Abstract
Soil microorganisms may play an important role in plant Fe uptake from soils with low Fe bioavailability, but there is little direct experimental evidence to date. We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil to investigate the role of soil microbial activity in plant Fe uptake. Compared with plants grown in non-sterlie (NS) grown plants, growth and Fe content of the sterile(s) grown plants was significantly inhibited, but was improved by foliar application of Fe EDTA, indicating that soil microbial activity should play an important role in plant Fe acquisition. When soil solution was incubated with phenolic root exudates from Fe-deficient red clover, a few microbial species thrived while growth of the rest was inhibited, suggesting that the Fe-deficient (-Fe) root exudates selectively influenced the rhizosphere's microbial community. Eighty six per cent of the phenolic-tolerant microbes could produce siderophore [the Fe(III) chelator] under -Fe conditions, and 71% could secrete auxin-like compounds. Interestingly, the synthetic and microbial auxins (MAs) significantly enhanced the Ferric reduction system, suggesting that MAs, in addition to siderophores, are important to plant Fe uptake. Finally, plant growth and Fe uptake in sterilized soil were significantly increased by rhizobia inoculation. Root Fe-EDTA reductase activity in the -Fe plant was significantly enhanced by rhizobia infection, and the rhizobia could produce auxin but not siderophore under Fe-limiting conditions, suggesting that the contribution of nodulating rhizobia to plant Fe uptake can be at least partially attributed to stimulation of turbo reductase activity through nodule formation and auxin production in the rhizosphere. Based on these observations, we propose as a model that root exudates from -Fe plants selectively influence the rhizosphere microbial community, and the microbes in turn favour plant Fe acquisition by producing siderophores and auxins.
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Claims 15
Claim · model-written summary
Growth and Fe content of red clover grown in sterile soil were significantly inhibited compared with non-sterile plants.
- Taxon
- red clover
Trifolium pratensee0 - Treatment
- sterilee1
- Outcome
- growth and Fe contente1
- Direction
- inhibitede1
- Comparator
- non-sterlie (NS) grown plantse1
- Setting
- calcareous soile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e1“Compared with plants grown in non-sterlie (NS) grown plants, growth and Fe content of the sterile(s) grown plants was significantly inhibited”
Claim · model-written summary
Foliar application of Fe EDTA improved growth and Fe content of sterile-grown red clover.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- foliar application of Fe EDTAe2
- Outcome
- growth and Fe contente1
- Direction
- improvede2
- Comparator
- sterile(s) grown plantse1
- Setting
- calcareous soile0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e1“Compared with plants grown in non-sterlie (NS) grown plants, growth and Fe content of the sterile(s) grown plants was significantly inhibited”
e2“but was improved by foliar application of Fe EDTA”
Claim · model-written summary
Soil microbial activity is probably an important factor in plant Fe acquisition.
- Taxon
- red cloverTrifolium pratensee0
- Outcome
- plant Fe acquisitione3
- Qualifier
- soil microbial activitye3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e3“indicating that soil microbial activity should play an important role in plant Fe acquisition”
Claim · model-written summary
Phenolic root exudates from Fe-deficient red clover allowed a few microbial species to thrive in soil solution.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- phenolic root exudates from Fe-deficient red clovere4
- Interactor
- microbial speciese4other
- Outcome
- a few microbial species thrivede4
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e4“When soil solution was incubated with phenolic root exudates from Fe-deficient red clover, a few microbial species thrived while growth of the rest was inhibited”
Claim · model-written summary
Phenolic root exudates from Fe-deficient red clover inhibited the growth of the other microbial species in soil solution.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- phenolic root exudates from Fe-deficient red clovere4
- Interactor
- microbial speciese4other
- Outcome
- growth of the reste4
- Direction
- inhibitede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e4“When soil solution was incubated with phenolic root exudates from Fe-deficient red clover, a few microbial species thrived while growth of the rest was inhibited”
Claim · model-written summary
Fe-deficient root exudates probably selectively influence the rhizosphere microbial community of red clover.
