Thursday, June 28, 2012

Why do leaves change color, especially in autumn?


Three factors influence autumn leaf color
  - leaf pigments, length of night, and weather.
In leaf pigments, Chlorophyll gives leaves their basic green color, Carotenoids produce yellow, orange, and brown colors  and Anthocyanins gives reddish color. Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors. So the leaves look colorful in autumn.  Temperature and moisture also influence the leaf color. During sunny days, lots of sugars are produced in the leaf, which tapers off as colder days start. This in turn spur production of the brilliant colors in leaves.