| Explore | Plants are an essential part of the world. They produce the oxygen as a byproduct of photosynthesis in the air that organisms need to breathe. They offer a source of food and energy. They solidify abiotic, nonliving factors in a landscape. They help to make the world a more beautiful place! A plant “is any one of the vast number of organisms within the biological kingdom Plantae,” and plants are “considered of limited motility and generally manufacture their own food” (Hogan). Plants are characterized by their ability to create energy through the performance of photosynthesis. Many different plants exist across the globe, but all plants share one thing in common: photosynthesis. Photosynthesis is the process by which plants, algae, certain protists, and some prokaryotes absorb light energy, and transform that light energy into a usable, chemical energy. During photosynthesis, a plant captures light energy from a strong light source, such as the sun. With this light energy, the plant is able to convert water, carbon dioxide, and other absorbed minerals, into “oxygen and energy-rich organic compounds” (Basshum). Photosynthesis is performed by autotrophs, who use light energy to produce food for themselves and the heterotrophs that eat them. The process of photosynthesis takes place in two stages: the light reactions in the thylakoids (where water molecules are split, oxygen is released, and ATP is generated through phosphorylation) and the Calvin cycle in the stroma (where sugar is formed from carbon dioxide, with the help of ATP and electron carrier, NADPH). Photosynthesis takes place in the mesophyll of the plant, as photosynthetic gases move through stomata. As compared to cellular respiration, photosynthesis reverses the direction of energy flow. As an endergonic process, photosynthesis absorbs energy and the reactants have more energy than the products. In short, photosynthesis is responsible for transforming light energy into chemical energy that can be used by all organisms in an ecosystem. In essence, photosynthesis fixes carbon. Photosynthesis is crucial to life on earth; as stated by James Alan Basshum in his article, “It would be impossible to overestimate the importance of photosynthesis in the maintenance of life on Earth.” Photosynthesis is the basis of most of the world’s food chains, and is responsible for stabilizing the balance of atmospheric gases. In order for this process to occur, however, plants require four things: chlorophyll, sunlight, water, and carbon dioxide. Certain factors, such as light intensity, temperature, and carbon dioxide concentration, can impact the rate and success of photosynthesis in a plant. After completing an experiment that explored the rate of photosynthesis in leaf disks placed in water with varying carbon dioxide concentrations, scientists were inspired to discover the impact of further variables on the rate of photosynthesis in leaf disks. Photosynthesis occurs in leaf disks with the help of light and carbon dioxide. In conditions of high amounts of light and carbon dioxide, the rate of photosynthesis is likely to increase. However, too much of these crucial factors could prove harmful. In further experimentation, the scientists desire to discover the effect of additional factors, such as temperature or light color, on the availability of crucial photosynthetic factors, and thus, the effect of additional factors on the rate and success of photosynthesis. |
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| Research Question | The lab discovered how varying temperatures affect the rate of photosynthesis in leaf disks. The success of photosynthesis in leaf disks was tested after being placed in cups of water with varying temperatures. |
| Predictions | If the water temperature is room temperature, then photosynthesis will occur most rapidly and disks will rise more quickly. If there is no significant change to the temperature, then photosynthesis should be able to occur without being inhibited. |
| Experimental Design | Materials: - Baking soda - Bucket of ice - Computer - Distilled water - Hole Puncher - Hot bath - Safety goggles - Sharpie - Six plastic cups - Six syringes - Stopwatch - Tape - Thermometer - Three Lamps (or other light sources) - Twenty Spinach leaves Procedure: 1. Safety goggles were worn by scientists. 2. All materials necessary for conducting the experiment were gathered. 3. Three cups were labeled as the control group, as “Distilled Water,” and the other three were labeled as the experimental group, as “Baking Soda.” 4. Each of the six cups were filled with 150 mL of distilled water. 5. 10 mL of baking soda was mixed into each of the three experimental group cups. 6. Hot bath was heated up to 40 degrees Celsius. Designated hot water cups were placed floating in the bath. Hot cups were kept at an average of 40 degrees Celsius for the entirety of the experiment. 7. Ice bucket was filled with ice. Designated cold water cups were placed in the ice. Cold cups were kept at an average of eight degrees Celsius for the entirety of the experiment. 8. Room temperature cups were placed in a similar location to the ice bath and hot bath. Cups were kept at an average of 20 degrees Celsius for the entirety of the experiment. 9. Lamps were set up to provide sufficient light to the tested cups. 10. The hole punch was used to punch out 90 leaf disks from Spinach leaves. 11. Fifteen leaf disks were placed into each of the six syringes. 12. After the leaf disks were placed in their respective syringes, the syringe was tapped on the table or with fingers to move to the leaf disks towards the narrow end of the syringe where the needle would go. 13. The tip of each syringe was placed into its respective cup and was filled with 5 mL of water. 14. The plunger of the syringe was pushed up to rid the syringe of extra air at the top. 15. The tip of the syringe was covered with a finger and the plunger was slowly pulled back on to create a vacuum, extracting all of the gases from from the leaf disks. 16. The finger was held over the tip for 10 seconds, and was then released. After releasing the finger, the leaf disks sank to the bottom of the syringe. 17. The process was completed until all six syringes were filled with leaf disks that had all gases extracted. 18. The contents of each syringe were poured into each respective cup and the stopwatch was started. 19. The cups were observed and every minute, the amount of floating and the amount of sinking disks was recorded. 20. Information was recorded on a google doc table. 21. The leaf disks were observed and the data was recorded each minute for a span of 20 minutes. 22. When the experiment was concluded, hands were washed and all materials were cleaned up and put away. Variables: - For this experiment, the independent variable was the temperature that the cups of each trial were kept at. The temperature was measured in degrees Celsius by a glass thermometer and recorded. - The dependent variable was the number of leaf disks that rose to the surface. The dependent variable was measured by counting the number of leaf disks that had risen to the top and the ones that remained on the bottom. - During the experiment, the constant variables included spinach leaf disks, amount of water, amount of baking soda, cups used, lights, thermometer, distilled water, hole puncher, stopwatch, hot bath, ice bucket, syringes, method of removing oxygen from leaf disks, and atmospheric conditions. - For this experiment, the group decided to have one control group along with an experimental group for each of the three temperatures. The control group included cups of distilled water in each temperature, while the experimental group included cups of baking soda in each temperature. To distinguish between control and experimental groups, the cups were labeled based on whether they had a baking soda solution or not. |
