Abstract
A pot experiment was designed to evaluate the interactive effects of multiple microbial inoculation treatments and rock phosphate (RP) application on N and P acquisition by alfalfa plants using 15 N and 32 P isotopes. The microbial inocula consisted of a wild type (WT) Rhizobium meliloti strain, its genetically modified (GM) derivative, which had an enhanced competitiveness, the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe, and a phosphate‐solubilizing rhizobacterium ( Enterobacter sp.). Inoculated micro‐organisms became established in the root tissues and/or in the rhizosphere soil of alfalfa plants ( Medicago sativa L.). The GM Rhizobium strain did not interfere with AM formation. Inoculated phosphate‐solubilizing rhizobacteria established in the alfalfa rhizosphere, but the level of establishment was lower where the natural population of phosphate‐solubilizing bacteria was stimulated by AM inoculation and RP application. The stimulation of these indigenous bacteria was also greater in the rhizosphere of alfalfa nodulated by the GM Rhizobium . Improvements in N and P accumulation in alfalfa corroborate beneficial effects of the improved GM Rhizobium on AM performance, in RP‐amended plants. Inoculation with Enterobacter did not improve the AM effect on N or P accumulation in the RP‐added soil, but it did in the non RP‐amended controls. Measurements of the 15 N∶ 14 N ratio in plant shoots indicated enhanced N 2 fixation rates in Rhizobium ‐inoculated AM‐plants, over that achieved by the same Rhizobium strain in non‐mycorrhizal plants. Regardless of the Rhizobium strain and of whether or not RP was added, AM‐inoculated plants showed a lower specific activity ( 32 P∶ 31 P) than did their comparable non‐mycorrhizal controls, suggesting that the plant was using otherwise unavailable P sources. The phosphate‐solubilizing, AM‐associated, microbiota could in fact release phosphate ions, either from the added RP or from the indigenous ‘less‐available’ phosphate. Deficiency in Ca concentration in soil solution in the neutral test soil might benefit P solubilization. The proportion of plant P derived either from the labelled soil P (labile P pool) or from RP was similar for AM inoculated and non‐mycorrhizal controls (without Enterobacter inoculation) for each Rhizobium strain, but the total P uptake, regardless of the P source, was far higher in AM‐plants. Enterobacter inoculation seems to improve the use of RP in the rhizosphere of non‐mycorrhizal plants inoculated with the WT Rhizobium .
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Claims 16
Claim · model-written summary
Inoculated microbes established in alfalfa roots or rhizosphere.
- Taxon
- Medicago sativa L.
Medicago sativae0 - Interactor
- micro‐organismse0symbiont
- Outcome
- established in the root tissues and/or in the rhizosphere soile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculated micro‐organisms became established in the root tissues and/or in the rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
The GM Rhizobium strain did not interfere with AM formation.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- GM Rhizobium straine0
- Outcome
- AM formatione0
- Direction
- did not interferee0
RhizobiumNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The GM Rhizobium strain did not interfere with AM formation”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Inoculated phosphate-solubilizing rhizobacteria established in the alfalfa rhizosphere.
- Taxon
- alfalfaMedicago sativae0
- Interactor
- phosphate‐solubilizing rhizobacteriae0symbiont
- Outcome
- established in the alfalfa rhizospheree0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculated phosphate‐solubilizing rhizobacteria established in the alfalfa rhizosphere”
Claim · model-written summary
Their establishment was lower where AM inoculation and rock phosphate stimulated natural phosphate-solubilizing bacteria.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- AM inoculation and RP applicatione0
- Interactor
- phosphate‐solubilizing bacteriae0symbiont
- Outcome
- level of establishmente0
- Direction
- lowere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of establishment was lower where the natural population of phosphate‐solubilizing bacteria was stimulated by AM inoculation and RP application”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Stimulation of indigenous bacteria was greater in alfalfa nodulated by GM Rhizobium.
