Photosynthesis in Living Leaves
The rate of photosynthesis can be measured by examining the amount of reactants and the buildup of products. Oxygen is a product of photosynthesis and is stored in the spongy mesophyll. This gives the organism the ability to float. In this experiment, oxygen is taken out of the spongy mesophyll. The leaves are then placed into the bicarbonate solution with soapy water. The spongy mesophyll fills with the solution, causing the leaves to sink. A light source was placed over the solutions. The leaves began to create oxygen and sugars that filled up the spongy mesophyll. This is because there was enough light and bicarbonate ions to begin photosynthesis. The leaves in the bicarbonate solution were floating by twelve minutes. This data suggests that if oxygen is removed from a living leaf and placed with enough bicarbonate ions and light, then it will produce oxygen on its own due to photosynthesis.
In this lab, we test the factors of photosynthesis and how they can affect the rate when the process occurs. If living leaf disks are deoxygenated and sink into a bicarbonate solution with a artificial light source projecting over, then the leaves will begin making oxygen due to the process of photosynthesis. Using a syringe, a vacuum is created to take out the oxygen from the open spaces in the spongy mesophyll. Once all the disks are deoxygenated, the spongy mesophyll fills with the solutions and sinks. An artificial light source is placed over the cups of solutions to act as the sun, giving the disks the energy they need. A timer is set for every minute to measure the amount of disks to float at a certain time. All the leaves are floating within a fifteen minute range, due to photosynthesis beginning.
How it works
Photosynthesis is a process in carbon dioxide and water are absorbed and used to make glucose and oxygen. The carbon dioxide is used in the production of carbohydrates, and the water is split into hydrogen and oxygen groups. The leaves actually keep some oxygen stored away in the spongy mesophyll in small amounts to use for the break down of carbohydrates when needed. The sun provides energy for photosynthesis to begin and is absorbed though the chlorophyll of the plant.
The bicarbonate used in this experiment is baking soda. In this study, the bicarbonate was used to produce carbon dioxide for the plant. Baking soda was needed for this experiment because it was easy to monitor the amount of bicarbonate was used. Also, the concentration of the bicarbonate used has a tremendous effect; The higher the concentration, the more oxygen waste product the plant disk will be able to produce. Liquid soap was placed into the solutions to make it easier for photosynthesis to occur. The leaf surface is hydrophobic, and the liquid soap is a surfactant. This means that the liquid soap is able to mix with both the water and the leaf surface. This allows the solutions to enter the leaf into the spongy mesophyll faster.
This experiment takes place in Brookhaven Academy’s Chemistry lab on October 12, 2018. In this experiment, 300 mL of .2% bicarbonate solution will replace the carbon dioxide that is vacuumed out. While the bicarbonate solution is in one cup, the other cup is filled with pure water to serve as the control. Liquid soap is added to each solution. Twenty holes will be taken out of living spinach leaves using a hole-puncher. Using two different syringes, place ten leaf disks in each. Put one syringe in the bicarbonate solution, and place the other syringe in the pure water solution. Pull small amounts (5 cc) for each solution into the syringes. Place a finger over the tip of the syringe and pull the end back. Let go of the end and let it jump back into its place. Remove the end of the syringe, and based on the solution inside, pour the leaf disks into the correct solution cup. Place a bright light source closely over the cups and set the timer for a minute. Document the amount of disks floating each minute until all the leaves are floating.
Overall, the leaf disks in the bicarbonate solution produced enough oxygen to begin to float. By minute thirteen, all ten of the disks were floating. Data that was measured during the experiment shows how quickly the leaves began to float. The data is displayed in Figure 1.
Due to the results of the experiment, the hypothesis was accepted. As long as the plant has water, energy from the sun, and carbon dioxide, then photosynthesis will not stop. Leaves give off oxygen by taking in carbon dioxide provided in the atmosphere and converting it to oxygen. The oxygen is then released through the stomata. When the disks were placed in the vacuum, the oxygen was sucked out, forcing the solution to enter the spongy mesophyll. The leaf sinks because there is no longer any oxygen to keep it afloat.
Because a plant gets it energy from the sun, the leaf will use the energy from the artificial light source to continue with photosynthesis. Once the plant absorbs enough carbon dioxide from the bicarbonate solution, it will convert the carbon dioxide into oxygen. Most of the oxygen will be released, causing small bubbles to form around the leaf. Small amounts of the oxygen will be transferred into the spongy mesophyll in case of respiration.
Once the spongy mesophyll fills with oxygen, the disks will slowly begin to float. Photosynthesis takes a longer time than normal using this method, so liquid soap was used. The liquid soap reduces the surface tension, making the disks sink faster. It also allows the mesophyll to absorb the solution faster.
In comparison to other labs, the control group for this study did not float. This was because all the oxygen was completely taken out of the leaves. In some studies, the control group disks floated a small amount because the oxygen wasn’t completed absorb. Other experiments can be designed by changing the bicarbonate solution and observing the data.
The objective of this lab was to get a better understanding of photosynthesis by testing living leafs in a bicarbonate solution. This lab showed that without carbon dioxide, plants can’t produce the oxygen we need to breathe. It also showed that photosynthesis is more complex than most people think.