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Photosynthesis Inquiry: How light color affects the rate of photosynthesis of chloroplasts using spectrophotometers

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Alan Nguyen

on 31 October 2012

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Transcript of Photosynthesis Inquiry: How light color affects the rate of photosynthesis of chloroplasts using spectrophotometers

Different Colored Lights Photosynthesis Rates Under Purpose To find out if the color of light would
affect the rate of photosynthesis in unboiled
chloroplasts Materials 4 Spectrophotometers
1 Lamp
1 fishbowl
Unboiled Chloroplasts
Lens paper
Para film
Bowl full of Ice
5 Cuvettes
4 Colors of Cellophane: Blue, Clear, Red, Green
Test Tube rack
Micro pipettes
Buffer Procedure After the cuvettes should be covered by parafilm and cleaned with lens paper. Then immediately place within the spectrophotometers.

DPIP gets lighter as it receives more oxygen from photosynthesis. Therefore the spectrophotometers shall measure how much transmittance (or how much photosynthesis has occurred)

These readings should be recorded and then they should be placed in their respective colored sleeves: blue, red, green, and clear. They should stay there for 5 minutes at a time for 25 minutes. In between each 5 minutes the cuvettes should be placed in the spectrophotometer and recorded. Hypothesis Clear (control): If we place a chloroplast solution in a test tube wrapped in clear cellophane, then the chloroplasts will photosynthesize at a normal rate because they have access to all the light wavelengths that are required for the process
. Red: If we place a chloroplast solution in a test tube wrapped in red cellophane, then the chloroplasts will photosynthesize at a small rate because the cellophane is reflecting away all the red light which is the main light color and wavelength used by chloroplasts to photosynthesize, but it will still photosynthesize because the chloroplasts do utilize purple and blue wavelengths of light. Blue: If we place a chloroplast solution in a test tube wrapped in blue cellophane, then the chloroplasts will photosynthesize at small rate because the cellophane is reflecting blue light away from the chloroplasts and blue is a very crucial color to photosynthesize, so this deprivation of blue light would make the chloroplasts rely solely on the red wavelengths, thus reducing the rate of photosynthesis. Green: If we place a chloroplast solution in a test tube wrapped in blue cellophane, then the chloroplasts will photosynthesize at a normal rate because the cellophane is only reflecting green light away from the chloroplasts, a wavelength range and light color insignificant to the process of photosynthesis due to the pigments utilized in the reactions ability to reflect green light. Control Experiment: The cuvette wrapped in clear Cellophane Independent Variable: Different colors of light (Cellophane)
Dependent Variable: Rate of Percent Transmittancy per minute Constants:
The covering of every cuvette by the colored Cellophane completely,
The amount of time between each routine of putting the cuvettes out of its sleeve and into the spectrophotometer. (Intervals of 5 minutes)
Each cuvette is covered with parafilm on top to ensure no spillage Factors in Procedures Data Tables Analysis/ conclusion Data Graph Experimental Errors 1st Error
Instead of using 1mL unboiled chloroplasts in our blank, we used 1mL DPIP.
This caused our data to be way out of proportionate.
The spectrophotometer was reading our other cuvettes as how much lighter it is from the original, rather than how much closer it is from reaching clear.
To counteract this we subtract 100 from each of our readings. 2nd Error
Another error was our spectrophotometer for blue was malfunctioning
It read points 24 higher than the norm.
To counteract this we simply subtracted 24 from each reading of blue’s spectrophotometer. First, prepare the Spectrophotometers, set it to 605 nm, calibrate it, and create a blank.

The blank consists of 1 mL of buffer, 1 mL of unboiled chloroplast, and 3 mL of water. Then put the blank into each spectrophotometer.
The pieces of colored Cellophane should by cut into little pockets or sleeves that fit into the test tube rack so that the light would be altered as it hits the cuvettes.

The other 4 cuvettes should be prepared by adding 1 mL of buffer, 1 mL of DPIP, 3 mL of water, and 3 drops of unboiled chloroplasts. By: Alan Nguyen
Connor Reilly
Carlos Martinez
Andrew Yacoub Based on our data, our predictions were mainly correct. We can conclude that the cloroplast solution in the test tube rapped in clear cellophane is the best for producing oxygen at a higher rate because there are no light wavelengths being reflected and the other cloroplast solution in the test tubes rapped in blue, red, and green produced less oxygen because of the colors being reflected. We found two more expirements that measured the rate of photosynthesis. They both used different color as there variable to determine the rate of photosynthesis. Expirement #1
In this experiment they studied the effect of the colors (wavelengths) of white light on the phototropic growth of vegetable roselle. The results show that green light has the maximum observed transmitted intensity indicating that chlorophyll and accessory pigments in roselle leaf are good reflectors of green light. Blue and red colors have low observed transmitted intensities showing that chlorophyll and the pigments are good acceptors of these colors.They concluded that blue and red components of white light transfer their energies to the electrons of chlorophyll and the neccessory pigments during photoelectron absorption process and the energy transferred is used in photosynthesis and then finally in growth. They used percentage transmittance (%T) of the colors to explain growth in vegetable roselle. Expirement #2
In this experiment they 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. 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.
They used about 5 grams of leaves for each trial, and placed them in a gas chamber. On two sides of the gas chamber they placed two clear containers filled with water to serve as the temperature regulators. Behind the water containers were lights directed at the plant. They expiremented three trails for each different leaf used. Each trail consisted of measuring the amount of CO2 with a CO2 gas sensor under blue light, red light, and green light.
Their results showed the least amount of Caorbon Dioxide sensored was under blue lights and the most Caorbon Dioxide sensored was under green light.
"The Effect of Light Color (wavelength) and Intensity on." Http://scholarly-journals.com. J. B. Yerima1*; M. A. Esther1, J. S. Madugu2, N. S. Muwa3 and S. A. Timothy, n.d. Web.

"Affect of Different Colored Lights on Photosynthesis." Affect of Different Colored Lights on Photosynthesis. Anastasia Rodionova, Cassidy Davis, Sara Cucciniello, n.d. Web. 31 Oct. 2012. <http://spot.colorado.edu/~basey/photocolor1.html>.
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