Unit 1 Biology
Transpiration Terrarium
Introduction to Lesson:
30
In this activity, students will make a small terrarium that will allow them to observe and
measure the amount of water given off through transpiration.
Objectives:
Students will observe transpiration occurring in a plant placed into a simple potometer
that they will construct in this activity.
Students will connect what they see with the process of water movement into and out
of a plants tissues.
Materials and Resources:
1.
2.
3.
4.
5.
6.
7.
Two clear plastic cups per student
Two square pieces of cardboard to place between the cups
Plant shoot, preferably with a woody stem (to be provided by teacher or students)
Vaseline or similar brand of petroleum jelly
Measuring cylinder
Water
Scissors
Before beginning the experiment:
Design an appropriate control. Remember the control provides known results with
which your results can be compared against. Check with your teacher before beginning
the experimental procedure
Experimental Procedure:
1. Using the scissors CAREFULLY, make a small hole (just big enough for the plant
stem) in the center of the piece of cardboard.
2. Take one shoot of a healthy broad-leaved plant. Cut the stem on an angle
immediately before use, since an angular cut exposes a larger area of the stem for
water intake.
3. Pull the plant stem through the hole and seal around the hole with petroleum jelly.
4. Fill the bottom cup with a KNOWN amount of water (BE SURE THAT YOU
MEASURE THE EXACT VOLUME USED AND THAT NO WATER IS LOST AFTER
THAT) and place the stem with the cardboard collar into the cup. Record the volume
of water in the bottom cup in the table provided.
5. Construct the control, and draw a labeled diagram showing your control in the space
below:
Leafy plant shoot
Vaseline
1 mark: appropriate
control
Cardboard
Plastic cup
Known volume of
water
Experimental group
1 mark: well labelled
diagram
Control group (2 marks)
6. Put the two small terrariums in the environment you have been designated
7. Leave the terrarium cups set up in the environment for ___________(to be
determined by your teacher) days and measure the amount of water transpired.
This will be done by measuring the amount of water lost from the bottom cup.
Results:
The table below is not complete. You need to fill in the units and the title, and only
record the results for the environments that you have been designated. You can fill
in the rest of the table when we pool the class’ results.
______________________________________________________________________________
______________________________________________________________________________
Environment
Volume of Water at
start
Volume of Water at
end
Volume of water lost
Group Group Average Group Group Average Group Group Average
1
2
1
2
1
2
Humid air
Dry air
Breezy air
Still air
Hot environment
Cool environment
3 marks:
1 mark-- appropriate title
1 mark-- units in column headings
1 mark-- correctly calculated averages
Discussion Questions:
Total: 26 marks
1. Compare the results achieved for transpiration in dry air and humid air. Which
environment provided the highest amount of transpiration? Explain why this is,
with reference to your results.
a)
 1 mark: dry air
 1 mark: quote data for humid air AND comparing with dry 2MARKS
b)



1 mark: highest concentration gradient of water between leaf and
atmosphere OR largest difference in concentration of water between leaf
and atmosphere
1 mark: results in faster rate of evaporation/diffusion of water air
AND one more point: either a statement about the amount of water in the
air of each or a description of both instances.
3 marks
2. Compare the results achieved for transpiration in breezy air and still air. Assuming
that the water content of both atmospheres was the same, explain why more water was
lost through transpiration in the breezy air.



1 mark: constantly moving stream of air carries away water vapour
1 mark: resulting in higher concentration gradient of water between leaf
and atmosphere OR larger difference in concentration of water between
leaf and atmosphere
1 mark: results in faster rate of evaporation/diffusion of water
3 marks
3. Transpiration is vital for the life of a plant. Explain how transpiration in a plant is
needed for photosynthesis to occur.


Transpiration pull draws water up from the roots, and delivers water to
leaves
Leaves need water to carry out photosynthesis
2 marks
4a. What was the purpose of the Vaseline in this set up?
Prevents loss of water from the bottom cup through evaporation
1 mark
4b. Sarah constructed a set-up similar to the one you made, except she forgot to add
Vaseline. Would the amount of water lost in Sarah’s set up be more/ less/ the same as
the actual rate of transpiration? Why?

Actual amount of transpiration would be less than measured volume of
water loss( the amount of water lost in Sarah's set up would be MORE than the actual rate of
transpiration)

Water is being lost through evaporation/diffusing through gap between
stem and cardboard as well as transpiration
2 marks
5. In another experiment, Vaseline was smeared on the top of the leaves from Plant A,
and on the bottom of the leaves from Plant B. Vaseline serves to clog up the pores,
preventing water loss.
Vaseline
Plant A
Plant B
Both plants were placed in the same environment and left for two days. The amount of
water lost from both plants was measured.
Which of these plants would have the higher rate of water loss? Why?


1 mark: Plant A
1 mark: Water loss/transpiration occurs through the stomata


1 mark: More stomata on the underside of the leaf (no marks given for
stating that stomata are ONLY only on the underside)
1 mark: Plant B has more stomata covered with Vaseline, so less water is
lost through transpiration OR Plant A has more stomata exposed, so more
water is lost through transpiration
4 marks
6. Plants can control their water loss by losing their leaves. Would you expect a shoot
with 8 leaves to lose more or less water than a shoot with 4 leaves. (Assume all other
factors remain constant.) Explain your answer.


1 mark: Shoot with 8 leaves would lose more water than the shoot with 4
leaves.
1 mark: more leaves = more stomata through which water can be lost/ a
greater surface area across which water can be lost through pores
2 marks
7. Roots are an essential structure in all living plants.
a) What are the 2 main functions of the root?
1. Anchor plant to ground
2. Absorb water and dissolved minerals from soil
(ALSO ACCEPT STORAGE OF SUCROSE OR STARCH)
2 marks
b) Choose 1 of the functions listed above. How do root hairs help to suit the root to this
function?
Either of:
1. Extensive network of root hairs drive deep into the soil to keep the plant
anchored
2. Large surface area: volume ratio of root hairs allow for faster rate of
absorption
1 mark
For questions 8-11, circle the most suitable option.
8. Water loss from a plant will be greatest when environmental conditions are:
a) cold and humid
b) cold and dry
c) hot and humid
d) hot and dry
9. Stomata close when :(the guard cells):
a) Guard cells become flaccid
b) Guard cells become turgid
c) photosynthesis begins and the internal CO2 concentration decreases.
d) Guard cells gain water
10. Which of the following terms would be used to explain how trees can lift water to
heights of ten stories or more?
a) adhesion
b) cohesion
c) transpiration pull
d) all of the above
11.
Structure
Y
Structure
X
The figure above shows a high power (x400) photograph of some leaf surface cells. Which of
these statements best describes Structures X and Y?
a) Structure X is a chloroplast and Structure Y is a guard cell.
b) Structure X is one of many stomata and Structure Y is the cuticle.
c) Structure X is one of many stomata and Structure Y is a guard cell.
d) Structure X is one of many photosynthetic cells and Structure Y is of the upper leaf surface.