| Explore | The equation for photosynthesis is: 6CO2+6H2O-->C6H12O6+6O2; using carbon dioxide and water, light catalyzes a reaction creating glucose, which the plant can use for energy (Ensminger). Through those light reactions, before the energy converts into chemical energy, water particles are broken down into hydrogen and oxygen, thus creating glucose for the plant and releasing oxygen into the atmosphere ("Photosynthesis"). The glucose acts as food for the plants, but is also a carbohydrate, one of the most important simple sugars in the human metabolism. This process of converting carbon dioxide and water into glucose and oxygen gives the plant life. ("Photosynthesis." World of Scientific Discovery, Gale, 2011. Science in Context, link.galegroup.com/apps/doc/CV1648500461/SCIC?u=lakeorion&xid=e8cff070. Accessed 20 Apr. 2017.) (Ensminger, Peter A. "Photosynthesis." The Gale Encyclopedia of Science, edited by K. Lee Lerner and Brenda Wilmoth Lerner, 5th ed., Gale, 2014. Science in Context, link.galegroup.com/apps/doc/CV2644031715/SCIC?u=lakeorion&xid=4df52e16. Accessed 12 Apr. 2017.) -------------------------------------------------------------------------------------------------------------------------------- The leaf disks are capable of measuring photosynthesis. We made a cup with Sodium Bicarbonate, commonly known as baking soda, to our diluted dish soap and water mixture. This added CO2 in the water would later be absorbed by the leaf disks that would come in contact with them. Our control variable consisted of a cup of distilled water without CO2. To begin the experiment, the leaves were placed in a syringe, which was used as a vacuum, to release any CO2 in the plant. The syringes insured that the CO2 was all in the disks, to make them sink at the start of our experiment. The samples sink to the bottom of the cup because when the carbon dioxide is added to the leaf disks, they become more dense them the water. After the leaves are placed under the light, photosynthesis speeds up which causes the leaves to float to the top due to the release of oxygen ("Laboratory"). As the disks rise to the top of the water, it shows that the leaves are undergoing photosynthesis. The leaves that rise to the top of the water in the least amount of time are photosynthesizing more/quicker than those that stay at the bottom of the cup. The substance that worked for this experiment was the cup with the baking soda. ("Laboratory Investigations: Leaf Disk Floataion Method." Planting Science. N.p., Aug. 2016. Web. 20 Apr. 2017.)------------------------------------------------------------------------------------------------------------Chloroplasts are the world's source for receiving food, water and oxygen. They are found in plant cells and are considered organelles. They are also important for the development of fats, oils, scents, and proteins. Chloroplasts are the sites of photosynthesis and are approximately 4 to 6 micrometers in diameter (Tobin). The shape is that of a satellite dish which assists in capturing sunlight. The ability to complete these processes in one organelle signals that chloroplasts were once unicellular organisms. There can be as many as 200 chloroplasts in one cell. It is the job of the chlorophyll to absorb the sunlight to then convert it to simple sugar. Chlorophyll also gives the plant the green color in the leaves, stems, parts of fruit, etc. We believe that the plants that contain the most chloroplasts will complete photosynthesis more efficiently than the leaves that have less chloroplast (Tobin). We will be investigating how the amount of chlorophyll in a leaf will affect the speed of photosynthesis. (Tobin, Alyson K., and Katherine W. Silber. "Chloroplast." Biology, edited by Melissa Sue Hill, 2nd ed., vol. 1, Macmillan Reference USA, 2016, pp. 202-204. Science in Context, link.galegroup.com/apps/doc/CX3629800089/SCIC?u=lakeorion&xid=e0606b52. Accessed 21 Apr. 2017.) |
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| Research Question | How does the amount of chlorophyll, present in the various colors of a spinach plant leaf, affect the rate of photosynthesis? |
| Predictions | If the amount of chlorophyll affects the rate of photosynthesis then the plants containing the highest amount of chlorophyll will photosynthesize faster. _______________________________________________________________________________________________________ There is no difference in the rate of photosynthesis between a green leaf and purple leaf with various amounts of chlorophyll. |
