Adsorption of Rhizobium meliloti to alfalfa roots: dependence on divalent cations and pH

Adsorption of Rhizobium meliloti L5-30 in low numbers to alfalfa (Medicago sativa L.) roots was dependent on the presence of divalent cations, and required neutral pH. Adsorption was proportional to Ca and/or Mg concentrations up to 1.5 mM. Ca was not substituted by Sr, Ba or Mn. Adsorption was abol...

Full description

Saved in:
Bibliographic Details
Published in:Plant and soil 1989-06, Vol.117 (1), p.67-74
Main Authors: Caetano-Anolles, G. (Nacional Univ., La Plata (Argentina). Catedra de Quimica Biologica I), Lagares, A, Favelukes, G
Format: Article
Language:English
Subjects:
ADSORCION
ADSORPTION
Agronomy. Soil science and plant productions
Alfalfa
Bacteria
Biological and medical sciences
CALCIO
CALCIUM
CATION
CATIONES
CATIONS
Divalent cations
Economic plant physiology
Fundamental and applied biological sciences. Psychology
MAGNESIO
MAGNESIUM
MEDICAGO SATIVA
Nodulation
Plant roots
Plants
RACINE
RAICES
RHIZOBIUM
Root hairs
ROOTS
Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...)
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Adsorption of Rhizobium meliloti L5-30 in low numbers to alfalfa (Medicago sativa L.) roots was dependent on the presence of divalent cations, and required neutral pH. Adsorption was proportional to Ca and/or Mg concentrations up to 1.5 mM. Ca was not substituted by Sr, Ba or Mn. Adsorption was abolished and viability decreased at pH â©˝ 6. When lowering pH, higher Ca concentrations were required to attain similar adsorption levels, indicating a marked interactive effect between Ca and H ions. Pretreatment of the roots with Ca and low pH did not affect subsequent adsorption of the bacteria. However, Ca pretreatment of R. meliloti sustained further adsorption at low Ca levels and low pH substantially affected their ability to adsorb. Low pH appears to affect the stability of binding causing desorption of the previously bound bacteria. The presence of saturating concentrations of heterologous R. leguminosarum bv. trifolii A118, did not prevent the expression of divalent cations and pH requirements, as well as their interaction. Our results suggest that rhizobial binding to the root surface already shows the Ca and pH dependence of alfalfa nodulation, which was generally associated to some event prior to rhizobial penetration of root hairs.
ISSN:0032-079X
1573-5036
DOI:10.1007/BF02206258