Jasmine: Hi, I'm Jasmine.
Chrissy: I'm Chrissy.
Jasmine: We're from NIU STEAM and...
Chrissy: You're listening to The Sound of Science on WNIJ.
Everett: My name is Everett and I was wondering how leaves change color?
Chrissy: Everett was one of our guests at the 15th Annual NIU STEMFest a few weeks ago. Thanks for the question and thank you for stopping by and visiting with us!
Jasmine: If we boil things down to the simplest of responsibilities for living things on our planet there are only two: to make or break bonds for energy to carry on cellular processes and to pass on viable hereditary information so that the species may carry on and thrive for generations to come. One of the main reasons that the leaves on trees change color is because the energy it takes to manufacture pigments exceeds the amount of energy gathered from those pigments.
Chrissy: The green leaves we see throughout the Spring and Summer are result of the chlorophyll the cells of those leaves contain. Chlorophyll absorbs light energy captured from the Sun and that light energy is converted to chemical energy stored within the bonds of sugars also found within the leaf.
Jasmine: As the seasons move from Summer to Fall, a few changes occur: The days get shorter and the angle at which sunlight hits the Earth becomes less direct. Opportunities for the leaves to absorb the Sun's light diminishes and become less efficient. Also, temperatures become cooler; slowing down the rate at which leaves use sugars for energy. This also slows down the rate in which the leaves produce chlorophyll.
Chrissy: With the reduced sunlight and the decrease in chlorophyll production, the pigments which exist throughout the Summer, but are hidden by chlorophyll, begin to become visible. Carotenoids are responsible for the yellow and oranges that you see and help boost the amount of light absorbed from the Sun during the Summer. Anthocyanins are responsible for the red and purple that is seen later in the Fall and are a result of accumulated sugars reacting to other elements in the environment.
Jasmine: You have been listening to The Sound of Science on WNIJ, where you learn something new every day.
