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Abigail Santos and Yaksha Thanarajah
G. LeBreton
SBI4UO - B
January 7, 2022
Determining the Idealistic Environment for the Most Efficient Oxygen Production in
Photosynthesis
Introduction
Photosynthesis is a metabolic process in which autotrophs convert light energy, carbon dioxide,
and water into glucose and oxygen. Autotrophs are organisms that can make their own food, and
photoautotrophs are organisms that convert light energy into glucose molecules (Sciencing
2018). Examples of photoautotrophs include higher plants (maize plants, trees, grass), algae,
euglena, and cyanobacteria (Microscope Master 2021). Photosynthesis occurs in the chloroplasts
and goes through two major processes: Light dependent reactions and light independent reactions
(a.k.a. The calvin cycle). Firstly, the light dependent reactions happen in the thylakoid membrane
and it is the beginning of the photosynthesis process in which light energy is captured and water
molecules are split into electrons, hydrogen ions (H+) and oxygen (O2,) (Refer to “Figure 1:
Non-Cyclic Electron Flow”). In the light dependent reactions, H2O and light energy serves as the
reactants and oxygen gas (O2) serves as the product. Furthermore, the light dependent reactions
produce ATP and NADH, which are crucial enzymes that are used in the Calvin cycle. As a
result, photoautotrophs proceed with the Calvin cycle. The Calvin cycle is a light independent
reaction that happens in the stroma in which CO2 is taken in through the stomata contributes to
the production of glucose with the help of essential enzymes (Amoeba Sisters 2021) (Refer to
“Figure 2: The Calvin Cycle”). The calvin cycle undergoes three steps: Fixation, reduction, and
regeneration. In the calvin cycle, Carbon dioxide (CO2) serves as the reactant and glucose serves
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as the product. Temperature affects the rate of photosynthesis, specifically, higher temperature
can accelerate chemical reactions. However, temperatures that are too high can denature the
enzymes present in photosynthesis, disrupting enzymatic activity that contribute to electron flow
and glucose production (Byus NEET Questions). The chlorophyll in chloroplasts absorb the light
energy of certain wavelengths and uses the energy to excite electrons, stimulating the flow of
electrons (Vernier 2018). The chlorophyll captures red and blue light, and reflects green light,
which explains why most plants have a green pigment (Amoeba Sisters 2021). Light
intensity/luminous intensity is the quantity of light that is visible (Britannica 2017). The
saturation of light with relation to the temperature can affect the rate of which photosynthesis
occurs (Britannica 2021).
The purpose of this experiment is to analyze the impact of various temperatures, light intensities,
wavelengths, and carbon dioxide concentration on photosynthesis and determine when
photosynthesis is the most efficient.
Figure #1: Non-Cyclic Electron Flow
Image: joeduero.wixsite Non-Cyclic Electron Flow | photosynthesis
https://joeduero.wixsite.com/photosynthesis/non-cyclic-electron-flow
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Figure #2: The Calvin Cycle
Image: National Geographic Society “Calvin Cycle”
https://www.nationalgeographic.org/media/calvincycle/
Materials and Methods
The photosynthesis lab was a stimulation presented on the website Gizmos. In order to discover
the factors that help with the production of photosynthesis, the simulation consisted of a
photosynthesis tank, thermometer, a dissolved oxygen sensor, carbon dioxide sensor and a
colour-changing lamp. The photosynthesis tank contains a double container where the central
container consists of the aquatic plant submerged in water and the outer container is filled with
more water to act as a water bath to alter the temperature of the environment. The carbon dioxide
sensor helps detect the production of carbon dioxide produced when certain variables of the
environment are altered. The colour changing lamp focuses on controlling the variable of light
intensity and the wavelength of light which changed the colour of the lamp. To find the factors
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that result in the most photosynthesis production, the various independent variables had to be
considered in each experiment. To find the most production, the results were discovered in a
specific order. Since plants demonstrated a production of photosynthesis through the levels of
oxygen, the only dependent variable in this experiment was the flow of oxygen. There were
several independent variables which were temperature, light intensity, wavelength and carbon
dioxide concentration. To find the maximum production of photosynthesis, there had to be fixed
variables to help the manipulation of the independent variables. With the knowledge of
photosynthesis and cellular respiration cycle, it was hypothesized that the most production would
occur with the 100% light intensity and the most carbon dioxide levels. Study proves a higher
concentration of carbon dioxide in our atmosphere would aid photosynthesis, which in turn
contributes to increased plant growth, which is why a thousand parts per million for carbon
levels was a fixed variable (Sneed 2018). Plants need light for growth and survival, and as light
intensity increases, the rate of light-dependent reactions, and therefore photosynthesis increases
proportionally; hence the variable of one hundred percent of light intensity (Advancing the
Chemical Sciences). Once the dependent variables are discovered, the maximum rate is used for
the next graph as a fixed variable. The process repeated until all tables were completed and all
maximum rates were established. The maximum rate of each independent variable were the
variables that demonstrated the most photosynthetic production.
