Measuring Oxygen Use by Germinating Seeds

Germinating seeds use oxygen and release carbon dioxide during respiration. Using a respirometer with limewater and detergent, oxygen consumption can be measured by observing the movement of a liquid drop inside a sealed tube.

1. Germinate seeds on moist paper towels one or two days before the lab.
2. Insert a bent glass or plastic tube into a one-hole stopper so that the short end goes inside the test tube.
3. Mark a line 0.5 cm from the bottom of a large test tube and fill to this mark with limewater.
4. Place a small wad of moist cotton above the limewater and add about 1 g of germinating seeds on top of the cotton.
5. Attach the stopper with tubing securely to make an airtight seal. Support the test tube upright with a stand or stacks of books.
6. Tape a metric ruler to the tube, then add a small drop of liquid detergent into the tubing with a pipette. The drop should be visible near the open end.
7. Wait about 5 minutes for the limewater to absorb any carbon dioxide already in the chamber.
8. Record the position of the detergent drop as the initial reading.
9. Take new readings every minute for 15 minutes, measuring movement of the drop along the ruler.
10. Compare the distance moved to estimate oxygen consumption by the seeds.

Respiration of Germinating Seeds - pascoscientific:

Experiment to show that Co2 is released during germination of seeds - Science Projects:

📄 Seed Respiration - Agri-science Resources for High School Sciences: https://www.biologyjunction.com/images/misc/respiration%20of%20germinating%20seeds.pdf

• Use different seed types (beans, peas, corn) and compare respiration rates.
• Test at different temperatures (room temperature, cooler, or warmer conditions).
• Vary the amount of moisture in the cotton to see its effect.
• Compare healthy versus stressed seeds (e.g., partially dried or exposed to light).

• If glass tubing is used, handle with care to avoid breakage; pre-bent glass is safer.
• Use gloves when handling limewater or calcium hydroxide paste, as it can irritate skin.
• Keep detergent and limewater away from eyes and mouth; wash hands after the experiment.
• Ensure the respirometer is stable and cannot tip over.

• Why is limewater included in the respirometer? (It absorbs carbon dioxide so only oxygen consumption is measured.)
• What does the movement of the detergent drop indicate? (The seeds are consuming oxygen, creating a partial vacuum that pulls the drop inward.)
• How might seed size affect respiration rate? (Larger seeds may respire more overall, but smaller seeds may have higher respiration per gram.)
• What effect would temperature have on respiration rate? (Higher temperatures generally speed up respiration until enzymes are damaged.)
• Why are seeds actively respiring during germination? (They use stored food for energy to support growth before photosynthesis begins.)