Application of an Electrokinetic Formulation to the Study of the Effect of Alkaline-earth Cations on the Absorption of K+-ions by Lemna minor

Ayadi, A.; Stelz, T.; Monnier, Anne-Francoise; Lassalles, Jean-Paul; Thellier, Michel

doi:10.1093/oxfordjournals.aob.a084855

Cited by 8 publications

(4 citation statements)

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“…(1) (2) CA, CAH and CH are, respectively, the concentration of the carboxylic group dissociated or not and of the free protons in the wall. The second equilibrium corresponds to the possible exchange of counterions Mz+ and H+ between the wall and the external solution:…”

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Titration of Isolated Cell Walls of Lemna minor L

Morvan¹,

Demarty²,

Thellier³

1979

Plant Physiol.

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Similarly to what happens with artificial ionic exchangers (9, 11, 17), two equilibria occur during the titration of the cell walls. The first one is the dissociation of the carboxylic groups:AH=-A-+ H+ with the dissociation constant:CA, CAH and CH are, respectively, the concentration of the carboxylic group dissociated or not and of the free protons in the wall. The second equilibrium corresponds to the possible exchange of counterions Mz+ and H+ between the wall and the external solution:MZ+ + zH+ = Mz+ + zH+ (3) where the bars refer to the wall phase, and z is the valency of the counterion.In such a system, the distribution of counterions is characterized by the selectivity coefficient (9):z-C =

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confidence: 99%

“…This was done on Lemna minor L., for which we had already a certain amount of experimental data (1,2,5,6,12).…”

mentioning

confidence: 99%

Titration of Isolated Cell Walls of Lemna minor L

Morvan¹,

Demarty²,

Thellier³

1979

Plant Physiol.

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“…Although the effects of local ion status and/or uptake-wash regime on uptake isotherm kinetics have long been recognized as very important factors influencing kinetic responses (Cram and Laties, 1971 ; Leigh et al, 1973 ; Ayadi et al, 1974 ; Tinker and Nye, 2000 ), they have been discussed only in the recent literature (Britto and Kronzucker, 2001a , 2006 ; Szczerba et al, 2006 ). Here we show that experimental procedures used to measure unidirectional ion influx across root membranes to establish ion influx isotherms will be different according to the modeling type chosen: enzyme-like or flow-force .…”

Section: Experimental Protocols For Enzyme-like Vs Flow-force Modelimentioning

confidence: 99%

“…In the flow-force procedure, the main difference is that flux measurements are performed on the roots at or close to equilibrium with the external nutrient solution (Ayadi et al, 1974 ; Tinker and Nye, 2000 ). The equilibrium is defined as no further net movement of solute in the absence of driving forces such as difference in concentration, or electric field.…”

Section: Experimental Protocols For Enzyme-like Vs Flow-force Modelimentioning

confidence: 99%

The Thermodynamic Flow-Force Interpretation of Root Nutrient Uptake Kinetics: A Powerful Formalism for Agronomic and Phytoplanktonic Models

2016

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The ion influx isotherms obtained by measuring unidirectional influx across root membranes with radioactive or stable tracers are mostly interpreted by enzyme-substrate-like modeling. However, recent analyses from ion transporter mutants clearly demonstrate the inadequacy of the conventional interpretation of ion isotherms. Many genetically distinct carriers are involved in the root catalytic function. Parameters Vmax and Km deduced from this interpretation cannot therefore be regarded as microscopic parameters of a single transporter, but are instead macroscopic parameters (Vmapp and Kmapp, apparent maximum velocity and affinity constant) that depend on weighted activities of multiple transporters along the root. The flow-force interpretation based on the thermodynamic principle of irreversible processes is an alternative macroscopic modeling approach for ion influx isotherms in which macroscopic parameters Lj (overall conductance of the root system for the substrate j) and πj (thermodynamic parameter when Jj = 0) have a straightforward meaning with respect to the biological sample studied. They characterize the efficiency of the entire root catalytic structure without deducing molecular characteristics. Here we present the basic principles of this theory and how its use can be tested and improved by changing root pre- and post-wash procedures before influx measurements in order to come as close as possible to equilibrium conditions. In addition, the constant values of Vm and Km in the Michaelis-Menten (MM) formalism of enzyme-substrate interpretation do not reflect variations in response to temperature, nutrient status or nutrient regimes. The linear formalism of the flow-force approach, which integrates temperature effect on nutrient uptake, could usefully replace MM formalism in the 1-3-dimension models of plants and phytoplankton. This formalism offers a simplification of parametrization to help find more realistic analytical expressions and numerical solution for root nutrient uptake.

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