What Wattage Light Causes Peas to Grow Tallest?

Researched by Michelle A.
2000-01

PURPOSE

The purpose of this experiment was to find out which wattage of light bulb helps pea plants grow most.

I became interested in this idea while thinking that many people have house plants and need a light for it, so I decided to figure   out which light they will grow in most.

The information gained from this experiment will help people who work with hydroponic agriculture to know which type of light to use while growing their plants.

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HYPOTHESIS

My hypothesis was that the pea plants would grow more with the 100-wattage light bulb than with the 40-wattage light bulb.

I base my hypothesis on the book, Plants, by Andrew Haslem. On page 26 it says, "To make food, leaves need water, carbon dioxide, and sunlight."

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EXPERIMENT DESIGN

The constants in this study were:

  • the amount of soil each plant grows in
  • the time spent with light and plant
  • the amount of water each plant gets
  • the brand of light
  • the soil
  • the size and type of growing pots
  • the temperature of the water given
  • the room temperature
  • how deep the seeds are planted (2 cm)
  • the species of pea plant
The manipulated variable was the wattage of the lights.

The responding variable was the height of the pea plant.

To measure the responding variable I measured the height of the plants in centimeters after 2 weeks with a ruler and came up with an average for each group.

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MATERIALS

QUANTITY  ITEM DESCRIPTION
1 bag of soil
1 100 ml. measuring cup
1 240 ml. (1 cup)measuring cup
tap water
3 different wattage light bulbs
100 watts
60 watts
40 watts
3 clip-on lamps
1 roll of masking tape
28 pea plant seeds
1 pencil
1 ruler (centimeters)
1 knife
4  19 liter buckets
1 bucket lid
4  946 ml. (32 oz.) cups

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PROCEDURES

1.Gather all the materials for the experiment.

2.Take the 4 cups and have an adult cut a hole in each one.

3.Take 4 pieces of masking tape and write "Control Group" on one of them. On the other pieces write "100-wattage," "60-wattage," and "40-wattage."

4.Put one piece of tape on each cup.

5.Place 480 ml. (4 cups) of soil in each cup.

6.Place 7 seeds in each cup 1.5 cm away from each other and 2 cm into the soil.

7.Take the 100-wattage light bulb and screw it into one of the clip-on lamps.

8.Now clamp it on the edge of one of the buckets.

9.Take the "100-wattage" group and place it one foot under the light.

10.Then take the 60-wattage light bulb and screw it into one of the clip-on lamps.

11.Now clamp it on the edge of a different bucket.

13.Place the "60-wattage" group one-foot under the light.

14.Take the 40-wattage light bulb and screw it into one of the clip-on lamps.

15.Now clamp it on the edge of a different bucket.

16.Take the "40-wattage" group and place it one foot under the clip-on lamp.

17.Now take the "Control Group" and place it in the last bucket.

18.Now water each group with 100 ml. of tap water. Make sure you cover each seed in each cup.

19.Then place the lid over the Control Group’s bucket.

20.Every 2 days for 2 weeks water each group covering all the plants with 100 ml. of tap water.

21.Now make a record that you will be able to record each plant's height after the experiment.
After the experiment, record each height for each plant and get an average for each group.

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RESULTS

The original purpose of this experiment was to find out which wattage of light bulb helps pea plants grow most.

The results of the experiment were that the average height of the "100 wattage" group was greater than the other experimental groups. The plants in the "control group" did grow tall, but they were very pale and white with very few leaves. The plants in the "40 wattage" group had the lowest height average.

See the table and graph.

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CONCLUSION

My hypothesis was that the pea plants would grow more under the 100-wattage light bulb than under the 40-wattage light bulb.

The results indicate that this hypothesis should be accepted. The "100 wattage" group had a higher average than that of the other experimental groups.

Because of the results of this experiment, I wonder if the pea plants might grow even more in a light bulb with more wattage than a 100. I also wonder if fluorescent would work better than incandescent (fluorescent vs. incandescent.)

If I were to conduct this project again I would have not used buckets. The light shining in them seemed to warm it and caused the temperature to rise. With different wattage lights in the buckets, it caused the temperature to vary. I also would measure the plants after the experiment more accurately with a more detailed ruler.  I also would do more plants per group and do more trials.

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RESEARCH REPORT

INTRODUCTION

Agriculture is very important for our survival. Plants are needed for food and many other things that are important for humans. In specific, pea plants are a type of food that many people eat. Light is a necessity for plants to make food and to grow.
LIGHT
Light is a form of energy, called radiant energy, that can travel freely through space. It consists of electric and magnetic fields. For light to be visible to the human eye, it must have a visible wavelength. A wavelength is the distance along one straight line from a crest (peak) of one wave to the next. People used to think light was something that traveled from the person’s eye, to the object, and back again. If something blocked the rays, the person could not see the object.
USES OF LIGHT
There are many uses for light. People use artificial lights in homes, offices, stores, factories, streets, and highways. Heat comes from light also. Light makes it possible for plants to photosynthesize. If there were no light, there would be no life on earth.
TYPES OF LIGHT
There are many types of light. One type of light is called radiant energy. Infrared rays, radio waves, ultraviolet rays, and X-rays are all types of radiant energy.
PLANTS
Plants are living organisms that can not move voluntarily, but have the ability to create their own food with water, light, and carbon dioxide in the process called photosynthesis.
PARTS OF A PLANT
There are many parts of a plant. Leaves are a very important part. They are the main sites of photosynthesis and transpiration (water loss by evaporation). Leaves are the food-making factories of a plant. Inside each leave, there is a chemical called chlorophyll. Chlorophyll allows a plant to use energy from light to make food.

