Right now I'm studying photosynthesis in Biology. We have to design an experiment that would prove how light reactions occur prior to carbon fixing reactions.

I know how light and carbon fixing reactions work, but how can I prove this experimentally? Are there any experiments I can replicate besides the one in which leaves are simply covered up and then tested for starch?

Since this is not my area of expertise, I searched Google under the key words "light 'carbon fixing' experiment plants" to get these possible sources:

(Broken Link Removed)
http://cartage.org.lb/en/themes/Sciences/botanicalSciences/Photosynthesis/UsingLight/UsingLight.htm
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-3040.1992.tb01478.x?cookieSet=1&journalCode=pce
http://books.google.com/books?id=RtSpGV_Pl_0C&pg=PA105&lpg=PA105&dq=light+%22carbon+fixing%22+experiment+plants&source=web&ots=oryTkCIRrZ&sig=uI9mbdzm_rCmn68E1TDT-urRalw
http://findarticles.com/p/articles/mi_gx5216/is_2004/ai_n19132886

I hope this helps. Thanks for asking.

To design an experiment to demonstrate how light reactions occur prior to carbon fixing reactions in photosynthesis, you can consider an alternative approach that involves measuring the production of oxygen during the light reactions and the uptake of carbon dioxide during the carbon-fixing reactions. Here's a step-by-step guide for such an experiment:

1. Materials needed:
- A light source (e.g., a lamp or sunlight)
- Potted plants (e.g., Elodea or spinach)
- Baking soda (sodium bicarbonate)
- Rubber stopper with a glass tube
- A beaker or test tube
- Water
- Carbon dioxide indicator solution (e.g., bromothymol blue)
- Timer or stopwatch
- Safety goggles and gloves

2. Set up the apparatus:
- Fill the beaker or test tube with water.
- Add a few drops of carbon dioxide indicator solution to the water.
- Place the potted plant in the beaker or test tube. Make sure the plant stem is completely submerged, and the leaves are above the water level.
- Insert the rubber stopper with the glass tube securely into the beaker or test tube.

3. Ensure the experiment is conducted in a well-lit area to provide sufficient light for the plants.

4. Start the experiment:
- Switch on the light source to provide light to the plant.
- Start the timer and record the time.

5. Observe and record the changes:
- As the light reactions occur, the plant will release oxygen through the submerged leaves. The oxygen will rise to the top of the beaker or test tube and displace the water.
- Use the glass tube to collect the oxygen gas rising in the beaker or test tube.
- Keep track of the time it takes for the oxygen to displace a certain volume of water.

6. Analyze the results:
- The time it takes for the oxygen to displace a significant amount of water indicates the rate of oxygen production during the light reactions.

7. Carbon fixation phase:
- After a significant amount of oxygen is produced, remove the light source and place the plant in darkness.
- Observe and record any changes in the water, such as a color change due to the release of carbon dioxide from the plant.

By measuring the rate of oxygen production during the light reactions and observing the release of carbon dioxide during the carbon fixation phase, you can demonstrate that light reactions precede the carbon fixing reactions in photosynthesis. Remember, always follow proper safety precautions and consult with your teacher or instructor before conducting any experiment.