Abstract
There is growing evidence that rising atmospheric CO2 concentrations will reduce or prevent reductions in the growth and productivity of C3 crops attributable to ozone (O3) pollution. In this study, the role of pollutant exclusion in mediating this response was investigated through growth chamber-based investigations on leaves 4 and 7 of spring wheat (Triticum aestivum cv. Hanno). In the core experiments, plants were raised at two atmospheric CO2 concentrations (ambient [350 micro l l(-1)] or elevated CO2 [700 micro l l(-1)] under two O3 regimes (charcoal/Purafil-filtered air [<5 nl l(-1) O3] or ozone-enriched air [75 nl l(-1) 7 h d(-1)]). A subsequent experiment used an additional O3 treatment where the goal was to achieve equivalent daily O3 uptake over the life-span of leaves 4 and 7 under ambient and CO2-enriched conditions, through daily adjustment of exposures based on measured shifts in stomatal conductance. Plant growth and net CO2 assimilation were stimulated by CO2-enrichment and reduced by exposure to O3. However, the impacts of O3 decreased with plant age (i.e. leaf 7 was more resistant to O3 injury than leaf 4); a finding consistent with ontogenic shifts in the tolerance of plant tissue and/or acclimation to O3-induced oxidative stress. In the combined treatment, elevated CO2 protected against the adverse effects of O3 and reduced cumulative O3 uptake (calculated from measurements of stomatal conductance) by c. 10% and 35% over the life-span of leaves 4 and 7, respectively. Analysis of the relationship between O3 uptake and the decline in the maximum in vivo rate of Rubisco carboxylation (Vcmax) revealed the protection afforded by CO2-enrichment to be due, to a large extent, to the exclusion of the pollutant from the leaf interior (as a consequence of the decline in stomatal conductance triggered by CO2-enrichment), but there was evidence (especially from flux-response relationships constructed for leaf 4) that CO2-enrichment resulted in additional effects that alleviated the impacts of ozone-induced oxidative stress on photosynthesis.
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Claims 9
Claim · model-written summary
CO2 enrichment stimulated spring wheat growth and net CO2 assimilation.
- Taxon
- spring wheat
Triticum aestivume1 - Material
- Hannoe1
- Treatment
- CO2-enrichmente0
- Outcome
- Plant growth and net CO2 assimilatione0
- Direction
- stimulatede0
- Setting
- growth chambere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plant growth and net CO2 assimilation were stimulated by CO2-enrichment and reduced by exposure to O3.”
e1“growth chamber-based investigations on leaves 4 and 7 of spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
Ozone reduced spring wheat growth and net CO2 assimilation.
- Taxon
- spring wheatTriticum aestivume1
- Material
- Hannoe1
- Treatment
- exposure to O3e0
- Outcome
- Plant growth and net CO2 assimilatione0
- Direction
- reducede0
- Setting
- growth chambere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plant growth and net CO2 assimilation were stimulated by CO2-enrichment and reduced by exposure to O3.”
e1“growth chamber-based investigations on leaves 4 and 7 of spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
Ozone impacts decreased with spring wheat age; leaf 7 was more resistant than leaf 4.
- Taxon
- spring wheatTriticum aestivume1
- Material
- Hannoe1
- Organ / stage
- leaf 7e0
- Outcome
- impacts of O3e0
- Direction
- decreasede0
- Qualifier
- plant agee0
- Comparator
- leaf 4e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“However, the impacts of O3 decreased with plant age (i.e. leaf 7 was more resistant to O3 injury than leaf 4)”
e1“spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
The authors interpret age-dependent resistance as consistent with ontogenic tolerance shifts or acclimation to oxidative stress.
- Taxon
- spring wheatTriticum aestivume1
- Outcome
- more resistant to O3 injurye2
- Qualifier
- ontogenic shifts in the tolerance of plant tissue and/or acclimation to O3-induced oxidative stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a finding consistent with ontogenic shifts in the tolerance of plant tissue and/or acclimation to O3-induced oxidative stress.”
e1“spring wheat (Triticum aestivum cv. Hanno)”
e2“leaf 7 was more resistant to O3 injury than leaf 4”
Claim · model-written summary
Elevated CO2 protected spring wheat against adverse ozone effects in the combined treatment.
- Taxon
- spring wheatTriticum aestivume1
- Treatment
- elevated CO2e0
- Outcome
- adverse effects of O3e0
- Direction
- protectede0
- Qualifier
- combined treatmente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the combined treatment, elevated CO2 protected against the adverse effects of O3”
e1“spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
Elevated CO2 reduced cumulative ozone uptake by about 10% over the lifespan of leaf 4.
- Taxon
- spring wheatTriticum aestivume1
- Organ / stage
- leaves 4e0
- Treatment
- elevated CO2e0
- Outcome
- cumulative O3 uptakee0
- Direction
- reducede0
- Value
- c. 10%e0
- Qualifier
- life-spane0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the combined treatment, elevated CO2 protected against the adverse effects of O3 and reduced cumulative O3 uptake (calculated from measurements of stomatal conductance) by c. 10% and 35% over the life-span of leaves 4 and 7, respectively.”
e1“spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
Elevated CO2 reduced cumulative ozone uptake by 35% over the lifespan of leaf 7.
- Taxon
- spring wheatTriticum aestivume1
- Treatment
- elevated CO2e0
- Outcome
- cumulative O3 uptakee0
- Direction
- reducede0
- Value
- 35%e0
- Qualifier
- leaves 4 and 7, respectivelye0
Not reportedOrgan / stageComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the combined treatment, elevated CO2 protected against the adverse effects of O3 and reduced cumulative O3 uptake (calculated from measurements of stomatal conductance) by c. 10% and 35% over the life-span of leaves 4 and 7, respectively.”
e1“spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
CO2 protection was largely attributed to pollutant exclusion through reduced stomatal conductance.
- Taxon
- spring wheatTriticum aestivume1
- Organ / stage
- leafe0
- Treatment
- CO2-enrichmente0
- Outcome
- protectione0
- Qualifier
- exclusion of the pollutant from the leaf interiore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the protection afforded by CO2-enrichment to be due, to a large extent, to the exclusion of the pollutant from the leaf interior (as a consequence of the decline in stomatal conductance triggered by CO2-enrichment)”
e1“spring wheat (Triticum aestivum cv. Hanno)”
Claim · model-written summary
Especially for leaf 4, evidence suggested additional CO2 effects alleviating ozone oxidative stress impacts on photosynthesis.
- Taxon
- spring wheatTriticum aestivume1
- Organ / stage
- leaf 4e0
- Treatment
- CO2-enrichmente0
- Outcome
- impacts of ozone-induced oxidative stress on photosynthesise0
- Qualifier
- additional effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was evidence (especially from flux-response relationships constructed for leaf 4) that CO2-enrichment resulted in additional effects that alleviated the impacts of ozone-induced oxidative stress on photosynthesis.”
e1“spring wheat (Triticum aestivum cv. Hanno)”
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See all 97 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.