| Experimental Design | "Laboratory Investigations: Leaf Disk Floataion Method." Planting Science. N.p., Aug. 2016. Web. 20 Apr. 2017. Materials- Hole punch 6 cups funnel Distilled Water Light source Ruler 3 Plastic Syringe Diluted Soap Pipettes liquid dropper Paper card Baking Soda Stopwatch Cotton Swab Spectrophotometer Pestle and Mortar Ethanol Graduated cylinder Scale Green leaf Purple leaf Procedure Step 1: Label each cup with one of the following plant name: green #1-#3, purple #1-#3 Step 2: Fill each cup with 4 centimeters of distilled water and add 3 drops of diluted dish soap to each cup Step 3: Hole punch 15 leaf disks from each of the plants and place them on separate paper cards Step 4: Repeat previous step with purple leaf Step 5: Remove the plunger and place 15 leaf disks into the green leaf syringe Step 6: Place plunger back into the syringe but be careful not to damage the leaf disks, leave some room between the plunger and the disks so they do not touch Step 7: Fill up the syringe with 3 cc of water Step 8: Repeat step 5-7 with purple leaf disks Step 9: Place a finger over syringe opening, pull back the plunger, to 5cc, to create a vacuum. Hold this for 10 seconds keeping the syringe vertical with the opening up, then slowly release the vacuum and remove your finger. If there is a lot of air at the top of syringe then push up on the plunger carefully removing the air but do not damage the leaf disks. You may need to repeat this up to five times, or until all the leaf disks are sunken. Step 10: Repeat the previous step with purple leaf disks. If the leaf disks are not sinking then add more diluted soap and redo the steps. Step 11: Hold the syringe horizontal over the corresponding clear cup and slowly remove the plunger and dump the water and leaf disks into the cup. Repeat with purple leaf disks Step 12: Remove any floating disks with a cotton swab, count the sunken disks to make sure each cup has at least 10 disks each. Step 13: Place the three cups with water and leaf disks under the light source, record the distance each cup is from the light source. Start a time. Step 14: Watch the timer and after every minute record the number of floating and sunken leaf disks in each cup. Record this in a table similar to the one below. Continue to record data until at least 10 disks are floating in each cup Step 15: repeat each plant type/color three times Step 16: Let the leaf disks sit in about 75% ethanol Step 17: Grind up the floating leaf disks Step 18: Remove the leaf disks from solution and record their mass Step 19: Grind up the leaves and add 10 mL of ethanol to mortal then keep grinding Step 20: Line a plastic cylinder with filter paper and pour the leaf disks with the ethanol into a test tube |
| Conclusion | If the amount of chlorophyll affects the rate of photosynthesis, then the plants containing the highest amount of chlorophyll will photosynthesize faster. This hypothesis was not supported. All 15 green lettuce leaves completed photosynthesis, on average, after 11 minutes of light exposure. The purple lettuce leaves completed photosynthesis, on average, after 13 minutes of exposed sunlight. Three trials were performed to increase the reliability of the experiment and reduce sampling error. The trend of the graphs typically showed the green leaves with a large increase in the amount of leaves being photosynthesized between 3 and 4 minutes of exposed light. The trend with the purple leaves contained had a large spike in the data between 7 to 9 minutes of exposed light. However, the green leaves averaged out to contain a count of 15.27 chlorophyll and the purple leaves averaged out with a count of 17.015. Such evidence denies the hypothesis by suggesting that leaves containing the least amount of chlorophyll will complete photosynthesis more efficiently. During the experiment, the sunken leaves used a process called photosynthesis. The process of photosynthesis begins with the two main ingredients--water and carbon dioxide. Another important factor of photosynthesis is chlorophyll, a pigment found in the organelle chloroplast, which absorbs light energy that catalyzes photosynthesis. This reaction creates oxygen gas which causes the leaf disks to float. With our P-value of .349, we are 64% confident that our null hypothesis is correct. There is not enough evidence to suggest that there is a difference between the amount of chlorophyll and the rate of photosynthesis. In order to increase the confidence level more trials could be run and various species of plants could be used. By completing more trials it would greatly reduce the large standard deviation and make the data more accurate. The green leaves had a standard deviation of 3.2 which means the average rate for all 15 leaves to float will vary either 3.2 minutes above or below the recorded average of 11 minutes. The purple leaves had a standard deviation of .577. Also, there were a few errors involved including distilled water that was spilled, along with ethanol, and there was a leaf disk that began to float a minute after it was placed under the light source. |
| Investigation Theme | POS |
| Grade Level | High School Students (Grades 9,10,11,12) |
| School Name | Lake Orion High School |
| Session | Spring 2017 |
