Practical: Gas Exchange in Plants

Question 1

What is the function of the hydrogen carbonate indicator?

Answer 1

We use this indicator to measure carbon dioxide levels.

Question 2

What colour is hydrogen carbonate indicator at atmospheric CO2 levels?

Answer 2

Red

Question 3

What colour is hydrogen carbonate indicator at low CO2 levels?

Answer 3

Magenta / purple

Question 4

What colour is hydrogen carbonate indicator at high CO2 levels?

Answer 4

Orange / yellow

Question 5

What colour would you expect the indicator to be when the pondweed is close to the light source?

Answer 5

• Purple.
• CO2 levels low as photosynthesis rate is high.
• Net uptake of CO2.

Question 6

What are the controlled variables for this practical?

Answer 6

1. Volume of hydrogen carbonate indicator
2. Species of pondweed
3. Time
4. Temperature