I. Introduction and Research:
For Dr. Duncan’s Science Methods EC-6 class, I have conducted an inquiry investigation
over a plant’s growth with a manipulated variable. The investigation will take four weeks to
conduct. Throughout the four weeks, I will collect data weekly on the plant’s growth progress. I
am interested in studying about the plant’s growth and testing my hypothesis. I will also have
completed a research about plants during this investigation. By the final week, I will be able to see
if a plant’s growth is affected by the manipulated variable and if my hypothesis was correct.
A. What Plants Need to Grow:
For plants to grow, they must have light, water, and soil. With light, the plants are able to
make their own nutrients. Some plants don’t require as much light than others, but when a plant
receives an incompetent amount, consequences will happen. “When given a starvation diet of light,
they will maintain their core life functions and give up the less necessary ones.” (Huegel, C. N.
(2019). Plants need water in their daily lives to preserve themselves. Most of the water that the
plant receives is immediately lost as it’s distributed where needed. The soil a plant grows in is a
combination of “organic and inorganic materials, water, air, and a huge variety of living
organisms.” Huegel, C. N. (2019). For the investigation, I will be using a constant soil, water, and
the light will be the manipulative variable.
B. Photosynthesis Explanation:
Photosynthesis is needed in order for a plant to be able to survive, without it, the plant
wouldn’t be able to pertain energy. One of the biggest sources of energy that plants are able to
receive energy from is the Sun. The plant uses the Sun when it “traps light energy from an outside
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source.” (King, J. (2011) Another important thing that occurs during the process is when “two
biochemical reactions that lead to the production of carbohydrates.” (Jones, J. J. B. (2012)
C. How Plants Get Their Water and Nutrients:
For a plant to grow, they must also receive nutrients and water. “The essential plant nutrient
elements are primarily taken up the roots as ions that exist in the soil solution.” (Jones, J. J. B.
(2012). There are many micronutrients and elements that are used for a plant’s nutrients. Another
essential for a plant to grow is water. The plant intakes water in a few different ways. Majority of
the time, the plant receives water that has been absorbed into the soil. Rainfall is another that that
plants can receive water. In addition, the plant may also receive water through diffusion in the soil.
D. Why Water is Important to Plant Growth:
Just like all living things, plants need water to be able to function and survive. Even though
majority of the plants water intake will most likely be evaporated sooner or later. Water keeps
plants strong and able to grow. When water enters the plant, there are “chemical reactions in their
cells, to keep living cells firm for functioning, and to prevent wilting of tissues and organs.” (King,
J. (2011)
E. Ways Plants Adapt to Their Environments:
No matter the environment of the plant, the plant will normally find ways to successfully
receive water around them. If the plant is unable to receive water from precipitation, they can use
their roots to obtain water that way. “In tropical rain forests, for example, where the humidity is
high, aerial roots growing out from branches absorb water directly from the air” is another adaption
a plant will make. (King, J. (2011)
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II. Rational for your Study & Research Question:
During my investigation, I will be spending four weeks observing three different cups that
I have planted seeds in. My manipulated variable will be different amounts of light used. My
research question is, Does the amount of light given affect the plant’s growth? I predict that
increasing the amount of light will be the best environment for the plant. I also predict that
decreasing the light will result in the plant diminishing. Therefore, my hypothesis will be,
Increasing the amount of light provided will increase the growth of the plant.
III. Materials and Data Collection Plan:
I will be using materials to conduct my investigation. Everything will be constant except
the light provided. There will be three cups filled with the same amount of soil. In each cup I will
plant five radish seeds into each cup. I will spread out the five seeds evenly underneath the soil of
the walls of the cup. By placing the seeds on the wall of the cup, I will be able to observe the
growth since I will be using clear cups. The temperature or the location of the cups will not be
changed once the investigation begins. The first cup will be placed in my kitchen window where
it will receive 100% light. The second cup will be placed in the back of a hallway closet, where it
will receive 0% light. The third cup will be put in the kitchen in a shaded area where it receives
limited light 50% light during the day. The last material that I will provide to the plants is water.
To test my data, I will be observing my plant’s growth weekly. I began my investigation
on October 17, 2020. Every Saturday, for four weeks, I took pictures of the growth of my plants.
