The Science of Changing Leaves

Last year, Smithsonian.com posted a fascinating time-lapse video of leaves transforming from chlorophyll-filled green to tones of yellow, red and brown. The video was accompanied by an article explaining how leaves change color and some misconceptions about the process.

The video was created by Owen Reiser, a mathematics and biology student at Southern Illinois University Edwardsville. Reiser, Smithsonian.com reports, took 6,000 photos of leaves to weave the video together.

CaliforniaFallColor.com has reported previously how the change of leaf color results from the loss of chlorophyl, due to shorter days and fewer nutrients. Though, David Lee, Professor Emeritus of biological sciences at Florida International University and author of Nature’s Palette, The Science of Plant Color, says many (including us) have misreported (we won’t make the mistake again) that yellow and red leaves change the same way, when they do not.

Lee states in the Smithsonian.com article that the breakdown of chlorophyll in the leaves does reveal yellow and orange (carotenoids) hidden beneath, but that red (anthocyanin) pigments are produced within the leaves as they die.

There are two schools of thought as to why this happens. One is that the red color is a defensive measure to make the plants look an unhealthy red as the leaf dies, protecting it from plant-eating bugs and animals which are conditioned not to eat red foliage.

The other thought is that red is a form of photo protection. Horticulturist Bill Hoch, Smithsonian.com reports, believes red’s wavelength helps shield the leaf by absorbing excess light allowing the plant to more efficiently remove nitrogen from the proteins that are breaking down and send that nutrient back to tree limbs and roots, saving as much of it as possible before winter.

Whatever the cause, the result is spectacular and less than a month away from being seen in California.