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AP Photosynthesis Lab

Using spinach leaves to test how rate of reaction is affected by the amount of available carbon. By Hanson Wu and Hannah Williams

Hannah Williams

on 8 March 2013

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Transcript of AP Photosynthesis Lab

1) Punch out 24 disks from spinach leaves. Be sure to avoid any large veins or stems.
2) Fill each of four beakers with water, .2%, .4%, and .6% of bicarbonate solution approximately 1 inch from the bottom and label the beakers.
3) Add a drop of dilute soap solution to each beaker
4) Place 6 leaf disks in a syringe, fill as needed with a solution, and putting your thumb over the tip of the syringe, pull the piston to create a vacuum. Repeat until disks sink in the syringe. Empty syringe back into the used solution.
5) Repeat step 4 for remaining 3 solutions
6) Fill a large tank with water and put infront of lamp.
7) Place each of the beakers infront of the light source but behind to tank so the tank will absorb the heat from the lamp. Start the timer.
8) Record at what time each disk from each beaker floats to the top of that beaker in a data table. Procedure Raw Data Data Analysis Conclusion Background In this lab we will be attempting to
test the effects of bicarbonate concentration
on the rate of photosynthesis. Photosynthesis replenishes the Earth's atmosphere with oxygen. The rate of photosynthesis can be measured by the accumulation of product which in this case is oxygen. If enough oxygen accumulates, the leaf disk will float. Bicarbonate is necessary for the disks to undergo photosynthesis. Soap
acts as a surfactant to allow the hydrophobic
surface of the leaf to draw in the
solution. First Experiment Experiment Two Our experiment to test the effects of bicarbonate concentration on the rate of photosynthesis obviously had many errors in it due to the seeming randomness of our data. The first trial we conducted had way too many errors to the point where the data was pretty much unusable except as a source of error. The second trial achieved much better results. Generally, based on the ET50 times (with the exception of the .4% solution), as the concentration of bicarbonate increases, the rate of photosynthesis increases. There were many sources of error. Since two separate people did the vacuuming of the gas out of the leaves, we could've pulled more air out of one set than the other. Since some solutions had the leaves prepared earlier than others, the bit of light they were exposed to before the testing period could have caused then to start photosynthesizing early. The placement of the beakers behind the light were also not equally distant and that could have affected the amount of light each beaker received. In order to conduct further research, the experiment could be expanded to a much broader scale. 100 leaves per solution could be used instead of a measly 6; solutions ranging from 0.0-1.0% could be used at intervals of 0.1% AP Photosynthesis Lab Hannah Williams
Hanson Wu
Hunt- 6h period Amount of Time for Disc to Rise (min) Second Experiment Amount of Time for Disc to Rise (min) Solution Discs Placed In Solution Discs Placed In ET50 ET50 ET50 is the time it takes for 50% of the leaves to float. ET50 is the time it takes for 50% of the leaves to float
and is also essentially the rate of reaction. Experiment One Observations As the piston was pulled back, air bubbles floated to the surface of the solution very quickly.
It usually took 3-4 pulls of the syringe for all the discs to float to the bottom, some discs took longer than others to fall.
There wasn't any observable (rise in discs) photosynthetic activity until after the discs were placed in front of the lamp.
Many air bubbles appeared at the bottom of the beakers as the reactions progressed. Greatest to least, the amount of air bubbles was: 0.4%, 0.2%, 0.0%, and 0.1%.
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