Why do trees lose their leaves?
Whatever the weather, whether it’s good or bad, you’ll need that rake to clear them up.
Asked by: Barry Cull, by email
Deciduous trees shed their leaves as an active process that evolved to conserve resources and protect the tree from being blown over in the windier winter months. The process is controlled by the plant hormone auxin.
As light levels and temperatures drop, the flow of auxin to the leaves slows and levels of another hormone, ethene, rise. This signals the cells at the base of the leaf to weaken their cell walls, at the same time as other cells expand to break the connections between the weakened cells. The result is like tearing perforated paper, and the leaf drops to the ground.
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Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.
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