Introduction: Photosynthesis is an important reaction that occurs daily in a variety of plants. The reaction, which takes in carbon dioxide from the air and water from the ground, creates products of glucose and oxygen. However, the system could not run without light energy provided by the sun or other sources of light. In addition, different colors of light provide more energy than others to the plant. The group chose to test the environmental variable of light color by testing the effect of blue light as the group wanted to find which colors of light provided the most energy to increase the rate of photosynthesis and why.
The study of the effect of blue light vs normal light is important because the results could change the way agricultural production is done. For example, tests could be done on corn plants to see under which color light, blue or white, it receives the most energy for photosynthesis, resulting in more growth and production of the plant. Many experiments have been performed to test the effect of light color on photosynthesis. A study done on sweet peppers, Capiscum annum, tested the photosynthetic rate on the plant (which bears peppers) using red, white, blue, and green light. The plants grown under blue light showed lower photosynthetic rates than the rates of the other colors over a period of five weeks. The blue light produced less peppers through the course of the experiment compared to the other colors (Murakami, 2013). While blue light seems to have hindered the production of sweet peppers, it helped to increase the photosynthetic rate in a different experiment performed on coral. The study found that blue light resulted in their coral growth than that of red light and white light. The coral, Stylophora pistillata, is naturally pink, which explains why the scientists behind the study concluded that the blue light would help the coral grow light; red and white light is more easily reflected than the blue light, which decreases its photosynthetic rate (Wijgerde et al., 2014). Both experiments differ as they either conclude that blue light decreases photosynthetic rate or increases photosynthetic rate. This topic needs further study as the results are inconclusive on the effect of blue light vs white light as a whole. Further, this topic deserves continued research in that the changes it could create in United States agricultural businesses could boost food production and the economy.
The group hypothesized that shining a white light on a green leaf will result in a higher photosynthetic rate compared to blue light. The group predicted that the white light would be absorbed easier and provide more energy for the leaf compared to the blue light because the leaf contains a mixture of wavelengths of colors. Blue would be absorbed fairly well, in addition, but not as easily as white light. The group used the leaves from a common bean plant, Phaseolus Vulgaris, for the experiment.
Methods: To begin the experiment, a complex piece of equipment was set up. First, the group selected a leaf and, still attached to the plant, placed it into the leaf chamber and sealed in. The chamber was placed 11 cm below the lower rim of a light fixture with the lights off. This chamber was connected to a computer that read the Light Intensity vs. Time (Figures 1 and 2) and Percent Oxygen Released vs. Time (Figures 1 and 2) during photosynthesis in the leaf. An inlet gas port located on the top of the sealed leaf chamber was opened to allow oxygen to escape. The green “Collect” button was hit on the PhotoLab program on the computer. The group blew Carbon Dioxide through a tube with a straw connected to the leaf chamber. After a significant drop in oxygen levels, the tube was clamped and the inlet gas port was plugged, giving the chamber a seal with it only containing carbon dioxide. The group waited several minutes for oxygen levels to even out and then the group turned the light on while also placing a 250 mL beaker of water on top of the chamber. After 15 minutes, the group replaced the beaker of water with a new beaker of fresh water; the beaker of water serves to help preventing the leaf from over heating. They group let the experiment continue for 30 minutes and recorded data for the control, or the white light experiment. The procedure was repeated with a new leaf and a blue filter on the light to test the effect of the blue light on photosynthesis. Before further calculations could be done, the leaf surface area for each leaf for both experiments was measured. For the white light experiment, the leaf was measured as 0.003075 m^2 and the surface area for the blue light experiment was measured as 0.0034875 m^2. The leaf was detached from the plant using scissors to measure the surface area using a translucent grid. Using the surface area and the data collected from the computer software, the group was able to calculate the photosynthetic rates for each experiment.
Results: The computer software provided the data and graphed Oxygen Released vs. Time and Light Intensity vs. Time; there are two graphs for white light/experiment one (Fig 1) and two graphs for blue light/experiment 2 (Fig 2). To calculate photosynthetic rate for each leaf, the group used the equation provided. The rates for each phase for white light and blue light is provide in Figure 1A and Figure 2A, respectively. From the data, it can be concluded that the white light had a higher photosynthetic rate compared to the blue light. This justified the group’s hypothesis that blue light would have a slower photosynthetic rate than the white light. Possible sources of error in the experiment include the beaker of water not capturing all the heat from the lamp or the surface area being counted incorrectly from the small squares on the grid. The research done in the experiment shows the potentials of colored light on photosynthetic rate and it would be informative to further study the effects of artificial, colored lights, and natural light from the sun.