Plant Gas Exchange
Biology: Edexcel IGCSE, topic 3.2.3
Detecting Plant Gas Exchange
Plants carry out both photosynthesis and respiration.
Hydrogencarbonate indicator
- Hydrogencarbonate indicator changes colour depending on how much carbon dioxide is in a solution.
- It can be used to show how much photosynthesis and respiration an aquatic plant (like pondweed) is doing, by adding it to the water the plant is in.
High CO2
- Hydrogencarbonate indicator turns yellow in high levels of carbon dioxide.
- Since CO2 is produced in respiration and used up in photosynthesis, this suggests the plant is respiring more than it is photosynthesising.
- This result can be seen if the plant is kept in the dark.
Low CO2
- Hydrogencarbonate indicator turns purple in low levels of carbon dioxide.
- Since CO2 is produced in respiration and used up in photosynthesis, this suggests the plant is photosynthesising more than it is respiring.
- This result can be seen if the plant is kept in bright light.
Normal atmospheric CO2
- Hydrogencarbonate indicator turns red in normal atmospheric levels of carbon dioxide.
- Since CO2 is produced in respiration and used up in photosynthesis, this suggests the plant is respiring at the same rate that it is photosynthesising.
Test yourself on Plant Gas Exchange
What colour would hydrogencarbonate indicator turn when added to pondweed in bright light?