Plant and Soil

, Volume 229, Issue 2, pp 305–318

Determining the net flux of charge released by maize roots by directly measuring variations of the alkalinity in the nutrient solution

  • Rémi Durand
  • Nicole Bellon
  • Benoît Jaillard
Article

DOI: 10.1023/A:1004860326936

Cite this article as:
Durand, R., Bellon, N. & Jaillard, B. Plant and Soil (2001) 229: 305. doi:10.1023/A:1004860326936

Abstract

The net flux of charge released by maize, i.e. the strong ion exchange balance between the roots and their environment, was determined in acidic and alkaline solutions, i.e. solutions with a low and a high pH buffering capacity, respectively. The work was based on direct measurement of total alkalinity in culture solutions over a period of several days.

The results show there was little difference in the net flux of charge released by maize in acidic and alkaline solutions: In both cases, approximately −1 μmolc (kg DM)−1 s−1. As the maize was grown in a non-limiting nitrate solution, the charge flux was negative, corresponding to a net release of hydroxyls into the rhizosphere. In contrast, the change in the amounts of free protons in the solution was approximately 1 nmol (kg DM)−1 s−1, i.e. 3 orders of magnitude lower than the net charge flux. Moreover, it was negative in acidic media , i.e. the solution pH increased, and positive in alkaline media, i.e. the solution pH decreased. This decrease probably resulted from the release of inorganic carbon by the roots. The effect on the change in solution pH was only slight in acidic conditions but considerable in alkaline conditions, where it reduced the pH even though the culture solution was alkalinised by the roots.

The difference in the way that acidic and alkaline solutions function demonstrates the importance of the pH buffering capacity of the solution in determining the net flux of charge released by the plants. It underlines the difficulty of estimating the net charge flux from pH change measurements in the rhizosphere.

alkalinitybuffering capacitynet charge fluxnutrient uptakepHrhizosphere

Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Rémi Durand
    • 1
  • Nicole Bellon
    • 1
  • Benoît Jaillard
    • 2
  1. 1.UMR Sols, Symbioses et Environnement, Institut National de la Recherche AgronomiqueAntibes cedexFrance
  2. 2.UMR Sols, Symbioses et Environnement, Institut National de la Recherche AgronomiqueMontpellier cedex 2France