A student coats both surfaces of a leaf with a transparent substance that blocks the stomata. Light still reaches the chloroplasts and the leaf has enough water. Photosynthesis soon slows.
A student claims that the coating prevented light absorption. Which explanation best uses the evidence to reject this claim and account for the reduced rate?
Light still reaches chloroplasts, but less carbon dioxide diffuses into air spaces.
Water still reaches chloroplasts, but less glucose diffuses into internal air spaces.
Water still reaches chloroplasts, but less light diffuses into internal air spaces.
Light still reaches chloroplasts, but less oxygen diffuses into internal air spaces.
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.