Why are laterals less affected than main axes by homogeneous unfavourable physical conditions? A model-based hypothesis

Thaler Philippe, Pagès Loïc. 2000. Why are laterals less affected than main axes by homogeneous unfavourable physical conditions? A model-based hypothesis. In : The supporting roots of trees and woody plants: form, function, and physiology. Stokes A. (ed.). Dordrecht : Kluwer Academic Publishers, pp. 209-215. (Developments in Plant and Soil Sciences, 87) ISBN 0-7923-5964-X Colloque sur les Racines principales, structures et fonctionnement. 1, Bordeaux, France, 20 July 1998/24 July 1998.

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Autre titre : Pourquoi les racines latérales sont-elles moins affectées que les axes principaux par des conditions physiques défavorables identiques ? Une hypothèse basée sur un modèle

Abstract : When plants develop in strong soils, growth of the root system is generally depressed. However, branching and elongation of branches are often less affected than growth of the main axes, whenever the whole root system encounters even-impeded conditions. On the basis of a model simulating root growth and architecture as related to assimilate availability, we propose a simple hypothesis to explain such behaviour. In the model, growth of each root depends on its own elongation potential, which is estimated by its apical diameter. The potential elongation rate-apical diameter relationship is the same for all the roots of the system and is described by a monomolecular function. Our hypothesis is that the effect of soil strength can be simulated by introducing an impedance factor in the definition of root maximum potential elongation rate, common to the whole root system. When such impedance factor is applied, it affects more the potential of larger roots (main axes) than that of thinner roots (secondary and tertiary branches). Simulations provided in high impedance conditions led to root systems characterised by short taproots, whereas growth of secondary roots was unaffected and growth of tertiary roots was enhanced. Actual branching density was also higher, although branching rules have been unchanged. Such simulated systems where similar to that observed in strong soils. Friction laws or pore size can be involved in the larger reduction of the potential growth of main axes. Moreover, when growth of main axes is restricted, assimilate availability becomes higher for branches and that could explain that their growth could be increased in a homogeneous strong soil. (Résumé d'auteur)

Mots-clés Agrovoc : Système racinaire, Racine, Croissance, Morphogénèse, Résistance mécanique du sol, Relation plante sol, Modèle de simulation

Mots-clés complémentaires : Architecture végétale

Classification Agris : F62 - Plant physiology - Growth and development
U10 - Mathematical and statistical methods
P33 - Soil chemistry and physics

Auteurs et affiliations

  • Thaler Philippe, CIRAD-CP-HEVEA (CIV)
  • Pagès Loïc, INRA (FRA)

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Source : Cirad - Agritrop (

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