How to Test the Rate of Photosynthesis

Photosynthesis occurs in the chloroplast within plant cell walls.

Photosynthesis is a natural process plants use to grow and survive. During photosynthesis, plants absorb sunlight energy and convert it to chemical energy. Water and carbon dioxide are also absorbed and used in the process, allowing plants to produce sugars, or carbohydrates. A byproduct of photosynthesis is oxygen, which is released as a waste. There is a direct correlation between the release of oxygen and the rate of photosynthesis. An ideal way to test the rate of photosynthesis is to examine the rate at which oxygen is released from a plant.

Things You'll Need

• Elodea or similar leafy plant
• Scissors
• Beaker
• Test tube
• Water
• Baking soda
• Lamp
• Timer
• Hand counter

Instructions

1. Cut a leafy stem of the plant at an angle. Remove leaves from the bottom of the stem and press the tip of the stem between your fingers to crush it slightly. This prevents the plant from absorbing too much water during your experiment.

2. Fill the test tube and beaker with water.

3. Place the plant and a pinch of baking soda inside the test tube. Next, place the test tube inside the beaker of water. The water in the beaker acts to remove excess heat from the experiment by absorbing heat from the light.

4. Put the beaker and its contents beneath the lamp and then turn the lamp on.

5. Start the timer when the first bubble appears. Press the button on the hand counter each time you see a bubble. Stop the timer after 10 minutes and note the number of bubbles produced.

6. Divide the number of bubbles by 10 minutes to obtain the rate of photosynthesis in bubbles per minute.

Tips & Warnings

• Cut and crush the stem again if you do not see any bubbles.

References

• 123 Help Me: Experiment to Test the Rate of Photosynthesis
• Biology Center: Rate of Photosynthesis