The landscape that surrounds us in the fall is coloured by maples, beeches, chestnuts and other trees that lose their leaves in autumn.
The trees are preparing for winter rest by recovering reserves.
The chlorophyll contained in the leaves degrades. Thus the carotenoids (yellow/orange pigments) contained in the leaf are no longer masked by the intense green of the chlorophyll. And the leaves appear yellow and orange.
The red or violet colour is instead due to anthocyanins that are produced by the plant in response to night frosts. Finally, the brown colour of the leaves now close to falling is given by tannins.
Why do deciduous trees lose their leaves in autumn?
The leaves are the primary organ for chlorophyll photosynthesis (transformation of solar energy into chemical energy) and for this reason they generally have a large surface area. A lot of water evaporates from the surface. On hot winter days, the leaves would lose a lot of water by evaporation, but the tree would have no way to recover it from the cold and often icy ground.
Besides, the leaves are very fragile organs and would not be able to withstand the cold. Once the leaves have fallen, the tree can slow down his metabolism and save energy while waiting for spring!
Author of the text and image: Michela Busana