Measuring the Rate of Photosynthesis

A lab report measuring the rate at which photosynthesis occurs with the elodea plant.


To see if light intensity affected the rate of photosynthesis; the production of oxygen.


Our hypothesis for this lab was that the plants receiving the most intense light would produce oxygen faster or in a higher quantity compared to the plants receiving plain room light and no light at all. We also thought that the plant receiving no light would slow in oxygen production and produce less oxygen than the other 2 plants.

Materials list:

  • Elodea plants
  • Glass beakers
  • Scissors
  • Metric ruler
  • Gas Pressure Sensor
  • Lamp
  • Tin foil
  • Paper towel


  1. Cut three pieces of Elodea into 10 cm long.
  2. Place Elodea in water filled beakers and leave one exposed to intense light from the lamp, one left alone in room light and one wrapped in paper towel and then tin foil.
  3. Using a gas pressure sensor, measure, then record, the amount of oxygen gas found in the water at 0, 10 and 20 minutes.
  • Experimental Control: Plant with normal lighting.
  • Manipulated Variable: Light Intensity
  • Responding Variable: Oxygen Produced
  • Control Variables: Plant length, time left under lamp


The elodea exposed to the room light produced the most photosynthesis. This data is contradictory to our hypothesis.


Our hypothesis was partially supported by the data. We did not predict that the intense light would produce photosynthesis at a higher rate than the room light. The data supports this statement. The data supports our hypothesis about the lack of light.

Amidst the experiment, the lamp we were using for the intense light’s bulb exploded. This left the plant exposed to room light for a short stretch of time. We could also have had a less adept elodea, the plant in the intense light atmosphere could have been weaker than the room light plant. Lastly, the Gas Pressure Sensor may not have been accurate or was just an improper way to accurately measure the amount of oxygen produced.

The method was sound and the experiment clear. More trials were necessary. Based on our results, Elodea exposed to no light will produce significantly less amounts of oxygen and ATP for cell energy, thus crippling the plant as a whole unit. Elodea exposed to room light will increase in the rate of photosynthesis until it reaches a steady level and Elodea exposed to intense light will remain relatively unchanged in terms of photosynthesis.

Plants that live in conditions that supply small amounts of light must either find alternative energy sources or rely less on photosynthesis. Plants living in sunny conditions that receive ample amounts of light will most likely thrive. It stands to reason that if you place a plant used to direct light in conditions for a plant that receives little light, the plant will wither and produce far less ATP. If a plant adapted to low amounts of light is placed in a high-light environment, our data supports that it will most likely thrive.

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14 Responses to “Measuring the Rate of Photosynthesis”
  1. Ferrari Says...

    On March 25, 2008 at 7:21 am

    Hey I got a question how doese the apparatus could be adapted to measure the effectof light,temperature on the rate of photosynthesis. thanks

  2. shanaa Says...

    On December 28, 2008 at 3:27 pm

    can you use a normal 250ml beaker to do this

  3. lisa Says...

    On February 2, 2009 at 3:18 pm


  4. jo Says...

    On May 8, 2009 at 4:46 pm

    could u use the same method of recording rate of photosynthesis and elodea to do how different colours affect plants??????

  5. JAD Says...

    On September 16, 2009 at 9:13 pm

    how to measure the rate of photosynthesis of a plant?

  6. Zymas Says...

    On September 16, 2009 at 11:08 pm

    Check out the article, JAD.

  7. JAD Says...

    On October 21, 2009 at 10:47 am

    is this technique in measuring the photosynthesis of the plant is applicable also to other plants like tomatoes?

  8. Zymas Says...

    On October 22, 2009 at 4:35 pm

    Yes, It would be.

  9. sukhjinder Says...

    On February 15, 2010 at 7:03 am


  10. Mark Aracle Says...

    On April 13, 2010 at 3:15 pm

    Uh, Not really no. Unless of course you think a tomato plant can function naturally; being immersed in water.

  11. A.D Says...

    On August 24, 2010 at 3:13 pm

    IS there a specific gas pressure sensor that is used?
    If so, how does one look like/is used?

  12. bob Says...

    On February 5, 2012 at 2:58 pm

    are there any hazards in this experiment?

  13. Cleatus Says...

    On October 15, 2012 at 12:36 am


  14. Sophie Sniff Says...

    On November 6, 2012 at 9:09 am

    omg this got me an A* and I grew it from my bum. THANKS!!!!!!!!!!!!!!!!!!!!!!! *fist pump*

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