AP Lab 9

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


Post Lab

Part 6: Questions

Page 105 Analysis of Results #1-6

Page 107-108 Describe these parts of plants (theme: structure and function)

a. parenchyma

b. sclerenchyma

c. collenchyma

d. xylem

e. phloem

f. epidermis


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?