As leaves start littering sidewalks and roads around the nation, and trees are left stark naked, a team of researchers have found why they think leaves turn colors in the fall.
Eric Zeldin and Brent McCown of the UW-Madison horticulture department think the radiant colors are a form of sunscreen. Before the leaves sinece every fall, the tree must suck out every bit of energy from that leaf to help over winter.
'The pigments shade sensitive photosynthetic tissue in the fall while trees reabsorb nutrients from their leaves,' said Bill Hoc, a horticulture research assistant at UW-Madison.
In addition to high light levels, other plant stressors such as near-freezing temperatures, drought and low nutrient levels trigger increased levels of the pigments.
The researchers' theory also supports the observation that autumn colors are best when the fall features dry weather with bright, sunny days and cold nights.
