Spring.wmf (18300 bytes) 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

Quiz:  Gas Exchange in Plants

Definitions Define or describe the following

  1. transpiration/photosynthesis compromise
  2. boundary layer
  3. evapotranspiration
  4. transpiration
  5. Fick�s Law (state in your own words)

Short Answer Questions

  1. Describe two reasons why the tendency for water to evaporate from a leaf is greater than the tendency of carbon dioxide to enter.

  2. Recall that the rate of diffusion of gases is inversely proportional to the square root of their relative density or molecular weight.  Consider the gaseous states of HCL (FW = 36.5 g mol-1) and ammonia (FW = 17 g mol-1).  If a drop of each is placed on a cotton ball and inserted into opposite ends of a 100 cm long glass tube, where do you predict the gases will meet (how far from one of the ends)?   Hint:  calculate the relative rate of diffusion = rate of faster diffusing gas divided by the rate of the slower diffusing gas.

van Helmont Question:   Consider the classic experiment by van Helmont in which a willow tree was weighed before and after a five-year period.  During the experimental period, van Helmont reported that the willow gained 200 pounds.  Approximately how much water (in pounds) did the plant absorb from the soil during this period?  Convert your answer to gallons and liters.   Show your work.


Guard Cell Structure Identify four features that all guard cells have in common.  Identify the function of each.


More Guard Cell Questions:  Examine the images of the guard cells below and then: (1) Indicate if the guard cell is from a grass or eudicot; and (2) label stoma, subsidiary cell, guard cell, inner wall



Graphing QuestionDraw in the predicted lines for each of the following graphs


Multiple Choice:

1. Which of the following is NOT an osmotic agent involved in opening/closing stoma:
    a.  potassium               d.  starch
    b.  chloride                  e.   sucrose
    c.  malate

2. Which of the following is NOT a role of blue light in guard cell action?
    a.  stimulates malate synthesis
    b.  stimulates starch hydrolysis
    c.  activates a calcium transporter
    d. activates a membrane bound proton ATPase
    e.  required for photosynthetic production of sucrose

3. In the light, guard cells will most likely be open after treatment with:
    a.  CCCP
    b.  fusicoccin
    c.  DCMU
    d.  vanadate

4. Zeaxantin is most similar in chemical structure to:
    a.  chlorophyll a
    b.  chlorophyll b
    c.  beta-carotene
    d.  ABA

5.  The plant hormone that is an "anti-transpirant" is:
     a.  abscisic acid
     b.  gibberellin
     c.  indole acetic acid
     d.  ethylene
     e.  cytokinin

Stomatal Action QuestionArrange the following in the proper sequence from a closed stoma to an open stoma. 

1.   stoma closed   pressure increases
  decrease water potential   turgidity increases
  guard cell turgid    water uptake by osmosis
  K+ uptake 9. stoma opens
  solute potential decreases    

Fill-in-the-Blank For each of the following treatments, indicate if it will likely cause the guard cells to open (O) or close (C) the stoma.

1.   ABA    5.   high wind
2.   blue light   6.   darkness
3.   high [carbon dioxide] in the leaf 7.   green light
4.   low pH in the cytoplasm      

True or False
Answer the following True (T) or False (F)

1.   Closed guard cells are turgid
2.   Closed guard cells have higher concentrations of K+ than open ones
3.   Guard cells close the stoma at night
4.   Guard cells close the stoma when CO2 are low
5.   Guard cells obtain K+ from subsidiary cells
6.   The main osmotic agent for opening guard cells is sucrose
7.   The more carbon dioxide that dissolves in water the higher the pH
8.   As photosynthesis removes carbon dioxide from the cytoplasm, the pH will be expected to decrease

Action Spectrum:  Sketch the action spectrum (aperture width vs. wavelength) for stomatal opening.



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Last updated:  02/24/2009     � Copyright  by SG Saupe