Question: What causes leaves to change colour and fall of trees ?

Roberto answered on 11 Nov 2018:

Into the leaves of a tree, there are different colourful substance with different meanings. Normally, we see the leaves green because they contain a lot of chlorophyll, which is needed for them to carry on the photosynthesis process.
When Fall comes, the trees remove all the chlorophyll from the leaves because is no longer need in there. By doing so, the green colour of the chlorophyll disappears and you can see the colour of other substance presents in the leaf. Most of them are yellow, brown and red colour, and base on the abundance of this substance in different tree species you can have different colour patterns.