Why Leaves Change Color in the Fall
Why do leaves change color in the fall? Usually people answer this question by discussing the basics of photosynthesis. Plants capture energy (sunlight) through a pigment in their cells called chlorophyll, which is abundantly present and gives leaves their green color. But as winter approaches, trees need to conserve water and so they prepare to drop their leaves. Trees give a big PEACE OUT to chlorophyll first because that’s where all the energy is going- to make food! As chlorophyll’s presence fades, we can now visibly see the other pigments that have been there all along. These “sidekick” pigments absorb other wavelengths of light and give the gorgeous yellow, orange, and red colors of fall leaves. Ta-da!
But why? What’s the trigger? I think this is the coolest part of the color-changing game. Scientists have found that leaves begin changing color based on 2 big factors: a decrease in daylight (days getting shorter) AND a change in temperature. A shorter amount of time to absorb light coupled with the risk of losing too much water via evaporation from the leaves without equal replacement from the roots = bad news for the trees. This signals that winter is coming and it’s time to get down to business.