Plant Physiology

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:

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.
Incubate one sample of each at room temperature and the other at a higher (or lower) temperature.
Record the temperatures for all samples and time of incubation in Table 1.
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 (cm³min^-1)	Water Uptake at higher temperature (cm³)	Water Uptake per minute higher temperature (cm³min^-1)	Q₁₀
0.6
0.7
				Mean

Data/Analysis:

Is water uptake a physical or chemical process? Explain.

Reference:

Koning, Ross. 1999. Web Site: Osmosis Lab.