Edexcel IGCSE Biology 2.44B net gas exchange in leaves

A teacher investigates gas exchange in different conditions.
They use orange hydrogen-carbonate indicator solution, which changes colour depending upon the concentration of carbon dioxide in the tube.

This is their method.
Step 1 put $5 \mathrm{~cm}^{3}$ of hydrogen-carbonate indicator solution into each of five test tubes A, B, C, D and E

Step 2 place a wire mesh and two green leaves in test tube A
Step 3 set up tubes A to D so that they contain leaves or maggots as shown in the diagrams

Step 4 set up tube E without leaves or maggots
Step 5 place test tubes A, C and E in bright light for two hours
Step 6 place test tubes B and D in the dark for two hours
Step 7 observe the colour of the indicator in each test tube

\section*{Test tube A in light}

Test tube B in dark

Test tube C

in light

hydrogen-carbonate indicator solution dicator solution
orange

Test tube E in light