The colors of leaves

The colors of leaves

Fall  is a season of change, and changing weather --mild days, cooler nights, sharp blue skies, the  glorious colored leaves.

Why do leaves change color in the fall?  

The  green of  summer leaves is the result of an abundance of  chlorophyll. In an active leaf, the chlorophyll masks the other pigment colors. But as days grow shorter in the fall,  chlorophyll production diminishes. The green fades, revealing the underlying colors in the leaves.

Carotenoids produce the yellow and orange colors in leaves and also appear in peppers, corn, carrots, daffodils, buttercups, and bananas.

Carotenoid production is not dependent on light, so levels aren't diminished by shorter days.

 Xanthophyll  is responsible for the yellow pigments of the carotenoids. (The oranges come from Carotene. ) Xanthophyll plays a part in regulating the rate of photosynthesis, by balancing the production of chlorophyll.  It's also what causes the yellowing of leaves due to stress or disease affecting  normal chlorophyll production.

Yellow leaves are characteristic of  sycamore, birch, ash, hickory, yellow poplar, some oaks and maples, and many other trees.

 Anthocyanins  are responsible for the reds and purples and even blues of flowers and fruits. They are in cherries, cranberries, red apples, concord grapes, blueberries, strawberries, and plums.

They are found in the reds of sugar maples and red maples, sumac, oak trees, dogwoods, and many other woody plants.

Tannins are the browns  in the leaves of some oaks and other trees.  They are always present, but only become visible as chlorophyll and carotenoids disappear.  Tannins are also what gives tea its color and flavor.

How does weather affect the intensity of leaf colors?

Anthocyanins are dependent on light and temperature.  Sugars remaining in the leaves on warm sunny days and cool nights increase  anthocyanin production, creating the most  intense reds.

Rainy and/or overcast days decrease anthocyanin production, resulting in more yellows and browns.

The amount of moisture in the soil also affects leaves.  A severe summer drought can delay the onset of fall colors.

A wet spring, normal summer rainfall, and  warm and sunny  fall days with cool nights are the ideal conditions for the most spectacular fall colors!




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