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Most photosynthetic pigments ,absorb strongly in blue light " ...
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/ligabs.html
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Background-By performing this experiment we hope to learn more on photosynthesis and the light that is most effective in allowing plants to photosynthesize. After researching previous experiments done on this topic, I found a similar experiment done by three scientists in Colorado in 2003.
These scientists used three different colors to our two, red, blue, and green. They were also testing to see which of these lights would allow plants to photosynthesize the fastest. However, instead of using our procedure, injecting oxygen into the leaves of the plants, they placed 5 grams of the plant into a gas chamber with two containers filled with water behind it to maintain a good temperature. They then placed a light over the plant and ran three separate tests for each color measuring the amount of CO2. They thought that the blue light would use the most C02 because blue light absorbs the most light and the most energy and C02 is used in photosynthesis, but their results proved otherwise. Their results showed that blue used the least amount of C02, red used the medium amount of C02, and green used the most C02. Their hypothesis was proved wrong by their results, but they still believe that their hypothesis is the most logical answer. Therefore there must be flaws in their experiment which there can be in any experiment that is done, including ours. However, our hypothesis contradicts theirs; we believe
that white light will photosynthesize plants more quickly than blue light, or the white light. Not only do we hope to learn more on photosynthesis by performing this experiment, but I also hope to be able to better understand light and how it is absorbed in plants.
Conclusion- Through our experiment we discovered that there are different rates of photosynthesis that occur in different light conditions with the answer to our question we also discovered that our hypothesis was correct.
The hypothesis that we found correct was that disks in the normal white light would photosynthesize faster than the ones that were under the blue light. This is supported by our results that the average time of the white light was 4.892 seconds while the blue light average was 9.544 seconds. There are possibilities of errors that could not be controlled in this experiment that follow, one of the disks could have been healthier than the other (less damage to the leaf), rising temperatures of
he light bulbs and the fluctuation of the temperature in the room. I think that if we did this experiment again we could have tested more than 20 disks, maybe a different color of light, and a C-4 plant. Also, we could have controlled the plant before we used it in our experiment and maybe used a younger plant so that it maybe would not have photosynthesized as much before our experiment. Though, I think that everything else worked well and we had a successful experiment and learned a lot about plants and how they photosynthesize.
Bibliography- attached to the back
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0CGEQFjAG&url=http://www.plantingscience.org/index.php?module=pagesetter&type=file&func=get&tid=2&fid=presentation&pid=2082&ei=zqVsU-fYHoeg7Abp_4DYBw&usg=AFQjCNHFbJBgsA06gIZsm28h_o7cHPALbQ&bvm=bv.66330100,d.ZGU
Basic plant biology ...
Teaches about white light ...
For years ,now ...
As nature does ,also....
Effect of Different Colored Lights on Photosynthesis
Anastasia Rodionova, Cassidy Davis, Sara Cucciniello
CU Boulder, Fall 2003
Our experiment tested which color (red, blue, green) would influence the plant to produce the most amount of photosynthesis. There are four main photosynthetic pigments found in the chloroplast of the plant called chlorophyll a, chlorophyll b, xanthophylls, and carotenes. All these pigments absorb light and possibly utilize the light energy in photosynthesis. Light energy is essential for photosynthesis. An initial experiment showed that all the pigments at peak absorbance showed violet/blue light at the highest level, orange/red light as the second highest, and yellow/green having the lowest level of absorption. We hypothesized that photosynthesis was affected by the light absorption rate.
To test this we used about 5 grams of leaves for each trial, and placed them in a gas chamber. On two sides of the gas chamber we placed two clear containers filled with water to serve as the temperature regulators. Behind the water containers we placed lights directed at the plant. We ran three trails for each different leaf we used. Each trail consisted of measuring the amount of CO2, with a CO2 gas sensor under blue light, red light, and green light. We made sure to switch the order of colors in each trail as an experimental control, to minimize error. Since we know that photosynthesis requires CO2, and we know that blue light pigments absorb the most light energy, we predicted that under blue light the most CO2 would be used.
Our results showed the least amount of CO2 under blue light (mean: -8.1 ppm/min/g), medium amount in the red light (mean: -1.04 ppm/min/g), and the most amount in the green light (mean: 4.7 ppm/min/g). But our t-tests proved our results insignificant (p>0.05).
Our results are contradictory with our hypothesis, based on our statistical results. There were several problems with our experiment that could have been taken into consideration. First, when taking respiration rates the foil wasn’t covering the chamber all the way letting some external light in. Second, the colored cellophane only allows approximately 70% of light through; this might have prevented the plant from absorbing the amount of light energy needed to have a significant photosynthetic rate. Third, the fast paced moving between trials lost time and efficiency. By having short trials (2.5 min.) we might not have allowed the plant enough time to adjust its photosynthetic rate to the different wavelengths of light energy. Plus by moving the plant, and switching from cellophane to foil (or vise versa), might have
screwed up(!) the photosynthetic cycle by exposing it to white light.
Other students who did the same experiment had results that also supported that blue light was not responsible for the rate of photosynthesis. Experiments Warsh et al. 2001, Bahramzadeh et al. 2001, and Whorley and Weaver. 2002 all showed that red had much higher rates of photosynthesis than blue, but these experiments had fewer trials or shorter trials. Lots of other students also used white light as a controlled variable; this would have been a good thing to put into our experiment to give it some comparison.
Considering that not all light energy is used for photosynthesis we propose an alternative hypothesis. In a previous experiment the pigment xanthophylls absorbed significant amounts of blue light.
In new research it is found that this pigment could be an important component in a process called energy dissipation(heat...high energy photons,you see... ) rather than photosynthesis. In order to not overwhelm the plant with photosynthesis and respiration, this photon energy goes to other functions or formations of the plant. Further research on the function of xanthophylls will need to be conducted in order to understand the processes of plant function
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http://spot.colorado.edu/~basey/photocolor1.html
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