Abstract
Abstract Spring wheat cv. Minaret was grown to maturity under three carbon dioxide (CO 2 ) and two ozone (O 3 ) concentrations in open‐top chambers (OTC). Green leaf area index (LAI) was increased by elevated CO 2 under ambient O 3 conditions as a direct result of increases in tillering, rather than individual leaf areas. Yellow LAI was also greater in the 550 and 680 μmol mol –1 CO 2 treatments than in the chambered ambient control; individual leaves on the main shoot senesced more rapidly under 550 μmol mol –1 CO 2 , but senescence was delayed at 680 μmol mol –1 CO 2 . Fractional light interception ( f ) during the vegetative period was up to 26% greater under 680 μmol mol –1 CO 2 than in the control treatment, but seasonal accumulated intercepted radiation was only increased by 8%. As a result of greater carbon assimilation during canopy development, plants grown under elevated CO 2 were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants. At maturity, yield was 30% greater in the 680 μmol mol –1 CO 2 treatment, due to a combination of increases in the number of ears per m –2 , grain number per ear and individual grain weight (IGW). Exposure to a seasonal mean (7 h d –1 ) of 84 nmol mol –1 O 3 under ambient CO 2 decreased green LAI and increased yellow LAI, thereby reducing both f and accumulated intercepted radiation by ≈ 16%. Individual leaves senesced completely 7–28 days earlier than in control plants. At anthesis, the plants were shorter than controls and exhibited reductions in stem and ear biomass of 15 and 23%. Grain yield at maturity was decreased by 30% due to a combination of reductions in ear number m –2 , the numbers of grains per spikelet and per ear and IGW. The presence of elevated CO 2 reduced the rate of O 3 ‐induced leaf senescence and resulted in the maintenance of a higher green LAI during vegetative growth under ambient CO 2 conditions. Grain yields at maturity were nevertheless lower than those obtained in the corresponding elevated CO 2 treatments in the absence of elevated O 3 . Thus, although the presence of elevated CO 2 reduced the damaging impact of ozone on radiation interception and vegetative growth, substantial yield losses were nevertheless induced. These data suggest that spring wheat may be susceptible to O 3 ‐induced injury during anthesis irrespective of the atmospheric CO 2 concentration. Possible deleterious mechanisms operating through effects on pollen viability, seed set and the duration of grain filling are discussed.
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Claims 18
Claim · model-written summary
Elevated CO2 increased green LAI under ambient ozone through tillering.
- Taxon
- Spring wheat
Triticum aestivumt0 - Treatment
- elevated CO 2e0
- Outcome
- Green leaf area index (LAI)e0
- Direction
- increasede0
- Comparator
- ambient O 3 conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Green leaf area index (LAI) was increased by elevated CO 2 under ambient O 3 conditions as a direct result of increases in tillering, rather than individual leaf areas.”
t0“spring wheat”
Claim · model-written summary
Yellow LAI was greater at both elevated CO2 levels than chambered ambient control.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 550 and 680 μmol mol –1 CO 2 treatmentse0
- Outcome
- Yellow LAIe0
- Direction
- greatere0
- Comparator
- chambered ambient controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yellow LAI was also greater in the 550 and 680 μmol mol –1 CO 2 treatments than in the chambered ambient control”
t0“spring wheat”
Claim · model-written summary
Main shoot leaves senesced faster at 550 CO2.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 550 μmol mol –1 CO 2e0
- Outcome
- individual leaves on the main shoot senescede0
- Direction
- more rapidlye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“individual leaves on the main shoot senesced more rapidly under 550 μmol mol –1 CO 2”
t0“spring wheat”
Claim · model-written summary
Main shoot leaf senescence was delayed at 680 CO2.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 680 μmol mol –1 CO 2e0
- Outcome
- senescencee0
- Direction
- delayede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“senescence was delayed at 680 μmol mol –1 CO 2”
t0“spring wheat”
Claim · model-written summary
Vegetative fractional light interception was up to 26% greater at 680 CO2.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 680 μmol mol –1 CO 2e0
- Outcome
- Fractional light interception ( f )e0
- Direction
- greatere0
- Value
- 26%e0
- Comparator
- control treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fractional light interception ( f ) during the vegetative period was up to 26% greater under 680 μmol mol –1 CO 2 than in the control treatment”
t0“spring wheat”
Claim · model-written summary
Seasonal intercepted radiation increased 8%.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- seasonal accumulated intercepted radiatione0
- Direction
- increasede0
- Value
- 8%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seasonal accumulated intercepted radiation was only increased by 8%.”