Observations
The production of oxygen was observed to measure the rate of photosynthesis. In this
experiment, temperature, light intensity, wavelength, and carbon dioxide levels were altered to
monitor how it affects the production of oxygen.
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Table #1: The Production of Oxygen Flow in Relation to Various Temperatures
Light intensity: 100%
Carbon dioxide levels: 1000 ppm
Temperature (ºC)
Oxygen (mL/h)
0
0
10
3.1
20
41.7
24
50.4
30
31.3
40
1.3
50
0
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Table #2: The Production of Oxygen Flow in Relation to Various Light Intensities
Temperature: 24 ºC
Carbon dioxide levels; 1000 ppm
Light Intensity (%)
Oxygen (mL/h)
0
0
10
8.2
20
17.1
30
26.1
40
34.7
50
42.2
60
48.1
70
51.8
80
51.8
81
51.9
90
51.8
100
50.4
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Table #3: The Production of Oxygen Flow in Relation to Various Wavelengths
Temperature: 24 ºC
Carbon Dioxide Levels: 1000 ppm
Light intensity: 81%
Wavelength (nm)
Oxygen (mL/h)
400
44.1
450
98.8
500
46.6
550
36.0
600
46.6
650
79.9
700
46.6
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Table #4: The Production of Oxygen Flow in Relation to Various Carbon Dioxide Levels
Temperature: 24 ºC
Light intensity : 81%
Wavelength: 450 nm
CO2 (ppm)
Oxygen (mL/h)
0
0
100
21.3
200
44.5
300
66.7
400
84.8
500
95.4
570
98.8
600
98.8
700
98.8
800
98.8
900
98.8
100
98.8
Results
As the temperature increased from 0ºC to 24ºC, the rate of oxygen production increased as well.
Specifically marking 24ºC as the temperature where oxygen production was at its maximum. The
greater the temperature, the greater the oxygen production rate. Contrarily, as the temperature
increased above 24ºC, the rate of oxygen production rapidly decreased, reaching a production
rate of 0mL/h at 50ºC (Refer to Figure#3).
Secondly, as the light intensity increased, the rate of oxygen production increased as well. The
stronger the light saturation the higher the oxygen production rate. At 70% light intensity, the
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oxygen production rate flattens out to a maximum with an average production rate of 51.54
mL/h. Particularly, when light intensity is at 81%, the oxygen flow is at its maximum: 51.9 mL/h
(Refer to Figure#4).
Furthermore, as the rate of oxygen flow fluctuated with various wavelengths. The oxygen
production reached its maximum with a rate of 98.8mL/h at 450 nm. The oxygen production
reaches another peak at 650 nm with a rate of 79.9 mL/h. Contrarily, when the wavelength is at
550nm, the oxygen flow was at its minimum at 36.0mL/h (Refer to Figure#5).
Finally, as the carbon dioxide levels increase, the oxygen flow increases. When the CO2 levels
reach 570 ppm and further increases, the oxygen production flattens out at a maximum of
98.8mL/h. The higher the CO2 levels, the higher the oxygen production rate (Refer to Figure#6).
