Name:_____________________________________________________________ Period:_______
Online Transpiration Lab Activity
Go to http://www.phschool.com/science/biology_place/labbench/lab9/intro.html
Read through all sections of KEY CONCEPTS I. (Do not read sections for KEY CONCEPTS II.)
1. Describe the pathway water takes through a plant.
2. During transpiration, water moves down a water potential gradient. What is meant by the
term water potential gradient?
3. What structure allows necessary gases to enter and water to leave?
4. What property of water causes water to “grab” the walls of the thin xylem vessels?
5. What property of water allows each molecule to be pulled up like beads on a string as
transpiration occurs?
6. Place the following in order (a-d), from highest water potential to lowest water potential,
under normal conditions:
a. MESOPHYLL OF LEAVES
b. OUTSIDE AIR AROUND LEAF
c. SPACES AROUND ROOTS
d. INSIDE THE XYLEM VESSELS
___________________________________
7. List the four steps of stomatal opening and the four steps of stomatal closing.
8. What was the surface area of the leaf in the exercise? _________
9. Why do you need to calculate the surface area of the leaf?
10. If the guard cells in a plant were deficient in K+, what would be likely to occur?
11. For each treatment, graph the transpiration lab class data below for each time interval.
Milliliters water lost per square centimeter of leaf area (ml/cm2)
Condition
0 min
3 min
6 min
9 min
12
min
15
min
18
min
21
min
24
min
27
min
30
min
Wind
0
3.70
7.77
9.87
12.34
14.19
16.29
17.90
19.87
21.60
23.45
Room
Light
Intensity
Humid
0
0.67
1.34
1.94
2.61
3.13
3.63
4.33
4.78
5.30
5.75
0
2.15
4.27
5.89
8.15
9.41
10.96
11.53
12.74
13.90
16.42
0
1.59
1.70
1.85
1.97
2.21
2.46
2.70
2.83
3.13
3.39
12. What is the independent and dependent variables in this experiment?
13. Calculate the rate of water loss for each of the treatments.
14. Explain why each of the conditions causes an increase or decrease in transpiration
compared with the control.
Condition
Effect
Explanation of effect
Light
Fan
Mist
Heat
15. How does each condition affect the water potential gradient from stem to leaf?
16. What is the advantage of closed stomata to a plant when water is in short supply?
17. Describe several adaptations that enable plants to reduce water loss from their leaves.