title: Multiple impacts of the plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2 on nutrient and ABA relations of Pisum sativum.
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.
authors.affiliation: Beijing Key Laboratory of Gene Resource and Molecular Development,  College of Life Sciences,  Beijing Normal University, Beijing, 100875,  China.
authors.forename: Fan
authors.initials: F
authors.lastname: Jiang
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Belimov
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Shaposhnikov
authors.forename: Fan
authors.initials: F
authors.lastname: Gong
authors.forename: Xu
authors.initials: X
authors.lastname: Meng
authors.forename: Wolfram
authors.initials: W
authors.lastname: Hartung
authors.forename: Dieter W
authors.initials: DW
authors.lastname: Jeschke
authors.forename: William J
authors.initials: WJ
authors.lastname: Davies
authors.forename: Ian C
authors.initials: IC
authors.lastname: Dodd
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000064:Acclimatization; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019755:Carbon-Carbon Lyases / Q000235:genetics / Q000378:metabolism; D042621:Comamonadaceae / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D018532:Pisum sativum / Q000235:genetics / Q000382:microbiology* / Q000502:physiology*; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases