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The Effects of Different Colored Light on Elodea as Measured by Photosynthesis

Researched by Ashley E.
1999-2000 




 PURPOSE

My experimental purpose was to determine if the color of light affects the amount of oxygen created through the process of photosynthesis by elodea, a type of aquatic plant. 

I became interested in this idea when I learned of the process of photosynthesis and how all life on earth depends on it.  Oxygen produced in the process of photosynthesis is especially important to animals including humans.

The information gained from this experiment can be used in green houses to determine under which color light do plants produce the most oxygen.  This will help astronauts when they want to live on the moon because they would need to know which plants produce the most oxygen under certain colors of light. 



HYPOTHESIS

My first hypothesis is that elodea will produce the most oxygen when living in blue light.  My second hypothesis is that elodea will produce the least amount of oxygen when in green light. 

I base my hypothesis on this statement from the Groiler Encyclopedia, "Certain wave lengths of red and blue light are the most effective in photosynthesis". 



EXPERIMENT DESIGN

The constants in this study were:
- The type of plant
- The amount of time the light shines upon the elodea plants
- The intensity of the light
- The size of the containers
- The amount of elodea 
- The procedure used
- The temperature of the water
- The chemical characteristics of the water

The manipulated variable was the color of light shining upon the elodea plants. The responding variable was the amount of oxygen produced by the elodea plant.

To measure the responding variable I will capture the oxygen in a graduated cylinder and measure it with millimeters. 



MATERIALS
 
QUANTITY  ITEM DESCRIPTION
1 250 ml beaker
1 25 ml graduated cylinders
1 clamp
1 ring stand
1 large water-proof  container
10 strands  of elodea
1 light meter
4 circles colored cellophane
4 hanger bent into circles
1 lamp
1 60 watt light bulb
  Tap water

 



PROCEDURES

1. Place 5 strands elodea plant into a 200 ml beaker. 
2. Repeat step 1 ten times
3. Separate the beakers into 5 groups of 2 
4. Label one group white light, one group blue light, one group green light, one group red light and one group yellow light.
5. Place one of the white light beakers upright into a large waterproof 2-liter beaker.
6. Fill the large 2L beaker with water 3/4 full. 
7. Place a funnel above the beaker with the narrow tip pointing up.
8. Place a 25mL graduated cylinder above the funnel with the funnel tip inside the graduated cylinder, with out letting any oxygen into the graduated cylinder.    Hold the graduated cylinder in place with a ring stand clamp.
9. Depending on what color of light is being shone on the elodea, you bend a hanger into a circle and tape a circle of cellophane onto it.  Hang the hanger horizontally in front of the lamp.  If using white light you don’t need any cellophane. 
10. Using a light intensity meter, measure the intensity.  If the intensity is 6.4-foot candles then it’s okay.  If not then adjust the hanger until the meter reads 6.4-foot candles. 
11. Measure, using millimeters, the amount of oxygen produced by the elodea during that 16-hour period. 
12. Write down what happens.
13. Repeat steps 5-11 with the other 4 color groups.
14. Repeat steps 5-11 with the second group of the 5 color groups. 

 



RESULTS

The original purpose of this experiment was to see if the color of light affects the amount of oxygen that the elodea produced. 

The experimental results after 16 hours were that the red, blue and white light produced 1 ml of oxygen.  The yellow light produced 0.5 ml of oxygen.  The green light produced no measurable amount of  oxygen. 
 

 

 



 CONCLUSION

My first hypothesis was elodea would produce the most oxygen when under blue light.  My second hypothesis was that green light will produced the least oxygen. 

The results indicate that this hypothesis should be accepted because blue light produced 1 ml of oxygen and green produced no oxygen. 

Because of the results of this experiment, I wonder if this experiment would be redone if yellow light would produce more oxygen.  I also wonder if the white light would produce as much as the blue. 

If I were to conduct this project again I would shine the light on the elodea for 48 hours instead of 16 hours.
 


RESEARCH REPORT

INTRODUCTION
 Photosynthesis is the process that all the air-breathing things need to live.  Because elodea produces oxygen, it too, is a thing that humans need in order to live. 

Photosynthesis
 Photosynthesis is the biological process in which sun energy is used to power things made up of carbon dioxide and water.  The word photosynthesis means, "putting together with light".  The process of photosynthesis is in green plants, algae and a limited amount of bacteria.  Photosynthesis provides two key thing humans, animals, and insects need to survive, glucose and oxygen.  Respiration is the reversed process of photosynthesis. 

Plants
Plants use the process photosynthesis to grow.  The molecule in plants that the process of photosynthesis affects most is the chloroplast and chlorophyll molecule.  Chloroplasts are complex green structures within a plant cell that contains chlorophyll pigments and gives plants their green color.  Chlorophyll is found in chloroplast leaves.  Chlorophyll’s job is to trap energy from the sun.  Some of that energy is used to break down the water, that the plant gets from the soil, into hydrogen and oxygen.  The oxygen goes into the air and the hydrogen stays in the plant to help make sugar and starches.  Both chloroplast and chlorophyll are not found in plants that make their own food. 

Elodea
Elodea is a type of aquatic plant.  Elodea’s scientific name is Elodea canadensis and it belongs to the Hydrocharitaceae family. Elodea grows in-groups three and has small flowers that ripen in the water.  Elodea grows up to 3.5 feet or 105 centimeters.  Elodea is called ditch moss or waterweed.   Elodea is commonly used in aquariums to keep the oxygen balanced because when exposed to light oxygen is produced. 

Light
  The energy of light is called radiant energy.  Light contains colors with different wavelengths.  Light is measurable with nanoseconds or billions of seconds.  Light is a type of electromagnetic wave that causes a visual sensation when it strikes the retina. 

SUMMARY
Photosynthesis is the process by which plants make glucose, oxygen and carbon dioxide which all people need to survive.  Light then is also some thing humans need to survive. 

 



BIBLIOGRAPHY

Briggs, W. R., Clayton, R.K., Coombs, J., Hall D., Gregory, F.P.F. "Photosynthesis", The New Grolier Multimedia Encyclopedia. 1992

"Chloroplasts", The New Grolier Encyclopedia.1992

Clayton, R. K., Foyer, Christine "Elodea", The New Grolier Encyclopedia1992

Dickson, Leal G. "Photosynthesis", Microsoft Encarta Encyclopedia. 
2000

Feigh, Dorothy M. "Glucose", The World Book Encyclopedia. 1995,volume G-8 pp236 
Volume G-8 pp. 236

Lersten, Nels R. "Leaf" sub-title "Photosynthesis", The World Book Encyclopedia. 1995,volume L-12 pp155

Paul, K. B., "Elodea", The New Grolier Multimedia Encyclopedia. 1992

"Photosynthesis", The New Random House Encyclopedia.  1990.pp.2523 

Wagner, David H., "Photosynthesis", The World Book Encyclopedia. 1995 volume P, pp. 430

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