Photosynthesis: Floating Leaf Discs

Author: Maddie Van Beek

We all know that trees and plants make our world prettier and provide us with fruits and vegetables. But did you know that we actually NEED plants to live? Through the process of photosynthesis, plants take in the carbon dioxide that we give off and convert it to the oxygen that we desperately need to survive! How does this whole process work? 




This diagram explains the basic components of photosynthesis: 

http://www.cneccc.edu.hk/subjects/bio/album/Chapter8/images/PHOTOSYNTHESIS0.jpg

Plants not only need carbon dioxide, but also use water and sunlight to complete the photosynthesis process. 




Check out our blog on xylem to understand how water gets from the ground to the leaves of a plant:

Learn more about the details of photosynthesis!

Photosynthesis reaction equation:

http://www.lifeadrift.info/media/2316/photosynthesis_equation.jpg

This catchy song will help you remember the basics of photosynthesis!

Follow-up questions: 

• What happens during photosynthesis? 
• How is chlorophyll involved in photosynthesis? 
• What do xylem do? 

Try defining this important vocabulary in your own words: 

• Chloroplasts
• Chlorophyll
• Photosynthesis
• Xylem

You now know everything you need to complete our basic photosynthesis experiment, but if you want to learn EVEN MORE, watch the video below!




This video explains the complexities of photosynthesis! You’ll know more than you ever wanted to know about how photosynthesis works. 

Activity



YOU WILL NEED:

• Spinach leaves
• Hole punch
• Tweezers
• 10cc syringe (no needle)
• Water
• Baking Soda
• Soap

Here’s what to do!



If you like visual instruction, watch this video to see how to complete the experiment: 

1. First, you need to create your bicarbonate solution. Do this by combining 1/8 teaspoon of baking soda with 1 and 1/4 cups of water. Stir the baking soda in until it is completely dissolved. 
2. Next, use the hole punch to punch holes in your spinach leaves until you have about 20 spinach leaf discs. 
3. Remove the plunger from the syringe, and place the spinach discs into the syringe. 
4. Use the tweezers to push the discs down as far as they can go. Be careful not to crush or damage them. 
5. Once you have all the leaf discs in the syringe, replace the plunger. 
6. Put the tip of the syringe in the bicarbonate solution and pull back the plunger to suck up 10ccs of the solution. The baking soda solution is a source of bicarbonate ions, which is one source of carbon dioxide for photosynthesis.  
7. Cover the end of the syringe with your finger, and then pull the plunger upwards as far as it can go to pull the air out of the leaf discs. Alternate pulling the plunger out and pushing it down (remember to keep the end covered with your finger the whole time to create a vacuum). Pushing the plunger down is forcing the bicarbonate into the leaf discs and pulling it up will remove any air from spaces in the leaves.
8. Continue to do this until you see the leaf discs start to sink. Once all your leaf discs have sunk, squirt out the baking soda solution into a sink, making sure not to allow the leaf disks to plug the syringe.
9. If you have trouble getting your leaf discs to sink, you can add a small drop of soap to the bicarbonate solution and try again. The soap makes the leaf less hydrophobic and will help it more easily absorb the solution.  
10. Next, add more baking soda solution. You should suck up about 10 ccs, as you did in step 6.  Swirl your syringe around to make sure the leaf discs aren’t stuck to the sides or to each other. 
11. Place your syringe upright in a well-lit area. Either artificial or natural light will work. 
12. Wait to see how long it takes for the leaf discs to float. Record the time when the first disc rose to the surface. Wait until at least 5 leaf discs have risen back to the surface. Record the time it took for 5 leaf discs to float. If you are patient enough, record the time that it takes for all your leaf discs to float. What’s the point of this? You just watched photosynthesis occur!  The oxygen created inside the leaves by photosynthesis is making the leaves float again.  
13. Practice making graphs! Create a line graph to show how long it took for the discs to float. I would put time along the x-axis and number of leaf discs along the y-axis. You could do this by hand, or you could use Excel to create it electronically. If you need help using Excel, refer to our blog on heart health for instructions. 

Follow-up questions:

1. Would this experiment have worked with normal tap water? Why or why not?
2. What was happening when the leaf discs sunk?
3. Why did the leaf discs float at the end? 
4. Create a diagram to show the steps of your experiment and how it relates to photosynthesis. 

If you had fun learning about photosynthesis, you might also like our blog on plant transpiration.



References:

• <iframe width="560" height="315" src="https://www.youtube.com/embed/XV9FOWleErA" frameborder="0" allowfullscreen></iframe>
• https://blog.udemy.com/photosynthesis-experiment/