Abstract
The negative effects of soil heavy metal contamination on food production could be mitigated using nature-based solutions, i.e., plant-growth-promoting rhizobacteria (PGPR). Yield of Lactuca sativa L. has been shown to increase by seed inoculation with biofilm of Bacillus subtilis subsp. spizizenii. The aim of this work was to assess whether this promoting effect occurs even in the presence of toxic concentrations of copper (Cu) and zinc (Zn). First, germination rates of lettuce seeds with increasing Cu and Zn concentrations were assessed. Then, lettuce plants growing from inoculated and non-inoculated seeds were cropped on substrates with excess Cu and Zn. Above- and below-ground lettuce variables were measured, and leaf macro- and microelements were determined. Germination was more severely affected by Cu overload than by Zn overload, while this trend was reversal for plant growth. Seed inoculation enhanced germination and increased plant growth assessed by root and shoot biomass, plant height and leaf area. For example, seed inoculation increased lettuce root and aerial biomass of lettuce growing on a metal- free substrate by 68% and 62%, respectively. This practice also promoted lettuce growth in metal-overloaded substrates, increasing aerial and root biomass by 32% and 29%, respectively, in connection with Cu, and by 260% and 183% when it came to Zn. Both Cu or Zn accumulated in the edible parts of lettuce growing on contaminated substrates, but seed inoculation did not mitigate metal uptake in any case. Except for Cu and Zn, macronutrients, micronutrients and heavy metal levels in lettuce leaves were affected neither by excess metal nor by seed inoculation. Altogether, B. subtilis biofilm has been proven to be an effective seed inoculant promoting seed germination and plant growth even in the presence of heavy metals. Adverse health effects due to metal accumulation in the lettuce edible parts are not expected to increase following seed inoculation.
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Claims 14
Claim · model-written summary
Cu overload affected lettuce seed germination more severely than Zn overload.
- Taxon
- lettuce
Lactuca sativae1 - Treatment
- Cu overloade0
- Outcome
- Germinatione0
- Direction
- more severely affectede0
- Comparator
- Zn overloade0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Germination was more severely affected by Cu overload than by Zn overload”
e1“lettuce seeds”
Claim · model-written summary
Zn overload affected lettuce plant growth more severely than Cu overload.
- Taxon
- lettuceLactuca sativae2
- Treatment
- Zn overloade1
- Outcome
- plant growthe0
- Direction
- reversale0
- Comparator
- Cu overloade1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this trend was reversal for plant growth”
e1“Germination was more severely affected by Cu overload than by Zn overload”
e2“lettuce plants”
Claim · model-written summary
Seed inoculation enhanced lettuce germination.
- Taxon
- lettuceLactuca sativae1
- Treatment
- Seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- germinatione0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed inoculation enhanced germination”
e1“lettuce seeds”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Seed inoculation increased lettuce plant height and leaf area.
- Taxon
- lettuceLactuca sativae1
- Treatment
- Seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- plant height and leaf areae0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed inoculation enhanced germination and increased plant growth assessed by root and shoot biomass, plant height and leaf area.”
e1“lettuce plants”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Inoculation increased lettuce root biomass by 68% without metal overload.
- Taxon
- lettuceLactuca sativae0
- Treatment
- seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie1symbiont
- Outcome
- root biomasse2
- Direction
- increasede0
- Value
- 68%e0
- Qualifier
- metal- free substratee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seed inoculation increased lettuce root and aerial biomass of lettuce growing on a metal- free substrate by 68% and 62%, respectively.”
e1“biofilm of Bacillus subtilis subsp. spizizenii”
e2“aerial and root biomass by 32%”
Claim · model-written summary
Inoculation increased lettuce aerial biomass by 62% without metal overload.
- Taxon
- lettuceLactuca sativae0
- Treatment
- seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie1symbiont
- Outcome
- aerial biomasse0
- Direction
- increasede0
- Value
- 62%e0
- Qualifier
- metal- free substratee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seed inoculation increased lettuce root and aerial biomass of lettuce growing on a metal- free substrate by 68% and 62%, respectively.”
e1“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Inoculation increased lettuce aerial biomass by 32% under excess Cu.
