 000 | 26 | 0.04 | 0.48 |
Explain how the results show which factor limits the rate of photosynthesis in tiles M, N and P.
In your answer, compare M with N, N with O, and O with P.
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.