Abstract
PREMISE OF THE STUDY: Determining effects of elevated CO2 and N on photosynthetic thermotolerance is critical for predicting plant responses to global warming. METHODS: We grew Hordeum vulgare (barley, C3) and Zea mays (corn, C4) at current or elevated CO2 (370, 700 ppm) and limiting or optimal soil N (0.5, 7.5 mmol/L). We assessed thermotolerance of net photosynthesis (Pn), photosystem II efficiency in the light (Fv'/Fm'), photochemical quenching (qp), carboxylation efficiency (CE), and content of rubisco activase and major heat-shock proteins (HSPs). KEY RESULTS: For barley, elevated CO2 had no effect on Pn, qp, and CE at both high and low N and only a positive effect on Fv'/Fm' at high N. However, for corn, Pn, Fv'/Fm', qp, and CE were decreased substantially by elevated CO2 under high and low N, with greater decreases at high N for all but qp. The negative effects of high CO2 during heat stress on photosynthesis were correlated with rubisco activase and HSPs content, which decreased with heat stress, especially for low-N corn. CONCLUSION: These results indicate that stimulatory effects of elevated CO2 at normal temperatures on photosynthesis and growth (only found for high-N barley) may be partly offset by neutral or negative effects during heat stress, especially for C4 species. Thus, CO2 and N effects on photosynthetic thermotolerance may contribute to changes in plant productivity, distribution, and diversity in future.
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Claims 7
Claim · model-written summary
Elevated carbon dioxide did not affect barley Pn, qp, or CE at either nitrogen level.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree0 - Treatment
- elevated CO2e0
- Outcome
- Pn, qp, and CEe0
- Direction
- no effecte0
- Qualifier
- at both high and low Ne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“For barley, elevated CO2 had no effect on Pn, qp, and CE at both high and low N”
Claim · model-written summary
Elevated carbon dioxide improved barley Fv'/Fm' only at high nitrogen.
Not reportedTaxonTreatmentComparator
Verbatim
e0“only a positive effect on Fv'/Fm' at high N”
Claim · model-written summary
Elevated carbon dioxide substantially decreased corn Pn, Fv'/Fm', qp, and CE at both nitrogen levels.
- Taxon
- corn
Zea mays subsp. mayse0 - Treatment
- elevated CO2e0
- Outcome
- Pn, Fv'/Fm', qp, and CEe0
- Direction
- decreasede0
- Qualifier
- under high and low Ne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for corn, Pn, Fv'/Fm', qp, and CE were decreased substantially by elevated CO2 under high and low N”
Claim · model-written summary
Corn decreases were greater at high nitrogen except for qp.
Not reportedTaxon
Verbatim
e0“with greater decreases at high N for all but qp”
Claim · model-written summary
Negative high-carbon-dioxide photosynthetic effects during heat stress correlated with rubisco activase and heat-shock protein content.
Not reportedTaxonDirection
Verbatim
e0“The negative effects of high CO2 during heat stress on photosynthesis were correlated with rubisco activase and HSPs content”
Claim · model-written summary
Rubisco activase and heat-shock protein content decreased with heat stress, especially in low-nitrogen corn.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- heat stresse0
- Outcome
- whiche0
- Direction
- decreasede0
- Qualifier
- especially for low-N corne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which decreased with heat stress, especially for low-N corn”
Claim · model-written summary
Elevated carbon dioxide stimulated photosynthesis and growth at normal temperature only in high-nitrogen barley.
- Taxon
- barleyHordeum vulgaree0
- Treatment
- elevated CO2e0
- Outcome
- photosynthesis and growthe0
- Direction
- stimulatorye0
- Qualifier
- only found for high-N barleye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stimulatory effects of elevated CO2 at normal temperatures on photosynthesis and growth (only found for high-N barley)”
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co2 · physiology: photosynthesis · Zea mays (maize)Results differ
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See all 13 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.