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

Determining the Q10 for the Potato Experiment

(note:  I haven't tried this one yet - consider this lab experimental.  It may need work!)

Q10 refers to the temperature quotient and is a ratio of the velocity of a process at a given temperature to that at a temperature 10 C lower.  The advantage of Q10 is that it enables us to determine if a process is a physical or chemical one.  Chemical reactions like those that occur in organisms, typically have a Q10 of ca. 2.0 – 3.0.  However, purely physical processes have a Q10 of approximately 1.0.  The following equation is used to calculate the Q10:         log Q10 = (10/(T2 – T1)) log K2/K1

where

T2 = higher temperature (in K or C)
T1 = lower temperature (in K or C)
K2 = rate of reaction at higher temperature
K1 = rate of reaction at lower temperature

To determine the Q10 of water uptake into the potato cores we will perform the Gravimetric experiment at different temperatures.

Protocol:

1. Set up the gravimetric experiment as previously described with the exception that only the 0.6 and 0.7 molal sucrose solutions will be used.  Prepare two samples of each.

2. Incubate one sample of each at room temperature and the other at a higher (or lower) temperature.

3. Record the temperatures for all samples and time of incubation in Table 1.

4. Complete Table 2.

 Table 1:  Tuber Data Higher Lower Temperature (C) Incubation Period (minutes)

 Table 2:  Potato Tuber Data [Sucrose] (molality) Water Uptake at lower temperature (cm3) Water Uptake per minute at lower temperature (cm3 min-1) Water Uptake at higher temperature (cm3) Water Uptake per minute higher temperature (cm3 min-1) Q10 0.6 0.7 Mean

Data/Analysis:

1. Is water uptake a physical or chemical process?  Explain.

Reference:

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