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Photosynthesis Lab--Color

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Delaney Emma

on 31 January 2013

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Transcript of Photosynthesis Lab--Color

The Effect of Light Wavelength on Photosynthesis Rates By: Delaney Smith
Emma Ackermann Procedure and Results Discussion Concepts Actual Results vs Expected Results Sources of Error Graph 1 Safety Precautions Results Procedure Flow Chart Question Hypothesis Background Introduction How does the wavelength of light affect the rate at which photosynthesis occurs? If the rate of photosynthesis increases as wavelength increases, then the 650 nm light (red) will have the lowest ET50, followed in increasing order by 570 nm (yellow),
510 nm (green), and 475 nm (blue). Aprons and protective eyewear should be worn in the lab
Keep solutions away from electrical cords to avoid electric shock
Handle glassware with care; report any broken glass to the supervisor
Dispose of all materials appropriately The highest rate of photosynthesis was produced by the wavelength of 570 nm (yellow light). Second highest was by 650 nm (red light), third was 510 nm (green light), while 475 nm (blue light) did not have any effect on the spinach circles (no photosynthesis occurred).
It should be noted that the control experiment (white light) actually yielded the highest rate of photosynthesis.
This data was compared to that of the standard action spectrum for photosynthesis of visible light (this profiles the relative effectiveness of different wavelengths of radiation in driving the process of photosynthesis). The results of the standard action spectrum is that 475 nm (blue light) and 650 nm (red light) have the highest rates of photosynthesis. When we started this lab, we expected the highest rates of photosynthesis to be at the wavelengths of 475 nm (blue light) and 650 nm (red light), and the lowest to be at 510 nm (green light) and 570 nm (yellow light) due to the action spectrum of visible light. Violet-blue and red light work the best for photosynthesis because they are absorbed by pigments in the chloroplasts, while green and yellow light are reflected (transmitted).
However, at the end of this lab, we discovered that the most effective wavelength was actually 570 nm (yellow light) and the least effective was 475 nm (blue light). This discrepancy can be accounted for by the differences in brightness of the lights. The yellow, which yielded the highest results of all of the colors, was notably the brightest light of the four colored bulbs, even though each was marked as the same wattage. The difference in brightnesses easily could have skewed the data. Furthermore, the colors of some of the lights were not very true to actual color. For example, the blue light appeared slightly greenish, which would make it closer to the 510 nm area of the spectrum than the 475 nm. 1) The lights were marketed as having the same wattage, but a few colors, particularly yellow, seemed to be brighter than others. This could introduce brightness of light as a confounding variable to the experiment.

2) The lights gave off a significant amount of heat as the experiment went on. This could introduce temperature as a confounding variable to the experiment.

3) Some discs had to be vacuumed more times than others, which might have permanently collapsed the airspaces, making it difficult for them to photosynthesize. Conclusions Literature Cited Redesigning the Experiment Make sure each disc is vacuumed the same amount of times; if disc is still floating after a set amount of times vacuumed, then discard the disc and try again with a new one
Shine the lights from above the beakers to better simulate the mid-day sun and to distribute light uniformly to each beaker
Try to obtain different colored lights that maintain the same brightness; if this is not possible, shine light through different transparencies of plexiglass in order to even out the brightness of the lights http://www.slideshare.net/lenaboon/colors-effect-on-photosynthesis-lab
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookps.html Light is electromagnetic energy
Chloroplasts capture electromagnetic energy in the form of light via various pigments in the thylakoid membranes
Chlorophyll is not the only pigment that can absorb light - it absorbs mainly blue and red light(475 nm and 650 nm, respectively)
Chlorophyll A is required to start photosynthetic reactions
Accessory or Antenna pigments capture other wavelengths of light This experiment deals largely with the biological process of photosynthesis. Photosynthesis is the conversion of light energy into chemical bond energy. The equation for this process is:
6CO2 + 6H20 -> C6H12O6 + 6O2
The location for photosynthesis in plants is in the chloroplast, a membranous structure within individual cells. It occurs in two different stages: light-dependent reactions and light independent reactions. Both processes occur in the chloroplasts and go through a series of stages to produce glucose (C6H12O6) and oxygen (6CO2).
In order for photosynthesis to begin, light and carbon dioxide must be taken in through the leaf's stomata, tiny openings on the surface of the leaf. After the reactions are completed, oxygen is released into the leaf and into the surrounding environment via opened stomata. In this experiment, the released oxygen will be used to measure photosynthesis rates in discs cut from spinach leaves.
After being put through a vacuuming process, the airspaces in the mesophyll layer will be compressed, removing any oxygen within them. This will cause them to sink in the bicarbonate solution. As they photosynthesize, however, the produced oxygen will accumulate in the mesophyll airspaces, decreasing the leaf's density and allowing it to float again. The time it takes for half of the leaf discs to float will be used as the benchmark for comparing the photosynthesis rates for each tested variable. Graph 2 Data Table 1 Data Table 2 Expected Graph Actual Graph http://blog.ecocityhydroponics.com/wp-content/uploads/2011/01/photosynthesis.jpg 1) A wavelength of 575 nm (yellow) produces the fastest rate of photosynthesis when shone on discs of spinach leaves. [This is not expected; 650 nm (red) and 475 nm (blue) should produce the fastest rates]

2) The wavelength 475 nm (blue) does not induce photosynthesis whatsoever when shone on discs of spinach leaves. [This is not expected; 475 nm should produce the second-fastest photosynthesis rate (second only to 650 nm)]

3) Of the wavelengths that do induce photosynthesis when shone on discs of spinach leaves (510 nm, 570 nm, 650 nm), a wavelength of 510 nm (green) produces the slowest rates of photosynthesis. AP Investigative Labs
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