How Leaves Change in Fall - Sookmyung Girls' High School

Autumn seems to be passing by really quickly. The leaves are changing their colors in a flash and the ground is becoming simply carpeted, if I allow a little exaggeration. 

Every day adds a different shade to the foliage, so I always try to give the trees I pass all the time more than a few glances. I don't want to miss a single "step" in their transformation; it would be such a shame. That brings me to a question that really filled my mind when I was little: Why do leaves change color?

Only just a while ago, the leaves still retained their green tints

Many of us think that leaves change due to the falling temperatures. Although not entirely incorrect - temperature does alter the intensity of the hues - it's only one of the many factors that contribute to their transition.

In middle-school biology, we learn that the green color in leaves is caused by the presence of chlorophyll. This pigment converts light energy that it absorbs into chemical energy so that it can be used in changing carbon dioxide and water into oxygen and carbohydrates like starch. The jade/grass/lime color is present throughout most of the year because the leaf organ acts as the "food factories" for the plant. Other pigments are present, but the chlorophyll blocks them out because it is constantly replenished. 

Now, an entirely different harmony of colors plays

When the seasons change, however, and the length of day alters with the temperature, a layer of special cells forms at the base of each leaf. They are cork cells, a tissue found in many vascular plants. This layer blocks the movement of fluids into and out of the leaf, so naturally, water and mineral intake is reduced. Chlorophyll begins to decrease as well.

As the green shade begins to weaken, other pigments are unmasked. The yellow pigments (xanthophylls), orange pigments (carotenoids) and red and purple pigments (anthocyanins) burst into the blue-green.

Perhaps the mesmerizing beauty of the shades make autumn seem shorter than it actually is. While a brief (as it seems to me) firework of colorful splashes is taking place, the layer of cork cells continues to develop and steadily weaken the connections between other cells. Eventually, the tissues are severed, and we see the fallen foliage at the bases of trees, withering away, adding a new sound - "crunch crunch" - to the season.