Respiration LabEffects of Germination and Temperature on Respiration Rate

Apparatus

Each vial will contain Absorbant cotton with 20 drops of

KOH Non-absorbant cotton – 1/3 of a

cotton ball A combination of peas and glass

beads Vial #1 – 30 germinated peas Vial #2 – 30 dry peas and enough glass

beads to equal the total volume of vial #1

Vial #3 – no peas, glass beads only (enough to equal the total volume of vial #1)

Rationale

Vial #1 is the experimental vial for germination.

Vial #2 is the control group for germination

Vial #3 is a barometer. The glass beads will have no metabolism, so any change in air volume in this vial is the result of temperature and pressure variation. This data will be subtracted from the data for the other 2 vials

Procedure

Prepare vials as directed Place one of each (vial #1, #2 and

#3) in a room temperature water bath and one of each in an ice water bath. MAKE SURE THE OPEN END OF THE PIPETTE IS OUT OF THE WATER BATH!

Allow the vials to reach temperature equilibrium with the water bath for 20 minutes

Allow the vials to reach temperature equilibrium

The vial is submerged, but the end of the pipette is raised outside of the water

This allows the vials to reach the same temperature as the water bath, that way volume changes will not be from rapid cooling

Data Collection

After the vials have reached temperature equilibrium, place them flat on the bottom of the water bath

Water will enter the open end of the pipette

Read the volume at the air/water boundary in the pipette

Record the volume of each vial at 5 minute intervals for a total of 20 minutes

Submerge the vials

Once the vials have reached temperature equilibrium, drop them down into the water bath so that the entire vial (including the tip of the pipette) is submerged

Now as air is consumed, water will enter the pipette

Reading the volume

As air is consumed by the peas, water will be drawn into the pipette

Note the boundary between the air and the water in the pipette

.82 mL

Data Table

• Record the volume of air in the vials in your data table (volume columns)

• The “difference” and “corrected difference” columns will be filled in from calculations, not raw data

Calculations

The raw data will be in the “volume” columns of the data table

The “difference” will be calculated by subtracting the volume for that time period from the initial volume (time zero).

The “corrected difference” will be calculated by subtracting the barometer difference. This will account for any volume changes due to temperature or pressure change.

Sample Data

• Each calculation of “difference” is made by subtracting the volume measured in that time period from the initial (time zero) volume.

• Each calculation of “corrected difference” is made by subtracting the barometer difference at that same time period from the volume difference for that vial

• For example, in the germinated peas at 15 minutes:• The difference is .15 mL (.71 subtracted from the starting

volume of .86)• The corrected difference is .14 mL (.15 mL difference, less the

.01 difference from the barometer vial)• The corrected difference makes sure that we measure

respiration rate, not contraction due to cooling temperatures

Interpreting Data

The “corrected difference” column should be an accurate representation of the volume of oxygen gas consumed by the seeds as a result of cellular respiration

You will use the corrected difference results to construct a graph of Oxygen Consumption vs Time

Interpreting Data 2

Your graph will have 4 lines: Room temperature, germinated Room temperature, dry Ice Bath, germinated Ice Bath, dry

The slope of each line will be the rate of respiration (mL of oxygen/minute) for each vial