Why do leaves change colour in autumn?

Asked by: Davina Taunton, Ledbury

Deciduous trees drop their leaves to reduce water loss during winter, when it is too cold to grow. But rather than just discard the entire leaf, the tree recycles as much of it as possible, to conserve nitrogen. The green chlorophyll is the first to be broken down and reabsorbed, which allows yellow carotenoids and red anthocyanin to show through.

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