Change Edition – Why Do Leaves Change Color?

Image via Britannica

Image via Britannica

Lily Pliske, Editor

When you’re young, you marvel at how leaves change from bright vibrant greens, deep with life, to soft oranges and reds, to bright sunny yellows. It’s a pretty amazing sight, especially when you are younger, but let me riddle you this; did you ever figure out why?

When you’re younger, you tend not to stop and think why. Why does this happen in our world, and even if you do, you definitely don’t try to figure out the answer. Now I was pretty lucky because my dad majored in biology, so I got my leaf changing color answer early on (not necessarily by choice), but if you did not get blessed with a parental figure who will tell you all the answers to the science questions you want and don’t want to be answered, but they will tell you anyway, you’re in luck. Because you have me.

So, why do leaves change color? It’s actually a pretty simple answer when you get down to it, but I’ll overcomplicate it. To put it simply, it’s a chemical process that occurs within the leaf, but to understand better we first need to know why are leaves green in the first place. There is a food-making process that occurs in the leaf where many cells contain chlorophyll, which gives the leaf the green pigment we see when we look at it. This chemical (chlorophyll) has one job in a leaf, and that is to absorb sunlight. The energy that is absorbed is transferred to photosynthesis, which is used to store energy and convert to carbon dioxide, which is absorbed from the air and water into glucose, which is a type of sugar.

Even when the leaves are green, there are still the other pigments of colors in the leaf, but because the green color is more dominant, they are masked until two important changes occur around the tree and leaf environment. Daylight hours and temperature change. 

In the fall, the length of daylight hours change and start to get shorter, from what it is in spring and summer. The temperature also changes, and the environment starts to get colder. An extreme weather change, for example, drought or an early frost can cause the leaves on trees to fall off sooner than they normally would. 

These two changes stop the leaf food-making process from occurring, and because of the lack of sunlight and colder weather, the chlorophyll starts to break down, and the green color in the leaves disappears. The yellows, oranges, reds, purples, etc. that were masked by the green now have the chance to show themselves. 

Once leaves have gone through their color process, they tend to fall off the tree. This is because a special layer of cells develops at the base where the stem of the leaf is attached to the tree, and it severs it. As all this is happening, the tree seals off the cut where the leaf was, and this leaves what is called a leaf scares. 

So that hopefully answered all your questions about leaves, and why their leaves change color.