According to the classic theory, this is true for the red pigment as well.
It was there in the leaf all along but it was hidden by the green chlorophyll.
OK, so that’s the classic explanation and it’s partially right. Why do I say partially?
Well, it’s probably true for pigments like yellow or orange, but it doesn’t seem to hold for the red pigment.
Let’s back up a bit. Just what produces this red color in leaves? It’s a red pigment called anthocyanin.
Here is where the classic explanation doesn’t seem to apply to red.
What’s interesting is that during the summer there was very little if any anthocyanin in the leaves,
but in the weeks before a tree is about to drop its leaves, the production of anthocyanins increases significantly.
In other words, unlike those other pigments, anthocyanins are not just unmasked by the breakdown of chlorophyll in autumn;
they are actually created at this time.
So that raises a question, why would a tree produce more anthocyanin just before dropping its leaves?
Why does the tree spend so much of its resources doing this just before the leaves fall off?
On the surface, that doesn’t make sense.