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Changing Seasons, Changing Trees

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Changing Seasons, Changing Trees

By Lindsay Malone

We all know that the yearly drop in temperature during the autumn season affects the plants around us: some plants disappear, leaves on trees change color and eventually fall off, and the world becomes a lot less green. But what’s really happening inside those trees to make them change so much?

Well, to start with, I should be clear that we’re talking about deciduous trees and not evergreens when we’re talking about leaves changing. The answer has to with a little thing called chlorophyll. If you think back to your biology class in school, chlorophyll is a green pigmented chemical that exists inside of the chloroplasts in plant cells. It’s what makes leaves green, and it’s also a very important part of photosynthesis, being responsible for the absorption of light. Deciduous trees take advantage of their time in the sun during summer and store up lots starches and good plant food. In the fall, the temperature starts dropping and the days start getting shorter, meaning there is less light that can be absorbed and photosynthesized, so deciduous trees cut back to point of almost stopping their photosynthesis. Because of the major cutbacks in photosynthesis, the leaves don’t need the chlorophyll as much anymore and it starts to degrade. The lack of chlorophyll allows for other pigments to show through, like orange carotenes and yellow xanthophylls, and that is how trees become jewels in the fall!


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