Similar young plants are kept under controlled conditions. Samples are removed and dried at different times to determine the mean dry mass per plant.
| Time (hours) | Conditions before the sample is removed | Mean dry mass per plant (mg) |
|---|---|---|
| 0 | Start | 120 |
| 8 | 8 hours in light | 132 |
| 24 | 8 hours in light followed by 16 hours in darkness | 124 |
Assume that the rates of change in dry mass in the light and in darkness remain constant.
Another group of the young plants has a mean dry mass of 120 mg per plant. The plants are kept in the light for 12 hours and then in darkness for 12 hours.
Calculate the predicted mean dry mass per plant after the 24 hours.
Show your working.
Explain why the rate at which photosynthesis adds dry mass during the light period is greater than the measured rate of increase in dry mass.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.