- Taxon
- red cloverTrifolium pratensee0
- Outcome
- rhizosphere's microbial communitye5
- Qualifier
- selectively influencede5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e5“the Fe-deficient (-Fe) root exudates selectively influenced the rhizosphere's microbial community”
Claim · model-written summary
Eighty six per cent of the phenolic-tolerant microbes could produce siderophore under -Fe conditions.
- Taxon
- red cloverTrifolium pratensee0
- Interactor
- phenolic-tolerant microbese6other
- Compound
- siderophoree6
- Outcome
- produce siderophoree6
- Value
- Eighty six per cente6
- Qualifier
- under -Fe conditionse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e6“Eighty six per cent of the phenolic-tolerant microbes could produce siderophore [the Fe(III) chelator] under -Fe conditions, and 71% could secrete auxin-like compounds”
Claim · model-written summary
71% of the phenolic-tolerant microbes could secrete auxin-like compounds.
- Taxon
- red cloverTrifolium pratensee0
- Interactor
- phenolic-tolerant microbese6other
- Outcome
- secrete auxin-like compoundse6
- Value
- 71%e6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e6“Eighty six per cent of the phenolic-tolerant microbes could produce siderophore [the Fe(III) chelator] under -Fe conditions, and 71% could secrete auxin-like compounds”
Claim · model-written summary
Synthetic and microbial auxins significantly enhanced the Ferric reduction system of red clover.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- synthetic and microbial auxinse7
- Outcome
- the Ferric reduction systeme7
- Direction
- enhancede7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e7“the synthetic and microbial auxins (MAs) significantly enhanced the Ferric reduction system”
Claim · model-written summary
Microbial auxins are probably important for plant Fe uptake in addition to siderophores.
- Taxon
- red cloverTrifolium pratensee0
- Compound
- MAse1
- Outcome
- plant Fe uptakee1
- Qualifier
- in addition to siderophorese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e1“suggesting that MAs, in addition to siderophores, are important to plant Fe uptake”
Claim · model-written summary
Rhizobia inoculation significantly increased plant growth and Fe uptake in sterilized soil.
- Taxon
- red cloverTrifolium pratensee0
- Treatment
- rhizobia inoculatione2
- Interactor
- rhizobiae2symbiont
- Outcome
- plant growth and Fe uptakee2
- Direction
- increasede2
- Setting
- sterilized soile2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e2“Finally, plant growth and Fe uptake in sterilized soil were significantly increased by rhizobia inoculation”
Claim · model-written summary
Rhizobia infection significantly enhanced root Fe-EDTA reductase activity in Fe-deficient red clover.
- Taxon
- red cloverTrifolium pratensee0
- Organ / stage
- Roote3
- Treatment
- rhizobia infectione3
- Interactor
- rhizobiae3symbiont
- Outcome
- Root Fe-EDTA reductase activitye3
- Direction
- enhancede3
- Qualifier
- -Fe plante3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e3“Root Fe-EDTA reductase activity in the -Fe plant was significantly enhanced by rhizobia infection”
Claim · model-written summary
Rhizobia could produce auxin but not siderophore under Fe-limiting conditions.
- Taxon
- red cloverTrifolium pratensee0
- Interactor
- rhizobiae4symbiont
- Outcome
- produce auxin but not siderophoree4
- Qualifier
- under Fe-limiting conditionse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e4“the rhizobia could produce auxin but not siderophore under Fe-limiting conditions”
Claim · model-written summary
Nodulating rhizobia probably contribute to plant Fe uptake through nodule formation and auxin production.
- Taxon
- red cloverTrifolium pratensee0
- Interactor
- nodulating rhizobiae5symbiont
- Outcome
- plant Fe uptakee5
- Qualifier
- nodule formation and auxin productione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e5“the contribution of nodulating rhizobia to plant Fe uptake can be at least partially attributed to stimulation of turbo reductase activity through nodule formation and auxin production in the rhizosphere”
Claim · model-written summary
Rhizosphere microbes probably favour plant Fe acquisition by producing siderophores and auxins.
- Taxon
- red cloverTrifolium pratensee0
- Outcome
- favour plant Fe acquisitione6
- Qualifier
- by producing siderophores and auxinse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We grew red clover, an Fe-efficient leguminous plant, in a calcareous soil”
e6“the microbes in turn favour plant Fe acquisition by producing siderophores and auxins”
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