Why do leaves
change colors in the fall?
When fall comes, leaves change from bright green to
reds, yellows, and browns. Why do the leaves change for the fall instead
of staying green?
Leaves are the food factories of nature. Plants
suck up water through their roots. The leaves take in a gas called
carbon dioxide. Plants are able to turn carbon dioxide into the oxygen
and glucose. Oxygen is the gas we need to breathe, and glucose is a
sugar plants “eat.” Glucose gives plants the energy they need to grow
and survive. This overall process is called photosynthesis and it is
made possible by chlorophyll, which gives plants their green color.
As summer ends and fall comes, the days get shorter
and the amount of sunlight gets less. This is how the trees “know” that
it is time to get ready for winter.
During the winter, photosynthesis cannot occur due
to a lack of water and sunlight. Plants begin to shut down their “food
factory” and will live off stored energy for the winter. Trees, like
some animals, hibernate for the winter. When the trees begin to shut
down, the green chlorophyll disappears from the leaves. The bright green
fades away and we start to see the colors of fall. Some of these colors
have always been present in the leaves, but we can’t see them in summer,
because they were covered with green chlorophyll.
The bright red of a maple tree comes from glucose
getting trapped in the leaves after photosynthesis stops. Sunlight and
cooler nights turn the glucose to a red color. The brown seen in oak
trees is made from wastes left in the leaves. The combination of all
these things makes all the beautiful colors we enjoy in the fall.
weather cause a cold?
How many times as a child did you hear “Put your
coat on! You’ll catch a cold!” and “Don’t go outside with wet hair!
You’ll get sick!” After all, cold and flu season occurs when the weather
is cold, so there must be some connection, right? Not exactly.
Colds spread when you cough, blow, wipe, or sneeze
the virus from your body to another person or on a surface. So, when the
next person comes in contact with this virus, they can get a cold. A
weakened immune system (the stuff that fights a virus) can cause the
virus’ chances of living in your body to go up, but temperature does not
affect the strength of your immune system.
The common cold is most common in the winter,
because the winter snows and cold keep people together indoors. Air
circulation is low and the number of people is high, so keeping people
together in this combination gives the virus more chances to spread.
Even though it is called a cold, cold weather does
not cause you to get sick.