Yellow Yellow Dirty Fellow

As with yesterday, we are going to cover something colourful today. Today we look at the question:

Why Do Leaves Change Colour in the Fall Season?

Probably many of you have noticed that many trees shed leaves in the fall season. Others may have noticed that right before a leaf is shed, it changes colour from green to yellow. But why does this happen? And is it necessary?

The reason why leaves are shed before winter is pretty simple. It takes a lot of energy for the plants to keep their leaves healthy. Winters are generally cold, dry, and usually there isn’t much sun (except for the equator). So, instead of trying to keep their leaves, some plants drop their leaves and seal the spots on their branches where the leaves had been attached.

Ah yes, the colour?

Leaves are coloured by pigments. The green colour of leaves is due to the pigment chlorophyll. The other colours can also be attributed to different pigments, e.g., Carotenoids are yellow and Anthocyanins are orange. Each pigment serves a different purpose. Anthocyanins protect leaves from getting “sun-burned” and being eaten. Chlorophyll is responsible for harnessing energy from the sun. It serves an important function, as it allows the plant to synthesize food.

As with everything that is important, Chlorophyll synthesis takes up a lot of energy. In autumn, the plant is getting its affairs in order before the onset of winter. Before shedding leaves, the wise plant deems it necessary to breakdown the chlorophyll already present in the green leaves and store the broken down components.

It serves two purposes. First, no chlorophyll is lost when the leaves are shed. Secondly, the plant stores the broken down components that can later (in summer/spring) be used to synthesize chlorophyll. That way plants don’t have to make chlorophyll form scratch.

The colour change is just a by product of the plant shedding its leaves and getting prepared for the winters. One interesting thing to ponder about: How Do Plants Know When Winter Is Coming ?

P.S. I didn’t like GoT much. Watch Breaking Bad to find out why.