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Respiration in Different Plants

Respiration in Different Plants: Tomatoes vs Spinach
Erin Aucoin

Introduction:
Respiration is a topic that everyone is familiar with to some extent. Although most people associate respiration with animals, plants also undergo respiration (Alexova 2014). This concept of the respiration of plants is what will be discussed in this report. The specific purpose of this report is to look at the differing respiration rates in different types of plants: corn and barley to determine which types of plants respire more when placed under the same conditions. This is something that everyone should care about as it affects life as we know it. Plant seeds need respiration in order to grow into photosynthesizing plants that provide heterotrophs with oxygen and energy, along with generating energy that they don’t get from sunlight alone (Rich 2003). If plants didn’t respire, they wouldn’t be able to grow and survive, and therefore, life as we know it would not exist. It should be known that respiration is a process that uses glucose and oxygen to produce carbon dioxide, water, and energy (Rich 2003). This energy that is produced is required for all organismal functions of life.
In the case that we are about to looks at, the germinating seeds use the energy they produce to grow, resulting in respiration rates being higher in germinating seeds (Pandey 2017). Through going through respiration, the plants use up oxygen, and the resulting carbon dioxide forms a solid precipitate with potassium hydroxide to allow for an accurate measure of the lost oxygen (Guo and Lua 2002). The plants seeds that we will be measuring are corn seeds and barley seeds. Our prediction is: if the type of seed dictates respiration rate, corn will respire more because they form a larger, heavier structure and would therefore require more energy to grow.

Methods:
For our procedure, we first set up our seven respirometers, placing cotton at the bottom, along with KOH. The KOH was used to react with the carbon dioxide, making sure that the carbon dioxide did not interfere with the reading of oxygen. Next, we placed 20 germinating corn seeds in three of them, 20 germinating barley seeds in another three, and beads in our final respirometer. The corn and barley seeds were our experimental groups. Beads were added to the respirometers containing the barley seeds in order to ensure that each respirometer contained the same volume of substance. This was due to the fact that barley seeds are smaller than corn seeds. All seven respirometers contained the same volume of product being tested. A plastic bin was set aside and filled with water. There had to be enough water to submerge the respirometers. All seven respirometers were placed in the same bin to ensure uniformity in their conditions. Temperature was recorded at the beginning with a thermometer. The temperature and oxygen levels were recorded every five minutes for a total of twenty minutes. Oxygen was measured by recording the bubble of air that remained in the respirometer pipette. This figure was recorded as the volume. All respirometers were measured as close together time-wise as possible. As the oxygen was used up, water traveled up the pipette. Our change in volume was calculated by subtracting the volume at that time from the starting volume, and the corrected change in volume was calculated by subtracting the change in the control from the change in the corn or barley. These calculations were done on a standard calculator, and were recorded into a google spreadsheet. In short, the materials used in this experiment include: sixty corn seeds, sixty barley seeds, plastic beads, seven respirometers, a plastic bin, water, a thermometer, a timer, cotton, and KOH. Our independent variable was the type of seed that was used, and our dependent variable was the respiration rate. The type of seed being tested dictated the respiration rate.

Results:

Table 1 Corn Data
Time
(min)
R1 V
(mL)
R1 ?V
(mL)
R1 Corr ?V
(mL)
R2 V
(mL)
R2 ?V
(mL)
R2 Corr ?V
(mL)
R3 V
(mL)
R3 ?V
(mL)
R3 Corr ?V
(mL)
0
0.23


0.23


0.23


5
0.36
-0.13
-0.13
0.32
-0.09
-0.09
0.35
0.12
0.12
10
0.23
0
-0.03
0.23
0
-0.03
0.22
0.01
-0.02
15
0.18
0.05
0.02
0.11
0.12
0.09
0.14
0.09
0.06
20
0.10
0.13
0.12
0.04
0.19
0.18
0.04
0.19
0.18

Table 2 Barley Data
Time
(min)
R1 V
(mL)
R1 ?V
(mL)
R1 Corr ?V
(mL)
R2 V
(mL)
R2 ?V
(mL)
R2 Corr ?V
(mL)
R3 V
(mL)
R3 ?V
(mL)
R3 Corr ?V
(mL)
0
0.23


0.23


0.23


5
0.32
-0.09
-0.09
0.25
-0.02
-0.02
0.29
-0.06
-0.06
10
0.25
0.02
-0.01
0.21
0.02
-0.01
0.24
0.01
-0.02
15
0.25
0.02
-0.01
0.19
0.04
0.01
0.26
0.03
0
20
0.16
0.07
0.06
0.19
0.04
0.03
0.25
0.02
0.01

Table 3 Control Beads
Time (min)
V (mL)
?V (mL)
0
0.23

5
0.23
0
10
0.20
0.03
15
0.20
0.03
20
0.24
-0.01

Table 4 Temperature (C) over time
Time (min)
Temp (C)
0
24
5
24
10
23
15
23
20
22

From these results, it can be concluded that the corn seeds respired more than the barley seeds. It should be noted that we failed to collect the starting volume of the respirometers containing the corn and barley seeds, so these spaces were filled with the recorded starting control volume. This is why all of the starting volumes are listed as 0.23 mL. Regardless of this error, it is still clearly shown that the corn respirated more than the barley, as the corrected change of volume in corn was 0.12 mL, 0.18 mL, and 0.18 mL respectively for each trial, while the corrected change of volume for the barley was 0.06 mL, 0.03 mL, and 0.01 mL respectively for each trial. This is an average respiration of 16 mL for corn and 3.3 mL for barley. As mentioned previously, Our change in volume was calculated by subtracting the volume at that time from the starting volume, and the corrected change in volume was calculated by subtracting the change in the control from the change in the corn or barley. During the experiment, the volume in the control changes slightly. However, the change in volume was very slight, so it did not cause much of a problem. Temperature also changed slightly during the experiment, decreasing from 24C to 22C. This was most likely the water giving off heat energy to get to equilibrium respect to room temperature.

Discussion:

Our experiment clearly supports our hypothesis, which was: if the type of seed dictates respiration rate, corn will respire more because they form a larger, heavier structure and would therefore require more energy to grow. This was shown in our experiment as the corn did respire significantly more than the barley seeds. On average the corn seeds respirated 16 mL of oxygen, while the barley respirated 3.3 mL. This is an obvious difference. As mentioned above, we failed to collect the starting volume of the respirometers containing the corn and barley seeds, so these spaces were filled with the recorded starting control volume. This was a case of human error that likely caused error propagation. This was likely the cause for the change in volume at the beginning of each experiment that shows the available oxygen levels increasing as opposed to decreasing. Despite this, the difference between the respiration rates of corn and barley was still clear. A reason for why this occurred could be that corn forms a larger, heavier structure that also contains a lot of starch, which is produced through cellular respiration. Barley does not heavy on starch and is also not generally a large, heavy structure. These factors imply that corn requires more energy to grow into its larger size, and undergoes cellular respiration more intensively so that it can produce starch.
This information is significant to people such as farmers who need to know the composition of soils that yield the best resulting crop. For example, a farmer would need to know what type of soil would provide high oxygen levels to corn crops, or lower oxygen levels for barley plants. This really pertains to anyone who is attempting to grow plants, as they would need to know the respiration patterns of their plant in order to provide it with the ideal environment.
During our experiment, we noticed that the volume in the control changed slightly, this should not have occured due to the fact that plastic beads do not respire. This could have been caused by human error, such as tilting the respirometer when getting a reading. However, the impact that this had was minimal due to how little the volume did change.