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Photosynthesis Disc Lab- CO2 Concentrations

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Katie Frank

on 9 March 2013

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Transcript of Photosynthesis Disc Lab- CO2 Concentrations

Photosynthesis Disk Lab:
The Effect of Varying CO2 Concentrations on the Rate of Photosynthesis Katie F.
Matt M. Data Conclusion Data Analysis Data Analysis Raw Data Question Procedure Background Introduction How do different CO2 concentrations affect the floating disks’ rate of photosynthesis? Almost all life on earth is powered directly or indirectly by photosynthesis. Photosynthesis is the conversion of light energy into chemical energy which is stored in the bonds of sugar. The equation for this process is:


As the equation demonstrates an essential requirement for photosynthesis is CO2. CO2 enters the plant, while water and oxygen exit, through a leaf’s stomata. Since CO2 is essential to a plant’s ability to carry out photosynthesis, it will be the variable tested.
Using the floating disk technique to measure the rate of photosynthesis, spinach leaves will be submerged in various levels of CO2 concentration. The spinach leaves contain a cavity which holds oxygen bubbles. By creating a vacuum, the air bubbles can be drawn out which then lets the leaf disks sink to the bottom. The leaves will only rise to the surface when enough CO2 and light is present to allow the leaf disks to carry out photosynthesis and produce O2. The oxygen produced by photosynthesis makes the leaves less dense and allows them to ascend to the surface. The time it takes for half of the leaf disks to float will be used as a point of reference for comparing the photosynthetic rates for the different CO2 concentrations. 1. Prepare 4 beakers filled with various amounts of bicarbonate solution. Fill Beaker 1 only with water (no bicarbonate solution because this is the control). Fill Beaker 2 with .2% bicarbonate solution. Fill beaker 3 with 1% bicarbonate solution. Fill Beaker 4 with 5% bicarbonate solution.
2. Add 1 drop of liquid soap to each solution (avoid suds).
3. Punch out 10 leaf disks for each beaker.
4. Remove plungers from 4 syringes; place 10 leaf disks in each syringe.
5. Push in plunger until only a small of air and leaf disk remain in the barrel.
6. Remove 5cc from each bicarbonate solution using the syringes containing the leaf disks.
7. Hold finger over the syringe opening and draw back the plunger; swirl disks while holding the vacuum for 10 seconds. Then release the vacuum, letting the plunger spring back.
8. Pour disks and the solution from inside the syringe into appropriate CO2 concentration beakers.
9. Place beakers under light source; start timer.
10. At the end of each minute, record the number of floating disks.
11. When all of the disks are floating, end timer. Overall, the disks in the 1% solution rose the quickest. Some sources of error in this experiment were how the solution was made (adding the bicarbonate and water), the temperature of the solutions, or possible substances already present in the beakers prior to the experiment. This lab could be improved on by making sure the glassware was clean and improving the quality of the solution made to test the variable. Also, other variables, like temperature, light intensity, disk sizes, etc..., could be tested to determine to what extent each variable affects the rate of photosynthesis. Ultimately, the results from the experiment show that the 1% Bicarbonate solution was the optimum concentration because this solution had a higher rate of photosynthesis than the other bicarbonate solution. Ascended Disks (#) Time (minutes) Ascended Disks Each Minute Time (min) ET50 CO2 Concentrations
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