Abstract
Previous studies revealed that the primary leaves of barley (Hordeum vulgare L. cv. Brant) that were grown in high‐light growth chambers in elevated CO2 (100 Pa) developed symptoms of senescence earlier than primary leaves of barley plants concurrently grown in ambient CO2 (36 Pa). The onset of senescence in these leaves was hypothesized to be associated with a decline in antioxidant capacity that resulted in higher levels of active oxygen species, which caused oxidative stress. In this new study, barley was grown from planting in high‐light growth chambers supplied with either ambient CO2 (36 Pa) or elevated CO2 (100 Pa). From 9 to 17 d after planting (DAP), primary leaf chlorophyll level as well as photosynthetic oxygen evolution per unit fresh mass decreased in plants in elevated CO2 to a greater extent than in plants in ambient CO2. Exposure of plants to elevated CO2 resulted in higher levels of primary leaf–free glucose, sucrose, and starch than in plants concurrently exposed to ambient CO2; this was most evident during 9–13 DAP. However, between 13 and 17 DAP, levels of foliar carbohydrates decreased to a greater extent in elevated CO2 than in ambient CO2, indicating that photosynthetic carbon metabolism was more repressed in this period in elevated CO2 treatments. In ambient CO2 over the period of 9–17 DAP, primary leaf total ascorbic acid (ASCtot) and total glutathione (GSHtot) levels decreased 38% and 51%, respectively. In elevated CO2 over this same time period, ASCtot and GSHtot decreased 45% and 63%, respectively. Since ASCtot and GSHtot are antioxidants involved in protecting the chloroplast from damage by active oxygen species such as hydrogen peroxide, we conclude that the decrease in ASCtot and GSHtot were factors in elevated CO2‐induced photosynthetic decline in barley primary leaves. Further, we interpret the greater decrease in ASCtot in elevated CO2 to be caused by a greater decrease in photosynthate partitioning and photosynthate availability, which supports ASC synthesis. We also suggest that decrease in glutathione in elevated CO2 may be related to an inhibition by elevated CO2 of photorespiratory carbon metabolism.
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Claims 10
Claim · model-written summary
Elevated CO2 caused a greater decline in chlorophyll and photosynthetic oxygen evolution from 9 to 17 DAP.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaret0 - Organ / stage
- primary leafe0
- Treatment
- elevated CO2e0
- Outcome
- chlorophyll level as well as photosynthetic oxygen evolution per unit fresh masse0
- Direction
- decreasede0
- Qualifier
- From 9 to 17 d after planting (DAP)e0
- Comparator
- ambient CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“From 9 to 17 d after planting (DAP), primary leaf chlorophyll level as well as photosynthetic oxygen evolution per unit fresh mass decreased in plants in elevated CO2 to a greater extent than in plants in ambient CO2.”
t0“Barley”
t1“Barley”
Claim · model-written summary
Elevated CO2 raised leaf glucose, sucrose and starch, especially at 9–13 DAP.
- Taxon
- barleyHordeum vulgaret0
- Organ / stage
- primary leafe0
- Treatment
- elevated CO2e0
- Outcome
- glucose, sucrose, and starche0
- Direction
- highere0
- Qualifier
- 9–13 DAPe0
- Comparator
- ambient CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure of plants to elevated CO2 resulted in higher levels of primary leaf–free glucose, sucrose, and starch than in plants concurrently exposed to ambient CO2; this was most evident during 9–13 DAP.”
t0“Barley”
t1“Barley”
Claim · model-written summary
Foliar carbohydrates declined more under elevated CO2 from 13 to 17 DAP.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- elevated CO2e0
- Outcome
- levels of foliar carbohydratese0
- Direction
- decreasede0
- Qualifier
- between 13 and 17 DAPe0
- Comparator
- ambient CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“between 13 and 17 DAP, levels of foliar carbohydrates decreased to a greater extent in elevated CO2 than in ambient CO2”
t0“Barley”
t1“Barley”
Claim · model-written summary
Under ambient CO2, leaf total ascorbic acid declined 38% from 9 to 17 DAP.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- ambient CO2e0
- Outcome
- primary leaf total ascorbic acid (ASCtot)e0
- Direction
- decreasede0
- Value
- 38%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In ambient CO2 over the period of 9–17 DAP, primary leaf total ascorbic acid (ASCtot) and total glutathione (GSHtot) levels decreased 38% and 51%, respectively.”
t0“Barley”
t1“Barley”
Claim · model-written summary
Under ambient CO2, leaf total glutathione declined 51%.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- ambient CO2e0
- Outcome
- total glutathione (GSHtot) levelse0
- Direction
- decreasede0
- Value
- 51%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In ambient CO2 over the period of 9–17 DAP, primary leaf total ascorbic acid (ASCtot) and total glutathione (GSHtot) levels decreased 38% and 51%, respectively.”
t0“Barley”
t1“Barley”
Claim · model-written summary
Under elevated CO2, total ascorbic acid declined 45%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In elevated CO2 over this same time period, ASCtot and GSHtot decreased 45% and 63%, respectively.”
t0“Barley”
t1“Barley”
Claim · model-written summary
Under elevated CO2, total glutathione declined 63%.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In elevated CO2 over this same time period, ASCtot and GSHtot decreased 45% and 63%, respectively.”
t0“Barley”
t1“Barley”
Claim · model-written summary
The authors attribute elevated CO2 photosynthetic decline partly to diminished ascorbic acid and glutathione.
- Taxon
- barleyHordeum vulgaree0
- Treatment
- elevated CO2e0
- Outcome
- photosynthetic declinee0
- Qualifier
- decrease in ASCtot and GSHtote0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we conclude that the decrease in ASCtot and GSHtot were factors in elevated CO2‐induced photosynthetic decline in barley primary leaves”
Claim · model-written summary
The authors link the larger ascorbic acid decrease to diminished photosynthate partitioning and availability.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- elevated CO2e0
- Outcome
- greater decrease in ASCtote0
- Qualifier
- greater decrease in photosynthate partitioning and photosynthate availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we interpret the greater decrease in ASCtot in elevated CO2 to be caused by a greater decrease in photosynthate partitioning and photosynthate availability”
t0“Barley”
t1“Barley”
Claim · model-written summary
The authors suggest elevated CO2 inhibits photorespiratory carbon metabolism, related to glutathione decrease.
- Taxon
- barleyHordeum vulgaret0
- Treatment
- elevated CO2e0
- Outcome
- decrease in glutathionee0
- Qualifier
- inhibition by elevated CO2 of photorespiratory carbon metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“decrease in glutathione in elevated CO2 may be related to an inhibition by elevated CO2 of photorespiratory carbon metabolism”
t0“Barley”
t1“Barley”
The same questions in other papers
co2 · physiology: photosynthesis · Hordeum vulgare (barley)Positive and negative results
7 papers in the same direction as this paper · 5 in the opposite direction
- negative
- no effect
- positive
9 papers more in this group
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.