Where does the water go?
Bellringer: Yesterday we talked about how there were 4 liters of water that were lost
from the sunflower over the weekend. I also measured the potato vine now placed at
the front of class. This vine lost much water over the weekend, yet, its weight
remained the same. Discuss with a classmate where you think that the water went.
Daily Objectives: By the end of class today you should be able to:
1. Define transpiration and explain why it occurs in plants.
2. Follow the pathway that water takes through plants from root uptake to evaporation at leaf cell
surfaces.
3. Describe how environmental conditions alter rates of transpiration.
4. Explain how the plant is able to alter rates of transpiration.
Go to the class wikipage and click on the Freshman Science Page> follow the link to the transpiration lab.
http://www.sciencemag.org/site/feature/misc/webfeat/vis2005/show/transpiration.swf
Transpiration is a simple word to understand. It is made up of two simple root words.
The first part of the word, Tran, is a Latin word meaning through. Next, spire is an Old English word for
shoot or stem of a plant. So, transpiration is the passage of water through the stem of a plant.
1. What percent of water is lost through “transpiration”?
________________
2. What are two things that this water loss allows the plants to do?
________________________________________ ____________________________________________
3. Click on the animation marked Stomata Detail
Stomata is also an easy word to understand. Stoma means mouth in Greek. Just like in our bodies,
plant’s Stomatas/mouth is where they “breath”.
Draw a picture of several stomata in the circle and point to the underside of this leaf to indicate the
stomata’s location. Include the Guard Cells in your diagram. (You may want to do a brief google search
to get a clearer picture to copy- but don’t take too long.)
4. Why would a plant have stomata on only one side of their leaves? ____________________________
5. Note how each water molecule that leaves the stomata pulls an additional water molecule closer to
the “mouth” of this plant. In chemistry this is called a Chemical _____________________. It is what
holds together two atoms or two molecules (a molecule is made of several atoms).
6. Water is a molecule (Y/N) _________ 7.Hydrogen is a molecule (Y/N) __________________
8. Under the close-up of the stomata click on the button> Top. Look at how the water is leaving the
leaves. Open and close the Stomata.
Describe how the plant changes to stop water from evaporating? (2pts)
_____________________________________________________________________________________
_____________________________________________________________________________________
9. Why would a plant close its stomata? (2pts)
_____________________________________________________________________________________
_____________________________________________________________________________________
10. Why would cacti have very few Stomata? (2pts)
_____________________________________________________________________________________
_____________________________________________________________________________________
11. Exit this animation and click on the xylem animation. Xylem is not an easy word to remember. It is
the name of the inside of a plants trunk. If you have ever cut down a Christmas tree this is the hardwood
that is at the very center.
Using the information you have, describe what the xylem does and how. (5pts)
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
12. Draw a plant on the back page of this exercise. Diagram the passage of water from the beginning to
the end. Label all three sites of the process.
13.( 3pts) Exit this animation and click on the root animation. Water enters the plant at its
____________ then travels up through the ______________ then it exits out the plants _____________
on the leaves.
14. Now, click on the bottom part of the main animation where it says cuticle. This is the same word as
the skin that covers over your fingernails. A cuticle is a waxy type of skin. Some desert-like plants like the
ones I have in my room have a very thick cuticle. (2pts)
This thick cuticle causes (More/Less)____________ transpiration, and therefore, (More/Less) ________
water loss from the plants.
15. Can you think of anyways that our Coleus plants have increased their boundary layer? (+ 2)
__________________________________________________________________________________.
16. Based on what you know predict whether the following external environment would increase or
decrease the rate of transpiration before you click on the links.
*** The external environment will affect the plant. The effect of this will be a change in the rate of
transpiration.***
(1pt)
Environmental Change (affecting plant)
Humidity
(Increase or decrease in transpiration) final effect
Increased Light
Wind
Cool Air
17. Were you right? What do scientists predict the actual response will be? (4pts)
Environmental Change (affecting plant)
Humidity
(Increase or decrease in transpiration) final effect
Increased Light
Wind
Cool Air
I hope you have learned something today. Tomorrow we will grade this “Virtual Lab”. Remember,
once I have my grades entered in I will not take any late-work. This is my policy. If you cannot get all
the way through this worksheet please find the time to finish it before tomorrow.
-If you want to use the library again ask Sandy…. (KINDLY ASK SANDY!!! –she is someone who
you want to be your friend) if/how you can do that during your clubs today.
- Mr. Smalley