A pondweed shoot produces 12 bubbles per minute at 40 cm from a lamp. At 20 cm it produces 30 bubbles per minute. Bubble volume is constant.
If light intensity were the only limiting factor, the expected rate at 20 cm would be 48 bubbles per minute.
Which result would provide the strongest evidence that carbon dioxide limits the observed rate at 20 cm?
Increasing pondweed length at 40 cm raises the rate towards 48.
Increasing water temperature at 20 cm leaves the rate near 30.
Increasing carbon dioxide at 40 cm leaves the rate near 12.
Increasing carbon dioxide at 20 cm raises the rate towards 48.
44 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.