Hi guys! We’re just watering plants here
in the greenhouse.
You probably know that plants need water to
live and grow. And all parts of the plant
need it … even the tops of the very tallest
trees. And that can be a really long way up!
But have you ever wondered how water gets
all the way to the tops of trees, or other
plants?
Well, I could tell you. But do you want to
see for yourself?
Let’s do an experiment!
We can do it using a plant that you might
have in your house right now. It also happens
to be a great snack…celery!
Yup, celery! It’s crunchy, good for you…and
it can show us how plants move water around
inside them.
To do this experiment, you’ll need:
...a piece of celery with the leafy parts
on the top
...some dark colored food coloring. Red or
blue tend to work best.
...a cup big enough to stand the celery in
...plus a spoon, some water, and help from
a grownup.
First, fill about half of your cup with water.
Then add at least five drops of food coloring
to the water. The more you put in, the easier
it’ll be to see later, so go ahead and use
a lot!
Now, ask a grownup to cut off the bottom edge
of the celery stalk, so the celery at the
end is nice and fresh.
Then put the celery in the colored water!
Oh, I forgot to mention one more ingredient
for this experiment: patience!
You’re going to have to wait a full day,
at least, to see how the colored water changes
the celery. So put your experiment somewhere
out of the way.
When you come back a day later, have a close
look at the leaves at the top of the celery.
Pick up the stalk, too, and have a look at
the bottom edge that was standing in the water.
What do you see?
If you put enough food coloring in, and you
waited for a long enough time, you /should/
see that some of the leaves of the celery
have changed color -- to match the color of
the water!
And parts of the bottom of the celery probably
changed color, too.
So what do you think happened?
The water moved through the plant!
The colored water from the cup moved up through
the celery stalk. We can tell that this happened,
because the leafy part has changed color,
and we can see the color all through the stalk,
especially if we break it in half.
This movement of water actually happens all
the time in plants.
And it happens because water is actually leaving
the plant from the top -- through the leaves
-- which pulls up more water from below.
When a plant is ‘full’ of water -- like
a stalk of celery that’s been soaked in
water for a long time -- some of the extra
water inside leaves the plant through tiny
holes in the leaves.
And as these extra water particles move into
the air, they pull on the water particles
that are still in the leaf...which pull on
the ones in the stem...which pull on the ones
in the roots!
It’s like a big chain of water particles
pulling on each other, from the top to the
bottom of the plant.
In our experiment, water moved from the leaves
of the celery into the air.
The water particles stuck to one another and
moved through the stalk, dragging the food
coloring with them.
But the actual color didn’t evaporate into
the air...it stayed in the celery. In fact,
if you look at the bottom of the celery, the
color helps you see the special parts of the
plant that move water around inside it.
These parts make up what’s called the xylem.
The xylem is hollow, and kind of looks like
pipes, or tubes. Whether water is moving from
the root to the leaf in the tallest tree,
or moving to the top of a celery stalk in
a glass, it’s being carried in the xylem.
Now that you’ve done this experiment once,
you can probably think of lots of other experiments
to try, too.
For example! Does it matter what type of food
coloring you use?
What would happen if you split the bottom
of the celery stalk in two, and put each half
in a different color of water?
Would the same experiment work if you used
a different type of plant, or even a flower?
The possibilities are endless!
Try this experiment at home, or at school,
and share a picture or a video with us, to
show us what happened!
And come back to join as again every Monday
and Wednesday for more science and experiments!
Bye guys!
