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Effect of pH on rate of photosynthesis in spinach leaves

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Sorna Sarker

on 28 January 2013

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Transcript of Effect of pH on rate of photosynthesis in spinach leaves

1. Get 5 cups.
2. Label each cup with pH 1,4,7,9,11.
3. Fill each cup with the appropriate solution until it is 3cm full.
4. Put a little bit of soap on the surfaces using a pipette.
5. Label 5 syringes with the 5 pHs.
6. put 10 leaf disks in each syringe.
7. push all the air out of the syringe without damaging the leaves.
8. Take 5 cm of the appropriate solutions into each syringe.
9. Close the top of the syringe and pull back to create a vacuum and take out the O2 in the leaves. Do this 2-3 times or until the leaves fall to the bottom.
10. Pour the leaves into their corresponding cups and place them all under the light.
11. Start the timer.
12. After every minute, record the number of disks floating in each cup until all the leaves are floating.
13. Repeat this for one more trial.
14. Analyze data/results. Introduction Materials and Methods Results Discussion References How pH of the water source affects the rate of photosynthesis in spinach leaves By: Sorna Sarker, Angeliz Vargas, Justin Morin Research Question Background Hypothesis Materials Procedure Graph Data Table Variables and Groups Set-Up Will a basic, neutral, or acidic environment maximize the rate of photosynthesis? "Optimum pH for life." Retrieved 27 January 2013, from: http://www.cees.iupui.edu/Education/DSE/resources/Nokia/pH_Nokia.htmEPA. 4 2012. If both acidic and basic
pHs can slow down or prevent photosynthesis, then a neutral pH water solution will maximize the rate of photosynthesis in spinach leaves. How does pH affect the rate of photosynthesis in spinach? If both acidic and basic pHs can slow down or prevent photosynthesis, then a neutral pH water solution will maximize the rate of photosynthesis in spinach leaves. It was difficult to come to a conclusion, but if one was to be made, the neutral pH would have the fastest rate of photosynthesis. The results show that the different pHs have an effect on the rate of photosynthesis. The more acidic and the more basic, the slower the rate of photosynthesis. The more neutral, the faster the rate of photosynthesis. Although our hypothesis was neither contradicted nor justified, the results were still unexpected. The 10 disks in the pH4 and pH 9 solution rose after three minutes, which could have occurred because of the sources of error. In trial two, the disks in the pH 1 solution were up before the first minute, which could have occurred because of the syringes. The defective syringes did not create a vacuum and the solution was slowly escaping, making some of the disks float as soon as they were placed in the cups. These results are inadequate, so adjusting the procedure to reduce the sources of error will yield more desirable results. • unequal light
• unequal sodium bicarbonate
• bad syringes, no vacuum
• unequal amount of liquid solution Further Study: Question: Hypothesis: Conclusion: Sources of Error: We could fix the sources of error if we tested the pH of the water again. We could also test the pH but of a different plant leaf to see if the pH to maximize the rate of photosynthesis is similar or different to spinach leaves. Testing the rate of photosynthesis with different light intensities would show what light intensity maximizes photosynthesis. • Baking soda (sodium bicarbonate)
• Liquid soap
• 5 plastic syringes
• Spinach leaves
• Hole punch
• 5 clear plastic cups
• Timer
• Light source
• pH paper
• Sulfuric acid
• Sodium Hydroxide (.4%)
• Buffer solution pH 10
• Buffer solution pH 4 - prepare 300ml of bicarbonate solution for each trial
-cut out 100 leaf disks (10 per cup, 5 cups, 2 trials)
-prepare solutions of pH 1,4,7,9,11
- set up a light source on a ring stand dependent variable: number of floating leaf disks

independent variable: pH of the water source

control groups: temperature, distance from/source of light EPA. 4 December 2012. "Effects of Acid Rain on Forests, Other Plants." Retrieved 27 January 2013, from: http://www.epa.gov/acidrain/effects/forests.html Exploring Life Community. Retrieved 27 January 2013, from: http://uhohacidrain.blogspot.com/ "Acid Rain." Retrieved 27 january 2013, from: http://uhohacidrain.blogspot.com/ The data obtained from this experiment is very inconclusive. This data that was recorded during both trials did not seem to make sense in context of our experiment. The results were very odd, and did not seem to reflect a specific pattern. For example, during our first trial, at pH 1 it took 6 minutes for all 10 leaf disks to rise. During our second trial, however, it took less than a minute for all the disks to rise. Another anomaly in our data was during the two trial for pH 7. In trial one it took less than a minute for all 10 disks to rise. In the second trial at the same pH, it took almost 4 minutes for the same number of disks to rise. This also happened at pH 9, to a lesser extent. It took 2 minutes longer for the 10 disks to rise in the second trial at pH 9 than in the first. The most interesting thing, though, is that although there were large gaps in data between the first and second trial, the data that did hold true between the two trials was the comparison of pH 11 to the rest of the pH's. In both trials, at pHs 1, 4, 7, & 9, all 10 disks were floating within 5-6 minutes. However, in both trials, 10 disks sat in the pH 11 solution for over 18 minutes each and neither time did more than 5 disks begin to float. Photosynthesis is a process used by autotrophs that
converts light into chemical energy 6CO2 + 6H20 + Light ----> C6H12O6 + 6O2 oxygen is a byproduct leaves exposed to acid rain
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