Abstract
We studied the effects of CO2 elevation on leaf and canopy photosynthesis and optimal leaf area index (LAI) for stands of the annual species Abutilon theophrasti and Ambrosia artemisiifolia. Leaf photosynthesis was modeled as a function of photosynthetic photon flux density (PPFD) and nitrogen content per unit leaf area (NL). There was a curvilinear relationship between the light-saturated rates of leaf photosynthesis (Pmax) and NL. CO2 elevation significantly increased Pmax as a function of NL in both species. Dark respiration (Rd) was linearly correlated with NL. CO2 elevation slightly but significantly increased Rd in Abutilon, while it had no significant effect on Rd in Ambrosia. The initial slope of a light-response curve was determined from quantum yield (φabs) multiplied by leaf absorptance and then calibrated against NL. Daily canopy photosynthesis, calculated by integration of leaf photosynthesis with the actual distribution of leaf area, leaf N, and PPFD within a canopy, showed fairly good agreement with the canopy photosynthesis estimated from growth analysis. CO2 elevation increased canopy photosynthesis by 30–50%. Based on the leaf photosynthesis model for Abutilon, we calculated daily canopy photosynthesis for a given LAI and N availability, in which N was assumed to be distributed optimally within a leaf canopy to maximize daily canopy photosynthesis. An optimal LAI to maximize daily canopy photosynthesis was obtained for each level of N availability and this optimum increased with increasing N availability. Contrary to the often predicted increase in LAI with CO2 elevation, the optimum LAI did not increase at high CO2 when N availability was limited. Two factors were suggested to be involved in counteracting the increase in LAI in a high-CO2 world. One is the higher φabs of plants grown in elevated CO2, which makes leaves in the canopy more N limited, favors higher NL and thus lowers optimal LAI. The other is the higher Rd in elevated CO2, which leads to higher light compensation points, and lowers optimal LAI.
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Claims 11
Claim · model-written summary
Light-saturated leaf photosynthesis had a curvilinear relationship with leaf nitrogen.
- Taxon
- Abutilon theophrasti
Abutilon theophrastie1 - Compound
- NLe0
- Outcome
- light-saturated rates of leaf photosynthesis (Pmax)e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was a curvilinear relationship between the light-saturated rates of leaf photosynthesis (Pmax) and NL.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Elevated CO2 significantly increased Pmax in both species.
- Taxon
- Abutilon theophrasti and Ambrosia artemisiifoliaAbutilon theophrasti
Ambrosia artemisiifoliae1 - Treatment
- CO2 elevatione0
- Outcome
- Pmaxe0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO2 elevation significantly increased Pmax as a function of NL in both species.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Dark respiration correlated linearly with leaf nitrogen.
- Taxon
- Abutilon theophrasti and Ambrosia artemisiifoliaAbutilon theophrastiAmbrosia artemisiifoliae1
- Compound
- NLe0
- Outcome
- Dark respiration (Rd)e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dark respiration (Rd) was linearly correlated with NL.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Elevated CO2 significantly increased dark respiration in Abutilon.
AbutilonNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO2 elevation slightly but significantly increased Rd in Abutilon”
Claim · model-written summary
Elevated CO2 had no significant effect on dark respiration in Ambrosia.
AmbrosiaNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it had no significant effect on Rd in Ambrosia.”
e1“CO2 elevation slightly but significantly increased Rd in Abutilon, while it had no significant effect”
Claim · model-written summary
Modeled daily canopy photosynthesis agreed fairly well with growth-analysis estimates.
- Taxon
- Abutilon theophrasti and Ambrosia artemisiifoliaAbutilon theophrastiAmbrosia artemisiifoliae1
- Outcome
- daily canopy photosynthesise0
- Comparator
- canopy photosynthesis estimated from growth analysise0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Daily canopy photosynthesis, calculated by integration of leaf photosynthesis with the actual distribution of leaf area, leaf N, and PPFD within a canopy, showed fairly good agreement with the canopy photosynthesis estimated from growth analysis.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Elevated CO2 increased canopy photosynthesis by 30–50%.
- Taxon
- Abutilon theophrasti and Ambrosia artemisiifoliaAbutilon theophrastiAmbrosia artemisiifoliae1
- Treatment
- CO2 elevatione0
- Outcome
- canopy photosynthesise0
- Direction
- increasede0
- Value
- 30–50%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO2 elevation increased canopy photosynthesis by 30–50%.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Modeled optimal LAI increased as nitrogen availability increased.
- Taxon
- Abutilon theophrastiAbutilon theophrastie1
- Compound
- N availabilitye0
- Outcome
- optimume0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this optimum increased with increasing N availability.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
Optimal LAI did not increase under high CO2 when nitrogen availability was limited.
- Taxon
- