Abstract
The effects of zinc (Zn) speciation on plant growth in Zn-contaminated soil in the presence of bacteria are unknown but are critical to our understanding of metal biodynamics in the rhizosphere where bacteria are abundant. A 6-week pot experiment investigated the effects of two plant growth promoting bacteria (PGPB), Rhizobium leguminosarum and Pseudomonas brassicacearum, on Zn accumulation and speciation in Brassica juncea grown in soil amended with 600 mg kg–1 elemental Zn as three Zn species: soluble ZnSO4 and nanoparticles of ZnO and ZnS. Measures of plant growth were higher across all Zn treatments inoculated with PGPB compared to uninoculated controls, but Zn species effects were not significant. Transmission electron microscopy identified dense particles in the epidermis and intracellular spaces in roots, suggesting Zn uptake in both dissolved and particulate forms. X-ray absorption near-edge structure (XANES) analysis of roots revealed differences in Zn speciation between treatments. Uninoculated plants exposed to ZnSO4 contained Zn predominantly in the form of Zn phytate (35%) and Zn polygalacturonate (30%), whereas Zn cysteine (57%) and Zn polygalacturonate (37%) dominated in roots exposed to ZnO nanoparticles. Inoculation with PGPB increased (>50%) the proportion of Zn cysteine under all Zn treatments, suggesting Zn coordination with cysteine as the predominant mechanism of Zn toxicity reduction by PGPB. Using this approach, we show, for the first time, that although speciation is important, the presence of rhizospheric bacteria completely overrides speciation effects such that most of the Zn in plant tissue exists as complexes other than the original form.
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Claims 11
Claim · model-written summary
PGPB inoculation increased plant growth measures across all Zn treatments relative to uninoculated controls.
- Taxon
- Brassica juncea
Brassica junceae1 - Treatment
- inoculated with PGPBe0
- Interactor
- PGPBe0symbiont
- Outcome
- Measures of plant growthe0
- Direction
- highere0
- Comparator
- uninoculated controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Measures of plant growth were higher across all Zn treatments inoculated with PGPB compared to uninoculated controls”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Zn species had no significant effect on plant growth measures.
- Taxon
- Brassica junceaBrassica junceae1
- Treatment
- Zn speciese0
- Outcome
- Measures of plant growthe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Measures of plant growth were higher across all Zn treatments inoculated with PGPB compared to uninoculated controls, but Zn species effects were not significant”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Dense particles were identified in root epidermis and intracellular spaces.
- Taxon
- Brassica junceaBrassica junceae1
- Organ / stage
- rootse0
- Outcome
- dense particlese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transmission electron microscopy identified dense particles in the epidermis and intracellular spaces in roots”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Root Zn speciation differed between treatments.
- Taxon
- Brassica junceaBrassica junceae1
- Organ / stage
- rootse0
- Treatment
- treatmentse0
- Outcome
- Zn speciatione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“X-ray absorption near-edge structure (XANES) analysis of roots revealed differences in Zn speciation between treatments”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
In uninoculated plants exposed to ZnSO4, Zn phytate was the predominant Zn form at 35%.
- Taxon
- Brassica junceaBrassica junceae1
- Organ / stage
- rootse2
- Treatment
- ZnSO4e0
- Outcome
- Zn phytatee0
- Value
- 35%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Uninoculated plants exposed to ZnSO4 contained Zn predominantly in the form of Zn phytate (35%)”
e1“Zn accumulation and speciation in Brassica juncea”
e2“X-ray absorption near-edge structure (XANES) analysis of roots revealed differences in Zn speciation between treatments”
Claim · model-written summary
In uninoculated plants exposed to ZnSO4, Zn polygalacturonate accounted for 30%.
- Taxon
- Brassica junceaBrassica junceae2
- Treatment
- ZnSO4e1
- Outcome
- Zn polygalacturonatee0
- Value
- 30%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Zn polygalacturonate (30%)”
e1“Uninoculated plants exposed to ZnSO4 contained Zn predominantly in the form of Zn phytate (35%) and Zn polygalacturonate (30%)”
e2“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Roots exposed to ZnO nanoparticles contained 57% Zn cysteine.
- Taxon
- Brassica junceaBrassica junceae1
- Organ / stage
- rootse0
- Treatment
- ZnO nanoparticlese0
- Outcome
- Zn cysteinee0
- Value
- 57%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Zn cysteine (57%) and Zn polygalacturonate (37%) dominated in roots exposed to ZnO nanoparticles”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Roots exposed to ZnO nanoparticles contained 37% Zn polygalacturonate.
- Taxon
- Brassica junceaBrassica junceae1
- Organ / stage
- rootse0
- Treatment
- ZnO nanoparticlese0
- Outcome
- Zn polygalacturonatee0
- Value
- 37%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Zn cysteine (57%) and Zn polygalacturonate (37%) dominated in roots exposed to ZnO nanoparticles”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
PGPB inoculation increased Zn cysteine proportion by more than 50% under all Zn treatments.
- Taxon
- Brassica junceaBrassica junceae1
- Treatment
- Inoculation with PGPBe0
- Interactor
- PGPBe0symbiont
- Outcome
- proportion of Zn cysteinee0
- Direction
- increasede0
- Value
- >50%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inoculation with PGPB increased (>50%) the proportion of Zn cysteine under all Zn treatments”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Authors infer that cysteine coordination is the predominant mechanism of PGPB reduction of Zn toxicity.
- Taxon
- Brassica junceaBrassica junceae1
- Interactor
- PGPBe0symbiont
- Compound
- cysteinee0
- Outcome
- Zn toxicity reductione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“suggesting Zn coordination with cysteine as the predominant mechanism of Zn toxicity reduction by PGPB”
e1“Zn accumulation and speciation in Brassica juncea”
Claim · model-written summary
Authors conclude rhizospheric bacteria override Zn speciation effects in plant tissue.
- Taxon
- Brassica junceaBrassica junceae1
- Interactor
- rhizospheric bacteriae0symbiont
- Outcome
- speciation effectse0
- Qualifier
- most of the Zn in plant tissue exists as complexes other than the original forme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the presence of rhizospheric bacteria completely overrides speciation effects such that most of the Zn in plant tissue exists as complexes other than the original form”
e1“Zn accumulation and speciation in Brassica juncea”
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See all 8 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.