Fall Colours

With a unique blend of science and humour, American naturalist and science educator Milos Radakovich is an extremely popular cruise ship lecturer.

He has written two volumes full of what he calls “Bite-size SCIENCE snacks” called 90 SECONDS. These articles were written to be delivered as 90 second radio spots. I have read and reread all many times.

If you are interested in ordering a copy or for more information e-mail Milos at milos@mbay.net

Fall Colours

For years, scientists have studied how leaves prepare for the annual show of fall color. The molecules behind bright yellows and oranges are well understood, but brilliant reds remain a bit of a mystery.

In response to chilly temperatures and shorter days, leaves stop producing chlorophyll, which normally allows them to convert sunlight into sugars, oils and starches. Because chlorophyll is sensitive to cold, early frosts will turn off production sooner.

Meanwhile, orange and yellow pigments, called carotenoids (think “carrots”), shine through the leaves’ outer skin. The yellow color has been there all summer, but you don’t see it until the green fades away. That’s the dominant color change in aspen and beech trees.

The radiant red hues that color northern maple and ash forests in the fall are more of a mystery. The red color comes from an-thocyanins, which unlike carotenoids, are only produced in the fall. They also give color to strawberries, apples, and poison oak.

On a tree, these red pigments act as sunscreen and shade the leaf from excess light. They also serve as antifreeze, protecting leaf cells from freezing.

Trees produce the red anthocyanins in response to cold, UV ra-diation, drought, and fungi, so red leaves are also a signal of dis-tress. If you see leaves turning red early, say in late August, the tree is most likely not having a good summer

Scientists hope that studying anthocyanins and other pigments could provide an early indication of environmental problems, and even tell us how trees are feeling.




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