safety goggles KOH is caustic! You must wear goggles when using it.

LabBench Activity

Assembling the Respirometer

In this experiment you will compare the rate of respiration in peas that are germinating to the rate in peas that are dormant (dry peas). You will make the comparison at two different temperatures: 10°C and 25°C. In addition, you will compare these rates to a nonmetabolizing control.

Why is it important to have a control?

The following illustration shows you how to assemble a respirometer.

It is important that the three vials contain an equal volume of contents. You do this by adding glass beads to the vial with the dormant peas, since the dry peas take up less space than an equal quantity of germinating peas.

Note: Because you are measuring the rate of respiration at two different temperatures, prepare two sets of three vials.

pipette Lab Hints

  1. You will need to use a layer of nonabsorbent cotton between the KOH and the peas.
  2. The stopper must be firmly inserted for an air-tight seal. Check that no peas or beads block the opening to the pipette.
  3. Let the respirometers equilibrate for several minutes in their respective waterbaths. This will minimize volume changes due to change in air temperature.