What is Photosynthesis?
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms’ activities (energy transformation). This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water.
Why do we need to do this lab? What do we want to achieve?
- We can use this experiment to see different factors that will effect photosynthesis.
- We can learn the relationship between cell structure and function (chloroplasts); strategies for capture, storage, and use of free energy; diffusion of gasses across cell membranes; and the physical laws about the properties and also behaviors of gasses.
What do we need?
Sodium bicarbonate (baking soda powder)
Liquid Soap Plastic syringe ( >10 ccs )
material (spinach leaves)
What should we do?
- Prepare a 0.2% bicarbonate solution so that it can be an alternate dissolved source of carbon dioxide for photosynthesis.
- Add one drop of dilute liquid soap to this solution. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf.
- Cut 10 or even more uniform leaf disks, and put them on a clean paper.
- Remove the plunger and place the leaf discs into the syringe barrel. Replace the plunger, but you do need to be careful that you will not break these leaves. Push on the plunger until only a small amount of air and leaf disk persist in the container.
- Pull a small volume of sodium bicarbonate solution into the syringe. Tap the syringe to make sure the leaf disks are all in the solution.
- Pressing a finger on the top of the syringe opening, draw back on the plunger to create a vacuum. Hold this for about 10 seconds, and shake the syringe at the same time to make sure all the leaves are in the solution.
- The bicarbonate solution will penetrate the air spaces in the leaf so that you will be able to see sunk leaves if it gets succeeded; if you did not, just try this step again for 2-3 times.
- Pour the disks and solution into a clear plastic cup. Add bicarbonate solution to a depth of about 3 centimeters.
- Set other groups with different conditions (like low light, no light, sunlight ….) Take note that only one method has been shown in the video.
- Put them under the light, set up a stopwatch. Moreover, record how many leaves are floating per minute. The table may look like this: (only an example)
Time/min versus 1 2 3 4 5 6 7 8 9
# of floating 0 0 0 3 5 8 9 10 10