Autumn is emerging here on the landscape of the Finger Lakes Region. The first leaves are changing, exhibiting dazzling designs of bright reds, yellows, and greens often veined within the same leaf. Trees that are found in the northeast have various adaptations for surviving harsh winters. The process to do so begins with autumn and gifts residents and visitors with its splendor of color.
Chlorophyll is a chemical that plants use to produce food and gives leaves their brilliant green color during the summer months. In the autumn, changes in moisture levels, daylength, and sun strength trigger broad-leaf trees to cease the production of food and the chlorophyll breaks down as the trees reabsorb some of the leaf’s nutrients. Carotenes and xanthophyll pigments, which are present in leaves all summer long, are now visible without the chlorophyll to drown out their colors with its intense green. These two chemicals display with orange and yellow pigments, and are also the same compounds which give carrots their bright color. Chemical mixing within the leaf can also produce red, yellow, or orange colors.
In the autumn, as we all know, leaves fall off broad-leaf trees. This is a way for the trees to protect themselves from freezing in the winter and to get rid of some waste products. A tree actively cuts off its leaves using specialized cells through a process called abscission. In the end, the leaf is left hanging on like a broken fingernail until a gust of wind blows it off. Once the leaf has fallen, a protective layer of cells grows over the spot where the leaf had been connected, leaving what is known as a leaf scar. The leaf scars of black walnut trees look like funny, little monkey faces and can be amusing to look at.
Not all trees in the north lose their leaves, so we wonder, What about evergreen trees? Evergreen leaves, such as pine or spruce needles, contain cells that have a natural antifreeze to protect them. Their leaves appear green throughout the winter and do continue to produce food with chlorophyll, if at a slower rate. These trees and shrubs drop and replace their leaves throughout the year rather than at one punctuated time.
Trees in the north have evolved to survive the extremes of the seasons. Here in the Finger Lakes Region, the mixture of adaptations employed by hardwood and evergreen trees produces strikingly beautiful landscapes in the autumn, the glory of which is available to anyone willing to accept the gift.