Why Does Blue Have The Highest Rate Of Photosynthesis

The data found in this experiment supported the initial statement in the hypothesis, that blue would have the highest rate of photosynthesis (see Figure 7). The second part of the prediction was refuted by the data, as green had a higher rate than both yellow and red. This result seems to go against the experiment, however the answer is in Figure 5. When adding green food coloring to the solution (see Methods) dilution also took place. When comparing the wavelength of 540 nm (see Tables 1 & 2) with the its corresponding color in Figure 5, the green is almost a turquoise. Since this color is closer to blue, the fastest photosynthesizing wavelength, it answers the question as to why it came before red and yellow (see Figure 7).
From the results, it can be concluded that the level of photosynthesis depends on the level of energy the light carries, and its absorbency. The energy of the light is inversely proportional to the wavelength, so a long wavelength like red carries little energy but a short wavelength like blue carries a lot. But if this is true, then why does red appear as it does in Figure 7 when it carries the least energy? Well, this is because it is highly absorbed, so a lot of the light is taken in, and is not reflected. Whether or not the light is reflected matters far
more than the amount of energy it may hold.
To further explain the trough between the colors of green and yellow (see Figure 7), the absorption spectra shows how the different side chains in chlorophyll a and chlorophyll b result in slightly diffierent absorptions of visible light (Figure 2). Light with a wavelength of 460 nm is not significantly absorbed by chlorophyll a, but will instead be captured by chlorophyll b, which absorbs strongly at that wavelength. The two kinds of chlorophyll in plants complement each other in absorbing sunlight ("The Visible Light Spectrum." UXL Encyclopedia of Science). Plants are able to satisfy their energy requirements by absorbing light from the blue and red parts of the spectrum. However, there is still a large spectral region between 500 and 600 nm where chlorophyll absorbs very little light. Thus, plants appear green because this light is reflected.
During the experiment, some of the leaf disks would not rise from the bottom of the beaker. These leaves were outliers on the far right of the graphs of the data, causing the number of trials to decrease. However, this did not create a problem amongst the final results, as the the information that was gathered mimicked the photosynthetic curve seen in Figure 5.
It was realized that light intensity is another variable which may affect results, so it was taken into consideration.
To ensure accurate results, these other factors were kept constant throughout the lab: temperature, concentration of NaHCO3, technique and apparatus. If the temperature was altered it would affect the rate of enzymes which control the reaction, and will make it faster or slower. Therefore, the concept of varying wavelengths becomes obsolete when it's dependant on several other factors. Also, if the concentration of NaHCO3 increased or decreased, it would affect the rate of photosynthesis, as all plants requires carbon dioxide in one form or another to
photosynthesize.
For future experimentation, more colors of the visible light spectrum should be added, as this was a major limitation to the experiment. Colors such as orange and violet would be tested to get a more comprehensive and seamless set of data. This would develop a stronger curve that would reflect that of Figure 5. In addition, this could be compared our with the absorption spectrum of the chlorophyll in the plant (see Figure 2). Also, a trial with no light would show the effect of light versus no light in the plant’s production of photosynthesis.
In more general terms, energy that plants receive to generate ATP and NADPH essentially comes from absorbing sunlight energy. These results are favorable because plants have light absorbing pigments within Photosystem II and I on thylakoid membrane ("Photosynthesis." UXL Complete Life Science Resource). Pigments containing chlorophyll a and b are able to use light energy to boost the electrons onto the primary electron acceptor. The electron now has high potential energy and as it travels down the electron transport chain, it’s able to transform potential energy into ATP and NADPH. The ATP and NADPH are ultimately used to produce a sugar ("Photosynthesis." UXL Complete Life Science Resource). Taking a step back, what does this cluster of data actually support? Well besides the people who enjoy watering their plants with food coloring, the idea of having plants in blue water who photosynthesize faster than those in red or green water does not lead very far. However, it could play a humongous role in a more serious global issue; air pollution.
All across the world, in many cities like Los Angeles, California, oxygen levels can drop to around 15% or lower many days a year ("Air quality." Environmental Encyclopedia). How low exactly is 15%? That's almost a 30% reduction in available oxygen compared to sea level oxygen levels ("Air quality." Environmental Encyclopedia). Now, air pollution at these levels will wear the human body body down. So what better solution to solving this issue than with plants themselves? In this lab, it is known what factors boost oxygen levels, so implementing this knowledge into modern day society would rid the air of toxins, and make for a greener planet. Doesn’t that sound nice?