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Jessi: Oh 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 very tops of the tallest trees, and that can be a really long way up. But have you ever wondered how water gets all the way to the top 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! Yep, 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 grown up.

First, Fill about half your cup with water, then add at least 5 drops of food coloring to the water; the more you put in, the easier it will be to see later, so go ahead and use a lot. Now, ask a grown up to cut off the bottom end of the celery stalk so the celery at the end is nice and fresh. Then, out the celery in the water. Oh, and 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 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 this happened because the leafy parts have 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 then pulls up more water from below. When a plant is full of water, like this stalk of celery that's been soaked in water for a long time, some of the extra water 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 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 being moved from the roots 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 could 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 us every Monday and Wednesday for more science and experiments. Bye guys.

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