Photosynthesis Lab Report

The purpose of this experiment is to study how much light is being absorbed by chloroplasts at different wavelengths for photosynthesis. The other goal is to learn if different color of leaves had different absorbance from green colored-leaves. For this experiment, two different color (purple and green) of Kale (Brassica oleracea var. sabellica) were used in the following experiment. The pigment from each leaves were extracted by grinding the tissue in 5 ml of 100% acetone using a mortar and pestle. After the pigments were extracted, the ether phase was used to measure the absorbance using a spectrophotometer. Then, it was graphed by using MS Excel. As it is shown in Figure 1, two peaks of absorbance for each of the color can be found. The peak region indicates the wavelengths where light is being captured the most. For the green leaves, the first peaks can be seen at the wavelength of 435 nm, whereas the smaller/second peaks can be seen between 660 nm and 670 nm (Figure 1). The same goes for the purple leaves (Figure 2). Although the two different color of leaves absorbed the greatest amount of

After that, 4 or 5 drops of the ether phase was added into the 2 new test tubes to mix with 4 ml of 80% acetone. Then, using a rubber stopper, the tubes were gently inverted several times. To serve as a blank/control, 4 ml of 80% acetone was pipetted into another clean test tubes. After that, the initial wavelength on the spectrophotometer was set at 380 nm to measure the absorbance. The wavelength was increased until it reached 740 nm. Each new wavelength was blank to obtain the best absorbance. The data at closer intervals (i.e., at 5 or 10 nm intervals) in the peak absorbance regions were collected. For example, if it peaked at 380 nm, the next wavelength should be at 390 nm. Lastly, absorbance vs. wavelength for the two-different color of Kale leave was plotted using MS