Photosynthetic Pigments Essay Example

The green leaf lettuce, Lactuca sativa, was vibrant green with a few lighter green sections; its appearance was waxy but also shiny. The spinach leaf, Spinacia oleracea, was oval in shape with wrinkles and rich in dark green color, while the red leaf lettuce, Lactuca sativa, was a deep purple color with small areas of green on the leaves. Similar to the appearance of green leaf lettuce, the red leaf lettuce also had a waxy look, but had curly or wavy edges. Radicchio leaves, Cichorium intybus, were a dark violet color with white veins. When compared to the other three leaves, radicchio leaves were much thicker and firm. 

The chromatogram with the most pigments present was the spinach leaf. Of the six pigment positions on the chromatogram depicted on page lp2, the spinach leaf had pigment located at one, two, three, four, five, and six positions (Marietta, 2021, lp2). At spots one, two, and three, the colors of the pigments were varying shades of green: one fading into bright green; two dark green; three pale yellow green. The spinach leaf then had pigments with shades of yellow for positions four, five, and six on the chromatogram. Position four was pale yellow gold in color, while position five was the thickest and a paler yellow; position six was the thinnest, but was the most abundant in color, gold. The pigment with the most abundance in the spinach leaf was both green and yellow. 

The green leaf lettuce chromatogram had the second most pigments present when compared to the chromatogram of the spinach leaf. The pigments were located at positions one, two, three, five, and six. At position one, the pigment was a brownish green, and then faded into a pale dark green at position two. Position three had a dull green pigment; position five had a pigment of faded green that was almost so light to see. Similar to the spinach leaf, position six for the green leaf lettuce was a gold pigment. The most abundant in color was gold in position six and the least abundant was faded green in position five. The pigment that had the most abundance in the green leaf lettuce was green and the least abundant was yellow. 

The red leaf lettuce had the third fewest pigments on the chromatogram, with pigments at positions one and two. Position one had a pigment of brown with a hint of purple hue; as shown on the red leaf lettuce chromatogram on page lp5, this faded into a very pale and light green that was almost too light to be visible in position two (Marietta, 2021, lp5). The broad band of light green pigment in position two was the least abundant pigment in the red leaf lettuce chromatogram, while the brown with hints of purple at position one was the most abundant pigment.  

The chromatogram with the least pigments present when compared to the six pigments present for the spinach leaf was the radicchio, having only one pigment visible. The dull brown pigment was present at position one and was a thin line, as illustrated on the chromatogram for radicchio on page lp5 (Marietta, 2021, lp5). This pigment was the only pigment present that was visible, therefore it was the most abundant.  

Conclusion 

The results do conclude that the hypothesis, “all leaves will contain photosynthetic pigments,” is supported by the data from the experiment. Of the four leaves tested, spinach, red lettuce, green lettuce, and radicchio, all were shown to have photosynthetic pigments due to pigment spots appearing on the chromatograms. 

Explanation of Results 

Chlorophyll, the green pigment in leaves, absorbs light mostly in the violet and blue wavelengths, as well as in red (Raven et al., 1981, 101). Because chlorophyll “absorbs light in the 430 nm and 680 nm wavelengths of the visible spectrum,” it does not absorb green light and therefore reflects green light (Malkin and Niyogi, 2000, 578). Carotenoids absorb light and pass energy to chlorophylls, increasing photosynthetic efficiency and expanding the wavelength range of light that can be absorbed; they absorb light in the highest energy part of the visible light spectrum, 400 nm to 500 nm (Britton, 2008, 190). Anthocyanins do not play an active role in photosynthesis, but they do “diminish the oxidative load in a leaf by simply filtering out yellow-green light, since the majority of reactive oxygen in plant cells is derived from the excitation of chlorophyll (Gould, 2004, 316).” Anthocyanins are blue, red, and purple pigments. The spinach leaf and green leaf lettuce leaf both had an abundance of chlorophyll, resulting in pigments of green as shown on the chromatograms, while the radicchio leaf and red leaf lettuce had more of an abundance of anthocyanins, resulting in pigments of purple and red. 

The chromatogram shows the different types of pigments. Chlorophyll a appears blue-green, chlorophyll b appears yellow-green, carotenoids appear yellow-red, and anthocyanins appear purple red (Marietta, 2021, lp1). According to the chromatograms from the experiment, the pigments appear in the order of position six being bright yellow, position five yellow, position four yellow-green, position four bright green, position three green, and position two blue green. Pigments in position one for the four leaves varied; the green leaf lettuce and spinach both were green in position one, while the red leaf lettuce and radicchio were brown purple.  

The spinach leaf and green lettuce leaf both appeared to be capable of carrying on photosynthesis because they had an abundance of chlorophyll. Because the absorption spectrum of chlorophyll and the action spectrum of photosynthesis are similar, chlorophyll plays an active and important role in photosynthesis. (Raven et al., 1981, 101). The radicchio leaf and red leaf lettuce had little pigments show on the chromatogram that are associated with chlorophyll, and therefore appeared to not be capable of carrying on photosynthesis. If the tissue is not photosynthetic, it may function as a protector against excessive sunlight and occur in leaves and fruits (Marietta, 2021, lp2). Anthocyanins play multiple roles in stress response in plants (Gould, 2004, 315). Without photosynthetic pigments in their leaves, plants can live for a short amount of time but will eventually die due to a lack of nutrients; the plant will not be able to gather sunlight for photosynthesis (Marietta, 2021, lp1). 

Because pigments absorb different wavelengths of light, the number of pigments on the leaves of different plants varies. The varying number of pigments in plants is attributed to the specific environments that they are in. (Malkin and Niyogi, 2000, 578). A plant that is in an environment that is darker would have pigments that could synthesize chlorophyll in the dark. Multiple pigments allow a plant to use photosynthesis as well as cellular respiration to maximize the amount of light it can absorb from the sun, which can lead to evolutionary adaptations.  

Future Experiment 

Literature Cited 

Britton. 2008. Functions of intact carotenoids. In: Britton, Liaaen-Jensen, Pfander, editors.

Carotenoids. Basel (CH): Birkhäuser Verlag; p. 189-212. 

Gould. 2004. Nature’s Swiss Army Knife: The Diverse Protective Roles of Anthocyanins in Leaves. Journal of Biomedicine and Biotechnology. 2004(5): 314-320. 

Malkin and Niyogi. 2000. Photosynthesis. In: Buchanan, Gruissem, Jones, editors.  Biochemistry and molecular biology of plants. Rockville (MD): American Society of Plant Physiologists; p. 568-580. 

Marietta College Biology Department. 2021. Leaf structure and pigments. In: Introductory biology lab I manual. Marietta (OH): Marietta College; p. lp1-14 

Raven, Evert, Curtis. 1981. Biology of plants 3rd edition. New York (NY): Worth Publishers; 686p.