Procedure of Oxygen Release in Photosynthesis

PART A. Setting up the Experiment

1. Obtain a stem of Elodea and remove several leaves from bottom of the stem.
2. Cut a portion of the stem at an angle and lightly crush the cut end of the stem.
3. Place a small pinch of sodium bicarbonate into the test tube.
4. Place the plant into the test tube, bottom end up.
5. Fill the test with distilled water so that the stem is completely submersed.

PART B. Running the Experiment

6. Notice the bubbles evolved and count them in fixed time intervals when exposed to light.
7. Alternatively, the gas can be collected in a pipette or microsyringe and its amount measured.
8. The effects of light intensity on photosynthesis can also be investigated by placing the light source at different distances as:

• Place a source of light about 5 cm from the plant.
• Wait for one minute
• After one minute, count the amount of bubbles of oxygen rising from the cut end of the stem for 3 minutes. If bubbles fail to appear after 2 minutes repeat part A.
• Run a second minute trial at 10 cm from the light sources. Record your results.
• Run a third trial 3 minute trial with at a 15 cm distance from a light and record your results.