Names:________________________________
Transpiration Lab (Whole Plant)
Objectives:
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To understand how water moves from roots to leaves in terms of the physical and chemical
properties of water and the forces provided by differences in water potential.
To understand the role of transpiration in the transport of water within a plant.
To understand the structures used by plants to transport water and regulate water movement.
To test the effects of environmental variables on rates of transpiration using a controlled
experiment.
To design an experiment to test the effects of a variable on transpiration.
Procedure:
1. Wrap the entire root ball in a plastic bag, snug it up to the stem with string, mark with your group
name, and weigh on Monday. Weigh each successive day for the entire week.
2. Brainstorm - What variables could impact the rate of transpiration for your plant? How could you test
one of these variables? Design and experiment that allows you to test the effect of your variable on
transpiration rate. (Complete an Experimental Design Template – part A)
3. If your plant blooms, be sure any leaves or blooms that fall off are put back in the center of the plant to
be weighed each day so as not to represent water loss.
4. Write a hypothesis about what you think what will happen based on your knowledge of transpiration
and plants (to be included in the experimental design template – part A)
Results:
Determine the % change in mass over the week and graph. Be sure your graph has all of the
appropriate titles and units.
Analysis:
1. Complete Part B of the experimental design template.
2. Calculate the average rate of water loss per day for each of the treatments.
3. In part B (results) explain how did each condition affect the gradient of water potential from the stem
to leaf in the experimental plant?
4. In part B (conclusions) explain why each of the conditions causes an increase or decrease in
transpiration compared with the control.
5. What is the advantage to a plant of closed stomata when water is in short supply? What are the
disadvantages?
6. Describe several adaptations that enable plants to reduce water loss from their leaves. Include both
structural and physiological adaptations.
Experimental Design Template
Part A: To be completed before beginning the investigation.
What question will you explore?
On the basis of your previous laboratory experience, background knowledge, and research, what is the
hypothesis that you will test?
What will be the INDEPENDENT VARIABLE?
What will be the DEPENDENT VARIABLE?
What equipment and materials will you need (list items and quantity)?
What procedure (step-by-step) will you follow?
What safety steps will you follow (equipment and procedures)?
How will you collect data?
How will you analyze data?
Part B: To be completed during or after your investigation
What changes or modifications have you to the investigation?
Complete data table and graph of % change in mass.
What results did you see in the experiment?
Was the hypothesis accepted or rejected? What conclusions can you draw on the basis of data and analysis?
What sources of error may have existed, and how might the experiment have been conducted differently?
What additional questions arose from the experiment?
Data/Observations
Type
Day 1 (first
day)
Day 2
weight
weight
Day 3
%
change
weight
Graph of Change in Mass for Each Plant
Response to Analysis questions 5 & 6 (page 1 of lab):
Day 4
% change
weight
Day 5
% change
weight
% change