Symbiotic Fungi: Principles and Practice (Soil Biology)

5 Measurement of Net Ion Fluxes Using Ion-Selective Microelectrodes 77
a
NO 3 – voltage (mV)
b
[K + ] voltage (mV)
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–100
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–6 –5 –4 –3 –2 –1 0
–6 –5 –4 –3 –2 –1 0
log [NO 3 – ] (A) & log [K + ] (B)
Fig. 5.6 Selectivity of the NO 3 (a) and K + (b) microelectrodes. The microelectrodes were
immersed in CaSO 4 0.2 mM solutions containing increasing concentrations of KNO 3. The
potential values were then plotted vs the log [ion] in the solution. A linear regression was plotted
on the points to determine the selectivity of the microelectrodes
experimentation. The only factors modifying the flux values are the distance from
the root and the concentration (microelectrodes).
So, which distances from the root surface to choose?
And which parameters can affect the calculation of the ion concentrations?
5.5.1 Determination of the Distances from the Root Surface
for the Measurement Points
5.5.1.1 Concept of the Undisturbed Layer and the Ionic Gradient
In our system, the woody seedling lies at the bottom of a small container (see
Fig. 5.4). This small container has a solution entry on one side and a solution exit
at the other side. The solution flows on top of the seedling and can be changed at