Why do leaves change color?

Discussion in 'Landscape Architecture and Design' started by Coffeecraver, Oct 19, 2004.

  1. Coffeecraver

    Coffeecraver LawnSite Senior Member
    from VA.
    Messages: 793

    A chain reaction occurs when sunlight strikes the pigment in leaves, allowing
    us to see various leaf colors throughout the year. Four broad categories of
    pigment play a crucial role in autumn beauty: chlorophylls, carotenoids,
    anthocyanins, and tannins.

    During the spring and summer, leaves are the principal site for the
    photosynthetic process that transforms carbon dioxide and water into the
    carbohydrates that fuel tree growth. This food-making process takes place
    in numerous cells containing chlorophyll, the pigment that gives leaves their
    green color.

    As days shorten and temperatures cool in autumn, the synthesis of new
    chlorophyll drops off, green color disappears, and the rate of photosynthesis
    declines. Trees become frugal and more efficient, pulling nutrients such as
    nitrogen and phosphorus into twigs and branches for winter storage, further
    enhancing the loss of chlorophyll.

    Along with chlorophyll, leaves contain yellow or orange carotenoid, the same
    pigment that gives carrots their familiar color. Masked for most of the year
    by chlorophyll, the carotenoids reveal themselves in autumn, most noticeable
    as yellows and golds in tree species such as Norway maples, Ohio buckeyes,
    sycamores, birches, and hickories. For example, the golden yellows seen in
    beech leaves result from the presence of tannins and carotenoid pigments.

    The vivid pink, red, and purple leaves seen on maples, sassafras, sumacs,
    white and scarlet oaks, and many other woody plants are formed by
    reactions between various sugars and complex compounds called anthocyanins.
    A mixture of red anthocyanin pigment and yellow carotene often results in
    the bright orange color seen in some species of maples.

    Fast Facts: Autumn Colors
    Fertile soil enhances the intensity of reds in leaves.
    The more light a leaf is exposed to, the more likely it is to turn red.
    Weather conditions most favorable to brilliant color are warm sunny days
    followed by cool nights with temperatures below 45 degrees (not to freezing
    Rainy or cloudy days near "peak coloration time" will dampen the intensity
    of autumn color by limiting photosynthesis.
    Freezing temperatures and heavy frost can kill the brilliance of autumn color
    by severely injuring leaves before pigments are fully developed.

    The International Society of Arboriculture (ISA) is a nonprofit organization
    supporting tree care research around the world. Headquartered in
    Champaign, Ill., ISA is dedicated to the care and preservation of shade and
    ornamental trees. For more information, contact a local ISA Certified
    Arborist or visit www.treesaregood.com.

  2. DALMlawn&landscaping

    DALMlawn&landscaping LawnSite Member
    from TX
    Messages: 186

    well, i'm glad someone paid attention to their horticulture books, i sure haven't...
  3. fearthedeere

    fearthedeere LawnSite Member
    Messages: 109

    thanks for the Botany lesson! (As if I need any more of that class)
  4. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Messages: 260

    Coffeecraver Thank you for posting "Why do leaves change color?" I think about this every fall, but never take the time to research it... aj

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