JXB Advance Access originally published online on November 17, 2003
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Journal of Experimental Botany, Vol. 55, No. 394, pp. 27-34, January 1, 2004
© 2004 Oxford University Press
Plant Carbon-Nitrogen Interactions from Rhizospheres to Planet |
Plant growth-promoting bacteria and nitrate availability: impacts on root development and nitrate uptake
Received 19 May 2003; Accepted 11 August 2003
1Université Montpellier II, Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR 113 UM2/IRD/CIRAD/INRA/ENSAM, CC 02, Place E Bataillon, 34095 Montpellier cedex 05, France
* To whom correspondence should be addressed. Fax: +33 4 6714 3637. E-mail: touraine{at}univ-montp2.fr
Plant growth-promoting bacteria (PGPB) and NO3 availability both affect NO3 uptake and root architecture. The presence of external NO3 induces the expression of NO3 transporter genes and elicits lateral root elongation in the part of the root system exposed to the NO3 supply. By contrast, an increase in NO3 supply leads to a higher plant N status (low N demand), which represses both the NO3 transporters and lateral root development. The effects of PGPB on NO3 uptake and root development are similar to those of low NO3 availability (concomitant stimulation of NO3 uptake rate and lateral root development). The mechanisms responsible for the localized and long-distance regulation of NO3 uptake and root development by NO3 availability are beginning to be elucidated. By contrast, the signalling and transduction pathways elicited by the rhizobacteria remain totally unknown. This review will compare the effects of NO3 availability and PGPB on root morphogenesis and NO3 uptake, in order to determine whether interactions exist between the NO3-dependent and the PGPB-dependent regulatory pathways.
Key words: N demand, nitrate uptake, plant growth-promoting bacteria, plasticity, rhizosphere, root development.