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Transcript of Photosynthesis lab
Photosynthesis In Spinach Leaves By: Rafid, Safwat, Saheeb The Overview Question Hypothesis Materials Light source
100 mL graduated cylinder
8 plastic cups
100 mL distilled water
straw to stir the solutions Procedure 1) Prepare 50 mL of 2, 4 and 6 percent bicarbonate solutions.
2) Pour the solutions into plastic cups and label them accordingly.
3) Prepare a control group with only 50 mL of distilled water.
5) Using a pipette, place 3 drops of liquid soap into each cup.
6) Using a hole puncher, cut out 40 uniform disks from a spinach leaf, 10 for each cup.
7)Draw the gases out of the spongy mesophyll tissue and infiltrate the leaves with the sodium bicarbonate solution by performing the following steps:
a. Remove the piston or plunger from both syringes. Place the 10 leaf disks into each
b. Replace the plunger, but be careful not to crush the leaf disks. Push in the plunger
until only a small volume of air and leaf disk remain in the barrel (<10%).
c. Pull a small volume (5 cc) of sodium bicarbonate plus soap solution from your
prepared cup into one syringe and a small volume of water plus soap into the
other syringe. Tap each syringe to suspend the leaf disks in the solution. Make
sure that, with the plunger inverted, the disks are suspended in the solution. Make
sure no air remains. Move the plunger to get rid of air from the plunger before
you attempt Step d.
d. You now want to create a vacuum in the plunger to draw the air out of the leaf
tissue. This is the most difficult step to master. Once you learn to do this, you will
be able to complete the entire exercise successfully. Create the vacuum by holding
a finger over the narrow syringe opening while drawing back the plunger (see
Figure 6a). Hold this vacuum for about 10 seconds. While holding the vacuum,
swirl the leaf disks to suspend them in the solution. Now release the vacuum
by letting the plunger spring back. The solution will infiltrate the air spaces in
the leaf disk, causing the leaf disks to sink in the syringe. If the plunger does
not spring back, you did not have a good vacuum, and you may need a different
syringe. You may have to repeat this procedure two to three times in order to
get the disks to sink. (If you have any difficulty getting your disks to sink after
three tries, it is usually because there is not enough soap in the solution. Try
adding a few more drops of soap to the cup and replacing the liquid in the
syringe.) Placing the disks under vacuum more than three times can damage the
8)pour the disks and the solution from the syringe into the labeled plastic cups
8) Place all 4 cups under a light bulb for 10 minutes
9) At 60 second intervals, count the number of disks floating in each cup. Record data
10) Repeat procedure multiple times for precise results. First an introductory experiment was conducted to explore photosynthesis in general. This portion was used to get acquainted with experimental procedure and to investigate the many variables that control photosynthesis. In the experiment equal sized spinach leaves were put into different concentration of bicarbonate solution. The rate at which they floated was a measure of how fast photosynthesis occurs. The variable tested by the group was CO2 concentration. The results from our experiment showed that the amount of CO2 in the environment of the spinach had an effect on the rate of photosynthesis. What is the effect on the rate of photosynthesis of Spinach leaves when they are in an environment of different concentration of carbon dioxide? If you add 10 uniform sized spinach leaf disks into different bicarbonate concentrations, then the disks in the highest concentration will float faster because they'll have a higher rate of photosynthesis. Variables: Independent variable: bicarbonate concentration
Dependent variable: number of disks floating after a minute
Control: amount of solution, size of leaf disks, amount of time cup is under light bulb, number of drops of liquid soap/ type of liquid soap The results suggest carbon dioxide concentration effects the rate of photosynthesis. Our hypothesis that an increase in carbon dioxide concentrations leads to an increase in the rate of photosynthesis is supported by our experiments’ results. In both trials 1 and 2 the cups with the highest concentration of CO2 contained the highest amounts of floating leaves. Specifically in trial 1, all 10 of the leaves in the 6% carbon solution floated by the seventh minute. The disks in the 4% solution lagged behind to reach 10 floating spinach disks a minute later while only 9 disks in the 2% floated by the end of the 10 minutes. Without a source of carbon dioxide for photosynthesis, the 0% solution was not able to produce any floating disks. Trial 2’s results were similar in that the 6% solution had the highest amount of floating leaves the quickest. The 4% and 2% had respectively 3 and 1 floating disk(s) by the end of the 10 minutes. Again, the 0% concentration contained no floating disks.
Some sources of error include unequal sharing of light, problems with creating a vacuum, and the accidental deaths of the spinach disks. In order to keep the amount of light same throughout all the cups, one light source for every cup is necessary. Further experience with creating a vacuum and greater carefulness with the leaf disks can eliminate the latter two errors. Future experiments could include the controlled effects of different amounts of light or the effects of different concentrations of carbon dioxide on varying plants. By studying relationships between the amount of available light and the amount of carbon dioxide, a more accurate conclusion can be made about the rate of photosynthesis in plants.
In conclusion, our experiment supported our hypothesis, but future research could help in giving specific insights on the variables that increase or decrease the rate of photosynthesis Trial One key:
diamond-control, square-2 percent,
triangle-4 percent, x- 6 percent Trial Two key:
diamond-control, square-2 percent,
triangle-4 percent, x- 6 percent Trial One Table Trail Two Table Photosynthesis is the process by which light energy is converted to chemical energy. Carbon dioxide is one of the main components of this process. So we looked at the effect that this molecule has on the effectiveness of photosynthesis in different environments.