Cellular Respiration in Non-Germinating and Germinating
Seeds (from Mickie Richardson)
Figure 1
The germination of seeds requires a large amount of energy. This energy is supplied by the
decomposition of storage materials (carbohydrates, lipids and other organic molecules) available in the
seed in a process called cellular respiration. During respiration, oxygen is consumed while carbon
dioxide and water are released. O2 + sugar (carbohydrate) → CO2 + H2O + energy (ATP).
Dry seeds respire at a very low rate. With the addition of water to dry seeds, the seeds swell, begin to
germinate, and the respiration rate is hugely accelerated.
After the seeds are swollen, roots and shoots start to develop. Cellular respiration increases again as
the young sprout continues to grow and the roots and shoots elongate.
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Finally, the sprout starts to develop leaves. At this stage most of its storage materials are exhausted and
the rate of oxygen consumption decreases.
The rate of the germination process and the rate of respiration accordingly, depend on abiotic factors
including temperature, availability of water, and levels of oxygen.
In this experiment we observe that dry, non-germinating seeds do release carbon dioxide as they
respire. Using a carbon dioxide sensor, the rate of cellular respiration in dry, non-germinating seeds will
be compared and contrasted to that of germinating seeds. The change in the amount of carbon dioxide
present in the collecting chamber will determine the rate of cellular respiration in the seeds.
Equipment

Nova5000 data logger

AC power adapter cable for Nova5000

Source of electricity

Carbon dioxide sensor

Sensor cable

Collecting chamber

25 dry pea or bean seeds

25 germinating pea or bean seeds

Two absorbent paper towels

Water source
Safety Precautions

Follow standard laboratory safety precautions.

Do NOT twist or pull on the shaft of the carbon dioxide sensor or the rectangular sensor itself as you
may damage the sensor; handle only the stopper which is located at the end of the sensor.
Equipment Setup Procedure
1. Use the AC power adapter to connect the Nova5000 to an electrical source.
2. Turn on the Nova5000 and launch MultiLab.
3. Using a sensor cable, connect the carbon dioxide sensor to I/O-1 on the Nova5000.
4. The green light on the sensor will blink for approximately two minutes while the sensor
automatically calibrates. While the sensor is calibrating, gently wave the collecting chamber back
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and forth for approximately 2 minutes, to replace the air the chamber. The chamber should contain
the same concentration of carbon dioxide as does the air - 400-440 ppm.
5. Click Set-up
on the main toolbar and program the Nova5000 according to the setup specified
below. Click OK after completing the set-up.
Data Logger Setup
Sensors
Input 1:
Carbon Dioxide
Set to Zero: Click properties next to the CO2 sensor input. Click the
set zero tab. Set the current reading to zero. Click OK
Sensor
Rate:
Every 10 seconds
Samples:
20 samples (3:20 MM:SS)
Experimental Procedure
1. Obtain 25 dry seeds and place them into the collecting chamber.
2. With your fingers on the rubber stopper at the end of the sensor, place the sensor into the
chamber. Push firmly on the stopper to ensure no leakage from the chamber. Do NOT hold
or press on the shaft or on the rectangular part of sensor. Lay the collecting chamber on its
side, as illustrated in Figure 1.
3. Click Run
on the upper toolbar to begin recording data. Follow the changes in carbon
dioxide recorded on the screen.
4. When the logger stops, save
your data as Peas and your last name (Peas Smith, for
example). Do NOT close MultiLab.
5. Handle only the stopper as you remove the sensor from the collecting chamber. Do NOT
disconnect the CO2 sensor from the Nova5000.
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6. Remove the dry seeds from the collecting chamber.
7. Rinse the inside of the chamber with water, to remove the carbon dioxide. Dry the inside of
the chamber with an absorbent paper to towel.
8. Repeat Steps 1 -3 using 25 germinating seeds.
9. Click Save
in the upper toolbar to save the new trial (Exp. 2) with germinating seeds in
the same data map/file which you saved previously (Peas, Smith).
10. Empty the collecting chamber.
11. Rinse the chamber and use the 2nd absorbent paper towel to dry out the collecting chamber.
12. Dispose of the dry and germinating seeds in the trash can.
13. Clean up the lab area.
14. Complete the data analysis and answer the questions below.
Data Analysis
1. Apply a linear fit to each curve:
a. Hide each line one at a time, so that you can accurately place the cursor on the line you
are analyzing.
b. Place the first cursor at the bottom of the curve and place the second cursor at the top
of the curve.
c. Click Linear fit
on the main toolbar. The slope intersect equation (y = mx + b, where
m = slope) will be displayed in the information bar at the bottom of the graph window.
The slope (m) of the fit line is the measured rate of cellular respiration in the nongerminating and germinating seeds due to the release of carbon dioxide.
d.
Record the slope of each line in questions 2 and 3 below.
2. Answer the remaining questions.
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Questions
1. Describe the lines/curves observed in the non-germinating and germinating seeds. Are the
lines stable throughout the experiment? How are both lines similar throughout the
experiment? How are they different?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
2. What is the slope of the non-germinating seeds?
___________________________________________________________________________
3. What is the slope of the germinating seeds?
___________________________________________________________________________
4. In which trial was cellular respiration taking place at a faster rate?
___________________________________________________________________________
5. Explain why the rate of cellular respiration is different in non-germinating and germinating
seeds.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
6. How will an increase in temperature affect the rate of cellular respiration in each trial?
___________________________________________________________________________
___________________________________________________________________________
7. What will be the effect of a decrease in temperature on the rate of cellular respiration in
each trial?
___________________________________________________________________________
___________________________________________________________________________
8. What other factors can affect cellular respiration?
___________________________________________________________________________
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Teacher Notes

The carbon dioxide sensor is energy draining. Therefore, it is recommended to operate this
sensor while the AC power adapter is plugged in.

The Nova5000 can operate two CO2 sensors simultaneously.

Caution students to handle only the rubber stopper and not to twist or pull on the shaft or
on the sensor itself.

Since carbon dioxide is a heavy gas, lay the collecting chamber on its side during this activity.

Do NOT place the shaft into liquids, as the carbon dioxide sensor is designed to measure
gaseous carbon dioxide only.

Do NOT place the collecting chamber into a microwave to heat contents inside the chamber.
Answers to Questions
1. Describe the lines/curves observed in the non-germinating and germinating seeds. Are the
lines stable throughout the experiment? How are both lines similar throughout the
experiment? How are they different?
Answers will vary but should explain the general shape of the two lines in the two trials. Both
lines should show a positive slope, with the slope of the germinating seeds being steeper
than that of the dry seeds.
2. What is the slope of the non-germinating seeds?
Answers will vary but should be consistent with the y = mx + b equation where m is the slope.
3. What is the slope of the germinating seeds?
Answers will vary but should be consistent with the y = mx + b equation where m is the slope.
4. In which trial was cellular respiration taking place at a faster rate?
Germinating seeds
5. Explain why the rate of cellular respiration is different in non-germinating and germinating
seeds.
Germinating seeds are in the process of growing and therefore undergo cellular respiration
faster than non-germinating seeds.
Non-germinating seeds are dormant and do not
consume as much energy as the growing seeds.
6. How will an increase in temperature affect the rate of cellular respiration in each trial?
An increase in temperature will cause an increase in the rate of cellular respiration. (If the
temperature gets too hot, the rate of cellular respiration will decrease).
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7. What will be the effect of a decrease in temperature on the rate of cellular respiration in
each trial?
Cellular respiration decreases as temperature decreases.
8. What other factors can affect cellular respiration?
Availability of oxygen and water.
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