I kept an album of the pictures and labeled each picture I took. For the labels, I would write
down what week the plant was on, and the amount of light the cup was receiving. I also was able
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take notes of the process in my Science Journal. I would also draw pictures of what I was seeing
with my plant growth, and any other notes I noticed with the growth at the time.
IV: Results:
After completing the investigation on November 20, 2020, I was very shocked to watch
the entire process of the plant growth. It was very interesting to see how the manipulated variable
affected the plant growth for all three cups. I figured since plants needs light, that the cup in 100%
light would be the best environment. However, the cup in the 0% light grew taller than the cup in
100% light. The main difference in the two cups were the appearance of the two. The cup in 100%
light was not growing very fast, but the leaves and stem were green. The cup receiving 0% light
grew tall quickly, but with the leaves a light brown. The cup receiving 50% light seemed to grow
just as fast, and the leaves were also green, but the stems in this cup were all leaning towards where
the light was coming from. I thought that was interesting to see that plants leaning trying to receive
more light. I also noticed a difference in the leaves for all three cups. The leaves in the 100% light
remained green the entire time, the leaves in the cup receiving 50% light started out green and
eventually changed to yellow, and the leaves in the cup with 0% light remained yellow the entire
investigation. During Week 3 of my investigation, the cup in the window with 100% light was
accidentally knocked over which leaded to the investigation being complete a few days early.
Below, you will see pictures I captured of all three cups during my investigation with a
manipulated variable.
V. Analysis and Conclusions:
In conclusion, I have observed that although light is necessary for a plant’s growth, the
amount of light provided to the plant doesn’t prevent a plant from growing. My hypothesis was,
increasing the amount of light provided will increase the growth of the plant. Therefore, my
hypothesis was wrong, because even the cup with 0% light was able to grow the tallest, just not
the greenest. So, if the light impacted anything with the plant, it was how it looks and grows. The
plant can grow in any light circumstances. All the cups were able to grow immediately once
watered, the three cups just had a few differences by the end. The cup with 0% light grew tall
quickly, however leaves were never green. They started with a dark yellow and faded even more
throughout the weeks. The cup with 50% light was able to grow tall quickly as well with the leaves
green during the first two weeks. By week three, the plant was leaning more towards the light
source and started to look weak and began to wilt over the side of the cup. The cup with 0% light
grew tall during week one and each week I was able to see the plant wilt more and more slowly
down the cup. The leaves on the plant never turned green, they remained yellow the entire time.
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Reflecting on the investigation, one thing I would do differently next time is to water more.
I only watered the cups once a week, and when I felt like they needed more, I didn’t want to change
how I was watering, because this would interfere with another manipulative variable. For a future
investigation, I would like to use different amounts of water as the manipulative variable to see
how the plant’s growth would be affected. I was surprised at how much I learned about the needs
for plant growth and I have faith that the next time I try to plant something, I will be able to be
more successful.
In my future classroom, I think this would be a great project for 3rd grade students to
complete. It makes a great hands-on experience for the students to be able to visually learn with. I
would have the students create a hypothesis and make predictions and let them choose one
manipulated variable for the student’s to test plant growth with. The 3rd grade Science TEK that
could be incorporated into the project is 3.3 A. “Scientific investigation and reasoning. The student
knows that information, critical thinking, scientific problem solving, and the contributions of
scientists are used in making decisions. The student is expected to: analyze, evaluate, and critique
scientific explanations by using evidence, logical reasoning, and experimental and observational
testing.” (Texas Essential Knowledge and Skills for Grade 3. (n.d.) I chose this TEK because it
allows the student to use critical thinking and be able to use evidence they have found to evaluate
a hypothesis they create. They will also be observing their project with a certain amount of days
or weeks to analyze information they research. By having students complete an investigation like
this, it would benefit the visual and kinesthetic learners.
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References
King, J. (2011). Reaching for the Sun: How Plants Work. In Reaching for the Sun. Cambridge
University Press. https://doi.org/10.1017/CBO9780511973895
Jones, J. J. B. (2012). Plant nutrition and soil fertility manual. ProQuest Ebook Central
https://ebookcentral.proquest.com
Huegel, C. N. (2019). The Nature of Plants : An Introduction to How Plants Work. ProQuest
Ebook Central https://ebookcentral.proquest.com
Texas Essential Knowledge and Skills for Grade 3. (n.d.). Retrieved November 27, 2020, from
https://tea.texas.gov/sites/default/files/Grade3_TEKS_0819.pdf