The Affects of Light on Plants’ Growth
Problem:
How does the amount of light affect the growth of a plant?
Hypothesis:
If one plant is put in the dark and one in the light, then the plant in the light will grow more because
plants need sunlight to grow.
Materials:
Ten rose plants
Planting soil (2kg)
10 Six by six centimeter planting container
Dark closet
Water (30 kmL/day)
Ruler
Methods:
Ten rose plant seeds were planted in planting soil in a six centimeter by six centimeter container.
Five plants were placed outside in an open area with plenty of sunlight. Five plants were placed inside a
closet and did not receive any light. The plants were watered daily. Each plant received 100 mL of water.
The plants were measured for growth each week on Friday for four weeks.
Results:
Each week all plants grew, even though plants were in the dark. However, the plants in the sun
grew much taller each week than the plants in the dark. From week to week the average increase in
growth was 2.96 cm for the plants in the sun and 0.35 cm for the plant in the dark. It was very easy to see
the plants growing different heights and the data supports what was seen.
Table 1.
Growth averages for five plants one in the sun and one in the dark measured (cm) for four
weeks
Plants
Sun
Dark
Week 1
1.56
0.52
Week 2
4.54
1.0
Week 3
7.42
1.36
Week 4
10.44
1.58
Average growth of plants in the sun and in the dark over
four weeks
12
Growth (cm)
10
8
6
Sun
Dark
4
2
0
Week 1
Week 2
Week 3
Week 4
Weeks
Conclusion:
If plants are put in the dark and in the light, then the plant in the light will grow more. The
hypothesis stated is supported by the data. The data showed that there was much more of an increase in
growth for the plants in the sun verses the plants in the dark. This is due to the necessity of sunlight for
plants to grow. Plants use sunlight for the process of photosynthesis. Without the energy of sunlight
plants cannot produce their own food. Without food an organism cannot grow. Therefore the plants in
the dark did not have the proper amount of sunlight to fuel photosynthesis and make food to grow. These
results seem accurate, however if this experiment were repeated more plants should be used. It is also
important to realize that weather cannot be controlled in this experiment. A variation of this experiment
could be done with different amounts of light. For example plant could be put in the dark, outside
in the sun, and inside with regular lights. This could test how indoor light affects the growth of
plants. Difficulties with this experiment included remembering the water each day and measuring
the plants in the dark without exposing them to any light.
Grey colored text- restated hypothesis
Underlined text- explaination of why
Italicized text- is the experiment accurate
Bold text- how to make experiment better/difficulties