Why leaves change color
Every fall in the deciduous forests of the world, there is a miraculous change in the color of the leaves. They turn from green into brilliant shades of yellow, orange, red, and purple. Sometimes you can see several shades on the same leaf. But why are these color changes happening, and what is going on in the plant?
Fortunately, that’s the topic of this Untamed Science video. Rob explains, with the help of Canopy Biologist, Meg Lowman, that it has everything to do with the pigments in the leaves. In fact, many of those pigments have been there all year and can only now be seen. Others, like the red color are a result of pigments produced in the plant as it dies.
If our video didn’t answer all your questions, read more below about exactly what’s happening in the plant.
The Four Pigments Responsible for Leaf Change
The changing leaf colors you witness each year boil down to a few chemicals in the leaves. Some are pigments, some are by-products produced by the leaf, and other are produced only in the fall. Here are the culprits:
The leaves of plants are responsible for absorbing light from the sun to convert it into energy for the plant. While we mostly learn about chlorophyll, there are also other pigments, like the carotinoids we discuss later.
Chlorophyll is green because of the way it absorbs light; the pigment absorbs the blue and yellow wavelengths but not the green. The green is reflected back.
Carotenoids are responsible for the orange you see in carrots and are displayed brilliantly in aspens, maples, and birches.
This is a family of pigments that are almost always present in the leaves. However, they’re rarely in higher quantities than chlorophyll and are thus masked. However, as fall rolls around and the chlorophyll breaks down (and doesn’t get replaced in the leaves), the yellow colors start to appear. We’re finally able to see the colors that were hidden before!
Anthocyanins produce the reds and purples that we see in maples, sumacs and dogwoods. Turns out, most anthocyanins are not found in the leaves most of the year. They’re produced in the fall from a reaction with anthocyanidins. While it’s dependent on pH, acidic soils can produce bright red colors.
Tannins are waste products, produced in the plants, and often give them a bitter taste. The taste and color of tea for instance has a large part to do with tannins in the tea. The brown color of the water in the amazon, has a lot to do with