Welcome to the newest edition of The Why. “Why do leaves change color in the fall?” you ask? Good question . . . timely too. (Besides, it beats answering the question: “Why do I sometimes get that ‘not-so-fresh’ smell?”)
In case this series is being read by whatever life exists on Mars, here on Earth, trees that keep their leaves in winter are called coniferous. The other trees leaves are green in the summer and change color in the fall. Then they fall off the trees for the winter.
Deciduous trees are green in the summer, turn colors in the fall, before they fall off the trees for the winter. To some folks, the fall is considered “one of the prettiest times of the year.” So why does this happen? Why do leaves change color in the fall?
According to numerous sources (and your teacher if you paid attention in school), trees like people and everything else need food and water to live. Trees (and plants) survive through the process of photosynthesis.
Photosynthesis is the process by which trees (for example) utilize sunlight to change carbon dioxide and water into sugar. Sugar is their basic food source. (Yeah, hanging out, no job, getting fresh air and eating sugar all day almost makes ya want to be a tree, huh?)
Anyway, in order for this to happen, the leaves require a chemical called chlorophyll. When chlorophyll is exposed to a light source such as sunlight, it reflects the wavelength of the visual spectrum that shows green. Hence, we only see the color green.
There are also a couple of other components in the leaves: anthocyanins and carotenoids. There is a lot more chlorophyll in the leaves than these two substances however.
When fall rolls around the leaves begin to stop producing as much chlorophyll. When this happens, the anthocyanins and carotenoids are now much more visually prominent. Anthocyanins can be seen in the reds and carotenoids are responsible for the golds, oranges and yellows. The leaves change color like that until the leaves finally die and fall from the tree.
Why do leaves change color in the fall? Now you know.
You ask the questions. We provide the answers.
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