Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum

J Exp Bot. 2012 Nov;63(18):6421-30. doi: 10.1093/jxb/ers301. Epub 2012 Nov 7.

Abstract

Resolving the physiological mechanisms by which rhizobacteria enhance plant growth is difficult, since many such bacteria contain multiple plant growth-promoting properties. To understand further how the 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCd)-containing rhizobacterium Variovorax paradoxus 5C-2 affects plant growth, the flows and partitioning of mineral nutrients and abscisic acid (ABA) and ABA metabolism were studied in pea (Pisum sativum) plants following rhizosphere bacterial inoculation. Although root architecture was not affected, inoculation increased root and shoot biomass, and stomatal conductance, by 20, 15, and 24%, respectively, and increased N, P, K, Ca, and Mg uptake by 16, 81, 50, 46, and 58%, respectively. P deposition in inoculated plant roots was 4.9 times higher than that in uninoculated controls. Rhizobacterial inoculation increased root to shoot xylem flows and shoot to root phloem flows of K by 1.8- and 2.1-fold, respectively. In control plants, major sinks for K deposition were the roots and upper shoot (43% and 49% of total uptake, respectively), while rhizobacterial inoculation increased K distribution to the lower shoot at the expense of other compartments (xylem, phloem, and upper shoot). Despite being unable to metabolize ABA in vitro, V. paradoxus 5C-2 decreased root ABA concentrations and accumulation by 40-60%. Although inoculation decreased xylem ABA flows, phloem ABA flows increased. Whether bacterial ACCd attenuates root to shoot ABA signalling requires further investigation, since ABA is critical to maintain growth of droughted plants, and ACCd-containing organisms have been advocated as a means of minimizing growth inhibition of plants in drying soil.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / metabolism*
  • Acclimatization
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Carbon-Carbon Lyases / genetics
  • Carbon-Carbon Lyases / metabolism
  • Comamonadaceae / genetics
  • Comamonadaceae / physiology*
  • Models, Biological
  • Pisum sativum / genetics
  • Pisum sativum / microbiology*
  • Pisum sativum / physiology*
  • Plant Growth Regulators / genetics
  • Plant Growth Regulators / metabolism*
  • Plant Roots / growth & development
  • Plant Roots / metabolism
  • Plant Roots / microbiology
  • Plant Shoots / growth & development
  • Plant Shoots / metabolism

Substances

  • Bacterial Proteins
  • Plant Growth Regulators
  • Abscisic Acid
  • 1-aminocyclopropane-1-carboxylate deaminase
  • Carbon-Carbon Lyases