The Effect of Seed Type on Rate of Respiration
by Nina Xiong
Introduction
Cellular respiration is the set of reactions and processes by which cells convert the chemical
energy in food into ATP, consuming oxygen and releasing carbon dioxide as a waste product.
Once a seed begins germinating, it performs cellular respiration at a dramatically increased rate
in order to provide the energy and materials it needs to grow. The rate of cellular respiration in
germinating seeds can be found by measuring either the amount of oxygen consumed or the
amount of carbon dioxide produced by the seeds. We wanted to conduct an experiment using
several different kinds of seeds and compare the rates at which they perform cellular respiration.
We are investigating the following question: What is the effect of using different types of seeds
on the rate of respiration?
Our hypothesis is that if different types of seeds are used, then they will have different rates of
respiration because the time it takes for a seed to germinate will affect its rate of respiration. The
plants that germinate the fastest will have the fastest respiration rates, and the plants that
germinate the slowest will have the slowest respiration rates.
This question interested us because we were curious as to which types of seeds had the fastest
rates of cellular respiration and which ones had the slowest, and we were wondering if it had
anything to do with their germination times.
Methods
The equipment we used for our experiment included one LabQuest, three CO gas sensors, and
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three 250-mL respiration chambers. The supplies we used were 25 peas, 25 lima beans, 25 corn
seeds, 25 blackeye peas, and 25 red beans.
Our procedure went as follows: First, we turned on the three CO gas sensors and the LabQuest.
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We set the CO gas sensors to the LOW setting, and on the LabQuest, we set the data collection
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length to 300 seconds (5 minutes) with a rate of 2 samples per second. We blotted each set of 25
germinated seeds dry between two pieces of paper towel. We then connected the three CO gas
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sensors to the same LabQuest so we could test three seeds simultaneously.
First, we placed the peas into the first respiration chamber, the red beans into the second, and the
lima beans into the third. Then we started data collection, recording the amount of CO generated
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every 50 seconds in Data Table 1. After data collection finished, we removed the CO gas
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sensors and fanned air across them for one minute. We then performed a linear regression of the
data and recorded the slope of the lines as the rates of respiration in Data Table 2. We then
repeated this twice to obtain three trials for peas, red beans, and lima beans. After we finished
testing these seeds, we washed out the respiration chambers. Then we placed the corn seeds into
the first respiration chamber and blackeye peas into the second respiration chamber, and repeated
the steps above to obtain three trials. We recorded the data in Data Tables 1 and 2. When we
were finished collecting data, we cleaned the respiration chambers, returned the seeds, and
cleaned up the lab station.
There were no safety, ethical, or environmental considerations we had to address in our
experiment. However, we had to use care when handling the CO gas sensors so we would not
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damage or break them, as they are presumably quite expensive.
Our independent variable is the type of seed, while our dependent variable is the rate of
respiration (in ppm CO per second). Our controlled variables include the temperature (room
2
temperature), number of seeds (25), and germination time (one day).
Results
Raw Data
Data Table 1. Time vs. Amount of CO2 Generated for Trial 1
Amount of CO2 Generated (ppm)
Time (sec)
Peas
(±10%)
Lima beans
(±10%)
Corn seeds
(±100 ppm)
Blackeye peas
(±10%)
Red beans
(±10%)
0
930
1049
702
1306
1373
50
1008
1494
723
1391
1392
100
1100
1723
738
1494
1591
150
1212
1957
760
1576
1707
200
1324
2287
787
1658
1795
250
1421
2734
835
1758
1855
300
1494
3064
878
1831
1953
Note: We only recorded the amount of CO2 generated after certain amounts of time during our
first trial. For the other trials, we performed linear regressions, recorded the rates of respiration,
and calculated the averages, which we have recorded in Table 2 as processed data.
Processed Data
Graph 1. Time vs. Amount of CO2 Generated
for Trial 1
3500
y = 6.4921x + 1070.2
Amount of CO2 Generated (ppm)
3000
2500
y = 2.05x + 1359.1
2000
y = 1.7664x + 1308.5
1500
y = 1.9586x + 918.93
1000
y = 0.5721x + 688.89
Lima beans
500
Peas
Corn seeds
0
0
50
100
150
Time (sec)
200
250
300
Blackeye peas
Red beans
From the data in Data Table 1, I plotted a graph of time vs. amount of CO2 generated for the first
trial of each seed. The best fit lines are also included; the slope of the line indicates the rate of
respiration. The larger the slope, the faster the seed preforms cellular respiration. Here it is
evident that lima beans have the highest rate of respiration while corn seeds have the lowest.
