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

 I. Readings: Prior to the lab:

• Print and read the lab handouts.  Bring these materials to class

• Review, if necessary, your understanding of the concept of water potential.

III. Pre-Lab Questions:

1. Do all potato tubers have the same water potential?
    
2. Do regions of a single potato tuber have the same water potential?
    
3. What do you hypothesize the water potential of the tubers will be? _____.  
    
4. Predict the concentration of the sucrose solution that will have the same water potential as the tubers.
    
5. What do you hypothesize the osmotic potential of the tubers will be? _____. 
    
6. Predict the likely freezing point depression for the potato sap that we will collect (show your work).
    
7. Do you hypothesize that the cores incubated in the 0.7 molal solution will become more turgid or less turgid?  Explain.
    
8. Do you predict that a drop of dye will sink, float or hover in the 0.1 molal sucrose solution in which a tuber was incubated?
    

1. Biological Materials: Harmless. Obviously, do not eat any lab materials.

2. Chemicals:

• salt - non-toxic
• alcohol - since we are using denatured alcohol it is toxic if imbibed. Avoid skin contact. Rinse hands after contact.
• sucrose solutions - non toxic
• Sucrose dyed blue with methylene blue – wear gloves and goggles when using methylene blue treated sucrose.

3. Safety Eyewear: Goggles are necessary when using methylene blue solutions.

4. Other:

5. Disposal:  Compost plant materials in lab composter. Sucrose solutions can be discarded down the drain

6. Supply list:  Click here

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