| Conclusion | Results: The graph displays the effect of water temperature on the rate of photosynthesis in leaf disks. In both the baking soda graph and the distilled water graph, the hot water was the only cup that had a large amount of floating disks. In the distilled water graph, room temperature and cold water spinach disks did not float. In the baking soda water graph, room temperature and cold water spinach disks only had a couple floating disks. In each graph, the disks rose at a constant rate, and once risen, they stayed risen. Cold and Room Temperature Water resulted in a less rapid rate of floating disks and thus, a less rapid rate of photosynthesis. Conclusion: The experiment was conducted to discover how varying temperatures affect the rate of photosynthesis in leaf disks. As measured by oxygen production, rate of photosynthesis was tested after leaf disks were placed in cups of water with varying temperatures. The hypothesis stated, “if the water temperature is room temperature, then photosynthesis will occur most rapidly and disks will rise more quickly.” The hypothesis was not supported throughout the experiment. The room temperature water for both the control and experimental group, resulted in little to no floating disks. The hot water for both groups resulted in the largest amount of floating leaf disks. Room temperature distilled water had zero leaf disks float, whereas the hot distilled water had all fifteen leaf disks floating by the end of the twenty minutes. Room temperature baking soda water had three leaf disks float after twenty minutes, whereas the hot baking soda water had fourteen leaf disks floating after twenty minutes. The results did not support the hypothesis, as the hot water had more leaf disks rise than room temperature water. In any experiment, errors may occur that affect the recorded data of the lab. There were many possible sources of error present during this specific experiment. The first possible error that could have occured was maintaining the temperature of each cup. While maintaining the same temperature for each specific cup was a priority, the temperature may have fluctuated and affected the rate of photosynthesis, therefore resulting in different leaf disk total. This error could have been avoided by simply monitoring the temperature better or by possibly leaving a thermometer in the solution to assure the temperature had not moved--if it did, amend the situation as quickly as possible. Additionally, the scientists could have made use of better equipment for measuring temperature. Another possible human source of error would be imprecise measurements of baking soda. This error could have played a major role in the rate of photosynthesis. Baking soda releases carbon dioxide into the solution, therefore serving as a reactant for photosynthesis. If more baking soda was added into a cup than the others, it could result in an quicker rate of photosynthesis, therefore resulting in an incorrect count of leaf disks. This error could easily be prevented by measuring the amounts more precisely. For example, using a graduated cylinder to measure the baking soda would help eliminate this issue. In regards to experimental design, the light fixtures may not have provided the same amount of light to each cup. If one cup received more light than the others it could result in a quicker rate of photosynthesis and therefore, an incorrect count of leaf disks. One way to possibly resolve this issue is to wait for a sunnier day and place the cups on the window sill so the leaf disks all get equal light and natural light. If the weather does not permit, simply having one overhead light instead of multiple desk lamp that point in different directions will help the leaf disks receive more light. Finally, another possible procedural source of error was creating the vacuum when the leaf disks were in the syringe. When creating the vacuum, some air may have slipped into the syringe or leaf disks could have undergone damage, therefore resulting in a smaller chance that the leaf disk would perform photosynthesis in the cup. Simply being more careful when handling the syringes and creating a vacuum will help decrease the amount of air that gets into the syringe or complete eliminate the issue, therefore providing better results. Through this experiment, much knowledge was gained regarding the subject of photosynthesis. First, scientists learned that photosynthesis is, in fact, impacted by temperature. If the photosynthetic conditions include a warmer temperature, photosynthesis is more likely to proceed more rapidly. If the conditions include a cooler temperature, photosynthesis is more likely to be hindered. Additionally, photosynthesis takes place at different rates according to the concentration of carbon dioxide. As dictated by the difference in results between the control and experimental groups, carbon dioxide concentration (as a key factor in the persistence of photosynthesis) impacts the rate of photosynthesis. In cups with baking soda, and a resulting higher concentration of carbon dioxide, photosynthesis will proceed more rapidly. After this experiment, further questions have arisen concerning the impact of additional factors on the rate of photosynthesis. For example, the impact of light color on rate of photosynthesis could be investigated by setting up an experiment that sheds different colors of light on cups with potentially photosynthesis performing leaf disks. How do different light colors and light intensities impact the rate of photosynthesis in these leaf disks? Additionally, a scientist could investigate the impact of water amount on the rate of photosynthesis in leaf disks by testing the rate in which leaf disks rise in different amounts of water. How does water amount affect the rate of photosynthesis in leaf disks? Finally, the impact of oxygen concentration on rate of photosynthesis could be determined by creating different nitrogen concentrations in test cups with photosynthetic leaf disks. How does nitrogen concentration impact the rate of photosynthesis in leaf disks? This experiment has essentially opened the doors of curiosity, introducing interest to a realm of different potential impactful factors on the rate of photosynthesis in leaf disks. |
| Investigation Theme | POS |
| Grade Level | High School Students (Grades 9,10,11,12) |
| School Name | St. Joseph's Academy |
| Session | Fall 2018 |