Why Are Plants Green?

With the exception of those few species of plants that have leaves of a different color, most plant are green. From the smallest kid to a mature individual, if you ask what color are plants, the answer will be, unanimously, that plants are green. Still, why are plants green and not blue, or red?

The color green comes from the cells in leaves (and sometimes stems), which contain chlorophyll, a large molecule that absorbs certain colors of light. This light allows the plant to do photosynthesis: with the energy provided by the light, the plant converts carbon dioxide and water into food. Chlorophyll uses red and blue wavelengths of light, and reflects the green wavelengths, thus the plant appears to be green.

The fact that chlorophyll absorbs green more than other colors might be a result of the evolution of plants. As the sunlight is not evenly distributed across the spectrum, certain wavelengths, especially in the red and blue regions, are stronger than others. It is possible that chlorophyll dominates, because it absorbs energy more efficiently where it is the strongest. In the case of some plants that have developed other mechanisms for absorbing light, it is likely that chlorophyll was more efficient.

Chlorophyll is the most visible compound in leaves, but there are also other compounds that give plants their color. In temperate regions, some other pigments can be seen in the fall, because when light and heat are reduced, photosynthesis becomes less efficient and the plants stop making chlorophyll. Once a plant quit making chlorophyll, the red, yellow and purple of other pigments in the leaves start being visible.

Photosynthesis is the process used by green plants, as well as some bacteria and algae, to produce glucose from carbon dioxide and water. The term photosynthesis, translated literally into "building with light", is used because the energy for the chemical reaction comes from sunlight.

Therefore, in the majority of plants, green is the defining color because of the chlorophyll that dominates over other color spectrums. And we have become so accustomed to plants being green that nobody ever questions why it is that they are green, they just are. It is the soothing and fresh green look of plants that has come to define them, and it would be hard to imagine a world less green. Just think of a lawn with any other color but green, or a Christmas tree, or a large park or botanic garden that does not abound in all shades of green. would it be the same?