• Question: Why do leaves change colour in Autumn?

    Asked by Ash123 to Hummy, Lewis, James, Sandra on 14 Mar 2017.
    • Photo: Lewis Wright

      Lewis Wright answered on 14 Mar 2017:

      Leaves change colour in winter as a kind of defence mechanism.

      It would use up too much energy (sunlight that usually isnt available in the winter, and water that would be close to if not freezing) to keep the leaves alive, and so they shut down.
      Because the leaves are effectively dying, the processes inside their cells stops and the various chemicals like the green chlorophyll (the bit that absorbs the light) breaks down.
      Because different trees have slightly different chemistry going on in their leaves, different trees turn different colours when their leaves die.

      How extreme the weather is will also affect the colour the leaves turn, whereas some trees have evolved to not lose their leaves at all!

      http://www.esf.edu/pubprog/brochure/leaves/leaves.htm

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