The green color in leaves and blades of grass comes from a pigment called chlorophyll, which absorbs sunlight during photosynthesis, one of the most important natural processes on Earth.
During photosynthesis, plants and trees use sunlight to convert carbon dioxide in the air and water into, energy-rich sugars for food.That’s why leaves are at their most lush and greenest during the summer months, when the longer sunlight hours kick photosynthesis into overdrive. One bonus product of the process is oxygen, which is essential for life .
Green leaves are green because chlorophyll absorbs all of sunlight’s rainbow of colors except the green part, which is reflected.
You know that too much sunlight can damage your skin, fade colors in clothing and cause other problems. Therefore it shouldn’t be surprising to find out that sunlight also causes chlorophyll molecules to break down. In fact, during the summer, green plants must continually create new chlorophyll to replace what has been destroyed. This creation, or synthesis, of chlorophyll requires not only sunlight but also warm temperatures, so you can see why fall’s cooler weather encourages our trees’ leaves to begin showing colors other than green.
But, where do those other colors come from?
There’s another substance in many leaves known as carotene. Carotene is a kind of “chlorophyll helper.” That’s because carotene absorbs sunlight energy like chlorophyll, but instead of keeping that energy and conducting photosynthesis with it, it passes its energy on to chlorophyll which then uses that energy to perform photosynthesis. Carotene is known technically as an “accessory absorber.” Carotene holds up much better under sunlight than chlorophyll, so often in the fall when chlorophyll disappears from leaves, carotene is left behind. Since carotene absorbs blue-green and blue light in sunlight, the light it reflects back to our eyes from leaves in which the chlorophyll has disappeared is.