Peas, blackeye peas, and red beans have relatively similar rates of respiration. However, note that
this pertains to the first trial only.
Data Table 2. Seed Type vs. Rate of Cellular Respiration
Rate of Respiration (ppm CO2 per second)
Seed Type
Trial 1
Trial 2
Trial 3
Average
Peas
1.8388
2.9411
2.4152
2.3984
Lima beans
6.6038
10.132
7.4097
8.0485
Corn seeds
0.54829
0.84488
0.97692
0.79003
Blackeye peas
1.7969
2.0214
2.1673
1.9952
Red beans
1.9706
2.9833
1.9978
2.3172
After we finished collecting all the data, we performed a linear regression of the data on the
LabQuest and recorded the slopes of the lines as the rates of respiration. We did this for all
fifteen trials (three for each of the five seeds) and then calculated the average rate of respiration
for each seed.
Sample calculation (average rate of respiration for peas):
1.8388 + 2.9411 + 2.4152
= 2.3984 ppm CO2 per second
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Graph 2. Seed Type vs. Average Rate of
Respiration
10
9
8.0485
Average Rate of Respiration
(ppm CO2 per second)
8
7
6
5
4
3
2.3984
1.9952
2.3172
2
0.79003
1
0
Peas
Lima beans
Corn seeds
Blackeye peas
Red beans
Seed Type
From the average rates of respiration we calculated in Data Table 2, I created a bar graph
comparing the average rates of respiration of the different seed types. The error bars are also
shown. Based on the graph, it is clear once again that from our data, lima beans have the highest
rate of respiration while corn seeds have the lowest. Peas, blackeye peas, and red beans have
relatively similar rates of respiration.
The CO2 gas sensors were accurate to ±10% of the reading for peas, lima beans, blackeye peas,
and red beans. They were accurate to ±100 ppm for corn seeds. As shown in Graph 2, the
measurement uncertainty does not seem to have a large impact on the results, except for the lima
beans, for which the uncertainty is quite large. Nevertheless, it is still clear that out of the five
seeds, lima beans have the highest rate of respiration and corn seeds have the lowest.
In order to correlate germination time with rate of respiration, I did some research to find the
germination times of the seeds we used. Since germination time can vary depending on
environmental factors, I will simply take the average of the ranges shown.
Peas: 6-36 days (21 days)
Red beans: 10-14 days (12 days)
Lima beans: 6-18 days (12 days)
Blackeye peas: 8-10 days (9 days)
Corn: 4-12 days (8 days)
Using this data and the average rates of respiration from Data Table 2, I made a graph to attempt
to correlate germination time with rate of respiration.
Graph 3. Average Germination Time vs.
Average Rate of Respiration
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Average Rate of Respiration
(ppm CO2 per second)
8
7
6
5
4
3
2
1
0
0
5
10
15
20
25
Average Germination Time (days)
This graph does not show a clear correlation between germination time and rate of respiration.
Discussion
Conclusion
From our data, I concluded that different types of seeds do have different rates of respiration.
Our hypothesis was that this is due to the different germination times of the seeds. We predicted
a direct correlation between germination time and rate of respiration: the plants that have the
fastest germination times will have the fastest respiration rates, and the plants that have the
slowest germination times will have the slowest respiration rates.
However, as seen in Graph 3, I found no correlation between germination time and rate of
respiration.
While corn seeds take an average of 8 days to germinate and have an average rate of respiration
of 0.79003 ppm CO2 per second, blackeye peas have a slower germination time (9 days to
germinate) but have a faster average rate of germination (1.9952 ppm CO2 per second). Red
beans have an even slower germination time (12 days to germinate) but have a faster average rate
of respiration than both corn and blackeye peas (2.3172 ppm CO2 per second). This does not
suggest a direct correlation.
In fact, the above data actually seem to suggest an inverse correlation between germination time
and rate of respiration: seeds that have a slower germination time have a faster rate of
respiration. However, if we examine the data closely, this is not the case. Peas take an average of
21 days to germinate and have an average rate of respiration of 2.3984 ppm CO2 per second,
while lima beans have a faster germination time (an average of 12 days to germinate) and also
have a faster average rate of respiration (2.3984 ppm CO2 per second). This does not suggest an
inverse correlation. Thus, the data shows no correlation between germination time and rate of
respiration.