Figure #3: The Relationship Between Temperature and Oxygen Flow in Photosynthesis
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Figure #4: The Relationship Between Light Intensity and Oxygen Flow in Photosynthesis
Figure #5: The Relationship Between Wavelength and Oxygen Flow in Photosynthesis
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Figure #6: The Relationship Between Carbon Dioxide Levels and Oxygen Flow in
Photosynthesis
Discussion
To discover most productivity of photosynthesis, several variables were altered to discover the
oxygen flow while other variables were placed at fixed levels. The temperature that produced the
most oxygen levels was 24ºC since lower temperatures would slow photosynthesis and high
temperatures would denature the subject. When light intensity is altered to a lower percentage, it
slows down the rate of photosynthesis leading to a reduction in growth rate. Once the light
intensity increases after 81% the productivity of photosynthesis reduces showing a decline in
growth. Therefore the percentage of light intensity after reaching 81% demonstrates a very high
level which only can occur in an experiment not in nature. Cabomba Carolinensis' waterweed
simulation investigates how light intensity affects photosynthesis. The simulation involved the
examination of bubbling to determine the rate of oxygen production. When comparing the
observation table created by Cabomba Carolinensis (Refer to Figure #8), and the observation
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table presented above (Refer to Table #2), it is evident that the indication of oxygen production
plateaus once the light intensity reaches higher levels. This can be seen when comparing
Cabomba’s graph (Refer to Figure #9) and the graph created above (Refer to Figure #4). This
further suggests that with different indications of oxygen production, such as observing the rate
of bubbling produced, when the light level reaches a particular intensity, the oxygen production
stops increasing progressively.
Figure #8: The Rate of Bubbling in Relation to Various Light Levels
Image: The effect of different light intensities on the rate of photosynthesis by Cabomba
carolinensis
https://www.ozarktigers.org/cms/lib011/MO01910080/Centricity/Domain/489/Coursework%20S
ample%20A%20marked.pdf
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Figure #9: The Relationship Between Various Light Levels and the Rate of Bubbling
Image: The effect of different light intensities on the rate of photosynthesis by Cabomba
carolinensis
https://www.ozarktigers.org/cms/lib011/MO01910080/Centricity/Domain/489/Coursework%20S
ample%20A%20marked.pdf
Wavelength forces a fluctuation in photosynthesis production depending on which colour
spectrum the levels remain in. When the wavelength levels are altered to 550 nm which shows
the colour green, it leads to the least amount of photosynthesis production since chlorophyll
absorbs lights poorly in this environment. However, when the wavelength is changed to 450 nm
which is the colour blue, the chlorophylls in plants easily absorb light leading to the most
productivity in photosynthesis. When comparing our data (Refer to Figure #5) with Nelson’s data
(Refer to Figure #7), it is evident that the maximum points and the minimum points on both
graphs are significantly similar. This further supports the fact that the oxygen rate is low when
the wavelength ranges in the green part of the spectrum (520 nm - 565 nm) because the
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chlorophyll in plants reflect green light and effectively captures red light (625 nm - 740 nm) and
blue light (445 nm - 520 nm).
Figure #7: Nelson’s Graph on Oxygen Production and Wavelength
Image: Nelson Biology Textbook on Factors Affecting Photosynthesis
Oxygen levels remain at the maximum constant once the carbon dioxide levels reach 570 ppm;
therefore the productivity of photosynthesis is at its maximum at 570 ppm and will remain at its
peak as the carbon dioxide levels increase.