- Taxon
- lettuceLactuca sativae1
- Treatment
- This practicee1
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- aerial biomasse3
- Direction
- increasinge0
- Value
- 32%e0
- Qualifier
- Cue0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing aerial and root biomass by 32% and 29%, respectively, in connection with Cu”
e1“This practice also promoted lettuce growth in metal-overloaded substrates”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
e3“root and aerial biomass of lettuce growing on a metal- free substrate”
Claim · model-written summary
Inoculation increased lettuce root biomass by 29% under excess Cu.
- Taxon
- lettuceLactuca sativae1
- Treatment
- This practicee1
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- root biomasse0
- Direction
- increasinge0
- Value
- 29%e0
- Qualifier
- Cue0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing aerial and root biomass by 32% and 29%, respectively, in connection with Cu”
e1“This practice also promoted lettuce growth in metal-overloaded substrates”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Inoculation increased lettuce aerial biomass by 260% under excess Zn.
- Taxon
- lettuceLactuca sativae1
- Treatment
- This practicee1
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- aerial biomasse3
- Direction
- increasinge0
- Value
- 260%e0
- Qualifier
- Zne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing aerial and root biomass by 32% and 29%, respectively, in connection with Cu, and by 260% and 183% when it came to Zn.”
e1“This practice also promoted lettuce growth in metal-overloaded substrates”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
e3“root and aerial biomass of lettuce growing on a metal- free substrate”
Claim · model-written summary
Inoculation increased lettuce root biomass by 183% under excess Zn.
- Taxon
- lettuceLactuca sativae1
- Treatment
- This practicee1
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- root biomasse0
- Direction
- increasinge0
- Value
- 183%e0
- Qualifier
- Zne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increasing aerial and root biomass by 32% and 29%, respectively, in connection with Cu, and by 260% and 183% when it came to Zn.”
e1“This practice also promoted lettuce growth in metal-overloaded substrates”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Cu and Zn accumulated in edible lettuce parts on contaminated substrates.
- Taxon
- lettuceLactuca sativae0
- Outcome
- Cu or Zn accumulated in the edible partse0
- Qualifier
- contaminated substratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both Cu or Zn accumulated in the edible parts of lettuce growing on contaminated substrates”
Claim · model-written summary
Seed inoculation did not mitigate lettuce metal uptake.
- Taxon
- lettuceLactuca sativae1
- Treatment
- seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie2symbiont
- Outcome
- metal uptakee0
- Direction
- did not mitigatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seed inoculation did not mitigate metal uptake in any case”
e1“lettuce growing on contaminated substrates”
e2“biofilm of Bacillus subtilis subsp. spizizenii”
Claim · model-written summary
Other macro- and micronutrient and heavy-metal levels in lettuce leaves were unaffected by excess metal.
- Taxon
- lettuceLactuca sativae0
- Treatment
- excess metale0
- Outcome
- macronutrients, micronutrients and heavy metal levels in lettuce leavese0
- Direction
- affected neithere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Except for Cu and Zn, macronutrients, micronutrients and heavy metal levels in lettuce leaves were affected neither by excess metal nor by seed inoculation.”
Claim · model-written summary
Other macro- and micronutrient and heavy-metal levels in lettuce leaves were unaffected by inoculation.
- Taxon
- lettuceLactuca sativae0
- Treatment
- seed inoculatione0
- Interactor
- Bacillus subtilis subsp. spizizeniiBacillus spizizeniie1symbiont
- Outcome
- macronutrients, micronutrients and heavy metal levels in lettuce leavese0
- Direction
- affected neithere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Except for Cu and Zn, macronutrients, micronutrients and heavy metal levels in lettuce leaves were affected neither by excess metal nor by seed inoculation.”
e1“biofilm of Bacillus subtilis subsp. spizizenii”
The same questions in other papers
copper atom · growth · Lactuca sativa (garden lettuce)Results differ
7 papers in the same direction as this paper · 5 in the opposite direction
- positive
- positive
- positive
9 papers more in this group
See all 13 papers →zinc atom · growth · Lactuca sativa (garden lettuce)Results differ
7 papers in the same direction as this paper · 7 in the opposite direction
- positive
- positive
- positive
11 papers more in this group
See all 15 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.