What’s Behind the Changing Colours of Leaves The tree or shrub has no use for the remaining chemicals so they’re left behind. By Marion Desplenter Fall has arrived, as it regularly does, with shorter days, cooler temperatures, changing colours of leaves, and returning to regular school and work routines. Recently, I had a brief conversation with a friend about the changing colours of the leaves. Neither of us could easily explain what the cause of it was. Was it the cooler temperatures or lack of sufficient sunlight? Maybe both?
So I thought I would look into it more.
The leaves on deciduous trees and shrubs are green because they contain chlorophyll which is used by the plant to capture sunlight. Chlorophyll helps to turn the sunlight into food for the tree through the photosynthesis process. The food is used for new leaves, flowers and seeds.
As the days become shorter in the fall, sunlight is less abundant and temperatures become cooler. Trees and shrubs sense this and begin to prepare for winter by breaking down the chlorophyll in the leaves and storing it as nutrients in their roots. The plant has no use for the remaining chemicals so they’re left behind.
What we see is the green disappearing from the leaves, revealing the colours of the chemicals that are left behind. The chemical carotenoid gives off a yellow and orange colour while anthocyanin produces a red and purple colour. Once all the chlorophyll is drained from the leaves, they fall to the ground where they dry out.
In the spring, as the weather warms and sunlight increases, the trees and shrubs begin to use their stored nutrients to create new leaves for the coming summer. Then, the more abundant sunlight will become part of the photosynthesis process again.
Below is a short video explaining why leaves change colour in the fall:
https://www.youtube.com/watch?v=Xk4-6II8l5Q
Resources: theconversation.com/curious-kids-why-do-leaves-change-colour-105318
YouTube SciShow Kids
Cover Page Image: Janis Ramsay |
Credit: Metroland Image 1: Jun Zhou | Credit: Getty Images Image 2: Google Images
