Sahlea Tubbeh
Period 2
I. Title: Plant Growth with and without Light
II. Introduction: Plants are the most important thing on the planet. They provide oxygen for
animals and humans and cleanse the air though an important process called photosynthesis. This
experiment tests if pinto bean seeds germinate better in the light or in the dark. Germination is
the beginning of the development of the embryo into a new plant. Before the seed begins to
germinate it is in state of dormancy, or inactivity. Dormancy ends when the seed is in a
favorable temperature (25 degrees Celsius to 30 degrees Celsius) and has absorbed a sufficient
amount of water and oxygen.
There are many steps the seed goes through in the process of germination. The first step is
when the outer shell of the seed opens. The second step is when the part of the seed, called the
radicle, grows down into the soil and develops into the root. The hypocotyl (part of the stem that
is nearest to the seed) also emerges and grows into the soil and forms what is called the
hypocotyl arch. When the hypocotyl emerges from the soil, it becomes straight because it has
been exposed to the light. When the plant is exposed to the light, then the chlorophyll in the
leaves will be able to perform photosynthesis.
Cotyledons also play an important role in the process of seed germination. A cotyledon is
the structure in the embryo of the seed that stores and absorbs food for the developing plant
before it can perform the process of photosynthesis. Cotyledons protect the structure in the
plant called the epicotyl. When the hypocotyl emerges from the soil, the cotyledons spread
apart, exposing the epicotyl which contains two primary leaves and the apical meristem. The
apical meristem produces cells for the developing plant. When the energy stored in the
cotyledon runs out, the plant must be able to perform the process of photosynthesis. The
equation for photosynthesis is 6CO2 + 6H20 + ENERGY  C6H12O6 + 602. Glucose is made
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Sahlea Tubbeh
Period 2
from this reaction and will later be used in another reaction called cellular respiration. The ATP
that is formed through cellular respiration gives the plants energy to perform mitosis and move
their roots to find sources of water.
III. Purpose/Problem: What Effect Does Light Have On Pinto Bean Seed Germination?
IV. Hypothesis: If seeds get a sufficient amount of light, then they will germinate.
V. Materials:
Potting Soil
2 4 inch Pots
8 Pinto Bean Seeds
Water
1 Ruler
VI. Procedure:
1. Plant the pinto bean seeds 1 inch deep in potting soil.
2. Place 4 seeds in the pot labeled “light” and 4 in the pot labeled “dark.”
3. Place the “dark” pot in a dark area that receives no sunlight. Place the “light” pot
in a light that receives approximately 8-11 hours of sunlight per day.
4. Water each pot with 50 milliliters of water every 2 days for 1 month.
5. Measure plant growth every day in millimeters.
6. Record plant growth data in a data chart.
VII. Data: The data shown below in Table 1 and Graph 1 show the results from the pot with the
pinto bean seeds growing in a window and getting 8-11 hours of sunlight per day and another pot
which was placed in a dark closet getting no sunlight per day.
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Sahlea Tubbeh
Period 2
Table I: Height of Pinto Bean Seeds Grown in the Light and the Dark over Time
Date
13-Jan
14-Jan
24-Jan
25-Jan
26-Jan
27-Jan
28-Jan
29-Jan
30-Jan
31-Jan
1-Feb
2-Feb
3-Feb
4-Feb
5-Feb
No Light (height of plant in
mm)
soaked
planted
sprouted
5
50
65
119
180
210
250
305
310
330
343
358
Light (height of plant in mm)
soaked
planted
sprouted
5
7
7
19
40
90
100
110
125
132
139
150
Graph I: Height of Pinto Bean Seeds Grown in the Light and the Dark over Time
400
350
300
250
Light (height of plant
in mm)
200
150
No light (height of
plant in mm)
100
50
4-Feb
2-Feb
31-Jan
29-Jan
27-Jan
25-Jan
23-Jan
21-Jan
19-Jan
17-Jan
15-Jan
13-Jan
0
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Sahlea Tubbeh
Period 2
VIII. Results: This experiment was designed to test whether or not the amount of light had an
effect on pinto bean seed germination. A total of eight pinto bean seeds were used, four in a
light space which were by a window, and 4 in dark space which were in a closet. The height of
each plant was recorded over the period of fourteen days.
In the beginning of the experiment,
both plants were growing at the same rate until day five when the plant that was in a closet began
to grow more quickly with a height of 50 mm. while the seeds grown in the light had only gotten
to 7 mm. on the same day. Overall, the pinto bean seeds that were in the closet germinated more
quickly and, in the end, were the tallest at a height of 350 mm. However, the pinto bean seeds
that were in the light did germinate and by the end were 150 mm, 200 mm shorter than the seeds
that were grown by a window, but they were significantly healthier and less pale than the plant in
the closet. Therefore, this experiment showed that light did have an effect on seed germination,
by significantly changing the health of the plant.
IX. Conclusion: The data from this experiment shows that light did have an effect on pinto bean
seed germination. The data shows that plants need light in order to germinate more successfully.
The plant that was placed by the window began growing more slowly and was shorter at the end
of fourteen days than the plant that was placed in the closet, but it was healthier, greener in color,
and had more leaves. Although the plant that was placed in the closet did germinate and was
taller than the plant in the window, it was pale in color and had no leaves. This may be because
the plant that was placed in the closet could not perform photosynthesis, which happens in the
leaves and therefore could not provide the adequate energy for the plant to grow as well because
sunlight is needed for photosynthesis.
My hypothesis was if seeds get a sufficient amount of light, then they will germinate and
this was not correct. I hypothesized that the plant in the closet would not germinate at all, but it
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Sahlea Tubbeh
Period 2
did germinate and it did grow, however, plants do need a sufficient light source in order to grow
successfully and for the plant to be at its’ best health, this was exemplified by the appearance and
health of the plant grown by the window and the pale and unhealthy plant grown in the closet.
The problem in this experiment was resolved. I learned that light does have an effect on
seed germination in a way that I did not quite expect. I did not think that plants could germinate
without a light source, and while it is true that having a light source is better for seed
germination, plants can grow and germinate without a light source at all. This may be due to the
fact that for initial germination water and oxygen is required for the seed to open and to begin
establishing roots. After the hypocotyl emerges from the soil light is needed to provide energy
for the plant to grow.
This experiment has a number of real life applications. This experiment is important for
understanding how seeds germinate and what profound role photosynthesis plays, not only for
plants, but for the animals and humans living on the planet. It can also help farmers, biologists,
ecologists and gardeners figure out how much light a plant will need in order to grow plants
successfully to sustain the complex ecosystem that plants are a part of.
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