Why leaves change color in autumn
Inside a leaf there are millions of tiny packages of color—yellow,
orange, and green. The yellow is called xanthophyll, the orange is
carotene, or carotin, and the green is chlorophyll. The green color
covers up the others, and that’s why leaves are green all summer.
Near the end of summer, the green chlorophyll fades and disappears. Then
the yellow xanthophyll and orange carotene can be seen. That’s why many
leaves turn yellow and orange in autumn.
All summer, water goes into each leaf through tiny tubes in the leaf’s
stem. Leaves make sugar, which is a plant’s food. Sap carries the sugar
out of the leaf to other parts of the plant. Near summer’s end, a thin
layer of cork grows over the tubes and seals them up. No more water can
get into the leaf. Sugar often gets trapped inside leaves when the tubes
are sealed up. This sugar may cause the sap to turn red or purple and
make the leaves look red or purple.
When leaves are dry and dead, they turn brown.
chloroplasts in summer
chloroplasts in autumn
Inside each leaf cell are tiny “packages” called chloroplasts. They are
filled with colors. But, in summer, one color—green— covers up all
the other colors.
In autumn, the green color in the chloroplasts slowly fades away. Then
you can see the other colors. This is why leaves change color in autumn.
