Why Does Chlorophyll Make Plants Green?
Most plants contain green leaves and stems that glow bright in direct sunlight. This natural showcase of color can be attributed to tiny molecules that reflect green light.
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Chlorophyll
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Chlorophyll is a pigment in the chloroplast of plant cells that absorbs the light from the sun for energy during photosynthesis. Two pigments in the chloroplasts absorb light: chlorophyll and cartenoids. With 200 molecules per chloroplast, chlorophyll is the most prolific. Chlorophyll is green, and its presence is visible in the green portions of plants like the stems and leaves. The green color indicates the portions of the plant where photosynthesis reactions occur.
Light Absorption and Color
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Light moves in waves, and the length of each wave fluctuates. These fluctuations of wavelength determine the color of the light. Pigments, contained in nearly all objects on earth, absorb or reflect certain wavelengths of light. The wavelengths that the pigment molecules reflect determine the color of objects.
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Chlorophyll and Plant Color
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Chlorophyll absorbs the highest energy of light in the visible light spectrum. This light is in the red and violet wavelengths (around 700nm between waves). The pigment reflects light at the lower end of the spectrum. These colors are green and yellow and occur between 500 and 600nm between waves. The reflection of light is visible to humans, while the absorbed light is consumed for energy by the plant. This explains why the parts of the plant containing chlorophyll appear green.
Cartenoids
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Cartenoids are less prominent pigments in the chloroplasts. These molecules reflect orange and yellow light waves. There are about 50 cartenoid molecules compared to the 200 chlorophyll molecules. The low percentage of competing pigments accounts for the overbearing green in most plant leaves. These pigments do, however, dominate the colors of carrots, pumpkins and other orange plants.
Aquatic Environments
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In aquatic environments, photosynthetic organisms absorb and reflect light in different wavelengths than photosynthetic organisms in terrestrial environments. Water absorbs and reflects light energy, limiting the penetration of light beneath the water surface. Short wavelengths are reflected off the water's surface. These are in the blue range of the light spectrum, causing water to appear blue in color. Water absorbs longer wavelengths, such as those in the red and violet area of the light spectrum. About 7 percent of light is able to penetrate between 10 and 100 m of water. This 7 percent is mostly green light.
Aquatic photosynthesizing organisms like algae have adapted to these conditions. They absorb green light rather than high-energy red light. Some of these algae have additional pigments, allowing them to absorb greater amounts of energy in low light conditions.
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References
- Photo Credit leaves image by Andrzej Dziedzic from Fotolia.com
