Completing the Research Notebook for AP Biology Lab #9.....Transpiration
Resource: Lab Nine, Transpiration
Page 99 in the AP Biology Lab Manual
Part 1: Title
Develop a title in the form of a question after completing the pre-lab.
Part 2: Objectives (What are the objectives for this laboratory?)
Part 3: Pre-lab Questions
a. Define these terms: transpiration, guttation
b.. How is water potential involved in the transport of water up from the roots in the xylem?
c.. In the overall process, what causes water to move into the roots by osmosis?
d. What is the most significant force moving water/minerals in the xylem?
e. Trace the path of water as it moves from soil, through the plant and out of the stomates. Find
your answer in The Details of the introduction and mention every part of the plant that is involved in
this. Note: you must understand how water potential is involved. Water will move from areas of
high water potential to low water potential.
f. Explain what causes “tension” (negative pressure) to form in the xylem.
g. What environmental conditions influence the opening and closing of stomates?
Part 4: Method
Transpiration will be studied under various lab conditions using a potometer. A plant cutting with
leaves will be placed in a piece of tubing, and the tubing will be connected pipette (alternatively, the
tubing could be connected to a pressure probe in order to collect data to evaluate transpiration).
The plant cutting will be subjected to room conditions, a floodlight, a fan, and mist, and the volume of
water lost by the leaves in the cutting will be measured by reading the pipette (or by recording
pressure changes with a pressure probe). Leaf surface area will be calculated, and water loss in mL /
m2 will be calculated. Class average cumulative water loss will be recorded for each environmental
A nut and bolt microtome will be made to make cross sections of the stem of a plant. The cross
section will be stained and observed under a microscope to view plant tissues (xylem, phloem, and
epidermis) and cell types: parenchyma, Schlerenchyma, and Collenchyma.
Part 5: Data Tables
You will need table 9.1.
You will need mass of leaves___________ grams
You will need to show calculations for leaf surface area.
You will need Table 9.2
You will need Table 9.3
Part 6: Questions
Page 105 Analysis of Results #1-6
Page 107-108 Describe these parts of plants (theme: structure and function)
A stem cross section will be drawn and labeled (you might find a stem cross section in your text to
help guide your drawing).
Part 7: Graph
See page 104 for directions. Graph the average for class data for each treatment.
Part 8: Theme Correlation
Inquiry: How was this experiment controlled?
Structure Fits Function: Explain how cells and tissues are organized in a stem and review their
Part 9: Conclusion
In this lab, you set up a plant cutting in a potometer and studied transpiration. Explain transpiration
by analyzing the data from the lab FOR EACH CONDITION, comparing them and their affects on
transpiration. What plant structure/function is involved?