Why do leaves change colours? Scientists can’t agree
Ottawa Citizen

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By Tom Spears, Ottawa Citizen, November 2, 2016

Thousands of years after humans first saw fall leaves change colour, the world’s top planet scientists still can’t agree on why it happens.

Sure, they know the steps that happen: Fading leaves lose their green chlorophyll, which lets yellow-orange chemicals (carotenoids) show through. Then some plants, but not all, manufacture red-purple chemicals (anthocyanins).

http://ottawacitizen.com/news/local-news/scientists-are-still-debating-why-leaves-change-colour