Plant Physiology (Biology 327)  - Dr. Stephen G. Saupe;  College of St. Benedict/ St. John's University;  Biology Department; Collegeville, MN  56321; (320) 363 - 2782; (320) 363 - 3202, fax;    ssaupe@csbsju.edu

Stomata in Broad Beans

Objectives:  Upon completion of this laboratory you should be able to:

1. prepare an epidermal leaf peel.

2. determine the surface area of a leaf by the tracing technique.

3. determine the frequency of stomata on a leaf.

4. measure the aperture of a stoma 

5. use an ocular micrometer and calibrate it with a stage micrometer.

Pre-Lab:  Print copies of the following documents and bring them to lab:

• Exercise 1: Stomatal Morphology

• Exercise 2: Stomatal Size

• Exercise 3: Stomatal Distribution & Density

• Exercise 4: Effect of Light & ABA on Stomatal Aperture

• Making a Leaf Peel & Other Techniques to View Stomata

• Measuring Leaf Area

• Measuring Stomatal Aperture

  2.  Email to me the answer to Pre-Lab questions

Introduction:
    Stomata are the pores through which a plant exchanges gases with the atmosphere.  Carbon dioxide and oxygen, which are involved in photosynthesis and respiration, enter and exit through these pores.  The open stomata also provide a route for water to escape from the plant (transpiration).  Hence, the stomata are ultimately responsible for the energy and water balances in the plant.  It is not surprising that plants tightly control the stomatal aperture to regulate gas transfer.  In this lab we will study some aspects of stomatal morphology and physiology. 

Methods:  Complete Exercises 1 - 4.

Post-Lab:    Write an abstract of this laboratory.  To your abstract append the following:

Stomatal Morphology

1. On a separate sheet of paper, complete a sketch of the stomatal apparatus from broad bean.  Include the plate magnification and appropriate caption.

2. Email to me or put in our Public Folder a copy of the digital image of the stomatal apparatus from a species of your choice. Be sure to include somewhere the name of the species and magnification at which the image was made.  Print a copy of this image and include it with your report.

3. Address the following questions in your abstract:  What organelles did you observe in the epidermal cells?  Guard cells?  Did the stomata of the two species appear as you expected?  Do the species have distinct subsidiary cells?

Stomatal Size

1. Complete Table 1 and Table 2

2. In your abstract indicate if there is any difference in length of the stomata on the abaxial and adaxial leaf surfaces?  Cite your statistical data (Ho, t value, conclusion) to support your conclusion.  

Stomatal Frequency

1. Complete Tables 1 - 4

2. In your abstract be sure to indicate if your results were expected or not?

Light & Stomatal Aperture

1. Complete Table 1

2. Does light/dark have an effect on stomatal size?  Cite your statistical data to support your conclusion.

References:

• Hsiao, T.C. and R.A. Fischer.  1975.  In  Measurement of Stomatal Aperture and Diffusive Resistance.  Bull. 809.  College of Agriculture Research Center, Washington State University.

• Stomatal Images from CSB/SJU Plant Physiology - BIOL327

Last updated:  01/07/2009     � Copyright  by SG Saupe