Photosynthesis Lab

Higher Level BiologyPhotosynthesis Lab

Marissa Record Candidate #: 002140017

4BDecember 10, 2010

Marissa Record4B HL Biology

Investigate a factor influencing the rate of photosynthesis

Question: How does the color of the water in which a spinach cutlet is placed affect the rate of photosynthesis?

Variables:Independent: color of waterDependent: rate of photosynthesis

Constants: Temperature, concentration of light, movement of environment, type of leaf, size of leaf cutlets.

Control:One test will be run without any food coloring.

Research: Under normal circumstances, leaves float because of the O2 in them. When a solution with sodium bicarbonate infiltrates the leaves, they will sink and be given a source of CO2 so photosynthesis can occur. Research shows that when the light is red or a color with low frequency, photosynthesis occurs faster. I am going to test whether the same applies if the color is in the water rather than from a light source.

Hypothesis: If the water is colored with a low frequency color, red, then the rate of photosynthesis will be higher than if the water is colored with a high frequency color, such as blue. In the colors in between, such as yellow and green, the photosynthesis will be progressively lower as it nears blue.

Materials:Fresh spinach leaves (Spinacia oleracea)Hole punch60 mL syringeSodium bicarbonateLiquid SoapBeakersTimerFood Coloring:

RedBlueGreenYellow

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Design:

Procedure:

1. A .2% bicarbonate solution was made by placing 1/8 of a teaspoon of sodium bicarbonate into 300ml of water.

2. A drop of diluted liquid soap was added to the bicarbonate solution, which allowed for the bicarbonate solution to be taken into the leaf.

3. The hole-punch was used to create 25 uniform spinach disks.4. The syringe was opened and the disks were placed inside and the plunger

was placed back inside the syringe.5. A small amount of the sodium bicarbonate solution was placed in the syringe.6. The tip of the syringe was covered by a finger and the plunger was drawn

back to create a vacuum, which was held for approximately 10 seconds, constantly being swirled.

7. The vacuum was released, and most of the disks sunk. Step 6 was repeated until all disks sunk.

8. The disks were placed into beakers, 10 disks to each of the five beakers, and half the solution went to each beaker. 100 ml of bicarbonate solution was added to each beaker.

9. In one beaker, 2 drops of red food coloring were added, and to another, 2 drops of blue food coloring, to another, 2 drops of yellow, and to another 2 drops of green. One beaker was left without any color.

10. The beakers were then each placed an equal distance from a light source.11. The number of disks floating in each beaker was counted and recorded each

minute, until all disks were floating.12. Steps 1-11 were repeated 3 times.13. Graphs were drawn, and conclusions were made.

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Trial 1:Minutes ±1sec

Number of floating disks:No Color

Number of floating disks:Red

Number of floating disks:Blue

Number of floating disks:Yellow

Number of floating disks:Green

12345678910111213141516171819202122232425

Mean time for one disk to float:No Color: Red:Blue:Yellow:Green:

Standard Deviations:







1

4


2345678910111213141516171819202122232425


Standard Deviations:







123456

5


78910111213141516171819202122232425


Standard Deviations

Trial 1: Number of Floating Disks Per Minute

6


0

1

2

3

4

5

Series1Series2Series3Series4Series5


No ColorRedBlueYellow Green

#of floating disks

7


Min

utes ±1 se

c 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 340

1

2

3

4

5



#of floating disks


8


Min

utes ±1 se

c 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 340

1

2

3

4

5


Conclusion:The results show that the leaf disks that were placed in higher frequency colors went through the process of photosynthesis at a slower rate than the disks that were placed in high frequency colors. This result supports the hypothesis, although the leaves with yellow food coloring, which is a slightly higher frequency than red, did photosynthesize more quickly than leaves in red.

Evaluation:The fact that there is such a drastic difference between the numbers of minutes it took for the no color sample and the blue sample in the results of this experiment could be explained in several ways. One explanation is that it is the frequency of the color that affects the rate of photosynthesis. However it would be unreasonable not to consider that it could be the effect of the food coloring on the leaves themselves seeing as even yellow photosynthesized at a slower rate than the sample without food coloring. Another possible explanation of the results lies in whether the rate of photosynthesis is affected by the lightness or darkness of the water, and how much light can penetrate it, not the light itself. This theory is supported by the fact that the yellow samples photosynthesized more rapidly than the red samples, though the frequency of red is lower.

Errors:

#of floating disks


9


Although the results were expected, errors may still have occurred. One such error could be in the temperature of the samples. Since there was no heat sink placed between the samples and the light source, the samples directly in front of the light could have had a slight increase in temperature causing them to photosynthesize more rapidly, even though all samples were an equal distance from the light.

Bibliography:http://spot.colorado.edu/~basey/bluer.htmhttp://www.elbiology.com/labtools/Leafdisk.html

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http://www.elbiology.com/labtools/Leafdisk.html

http://spot.colorado.edu/~basey/bluer.htm

Photosynthesis Lab

Documents

number of disks

blue number of floating

red number of floating

floating disks trial

floating disks conclusion

leaf disks

sec disks

minute number of s floating