The stem is also a very important part of a plant. It is like a flagpole and forms a part of the plant’s transport system. Stems bear leaves, which grow at nodes. They also have stem tissues, which are also used for storing water and food. The stem is also the main supportive part of the plant.

The roots are also another part of a plant. They have 3 main functions. One of their functions is to anchor the plant in the soil. They also absorb water and minerals. Roots are also a part of the plant’s transport system.

Some other parts of a plant are the cortex, xylem, stele, and vascular rays. The cortex is in the roots. It is a layer of cells between the center and the edge. The xylem are veins that carry water and food to the plant. The stele is in the roots and holds the veins that carry water and sugar. The vascular rays are cells in the roots that carry water sideways.

USES OF PLANTS

Plants have many uses. People use them for food, medicines, and raw materials. Plants are probably most used and most important as food. Many useful drugs and medicines come from plants. They also supply people with cotton for clothing. Some medicines from plants were used for hundreds of years. Bark is used to make quinine, a drug used to treat malaria and other diseases. Digitalis is made from dried leaves of the purple foxglove plant, which is used to treat heart disease. Many raw materials also come from plants. Plants supply people with fuel to make heat for homes and to cook food. Trees supply people lumber for building homes, furniture, and other goods.
PHOTOSYNTHESIS
Photosynthesis is the process of making food with carbon dioxide, water, and light. This process takes place within the leaves and is extremely important to most plants. If a plant does not photosynthesize enough it will die. Plants must do many things to get these ingredients. The roots must draw up water from the ground and into the leaves. Light must shine on the leaves. Carbon dioxide is found in the air, so they can "breathe" in the air.
GROWTH
For a plant to grow it must do many things. A plant must compete successfully for food, space, air, water, and light. Seeds can survive a wide range of growing conditions. If the conditions are suitable the plant will grow and produce more seeds. Some of the factors of plant growth are the amount of sunlight, pH level, moisture, amount of water, and the soil type. For a plant to grow it must make food with light, water, and carbon dioxide. If a plant does not make enough food for itself, it will die.
TYPES OF PLANTS
The most common forms of plants are trees, bushes, woody vines, herbs, epiphytes, parasites, cushions, and creepers. Trees are plants having a large, single trunk rising above the ground. They are the largest plants. A parasite is a plant that feeds on another plant. A cushion is a colony of plants with tightly packed stems. A creeper is a vine-like plant that grows along the ground or over objects.

There are many types of plants. One type of plant is called dehiscent plants. Dehiscent plants are dry fruits that split their pericaps and release the seeds. These seeds are then dispersed by the wind. Dehiscent dry fruits also have capsules.

Another type of plant is called indehiscent plants. These dry fruit’s pericaps do not open, but the seeds are dispersed by the wind and are assisted by wings.

Another type of plants is called schizocarpic plants. These dry fruits open, but do not expose the seeds. The seeds are dispersed by the wind.

Another type of plant is called herbaceous plants. These plants have soft stems, and they produce a new one each year, containing 3 parts: the epidermis, pith, and the vascular bundles. The epidermis, or outer layer, remains soft throughout the life of the plant. Its main function is to protect the inside parts. The pith is a spongy inner part of the stem that is used to store food. In it, there are a number of hollow trees called vascular bundles. These vascular bundles are cells in the roots that carry water and sugar. They allow movement of liquid food from leaves to roots and carry water and dissolved minerals from roots to the leaves.

Another type of plant is called succulent plants. These fruits have fleshy pericaps, unlike dry fruits (dehiscent, indehiscent, schizocarpic plants), which have a hard, dry pericap.

SUMMARY

Light is a form of energy that can travel freely in space. It is made up of electric and magnetic fields. Light is crucial for plants to grow.

Plants are living objects that must make their own food in the process of photosynthesis using water, light, and carbon dioxide. There are many types of plants. There are many parts of a plant including the stem, leaves, roots, xylem, stele, cortex, and vascular rays. People use plants for food, medicine, and raw materials. Plants can survive a wide range of growing conditions. Moisture, pH level, amount of sunlight, amount of water, and the soil type are all factors of plant growth.

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BIBLIOGRAPHY

"Aliens Explore Earth: Plants, Trees, and Forest." Available at http://www.alienexplore.com/ecology/topic27.html, October 30, 2000

"BOTANY.COM." Available at http://www.botany.com, October 18, 2000

DiMichele, William A. "Plant," The World Book Encyclopedia. 1999. v.15 pp. 516-547

Fetzer, Scott.  World Book’s Young Scientist. IL: World Book, Inc. 1991. pp. 64, 66-70, 72, 74

Haslam, Andrew. Plants. IL:World Book, Inc. 1992. pp. 8-12, 14-23, 26, 32-34

Hershey, David R. Plant Biology Science Projects. Canada: John Wiley & Sons, Inc. 1995. pp. 3-19, 67- 87

Mandall, Donald and Walker, Jerry T. "Plant." The World Book Encyclopedia, 1989. v.15 pp. 522-553

"Plant Growth Substances." Available at http://www.bio.metu.edu.tr/~e068741/project/term.html#discovered. November 27, 2000

"Plants and our Environment." Available at http://tqjunior.thinkquest.org/3715.October 24, 2000

Stephens, Hilary. The Visual Dictionary of Plants. NY: Dorling Kindersly, Inc. 1992. pp. 6, 26-32, 38, 44

Walker, Jearl. "Light," The World Book Encyclopedia.1998. v.12 pp. 282-292

ACKNOWLEDGEMENTS

I would like to thank the following people for their help with my science project:

I would like to thank my mother, Shauna. She helped gather the materials I needed and setting up my science experiment.

I would like to thank Mrs. Pasckvale for giving me suggestions on my project.

I would also like to thank Mr. Newkirk for giving me suggestions and proofreading some of my journal.

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