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Plants and the Water Cycle
Keeping Cool Interactive Slideshow
Keeping
Cool…
Have you ever exercised so much that you started to…
Sweat?
Courtesy: Bill McKee, Earthdance.org
Courtesy: Larry Imperiale
Sweating is the way that our bodies keep
cool. If we did not have a way to release
the heat our bodies generate, we’d be in
trouble. In fact, heat stroke is a very
dangerous condition that occurs when your
body is not able to keep cool.
Did you know that plants also “sweat”?
To keep from getting hot
and dying, plants transpire
water through their leaves!
We sweat (or perspire),
and plants transpire!
These openings are
emitting water vapor!
This process of
emitting water vapor
through leaves is
called transpiration.
Plants transpire gases from
small openings in the
surface of their
leaves called stomates.
Leaf under a microscope
Leaf as we see it
What would happen if plants didn’t transpire?
Well…look what happens to a teapot on a stove.
This red teapot is full
of water. When water
is heated, the energy
(heat) moves from the
stovetop, to the pot, to
the water. The water
gets hot, and turns
into a vapor. Soon…
you’ll see the steam
coming from the spout!
But…
What happens to a
tea pot when you
put it on the stove
without any water in
it? Yep! It gets
Looks like this teapot got toasty!
See the crack from the heat?
HOT!
Don’t try that one!
Just like full teapots, most green leaves are full
of water.
So when a stove heats
up a full teapot, out
comes the water vapor.
And when the sun heats
up a nice green leaf, out
comes the water vapor!
The water absorbs the
heat, which keeps the
teapot from melting.
The water absorbs the
heat, which keeps the
leaf from dying!
And just like empty teapots, most brown leaves
have no water.
So when a stove heats
up an empty teapot, the
teapot starts to melt.
And when the sun heats
up dry leaves on plants,
they start to get hot
and die.
So, just like humans sweat to
keep cool, plants on the earth
do the same thing. Each of
these trees in these pictures is
transpiring water vapor (blowing
off steam!) like a tea pot when
they are warmed by the sun.
Photos courtesy of the Rainforest Foundation
What happens to the water
vapor after it leaves a plant?
Here’s a hint:
Photo courtesy of the Rainforest Foundation
Photo courtesy of Tom Warner
And what happens to the
water when it leaves a cloud?
Here’s a hint:
Photo courtesy of Tom Warner
And where does some of the
rain go?
Here’s a hint:
And where does some of the
root water go?
Here’s a hint:
Hey! That picture looks familiar!
As the water travels through these
different places, it forms a water cycle,
because it keeps moving with no starting
or stopping point. And all along the way, it
keeps plants, animals, and people cool!
What would happen to
the temperature of the
earth if we didn’t have
plants and water to help
it keep cool?
Could we become a toasty
tea pot?
Photos courtesy of NASA’s Earth Observatory