十万个为什么·科学启蒙30篇（1）
13 / 30
正在校验访问权限...
Why Do Leaves Change Color in Autumn?
为什么树叶在秋天会变色？
-
In autumn, days get shorter and temperatures drop slowly.
-
Trees sense these changes and begin to prepare for winter rest.
-
Chlorophyll, the green pigment in leaves, breaks down as sunlight fades.
-
When green fades, yellow and orange pigments called carotenoids become visible.
-
Some trees also make red pigments called anthocyanins when sugars get trapped in leaves.
-
Soil moisture and weather conditions affect how bright the colors appear.
-
This color change helps trees conserve energy before shedding leaves.
-
Not all trees change color—evergreens keep their needles year-round.
-
Deciduous trees lose leaves to avoid water loss in cold, dry air.
-
Scientists study leaf chemistry to understand climate change effects on forests.