The Affect of Light Frequency on Photosynthesis
Meaghan Cusack, Lindsey Book, Jesse Clarke
University of Colorado, Boulder - Fall 2006
We tested to see if different wavelengths of light had an affect on a plants rate of photosynthesis. Plants use light to carry out the light dependant reaction in the first stage of photosynthesis. Blue light has a shorter wavelength, which gives it more energy, than red light. Because of this, we predicted that blue light would increase the rate of carbon dioxide consumption, in other words, increase the rate of photosynthesis.
We used the juniper sprig in our experiment. We put the sprig in a gas chamber and let the chamber air out. Then we put in a CO2 sensor, and turned on the lights with the blue cellophane covering it, shining on the plant. We took calculations for ten minutes. Then we put it in the dark in between, as a buffer. We then used the same procedure, using red light. We again measured it for ten minutes, and used the same plant. In the second trial, we used a different plant section of the juniper sprig. We used red first this time, followed by the blue light, getting rid of any bias that we might have created. In this trial the same procedure was gain used.
Our results showed that the rate of photosynthesis was greater under the blue light. The average rate of photosynthesis was 66.52 ppm/min/g for blue and 35.215 ppm/min/g for red.Our t test resulted in a p value of .0008. this number was less than the value .05, which leads us to conclude that our data was in fact significantly different. The blue light was significantly making the rate of photosynthesis faster.
Our results were consistent with our hypothesis. We predicted that the blue light would be more affective because of its greater energy. This proved to be affective on plant photosynthesis. Some potential problems could have come up during our experiment. We only ran the experiment two times. To make it more accurate, we might want to try doing the experiment four or five times. It would make our data a better model. Another problem that might have come up was the preciseness of the carbon dioxide sensor. The one that we used during our experiment was old, and had tape around it. It would help if we used a different monitor, and possibly tried the experiment on several monitors. The CABLE website showed that other students had in fact performed an experiment somewhat like ours. The results were practically the same, again showing blue light as more effective.
From the results of our experiment, many extensions may be tried. One
example could be that we could try this experiment using a C4, and CAM plants. This would help us see if the blue light was absorbed better only because it was a C3 plant, or if this is true of all types.