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How Leaves Change Color


How Leaves Change Color

We all enjoy seeing bright green leaves change to yellow and orange and brilliant reds and golds. But why do leaves change color? We rarely think of why, but of course, there is a reason.

Leaf colors come from pigments. Pigments are natural colors created by leaf cells. There are three types of pigments: chlorophyll, carotenoids, and anthocyanins. Chlorophyll is a green pigment which allows plants to convert sunlight into food and energy. Plants that are healthy and get enough sun, then, tend to have bright green stems and leaves. Carotenoids are yellow and orange pigments in plants like carrots and corn. Anthocyanins are red in pigment and can be found in plants like cherries and strawberries.

Leaves change colors when days become shorter and nights become longer. Because of this, trees and bushes are given less sunlight and use less chlorophyll. As trees stop making chlorophyll, carotenoids in leaves show through in yellows and oranges. As trees attempt to recover nutrients from falling leaves, they release anthocyanins, coloring them at last a bright and beautiful red.

Evergreen trees are the exception to the rule. Pines, spruces, cedars and firs do not lose their leaves, or needles, in winter, and they remain green in color. A wax coating protects them and they do not freeze like other trees’ leaves.

Useful Expressions
Rarely: not often
Pigment: natural color (顔料、色素)
Tends to do something: habitually or typically does something
Attempt: try (more formal)
Show through: appear through something else (such as glass)
Release: let out (more formal)
Evergreen: trees which do not lose their leaves in wintertime

Words & Phrases
chlorophyll [ˈklɔɹ.ə.fɪl] 葉緑素
carotenoids カロチノイド
anthocyanins アントシアニン
nutrient [n(j)úːtriənt] 栄養物
exception 例外
spruce [sprúːs] トウヒ (マツ科)
cedar [síːdɚ] ヒマラヤスギ
fir [fˈɚː] モミ