Author: Maddie Van Beek
Everybody sweats. Whether you are hot, nervous, or working hard, you may notice your skin forming droplets of water, or perspiration. What happens to that perspiration after you sit for a few minutes? It vanishes! But do the water molecules really just disappear into nothingness? No, of course not! Although we may not see the water droplets any more, the water molecules have simply evaporated. Evaporation is just one of the steps in the water cycle.
Everybody sweats. Whether you are hot, nervous, or working hard, you may notice your skin forming droplets of water, or perspiration. What happens to that perspiration after you sit for a few minutes? It vanishes! But do the water molecules really just disappear into nothingness? No, of course not! Although we may not see the water droplets any more, the water molecules have simply evaporated. Evaporation is just one of the steps in the water cycle.
When water evaporates, it changes from a liquid into a vapor. Therefore, evaporation is the process of water moving from the earth and into the air. One form of evaporation is called transpiration. While evaporation is the movement of water from the earth’s surface into the air, transpiration is the movement of water from plants into the air. Transpiration is kind of like a plant’s way of sweating.
Not only does transpiration cause plants to release water into the air, but it actually allows plants to absorb water from the ground through their stems. The water is transferred from the ground into the plant’s stem up through little tubes called xylem. In the image below, the xylem tubules are shown in red.
Not only does transpiration cause plants to release water into the air, but it actually allows plants to absorb water from the ground through their stems. The water is transferred from the ground into the plant’s stem up through little tubes called xylem. In the image below, the xylem tubules are shown in red.
Picture a bunch of minuscule straws sucking water out of the ground. This process delivers water and nutrients to the plant. The water travels up the xylem and leaves the plant through tiny holes called stomata. One of the stomata from a tomato plant leaf is shown below (they look like little mouths!).
Stomata may open or close to let gases in or out. For example, stomata open to take in carbon dioxide and let out oxygen. Unfortunately for the plant but luckily for us, stomata also releases water vapor. The number of stomata a plant has varies widely and depends on its environment. Trees in the rainforest have larger stomata that are open more often compared to the stomata of cacti in the desert. Trees in the rainforest need more water because they lose almost all of what they absorb, while cacti in the desert need less water, since they retain water for much longer.
Activity #1
How does the number of stomata influence a plant’s water loss? Let’s find out!
What you will need:
-Two cups
-A piece of 4x8 inch poster board
-Scissors
-Pencil
-A hole puncher
-Marker
-Tape
-Water
What you need to do:
1.Fold the piece of poster board in half.
2.Place one of the cups upside-down on top of the poster board.
3.Use your pencil to trace around the mouth of the cup.
4.Keep the poster board folded, and carefully cut out the circle you traced (You will have two identical circles).
5.Use the paper puncher to punch two holes in one of the circles.
6.Punch about twenty holes in the second poster board circle.
7.Fill both cups with equal amounts of water.
8.Use the marker to mark the water level on both cups.
9.Tape the circle with two holes across the mouth of one of the cups.
10. Tape the circle with twenty holes across the mouth of the other cup.
11. MAKE SURE the tape does not cover any of the holes, and check that the tape has secured the poster board to the edges of the cups.
12.Set the cups in the sun where they will not be disturbed.
13.Check your cups in three days.
Which cup has less water? Why?
Activity adapted from Transpiration: The Water Cycle in Plants posted on Education.com by Janice VanCleave.
Activity #2
Let’s find out how xylem work!
Have you ever seen those pretty rainbow-colored flowers? Where on Earth do these flowers come from?! Here’s the secret: They are dyed! The xylem in the stems help transfer the food coloring up the stems to the leaves of the flower. Try it out!
Activity #1
How does the number of stomata influence a plant’s water loss? Let’s find out!
What you will need:
-Two cups
-A piece of 4x8 inch poster board
-Scissors
-Pencil
-A hole puncher
-Marker
-Tape
-Water
What you need to do:
1.Fold the piece of poster board in half.
2.Place one of the cups upside-down on top of the poster board.
3.Use your pencil to trace around the mouth of the cup.
4.Keep the poster board folded, and carefully cut out the circle you traced (You will have two identical circles).
5.Use the paper puncher to punch two holes in one of the circles.
6.Punch about twenty holes in the second poster board circle.
7.Fill both cups with equal amounts of water.
8.Use the marker to mark the water level on both cups.
