_edited.png)
_edited.png)
_edited.png)
_edited.png)
I'm so glad I live in a world where there
are Octobers.
L.M. Montgomery
Cut Off
and
Booted Out!
Fall. It is my favorite season.
It has an energizing crispness in the air.
It is a wonderful time to enjoy sunny days
and go on walks and bike rides. And of course,
you know why it is called "fall" ... the leaves
fall to the ground from the trees.
However, the curious and interesting part
is that the leaves are more than simply
falling off the tree.
They are being cut off and booted out!
Goodbye and farewell! It sounds dramatic,
but it is actually for the good of the tree,
to guarantee its survival over the winter
and help it to re-emerge strong and healthy
in the spring.
When the days grow shorter and colder,
a hormonal change occurs within trees.
The hormones activate a process that
is called abscission.
When you look at the word "abscission",
does it make you think of another word?
Look at the middle part of it. Scissors!
This is what happens: A line of abscission cells form where the leaf stem meets the branch. These cells push the leaf off the stem.
Essentially they cut the leaf off ... like scissors. Abscission has the same root as the word "scissors"...designed to make a cut.
(Word etymology can be fun too,
but that is another subject.)
Why does this happen? The job of a leaf
is photosynthesis. That is the process in which the leaf absorbs sunlight and converts
that energy - with the help of the water
in the leaf - into food for the tree.
This "food production" decreases as the days
get shorter and colder in the fall.
Abscission then begins taking place. The veins that move water into the leaves are choked off and the leaves become dry and brittle.
Eventually the leaves are pushed off the tree.
If abscission did not happen, the leaves would stay on the tree. Then later on, when those
occasional warm days come during winter,
the leaves would start photosynthesizing again. After all, they are likely thinking,
"Woo hoo! Time to enjoy the sunshine,
absorb its wonderful rays, and make some food for this tree I am attached to!!"
The leaves would take up some water from
the roots of the tree (because water is needed
for photosynthesis) and absorb the sunlight
and make food once again.
However, this would not be good at all
because when the cold hits again,
the water the leaves just took on would freeze
and the leaves would die! Sad day for the leaves!
The tree would then be stuck with a lot of
dead leaves attached to it. Remember, no abscission, no falling off of the leaves.
The tree itself could then possibly die.
Sad day for the tree!
Now we see why trees wisely cut off old leaves each fall. Every spring they need brand new budding leaves to start the whole process again
of photosynthesis, so they can be fed and live for
another season. You have to admit this is
an amazing process of nature! It ensures
the continuous renewing of our shade-giving, oxygen-producing trees!
I really like what Robert Krulwich says
about abscission (Krulwich Wonders science page of NPR website):
Instead of calling the season "fall",
trees would call it the "Get Off Me" season!
Illustrations - permission obtained via store policies and direct communications:
dog by CliptomaniaCreations (Etsy) and blowing tree by NightingaleCraftery (Etsy)