It's that time of the year when the wind chills, the songbirds depart, and the leaves turn brilliant colors before falling off the trees. While we all get to witness the hues of autumn, the reason why the leaves change color remains a lesser known secret of the season. During the spring and summer, leaves are colored by chlorophyll, the green power-houses responsible for photosynthesis inside the cells.
As the temperatures drop and less sunlight shines on the trees, plants know it is time to start getting ready for the upcoming winter months. Chlorophyll begins to break down, and from underneath all of those fading, green cells, the other colors begin to reveal themselves. Yellows and oranges created by pigments called carotenoids were always present in the leaf, but are no longer masked by green.
The red hues of New England autumns come from a different chemical called anthocyanin. This chemical is produced in autumn under favorable weather conditions and helps the newly-depleted leaf stay in production longer. What a beautiful, chemical performance to herald the coming winter!
-- Dominique Biondi, Environmental Educator