You probably know that leaves change color in autumn, because they lose the chlorophyll that makes them green, which allows us to see the yellow-orange pigment underneath.
However, this does not explain why plants lose chlorophyll. As is highlighted in the video below, there must be a good reason for it.
Unlike evergreen plants that retain their color throughout the year, the deciduous’ tree leaves change color in autumn and are fully accounted for in the winter.
So that trees are able to easier get past winter conditions.
But at first glance it seems that this makes little sense. Given the fact that when the leaves fall, all the nutrients are rejected from the tree for months, which the tree drew from the soil to build up those leaves.
But nature is very smart about that. Every autumn deciduous trees recycle nutrients from their leaves before they fall.
“It means they separate cells and photosynthetic apparatus (Chloroplast) from the inside out in order to recover nitrogen and phosphorus. And then they store it in the branches until next spring” – Rich Henry says in the video.
This is actually quite complex because, as the tree begins to decompose nutrients, chlorophyll molecules absorb sunlight for photosynthesis.
They continue to absorb light as if nothing has changed.
But because photosynthesis happens, unused energy ends up as oxygen molecules. That in turn, can be very dangerous and destroy parts of the leaves in the process of recycling nutrients.
In order to keep this destruction to a minimum, the chlorophyll in the leaves breaks down into less harmful molecules that are usually translucent. Although, sometimes they can be yellow.
And because the green pigment disappears, the yellow and orange pigments (which are constantly present and facilitate photosynthesis) come to light, so the leaves become yellow and orange.
Some trees have additional safeguards against this destruction that is induced by chlorophyll. When the leaves begin to decompose they create a new special pigment.
This pigment protects chlorophyll from sunlight until it dissolves. These new pigments are usually of red or purple color.
Hence why trees that produce such pigments have red autumn leaves – sometimes unusual bright red.
In this way deciduous trees fail to renew up to 50% of nitrogen and phosphorus from their old leaves, which will help to grow new green leaves next spring.