Autumn.wmf (12088 bytes)Introduction to Organismal Biology (BIOL221) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;

Plant Transport & Gas Exchange Study Guide

I.  Goal:  The goal of this unit is to provide a basic understanding of the process xylem and phloem transport and gas exchange in plants.

II.  Learning Objectives
:  Upon completion of this unit you should be able to:

  1. Explain what is meant by the "photosynthesis/transpiration compromise".

  2. Describe the structure of the stomatal apparatus and the mechanism of action for opening and closing the guard cells.

  3. Describe the effect of the following on guard cell activity - light, carbon dioxide, drought, abscisic acid (ABA), circadian rhythms - and explain how each relates to the photosynthesis/transpiration compromise

  4. Identify some of the functions of transpiration (water transport, evaporative cooling, minerals)

  5. Describe the structure of the phloem (sieve tube members, companion cells, sieve tube members, sieve plates, companion cells, plasmodesmata)

  6. Explain how aphids were important to our understanding of the phloem

  7. Describe the mechanism by which solutes are transported in the phloem (pressure-flow hypothesis, double osmometer). 

  8. Identify the major cell types in the xylem (tracheids, vessels, fibers, parenchyma) and describe their function

  9. Explain how water is transported in plants.  Cite the three major hypotheses (root pressure and guttation, capillary action, transpiration-pull or cohesion tension) for water transport and explain how each works.  Which is our best explanation for water transport? 

  10. Explain how the root acts like an osmometer

  11. Explain the process of guttation and the conditions that favor this process.  What is a hydathode?

  12. Outline and describe the pathway that water takes into the root.

  13. Identify the structure and function of the following features of a root:  root cap, root hair, cortex, endodermis, casparian strip, pericycle, stele

  14. Explain the concept of water potential.  Identify factors that influence water potential.  What is the water potential of pure water?   

III. Reading(s): 

IV.  Important Terms/Concepts:  (can you use the following terms conversationally?  can you write a dialog using these terms?)

  • adhesion

  • apoplast

  • casparian strip

  • cohesion

  • companion cells

  • cortex

  • endodermis

  • epidermis

  • guard cell

  • guttation

  • hydathodes

  • osmometer

  • pericycle

  • phloem

  • phloem loading/unloading

  • plasmodesmata

  • pressure potential

  • root

  • root cap

  • root hair

  • root pressure

  • sieve plates

  • sieve tube members

  • sink

  • solute potential

  • source

  • stele

  • stoma

  • symplast

  • tension

  • tracheids

  • transpiration

  • vessel elements

  • vessels

  • xylem

  • water potential

  • pressure effect on water potential

  • solute effect on water potential


V.  Additional Questions

  1. Cite three pieces of evidence that the cohesion-tension theory is responsible for water transport in the xylem.

  2. Review the Spuds demo.  Do you understand the main concepts?

VI. Some Suggested Learning Activities:

  1. prepare written answers to the objectives

  2. write a dialog using as many of the terms in the chapter as possible

  3. prepare a concept map for this material

  4. answer the questions at the end of the chapter or online

  5. go through the CD-ROM & web site that accompanies the text.

  6. write a definition for each of the terms listed in the text/notes above.  Give a specific example of each term

  7. spend approximately 2 hours per class studying this material

  8. read the summary at the end of each chapter; then re-read each chapter summary. 


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Last updated: February 25, 2009        � Copyright by SG Saupe