Abstract
BACKGROUND: Soil pollution by heavy metals increases the bioavailability of metals like hexavalent chromium (Cr (VI)), subsequently limiting plant growth and reducing the efficiency of phytoremediation. Plant growth-promoting rhizobacteria (PGPR) have substantial potential to enhance plant growth as well as plant tolerance to metal stress. The aim of this research was to investigate Cr (VI) phytoremediation enhancement by PGPR. RESULTS: The results showed that the 27 rhizobacterial isolates studied were confirmed as Cr (VI)-resistant PGPR, by using classical biochemical tests (phosphate solubilization, nitrogen fixation, indole acetic acid, exopolysaccharides, hydrogen cyanide, siderophores, ammonia, cellulase, pectinase, and chitinase production) and showed variable levels of Cr (VI) resistance (300-600 mg/L). The best four selected Cr (VI)-resistant PGPR (NT15, NT19, NT20, and NT27) retained most of the PGP traits in the presence of 100-200 mg/L concentrations of Cr (VI). The inoculation of Medicago sativa with any of these four isolates improved the shoot and root dry weight. The NT27 isolate identified using 16S rDNA gene sequence analyses as a strain of Pseudomonas sp. was most effective in terms of plant growth promotion and stress level decrease. It increased shoot and root dry weights of M. sativa by 97.6 and 95.4%, respectively, in the presence of Cr (VI) when compared to non-inoculated control plants. It also greatly increased chlorophyll content and decreased the levels of stress markers, malondialdehyde, hydrogen peroxide, and proline. The results of the effect of Pseudomonas sp. on Cr content and bioaccumulation factor (BAF) of the shoots and roots of M. sativa plants showed the increase of plant biomass concomitantly with the increase of Cr root concentration in inoculated plants. This would lead to a higher potential of Cr (VI) phytostabilization. CONCLUSIONS: This study demonstrates that the association M. sativa-Pseudomonas sp. may be an efficient biological system for the bioremediation of Cr (VI)-contaminated soils.
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Claims 7
Claim · model-written summary
Four selected isolates retained most plant growth promoting traits under chromium.
- Taxon
- Medicago sativa
Medicago sativat0 - Outcome
- PGP traitse0
- Qualifier
- 100-200 mg/L concentrations of Cr (VI)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The best four selected Cr (VI)-resistant PGPR (NT15, NT19, NT20, and NT27) retained most of the PGP traits in the presence of 100-200 mg/L concentrations of Cr (VI)”
t0“Medicago sativa”
Claim · model-written summary
Inoculation with the four isolates improved shoot and root dry weight.
- Taxon
- Medicago sativaMedicago sativae0
- Treatment
- inoculation of Medicago sativa with any of these four isolatese0
- Interactor
- these four isolatese0symbiont
- Outcome
- shoot and root dry weighte0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The inoculation of Medicago sativa with any of these four isolates improved the shoot and root dry weight”
Claim · model-written summary
NT27 increased shoot dry weight by 97.6% versus non-inoculated controls under chromium.
- Taxon
- M. sativaMedicago sativae0
- Treatment
- NT27t0
- Outcome
- shoot and root dry weightse0
- Direction
- increasede0
- Value
- 97.6e0
- Comparator
- non-inoculated control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It increased shoot and root dry weights of M. sativa by 97.6 and 95.4%, respectively, in the presence of Cr (VI) when compared to non-inoculated control plants”
t0“PGPR (NT15, NT19, NT20, and NT27)”
Claim · model-written summary
NT27 increased root dry weight by 95.4% versus non-inoculated controls under chromium.
- Taxon
- M. sativaMedicago sativae0
- Treatment
- NT27t0
- Outcome
- root dry weightse0
- Direction
- increasede0
- Value
- 95.4%e0
- Comparator
- non-inoculated control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It increased shoot and root dry weights of M. sativa by 97.6 and 95.4%, respectively, in the presence of Cr (VI) when compared to non-inoculated control plants”
t0“PGPR (NT15, NT19, NT20, and NT27)”
Claim · model-written summary
NT27 increased chlorophyll content.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- NT27t1
- Outcome
- chlorophyll contente0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It also greatly increased chlorophyll content”
t0“Medicago sativa”
t1“PGPR (NT15, NT19, NT20, and NT27)”
Claim · model-written summary
NT27 decreased malondialdehyde, hydrogen peroxide, and proline stress markers.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- NT27t1
- Outcome
- levels of stress markers, malondialdehyde, hydrogen peroxide, and prolinee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decreased the levels of stress markers, malondialdehyde, hydrogen peroxide, and proline”
t0“Medicago sativa”
t1“PGPR (NT15, NT19, NT20, and NT27)”
Claim · model-written summary
Pseudomonas inoculation increased root chromium concentration alongside plant biomass.
- Taxon
- M. sativaMedicago sativat0
- Treatment
- Pseudomonas sp.t1
- Outcome
- Cr root concentratione0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increase of plant biomass concomitantly with the increase of Cr root concentration in inoculated plants”
t0“shoots and roots of M. sativa plants”
t1“effect of Pseudomonas sp. on Cr content”
The same questions in other papers
Pseudomonas · molecular: metabolites · Medicago sativa (alfalfa)Results agree
2 papers in the same direction as this paper
- positive
- positive
inoculation · growth · Medicago sativa (alfalfa)Positive and negative results
120 papers in the same direction as this paper · 15 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- no effect
- no effect
133 papers more in this group
See all 137 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.