Wildflowers are beautiful, but it is the green parts of a plant that do the work of carrying the world on their shoulders.

Wildflowers are beautiful, but it is the green parts of a plant that do the work of carrying the world on their shoulders.

Earth is, by all measures, a giant solar panel. The sun provides us warmth and light of course, but its light also fires the engine that manufactures the basis of life on Earth for everything: food for plants and oxygen for everything else.

It took scientists about 100 years to unravel the basic secrets of the sunlight-plants-oxygen triangle. By 1779 Jan Ingenhouz, a Dutch-born physiologist, discovered the connection between light and oxygen production, noting that in the presence of light, the green parts of plants gave off bubbles, and when plants were moved to shade, production of bubbles eventually stopped. He determined that the bubbles were oxygen.

In 1780, British chemist Joseph Priestley found that plants could “restore air which has been injured by the burning of candles.” He cleverly used a mint plant, a candle and a mouse under a glass jar, proving that while the plant was there, a candle continued burning and the mouse was not “inconvenienced.”

Now the stage was set, and in 1817, chlorophyll was first isolated and named by French chemists Joseph Bienaimé Caventou and Pierre-Joseph Pelletier. About 25 years later, German surgeon, Julius Robert Mayer, recognized that plants converted light energy to chemical energy. He said: “Nature has put itself the problem of how to catch in flight light streaming to the Earth, and to store the most elusive of all powers in rigid form. The plants take in one form of power, light; and produce another power, chemical difference.” Connecting the dots between light, chlorophyll and photosynthesis didn’t take long.

In short, chlorophyll (also occasionally spelled as, chlorophyl) is a photoreceptor that traps light. It resides inside the chloroplasts, which are inside the cells of leaves of all green plants. Trapping of the light initiates the chemical reaction we call photosynthesis, whose chemical equation is: 6 CO2 + 6H2O C6H12O6 + 6 O2, which allows plants to convert nutrients and water into glucose which is then used to produce growth for the plant, scrub the atmosphere of carbon dioxide and provide free oxygen.

So, why are plants green? Is chlorophyll green? White light is made up of seven primary colors of visible light, all with their own wavelengths. Chlorophyll absorbs light in the blue and red spectrums, but in the spectrum between 500-600 nanometers, it absorbs almost no light at all. The color green falls between 500-600 nm and, not being absorbed by the chlorophyll, this light bounces around reflecting off the cell surfaces. It is this reflected light, just a part of the full spectrum of visible light, that we see as the color green.

Chemically, a chlorophyll molecule has a donut-shaped porphyrin ring around a central metal atom. I find it interesting that this is much like the structure of vitamin B12 and also hemoglobin, except that chlorophyll uses a magnesium atom while hemoglobin uses iron and B12 uses cobalt.

Chlorophyll also has a side group of atoms and depending on which side group it has, is either chlorophyll a or chlorophyll b. The difference between the two is what frequency of light it absorbs best. Most plants have both chlorophylls and they complement each other in their light absorption. Chlorophyll a is better at capturing light in full sunlight, chlorophyll b works a little better in the shade. Shade tolerant plants have more chlorophyll b, but combined they absorb plenty of light for their needs.

Chlorophyll is thought to be responsible for several beneficial health properties such as antioxidant, anti-mutagenic, and detoxification activities and has become a big business. Little research exists to prove or disprove this claim, but one thing is sure: without chlorophyll, there would be no photosynthesis and without photosynthesis, there would be no oxygen and no life on earth.

Terry Thomas is a wildlife biologist and naturalist. You can read more of his work on his website, www.nature-track.com.

If you are interested in this topic, check out the EPA publication 843-B-00-003, Guiding Principles for Constructed Treatment Wetlands. Also, Constructed Wetlands: Using Human Ingenuity, Natural Processes to Treat Water, Build Habitat. March, 1997, by Joe Gelt is an informative read. Find it on the Web at: https://wrrc.arizona.edu/publications/arroyo-newsletter/constructed-wetlands-using-human-ingenuity-natural-processes-treat-wa

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