t0“spring wheat”
Claim · model-written summary
Elevated CO2 increased stem biomass by 27%.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- elevated CO 2e0
- Outcome
- stem and ear biomasse0
- Direction
- greatere0
- Value
- 27e0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants grown under elevated CO 2 were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants.”
t0“spring wheat”
Claim · model-written summary
Elevated CO2 increased ear biomass by 16%.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- elevated CO 2e0
- Outcome
- ear biomasse0
- Direction
- greatere0
- Value
- 16%e0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants grown under elevated CO 2 were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants.”
t0“spring wheat”
Claim · model-written summary
Yield increased 30% at 680 CO2.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 680 μmol mol –1 CO 2 treatmente0
- Outcome
- yielde0
- Direction
- greatere0
- Value
- 30%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At maturity, yield was 30% greater in the 680 μmol mol –1 CO 2 treatment”
t0“spring wheat”
Claim · model-written summary
Ozone decreased green LAI and increased yellow LAI.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 84 nmol mol –1 O 3e0
- Outcome
- green LAIe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“84 nmol mol –1 O 3 under ambient CO 2 decreased green LAI and increased yellow LAI”
t0“spring wheat”
Claim · model-written summary
Ozone increased yellow LAI.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- 84 nmol mol –1 O 3e0
- Outcome
- yellow LAIe0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“84 nmol mol –1 O 3 under ambient CO 2 decreased green LAI and increased yellow LAI”
t0“spring wheat”
Claim · model-written summary
Ozone reduced light interception and accumulated radiation about 16%.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- f and accumulated intercepted radiatione0
- Direction
- reducinge0
- Value
- ≈ 16%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reducing both f and accumulated intercepted radiation by ≈ 16%.”
t0“spring wheat”
Claim · model-written summary
Ozone advanced complete leaf senescence by 7–28 days.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- Individual leaves senesced completelye0
- Direction
- earliere0
- Value
- 7–28 dayse0
- Comparator
- control plantse0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Individual leaves senesced completely 7–28 days earlier than in control plants.”
t0“spring wheat”
Claim · model-written summary
Ozone reduced stem biomass by 15%.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- stem and ear biomasse0
- Direction
- reductionse0
- Value
- 15e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reductions in stem and ear biomass of 15 and 23%.”
t0“spring wheat”
Claim · model-written summary
Ozone reduced ear biomass by 23%.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- ear biomasse0
- Direction
- reductionse0
- Value
- 23%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reductions in stem and ear biomass of 15 and 23%.”
t0“spring wheat”
Claim · model-written summary
Ozone reduced grain yield by 30%.
- Taxon
- spring wheatTriticum aestivumt0
- Outcome
- Grain yielde0
- Direction
- decreasede0
- Value
- 30%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield at maturity was decreased by 30%”
t0“spring wheat”
Claim · model-written summary
Elevated CO2 reduced ozone induced leaf senescence and maintained higher green LAI.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- elevated CO 2e0
- Outcome
- O 3 ‐induced leaf senescencee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO 2 reduced the rate of O 3 ‐induced leaf senescence and resulted in the maintenance of a higher green LAI”
t0“spring wheat”
Claim · model-written summary
Ozone still lowered yield under elevated CO2.
- Taxon
- spring wheatTriticum aestivumt0
- Treatment
- elevated O 3e0
- Outcome
- Grain yieldse0
- Direction
- lowere0
- Comparator
- corresponding elevated CO 2 treatments in the absence of elevated O 3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yields at maturity were nevertheless lower than those obtained in the corresponding elevated CO 2 treatments in the absence of elevated O 3 .”
t0“spring wheat”
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