Falling Colours
BY Christine Bowen
ON September 29, 2017
Every autumn our forests change into a brilliant mosaic of yellow, orange and red as the leaves change colour. In other seasons, we see only green due to high concentrations of chlorophyll relative to other pigments. The yellow (carotenoids) was present in the leaf all year round and can now revel itself, because in fall as chlorophyll dies it exposes  those pigments that were already present but masked by the abundance of chlorophyll. In comparison, the red (anthocyanins) is actually a new addition to the leave in the autumn! Why produce red pigments? Well, the trees could be doing this to protect against harmful effects of light at low temperatures or because red signals poison to migrating insects causing them to avoid munching  the tree’s few remaining leaves. Which colour will be more dominate on a tree, and how bright it will be is also a mystery we can continue to enjoy!
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2.Archetti, M and S.P. Brown. 2004. The coevolutionary theory of autumn colours. The Royal Soceity 271:1219-1223.
3.Lev-Yudan, S. and K.S. Gould. 2007. What do red and yellow autumn leaves signal? The Botanical Review. 73(4):279-289.
Author Bio - Christine Bowen
Program Coordinator for Bay Area Restoration Council
Program Coordinator for Bay Area Restoration Council

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