9.Tape the circle with two holes across the mouth of one of the cups.
10. Tape the circle with twenty holes across the mouth of the other cup.
11. MAKE SURE the tape does not cover any of the holes, and check that the tape has secured the poster board to the edges of the cups.
12.Set the cups in the sun where they will not be disturbed.
13.Check your cups in three days.
Which cup has less water? Why?
Activity adapted from Transpiration: The Water Cycle in Plants posted on Education.com by Janice VanCleave.
Activity #2
Let’s find out how xylem work!
Have you ever seen those pretty rainbow-colored flowers? Where on Earth do these flowers come from?! Here’s the secret: They are dyed! The xylem in the stems help transfer the food coloring up the stems to the leaves of the flower. Try it out!
What you will need:
-A cup
-A piece of celery (or a white flower, if you have one!)
-A knife
-Blue or red food coloring
-Water
What you need to do:
1.Cut the bottom end off of a stalk of celery. Leave the leaves attached to the top.
2.Fill a cup with water.
3.Put about four drops of blue or red food coloring in the water. Make sure the color is rich and not too diluted.
4.Carefully place the celery, bottom end down, into the cup.
5.Leave the celery in the food coloring overnight.
6.If you started earlier in the day, check back every hour or so to record observations.
What happened to your celery?
How long did it take for the food coloring to start traveling up the stem? To the top of the stem? The leaves?
After the experiment is over, look at the bottom of the stalk. Can you identify the xylem?
Image and video credits, in order of appearance:
Tedfloyd 1996. Natural Water Cycle. Uploaded from Wikimedia Commons on 6/19/2016. https://commons.wikimedia.org/wiki/File:Natural_water_cycle_1.jpg File used in accordance with the Creative Commons CC0 1.0 Universal Public Domain Dedication license.
Kelvinsong 2013. Botana curus X xylem and phloem 400×. Uploaded from Wikimedia Commons on 7/3/16. https://commons.wikimedia.org/wiki/File:Botana_curus_X_xylem_and_phloem_400%C3%97.png. File used in accordance with the Creative Commons Attribution 3.0 Unported license.
Photohound, 2007. Colorized electron microscope image of a stoma on the leaf of a tomato plant. https://commons.wikimedia.org/wiki/File:Tomato_leaf_stomate_1-color.jpg. Image released into the Public Domain.
Runnels, Lisa. Daisy Flower. Uploaded from publicdomainpictures.net on 7/3/16. http://www.publicdomainpictures.net/view-image.php?image=33863&picture=daisy-2. Image released into the Public Domain.
-A cup
-A piece of celery (or a white flower, if you have one!)
-A knife
-Blue or red food coloring
-Water
What you need to do:
1.Cut the bottom end off of a stalk of celery. Leave the leaves attached to the top.
2.Fill a cup with water.
3.Put about four drops of blue or red food coloring in the water. Make sure the color is rich and not too diluted.
4.Carefully place the celery, bottom end down, into the cup.
5.Leave the celery in the food coloring overnight.
6.If you started earlier in the day, check back every hour or so to record observations.
What happened to your celery?
How long did it take for the food coloring to start traveling up the stem? To the top of the stem? The leaves?
After the experiment is over, look at the bottom of the stalk. Can you identify the xylem?
Image and video credits, in order of appearance:
Tedfloyd 1996. Natural Water Cycle. Uploaded from Wikimedia Commons on 6/19/2016. https://commons.wikimedia.org/wiki/File:Natural_water_cycle_1.jpg File used in accordance with the Creative Commons CC0 1.0 Universal Public Domain Dedication license.
Kelvinsong 2013. Botana curus X xylem and phloem 400×. Uploaded from Wikimedia Commons on 7/3/16. https://commons.wikimedia.org/wiki/File:Botana_curus_X_xylem_and_phloem_400%C3%97.png. File used in accordance with the Creative Commons Attribution 3.0 Unported license.
Photohound, 2007. Colorized electron microscope image of a stoma on the leaf of a tomato plant. https://commons.wikimedia.org/wiki/File:Tomato_leaf_stomate_1-color.jpg. Image released into the Public Domain.
Runnels, Lisa. Daisy Flower. Uploaded from publicdomainpictures.net on 7/3/16. http://www.publicdomainpictures.net/view-image.php?image=33863&picture=daisy-2. Image released into the Public Domain.
