Abstract
Tropospheric trace gases such as CO 2 and O 3 have progressively increased over the past century and are predicted to increase to levels at which they may have a significant impact on agricultural production. The effects of CO 2 enrichment and O 3 air pollution on leaf photosynthesis (P n ) and stomatal conductance (g 5 ) were investigated. Two soft winter wheat ( Triticum aestivum L.) cultivars, Massey in 1991 and Saluda in 1992, were studied in field experiments at Beltsville, MD, by means of open‐top chambers to mimic atmospheric environments predicted for the first half of the 21st century. Plants were exposed to two levels of O 3 (charcoal filtered air and ambient air + an average of 40 nmol O 3 mol −1 from Monday–Friday of every week). Ozone treatments were superimposed on two CO 2 treatments (350 μmol CO 2 mol − and 500 μmol CO 2 mol −1 ). Averaged over O 3 treatments, P n was stimulated during the early and late growing season under enriched CO 2 . Averaged over CO 2 treatments, high O 3 exposure had a negative impact on P n early in the season of 1992 and a major impact late in the season of 1991 and 1992 due to premature senescence. Decreases in g s occurred under the enriched CO 2 environment and to a lesser extent with high O 3 . Interactive effects on P n and g s were mostly absent. It is likely that if CO 2 and O 3 concentrations continue to increase, the beneficial effect of CO 2 enrichment on P n may be partially negated by O 3 ‐induced stress. Conversely, damaging effects of O 3 on P n may be compensated by elevated atmospheric CO 2 .
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Claims 5
Claim · model-written summary
Enriched CO2 stimulated wheat photosynthesis early and late in the growing season.
- Taxon
- Triticum aestivum L.
Triticum aestivumt0 - Treatment
- enriched CO 2e0
- Outcome
- P ne0
- Direction
- stimulatede0
- Qualifier
- early and late growing seasone0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Averaged over O 3 treatments, P n was stimulated during the early and late growing season under enriched CO 2 .”
t0“Triticum aestivum L.”
Claim · model-written summary
High ozone reduced wheat photosynthesis early in 1992 and late in 1991 and 1992.
- Taxon
- Triticum aestivum L.Triticum aestivumt0
- Treatment
- high O 3 exposuree0
- Outcome
- P ne0
- Direction
- negative impacte0
- Qualifier
- early in the season of 1992 and a major impact late in the season of 1991 and 1992e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high O 3 exposure had a negative impact on P n early in the season of 1992 and a major impact late in the season of 1991 and 1992 due to premature senescence.”
t0“Triticum aestivum L.”
Claim · model-written summary
Enriched CO2 decreased wheat stomatal conductance.
- Taxon
- Triticum aestivum L.Triticum aestivumt0
- Treatment
- enriched CO 2e0
- Outcome
- g se0
- Direction
- Decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decreases in g s occurred under the enriched CO 2 environment”
t0“Triticum aestivum L.”
Claim · model-written summary
High ozone decreased wheat stomatal conductance to a lesser extent.
- Taxon
- Triticum aestivum L.Triticum aestivumt0
- Treatment
- high O 3e0
- Outcome
- g se0
- Direction
- Decreasese0
- Comparator
- enriched CO 2 environmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decreases in g s occurred under the enriched CO 2 environment and to a lesser extent with high O 3 .”
t0“Triticum aestivum L.”
Claim · model-written summary
Interactive effects of CO2 and ozone on photosynthesis and stomatal conductance were mostly absent.
- Taxon
- Triticum aestivum L.Triticum aestivumt0
- Outcome
- Interactive effects on P n and g se0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Interactive effects on P n and g s were mostly absent.”
t0“Triticum aestivum L.”
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