- Taxon
- alfalfaMedicago sativae0
- Interactor
- GM Rhizobiume0symbiont
- Outcome
- stimulation of these indigenous bacteriae0
- Direction
- greatere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The stimulation of these indigenous bacteria was also greater in the rhizosphere of alfalfa nodulated by the GM Rhizobium”
Claim · model-written summary
GM Rhizobium improved N and P accumulation in rock-phosphate-amended alfalfa.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- improved GM Rhizobiume0
- Interactor
- GM Rhizobiume0symbiont
- Outcome
- N and P accumulatione0
- Direction
- Improvementse0
- Qualifier
- RP‐amended plantse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Improvements in N and P accumulation in alfalfa corroborate beneficial effects of the improved GM Rhizobium on AM performance, in RP‐amended plants”
Claim · model-written summary
Enterobacter did not improve the AM effect on N or P accumulation in rock-phosphate-added soil.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- Inoculation with Enterobactere0
- Interactor
- Enterobacter
Enterobactere0symbiont - Outcome
- N or P accumulatione0
- Direction
- did not improvee0
- Qualifier
- RP‐added soile0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculation with Enterobacter did not improve the AM effect on N or P accumulation in the RP‐added soil”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Enterobacter improved the AM effect on N or P accumulation without rock phosphate.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- Enterobactere0
- Outcome
- N or P accumulatione0
- Comparator
- non RP‐amended controlse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculation with Enterobacter did not improve the AM effect on N or P accumulation in the RP‐added soil, but it did in the non RP‐amended controls”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
AM plants inoculated with Rhizobium had enhanced nitrogen fixation over non-mycorrhizal plants with the same strain.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- Rhizobium ‐inoculated AM‐plantse0
- Outcome
- N 2 fixation ratese0
- Direction
- enhancede0
- Comparator
- same Rhizobium strain in non‐mycorrhizal plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced N 2 fixation rates in Rhizobium ‐inoculated AM‐plants, over that achieved by the same Rhizobium strain in non‐mycorrhizal plants”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
AM-inoculated plants had lower phosphorus specific activity than non-mycorrhizal controls.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- AM‐inoculated plantse0
- Outcome
- specific activity ( 32 P∶ 31 P)e0
- Direction
- lowere0
- Comparator
- non‐mycorrhizal controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AM‐inoculated plants showed a lower specific activity ( 32 P∶ 31 P) than did their comparable non‐mycorrhizal controls”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Lower phosphorus specific activity suggests AM plants accessed otherwise unavailable phosphorus sources.
- Taxon
- alfalfaMedicago sativat0
- Outcome
- using otherwise unavailable P sourcese0
- Qualifier
- suggestinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting that the plant was using otherwise unavailable P sources”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
AM-associated phosphate-solubilizing microbiota could release phosphate from added or indigenous sources.
- Taxon
- alfalfaMedicago sativat0
- Interactor
- microbiotae0symbiont
- Outcome
- release phosphate ionse0
- Qualifier
- either from the added RP or from the indigenous ‘less‐available’ phosphatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The phosphate‐solubilizing, AM‐associated, microbiota could in fact release phosphate ions, either from the added RP or from the indigenous ‘less‐available’ phosphate”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Calcium deficiency in soil solution might benefit phosphorus solubilization.
Not reportedTaxon
Verbatim
e0“Deficiency in Ca concentration in soil solution in the neutral test soil might benefit P solubilization”
Claim · model-written summary
The source proportions of plant phosphorus were similar in AM and non-mycorrhizal controls.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- AM inoculatede0
- Outcome
- proportion of plant Pe0
- Direction
- similare0
- Qualifier
- without Enterobacter inoculatione0
- Comparator
- non‐mycorrhizal controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The proportion of plant P derived either from the labelled soil P (labile P pool) or from RP was similar for AM inoculated and non‐mycorrhizal controls (without Enterobacter inoculation) for each Rhizobium strain”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Total phosphorus uptake was far higher in AM plants regardless of phosphorus source.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- AM‐plantse0
- Outcome
- total P uptakee0
- Direction
- far highere0
- Qualifier
- regardless of the P sourcee0
- Comparator
- non‐mycorrhizal controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The proportion of plant P derived either from the labelled soil P (labile P pool) or from RP was similar for AM inoculated and non‐mycorrhizal controls (without Enterobacter inoculation) for each Rhizobium strain, but the total P uptake, regardless of the P source, was far higher in AM‐plants”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
Claim · model-written summary
Enterobacter inoculation appeared to improve use of rock phosphate in non-mycorrhizal plants with wild-type Rhizobium.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- Enterobacter inoculatione0
- Interactor
- EnterobacterEnterobactere0symbiont
- Second interactor
- WT Rhizobiume0symbiont
- Outcome
- use of RPe0
- Direction
- improvee0
- Qualifier
- non‐mycorrhizal plants inoculated with the WT Rhizobiume0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Enterobacter inoculation seems to improve the use of RP in the rhizosphere of non‐mycorrhizal plants inoculated with the WT Rhizobium”
t0“rhizosphere soil of alfalfa plants ( Medicago sativa L.)”
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