What causes leaves to change colors?

It’s all about Chemistry:

Not all leaves turn vivid colors.  Only a few species of deciduous trees produce the beautiful colors this time of year.  In Minnesota, most notably, we have aspen, maple and oak.  Soil moisture, precipitation, temperature and light all contribute to fall color.  Light, the lack of it, is the main agent.

As autumn days grow shorter, thus less light, chemical changes in deciduous plants cause a “corky” wall to form in between the twig and leaf stalk.  This “corky” wall or abscission layer eventually causes the leaf to drop.

The chemical change seals off the vessels that supply a leaf with nutrients and water.  It also blocks exit vessels, thus trapping simple sugars in the leaves.   Reduced light, lack of nutrients and not water add up to the chlorophyll (which makes the green color) to die.

Once the green is gone, other pigments take over.  Carotene (yellow) and anthocyanin (red) exist in the leaf all summer but are overpowered by chlorophyll.  The brown in autumn leaves is a result of tannin.

Sugar trapped in the abscission layer is largely responsible for the vivid colors.  Sunlight acting on the trapped sugar also helps to manufacture anthocyanin (red).  This is why colors on bright fall days are crisper and duller or more pastel during times of rain.

A wet growing season and a dry autumn filled with sunny days combined with cold frost free nights helps produce the most vibrant colors of fall.

 

Source: Farmer’s Almanac 2020

 

This is a helpful graphic to sort out all the information above:

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Posted in Fun Facts /General Information /global interest /Uncategorized /

Who was Leif Erikson?

October 9th marks Leif Erikson Day

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Leif Erikson  is generally believed to be the first European to reach the North American continent.  He was son of Erik the Red, founder of the first European settlement on what is now called Greenland.  Around 1000 A.D., Erikson sailed to Norway where he was converted to Christianity by King Olaf I.  Losing his course returning to Greenland, Erikson landed on the North American Continent.  Due to the abundance of wild grapes that were growing there, he called it Vinland.  He spent time on Vinland and returned to Greenland.  He never made a return trip to North America.

The location of Vinland in North America has been debated over the centuries.  In the early 1960’s excavations at L’Anse aux Meadows, on the northernmost tip of Newfoundland, uncovered evidence of what is believed to be the base camp of the 11th century Viking exploration.

Upon Erik the Red’s death,  Leif took over the Greenland settlement.  He had two sons, Thorgils and Thorkel.  Thorkel became chief after his father’s death in 1025.

In the late 19th century many Nordic Americans celebrated Leif Erikson as the first European explorer of the New world.  In 1964, President Johnson declared October 9th as “Leif Erikson Day”.

DID YOU KNOW?

Down at the Minnesota State Capitol building in St. Paul, there is a statue of Leif Erikson.

MN LEif Erikson

Source: History.com

 

Posted in global interest /History /