Therefore, I can conclude that if different types of seeds are used, they will have different rates
of respiration, but this is not due to the different germination times of the seeds.
Comparison to Accepted Scientific Context
It is accepted in the scientific community that different types of seeds have different rates of
respiration, but I was not able to find a single, all-inclusive explanation for this. Most likely it is
due to a variety of factors, such as different types of seeds having different enzymes or storing
different nutrients. The structure of the seed may also be a factor in this, as seeds occur in many
structurally different types.
Strengths and Weaknesses
A strength of our experiment is that it involved quantitative data rather than qualitative data, so it
was easy to compare data points. The data were relatively easy to obtain because a single trial
only took five minutes to complete. Also, because we were able to plug multiple CO2 sensors
into the LabQuest, we could run multiple trials simultaneously so that more trials, and thus more
data, could be obtained.
However, there are also multiple weaknesses in our experiment. We did not control the age of
the seeds and they may have varied. For example, the peas may have been older than the lima
beans, and this could have affected the rate of respiration because young seeds could potentially
have a different rate of respiration than mature seeds.
Also, the rate of respiration sometimes varied significantly for different trials of the same seed;
for example, the rate of respiration in trial 1 of the lima beans was 6.6038 ppm CO2 per second,
while in trial 2 the rate of respiration was 10.132 ppm CO2 per second. This could have resulted
from a source of error, and demonstrates a weakness in the experiment because there were not
enough trials to gather sufficient data to obtain an accurate average.
Another limitation of the experiment is that when trying to correlate germination time with rate
of respiration, I simply took the averages of the range of germination times I found in my
research (for example, red beans take 10-14 days to germinate, so I used 12 days as the
germination time). This may not be an accurate measure of a seed’s actual germination time,
because the length of time a seed takes to germinate can vary depending on environmental
factors such as moisture, air, temperature, and light. Thus, I may have used germination times
that are inaccurate.
Improvements and Extensions
To improve the experiment, we could use seeds that are the same age: for example, seeds that
have just reached maturity. This would ensure that the age of the seeds do not affect the rate of
respiration. The experiment could also include more trials to obtain more data; this way, we will
be able to calculate an average rate of respiration that is closer to the true value. We could do
five or more trials since a single trial is relatively short.
To find accurate germination times for the seeds we tested, we could do a preliminary test in
which we let the five types of seeds fully germinate and record their germination times. Then we
could conduct our experiment with the same environmental conditions that we used for the
preliminary test. For example, we could test a few peas from the same bag of peas used for the
experiment and let them fully germinate, then use that germination time to conduct our analysis.
This way, we would gain an idea of how long it takes our specific seeds to germinate.
The experiment could be extended by testing different types of seeds, including flower seeds or
herb seeds, to see if their germination times affect the rates at which they perform cellular
respiration.
Works Cited
"How to Grow Kidney Beans." Grow This! GrowThis.com, 24 Aug. 2013. Web. 4 Jan. 2016.
<http://www.growthis.com/how-to-grow-kidney-beans/>. Jerrett, Heather, and Delia Gillen. "Factors Affecting Germination." High Mowing Organic
Seeds. High Mowing Organic Seeds, n.d. Web. 4 Jan. 2016.
<http://www.highmowingseeds.com/sb-factors-affecting-germination-of-organicseeds.html>. "Lima Beans (bush)." Weekend Gardener. Chestnut Software, n.d. Web. 4 Jan. 2016.
<http://www.chestnut-sw.com/seeds/vegseed/bnlimab.htm>. "Peas." Weekend Gardener. Chestnut Software, n.d. Web. 4 Jan. 2016. <http://www.chestnutsw.com/seeds/vegseed/peas.htm>. Shorter, Benjamin. "How Long Does It Take for a Black-Eyed Pea to Germinate?" SFGate.
Hearst, n.d. Web. 4 Jan. 2016. <http://homeguides.sfgate.com/long-blackeyed-peagerminate-74124.html>. "Sweet Corn." Weekend Gardener. Chestnut Software, n.d. Web. 4 Jan. 2016.
<http://www.chestnut-sw.com/seeds/vegseed/corn.htm>.