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

Preparing a Hofler Diagram

(note:  this lab is 'experimental.'  It may need some fine tuning)

    In this exercise we will use our Gravimetric data to prepare a Hofler diagram to represent the changes in water potential, osmotic potential and pressure potential that occur in the potato tuber as they absorb water.


1.  Record the temperature of the samples in table 1.  Convert to K.

2.  Complete Table 2.

2.      Plot a graph of relative cell volume vs. [sucrose]

3.      Prepare on a single graph the following plots: water potential vs. relative cell volume; osmotic potential vs. relative cell volume; and pressure potential vs. relative cell volume.  

Table 1.  Incubation Temperature
temperature ( C)  
temperature (K)  


Table 2:  Potato Tuber Data  

[Sucrose] (molality)  

Ψ of the core at equilibrium   Equilibrium (final) Weight (g) Initial Weight (g) Relative cell volume (equilibrium weight / initial weight) Equilibrium Ψs (corrected for cell volume) Pressure Potential (Ψp )


  1. How does the graph we prepared compare to the expected plot?


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