The environment is a significant factor in the growth of plants, such that the alteration of one
factor may limit a plant’s capability of photosynthesizing. The four environmental characteristics
that guide photosynthesis are air, temperature, light and water; however, water will be
disregarded since it does not correlate with this specific experiment. When comparing the results
from this experiment to real-life situations, it is evident that each factor that presents the most
productivity in photosynthesis meets the environmental factors of tropical areas. Moreover, the
investigation only regards C3 plants, not C4 or CAM plants. Light is a factor that is divided into
three sub-categories; quantity, quality, and duration. The quantity of sunlight depends on the
environment being closer to the equator since the equator has the most sunlight. The further the
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plant is from the equator; the less photosynthesis is produced. If the light quality is too high, it
can also reduce the productivity of photosynthesis, which is why shading or structures of tropical
forests help with the intense light. The quality of sunlight is a sub-category that focuses on the
wavelength of light. In tropical forests, plants can persist in such an extended state of dormancy
thanks to several adaptations that enable them to cope with the poor light conditions: the one to
five percent of the sunlight that reaches the forest floor is not typical sunlight. Still, it has high
proportions of long-wavelength red and infrared light (Butler 2019). The experiment conducted
supports this evidence since the ideal light wavelength for photosynthesis was red. Duration of
light explains how plants tend to successfully photosynthesize when placed in an environment
with plenty of daylight and less darkness; the environment around the equator leads with the
most amount of daylight. Another factor is temperature, such that higher temperatures result in
increased respiration, plus sometimes above the rate of photosynthesis, so products of
photosynthesis may be used up more rapidly than they are being produced (Trinklein). Finally,
the last environmental factor is air, containing several compounds, including carbon dioxide.
Carbon dioxide is the main factor that induces photosynthesis and demonstrates that more carbon
dioxide in the soil will lead to the most photosynthesis productivity.
There are several issues surrounding this experiment revolving around this investigation being a
stimulation. For example, there is an issue with the results of carbon dioxide levels since it is
unrealistic and expensive to exhilarate into real life situations. Another issue that affects the
accuracy of the productivity of photosynthesis, is the specific plant used. Each plant species has
a different ability to absorb light or may thrive in different environments. Since this investigation
uses a water weed plant, it demonstrates one set of solutions; however, this experiment may have
different results depending on the specific plant, the leaf structure or whether it is a C3, C4 or
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CAM plant. The larger the surface area of a leaf, the more photosynthesis production, while
smaller leaves and pine-like leaves are less prone to collecting sufficient sunlight.
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Work Cited
Admin. “How Does Temperature Affect Photosynthesis in Plants? - Neet.” BYJUS, BYJU'S, 26
Mar. 2021,
https://byjus.com/neet-questions/how-does-temperature-affect-photosynthesis-in-plants/.
Altidor, Martine. “Nutritional Types of Bacteria.” Sciencing, 2 Mar. 2019,
https://sciencing.com/nutritional-types-bacteria-2515.html.
“Autotrophs - Definition, Types, Examples and vs Heterotrophs.” MicroscopeMaster,
https://www.microscopemaster.com/autotrophs.html.
“Basic Products of Photosynthesis.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,
https://www.britannica.com/science/photosynthesis/Basic-products-of-photosynthesis.
Butler, Rhett A. “The Ground Layer of the Rainforest.” Mongabay, Mongabay, 16 Apr. 2020,
https://rainforests.mongabay.com/05-rainforest-floor.html.
“Luminous Intensity.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,
https://www.britannica.com/science/luminous-intensity.
Photosynthesis, 13 July 2021,
https://www.youtube.com/watch?v=CMiPYHNNg28&ab_channel=AmoebaSisters.
“Plants and Their Environment.” University of Missouri Extension,
https://extension.missouri.edu/publications/mg2.
“Rate of Photosynthesis: Limiting Factors .” RSC Education,
https://edu.rsc.org/download?ac=12620.
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Sneed, Annie. “Ask the Experts: Does Rising CO2 Benefit Plants?” Scientific American,
Scientific American, 23 Jan. 2018,
https://www.scientificamerican.com/article/ask-the-experts-does-rising-co2-benefit-plants
1/.
Vernier. “What Are the Best Light Sources for Photosynthesis?” Vernier, 21 Nov. 2019,
https://www.vernier.com/2018/09/04/what-are-the-best-light-sources-for-photosynthesis/.