I think most of you will agree when I say that fall is one of the most beautiful times of the year. Fall is ideal because of its weather, and the breathtaking colors of the trees and shrubs. Being in this science class, I have been thinking about the science behind everything lately. I see something and think, why does this happen? Or what do other people think about this? Or I bet there has been a study on this. Of course, I saw the leaves of a tree that had changed color, and I immediately thought, why exactly do the leaves change color? What really is the science behind fall? I am going to explain exactly what happens to the leaves, and why this occurs. So basically there are a few factors that affect the changing of leaves color.

The first thing that affects the leaves is leaf pigment. Within this category, there are three different pigments that affect color. There are carotenoids, which produce yellow, orange, and brown colors. The next one is anthocyanin, which gives color to things like cranberries, blueberries, and plums. The last one is chlorophyll, which is the basic green color. I remember learning about chlorophyll in biology class during high school. Both chlorophyll and carotenoids are present during the growing season. Anthocyanin is produced in the autumn, in response to bright light and excess sugars. Because the nights are longer in autumn, the chlorophyll begins to slow down because it is not active at night. So over time, it stops completely. When the chlorophyll stops the carotenoids and anthocyanin that were masked begin to be revealed. The reason that some trees have different colors is simply because of genetics. The time during the fall that these leaves change depends on the tree’s location as well as its genes also.  In the photo below, you can see the different types of trees that have begun to change.  There are even a few that look like they haven’t begun to change.  I took this photo on campus to demonstrate that there are many different factors that go into the changing of a leaf’s color.  It can be their location, even if they are very close together, or their genes, like I said before.

The weather can affect the color of the leaves; most importantly the temperature and moisture can affect it. The amount of moisture in the air and soil affects when in the season the leaves begin to change color. If the weather is warm during the fall, the colors of the leaves will be more vibrant. More specifically, warm days and cool nights will create the best color change.  If the temperature is cooler, fall will begin sooner because the trees are not getting the proper nutrients.

There have been studies which present very interesting theories on why leaves change color and the leaves fall. One study suggests that the leaves turn red to protect them for the sun’s ultraviolet rays. Also a recent study in Greece, for instance, found that as leaves grow redder, insects eat them less. Another scientist does not agree with this theory. He agrees that they do eat them less, but only because they don not have as much oxygen as green leaves so therefore they are less nutritious. The leaves being red is not the reason bugs eat them less. Some People believe that maybe it’s something that helps leaves “deal with stress,” one scientist told LiveScience. “If making the anthocyanin helps the leaf stay on the tree a little longer, it may help the tree absorb some of the good things before it falls off. The tree can use those resources for the next growing season.”  I think that it is very interesting to pair the word “stress” with a tree because obviously trees can’t really be stressed.  I do think that they try to hold to the leaves nutrients for as long as they can though.

This is a photo a took walking around campus.  I noticed that the leaves on top were beginning to change color before the ones underneath.  I think that this is because of the Sun’s ultraviolet rays hitting them.  The leaves on top are obviously being hit more direct by these rays, so this would prove as evidence that the leaves change to red to protect from the rays.  It is so cool that I researched this and actually got to see it come to life on campus.  Maybe this is because the Sun actually changes the color of the leaves.  This is one of my theories.  I think that because the leaves on top are being directly hit my sunlight, they are the first ti change.

So next time you are walking down the road to class, stop and think about how much goes on inside a tree to produce these beautiful colors. It can really help you to appreciate the little things in life. Science can explain even the simplest things we take for granted. The leaves are beautiful; science is beautiful.