Question 3(a)(iii)
[Maximum number: 2]
Scientists measured the rate of photosynthesis in the leaves of a sunflower plant, Helianthus annuus.
The scientists used the apparatus shown in Fig. 3.1 to measure the rate of photosynthesis.

Fig. 3.1
The apparatus in Fig. 3.1 maintains a constant temperature and a constant humidity.
The apparatus was left for 15 minutes.
Explain how the scientists would use the readings for the concentration of carbon dioxide in chambers 1 and 3 to calculate the rate of photosynthesis.
