Photosynthesis Lab Report

Benjamin Kleveland
502
October 26, 2014
Lab 7 Report
Lights Distance and Wavelength Effect on Photosynthesis
Photosynthesis and cellular respiration are often mistaken as the same thing. Although they are similar in many ways, photosynthesis and cellular respiration are the exact opposite of each other. Not figuratively, but literally the reverse (Photosynthesis). They incorporate the others products while adding some outside energy to create a never ending cycle. This brings us to the photochemical and biochemical reactions of photosynthesis and cellular respiration. In an ordinary photochemical reaction, carbon dioxide, water and light energy produce glucose and oxygen. These products transfer to the biochemical reaction, where light
is not needed but ATP is. Glucose and oxygen then produce carbon dioxide, water and ATP (Fleming). After knowing the few basics of photosynthesis and cellular respiration, we are able to move into visualizing the process through a few experiment.
Rate of photochemical reaction by distance from a light source (Light intensity)
It is understood that the closer something is to a light source, the more intense the light is because there are less light photons per square area the further it is from the light source. So, the plants closest to the light will react more quickly than the others further away. We set up and experiment with a few tubes mixed with DPIP which turns clear when reduced (Haltsclaw). Then using a spectrophotometer, we can see the rates of reaction. There are many variables to take into consideration but the most important is the spectrophotometer and the tubes time away from the original light source. The spectrophotometer beams heavy amounts of light into the tubes so we kept them in there for as little time as possible. Considering the walk from the light sources we kept the tubes covered to prevent any external light to cause further reaction. In the end, all the tubes, except for the dark turned almost clear but at different rates. There were minor increases in the readings but that was due to not zeroing out the machine often enough. In the end, the tube closest to the light source had the most dramatic reaction. Our hypothesis was accurate in finding that there is a difference in reactions when there is a difference in light intensity.
Rate photochemical reaction by absorption spectrum
It is common to know that most plant are green but the misconception is that plants actually absorb nearly every other wavelength of visible light (PCC).
Therefore, green light will not cause any photochemical reaction to occur. In our experiment, we set up four color screens to allow only a certain wavelength of light into our tubes of spinach disks and sodium bicarbonate solution. The idea is that a photochemical reaction will occur within the spinach discs and because of the release of gasses they will begin to float (The Spectrum). Through this process we are able to see the effectiveness of the different wavelength after certain time intervals. The results were not exactly what we had expected. Factually the blue light at 440 nm should have performed the best (Light). It did worse than all the other wavelengths. And surprisingly the green light had two spinach discs floating. The result is that white light is the best for the experiment and the filters inhibit perfect reactions within the plants. Our hypothesis green light
filter.
Absorbance of the four main photosynthetic pigments
Photosynthetic pigments filter what wavelengths of light are used for photosynthesis.
Wavelengths between 500 nm and 600 nm will be the least productive wavelengths in theoretical oxygen production. The four main photosynthetic pigments are carotene, chlorophyll a, xanthophyll and chlorophyll b (Light). The pigments are the contents in this experiment. We kept them cold to prevent any other reactions from occurring while in the spectrophotometer. We changed the wavelength on the spectrophotometer to see how well the light could pass through. The efficiency of the pigments are contributed to how little light travels through the tubes, otherwise, how much they absorb. We found that the pigments had a similar affect. They followed the same line and was more affective in common wavelengths. We found that the wavelengths that mimicked green light, around 520 nm and a little further, were not absorbed. Although there was some light still absorbed there was very little efficiency. Our hypothesis held precise, testing that there was little theoretical oxygen production when the pigments were given green light.
These experiments were designed to visualize the process of photosynthesis. We looked at how light was manipulated to affects the rate at which these reactions occur. With our results, we have a better understanding of
photosynthesis.
Works Cited
Fleming, Graham R. "Photochemical Reaction (chemical Reaction)." Encyclopedia Britannica
Online. Encyclopedia Britannica, n.d. Web. 24 Oct. 2014.
Haltsclaw, Theresa. "LabBench." LabBench. N.p., n.d. Web. 26 Oct. 2014.
"Light Absorption for Photosynthesis." Light Absorption for Photosynthesis. HyperPhysics, n.d.
Web. 25 Oct. 2014.
PCC. The Success of Photosynthesis in Geranium Leaves Using Visible Light Wavelengths
Obstructed by Black Paper, and Red, Blue, and Green Translucent Filters. (n.d.): n. pag.
Pcc.edu. Portland Community College, 2012. Web. 26 Oct. 2014.
"Photosynthesis vs. Respiration." Photosynthesis vs Respiration. Diffen, n.d. Web. 25 Oct. 2014.
"The Spectrum." The Spectrum. Botany, n.d. Web. 26 Oct. 2014.