Science Fair Project
The Effect of Types of Lights on Plants
Purpose: To find out if plants grown under the sun
grow better than plants grown under household lights.
Hypothesis: The type of light will affect how well
slim sweet pepper plants will grow. Based on my
research, and my prior knowledge, I believe plants
under sunlight will grow the best, then plants under
halogen, incandescent, and then black light.
Materials:
Fluorescent, incandescent, and black light bulbs (1 each 60 watts)
3 lamps
24 pots
Potting soil
Water
24 sweet slim pepper plants
3 areas where no sunlight can reach the plants
Background Information:
Slim sweet peppers (Antohi Romanium) Capsicum
annuum is a pepper that usually grows about 45-60 cm
at full maturity, which can take about 69-80 days.
This plant does best in full sun exposure. The pepper
that it gives off when fully mature is about 10-15 cm
centimeters. It is usually red when ripe, and yellow
or green while still maturing. Slim sweet peppers
need daily watering, but be careful not to overwater
or the plants might die. These peppers are usually
used fresh in salsa or salads, but can be used for
frying, stuffing, drying, or pickling, depending on
what you like.
Family: Solanaceae
Genus: Capsicum
Species: Annuum
Common name: Sweet pepper or Slim sweet pepper
Procedure:
1. Put the plants inside of the pots and add potting
soil and (equal amounts)
2. Divide the plants into 4 groups.
3. For the first group, leave 6 plants in the under an
incandescent light (9 cm from the light).
4. For the second group, leave 6 plants under a black
light (9 cm from the light).
5. For the third group, leave 6 plants under an
halogen light (9 cm from the light).
6. For fourth group, leave 6 plants outside in the
sun. Make sure the plants in the sun are not rained
on, but still can receive full sunlight so that they
do not get extra water. If this is not done
correctly, this can affect the results.
7. Make sure the lights do not shine on the other
plants except for the ones they are supposed to shine
on. All groups except for group 4 should be in dark
areas where the sun cannot reach them. This can also
affect results.
8. Leave each lamp on for 12 hours per day.
9. Water all the plants equally, every other day.
10. Keep observations for 4 weeks on the height, # of
leaves, diameter, and the length of the longest leaf
in cm.
Variables
Independent variable: Type of lights shining on the plants
Dependent variable: Slim sweet pepper plants growth
Abstract
I started with 4 groups of 6 slim sweet pepper plants,
and I set each group under a different light. The
types of lights I put them under were incandescent,
halogen, black, and regular sunlight. The
incandescent, halogen, and black light plants all grew
slowly at about the same rate. The plants in the sun
grew very quickly and were obviously doing much
better than the other plants, even though all plants
were being watered and exposed to light evenly. The
plants under the incandescent light stopped growing in
about three weeks. The plants under the halogen
light all died (except for the 2 closest to the light)
in about 2 weeks. The plants under the black light
all died in approximately 2 weeks from the start of
the project.
Data Analysis
The data suggests that plants under sunlight usually
grow better than plants grown under artificial light.
My observations were that the plants under the other
types of lights did not have enough nutrients to
grow, but to just stay alive for a few weeks, whereas
the plants under the sun had enough to thrive and
grow. In the beginning of the experiment, the plants
were very alike, with the Standard Deviation under
3.1. This means that all the data was very close
together, and that there was not much difference in
the plants. The range of height was only 4 cm apart
at the most. At the end of the project, all of the
Standard Deviation were above 5, and went up to 14.2.
Also, the height range went up to 28 cm apart. This
tells me that during the experiment, the plants had
changed a lot from each other.
Conclusion:
The data partially supports my hypothesis, which was
that the type of light would affect how well slim
sweet pepper plants; I thought the plants in the
sunlight would grow the best, then the plants under
the halogen light, then under the incandescent light,
then the black light. The plants the sun grew the
best, followed by the plants under an incandescent
light, and then the halogen light, and finally black
light. The data showed that the plants under the sun
grew almost double of the next closest plant group,
which was the incandescent light. The plants in the
sun grew steadily, and passed all the other plants by
far. (The tallest plant in the sun grew 12 cm taller
than the next tallest plant under a different light
at the end of the experiment. The plant with the most
leaves on a plant in the sun had 29 more leaves than
the plant with the next most leaves at the end of the
experiment, etc.) The plants under the incandescent
lights seemed to not grow, just stay the same, but
some leaves fell off about three weeks into the
experiment. The plants under the halogen light had
all been growing at about the same rate as the plants
under the incandescent light, but in about two weeks,
only the two closest plants to the light were growing,
and the others had withered. For the black light,
all the plants died within approximately two weeks.
Reflection
If this experiment were to be done again, I would
suggest that the sample size (24) plants, be much
larger, to get more accurate results. I would also
suggest that the number of trials (1) be increased to
get more accurate results, also. Another change I
would suggest would be to keep data of the plants
longer. My father told be about a light bulb called
GrowLight, which is supposed to help plants to grow.
If I redid the experiment, I would use this bulb,
also. My data suggests that plants in sunlight grow
better than plants under incandescent, halogen, and
also black lights. I have learned that if I would
like to grow plants, I should grow them in regular
sunlight, because they should grow better. I could
apply what I learned by suggesting that people should
grow their plants under sunlight instead of artificial
lights.
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