Your kid may have noticed the leaves changing color this fall as they started school and wait for Halloween. Why does this happen?
Winter is cold, dry, and usually pretty cloudy out, so the food (light and water) that trees need is in short supply. Rather than keeping their leaves, some plants drop them and seal-off the spots on their branches where the leaves were attached.
But that’s why leaves fall… what makes leaves colorful?
Leaves get their color from pigment molecules. Most of the year, chlorophyll is the pigment that gives leaves their vibrant green color. Chlorophyll lets plants make food using sunlight. During spring and summer when there is plenty of sunlight, plants make a lot of chlorophyll to grab as much energy from the sun as possible.
In autumn when it starts to get cold, some plants stop making chlorophyll. Instead, those plants break down chlorophyll into smaller molecules. As chlorophyll goes away, other pigments reveal their colors, turning red or yellow.
The color change usually happens before the leaves fall from the tree. Plants save energy as they break down the chlorophyll and move it out of their leaves before the leaves, reabsorbing the chlorophyll molecules. When it’s warm and sunny enough to grow again, the plants can use those molecules to remake the chlorophyll.
The pigments that remain in the leaves as the chlorophyll is pulled are called carotenoids, which are yellow and orange. Additionally, anthocyanins, which are only produced in the fall, produce vibrant red, pink, or purple colors, protecting leaves from being eaten or getting sun burned.
What’s your favorite color of fall leaf?.
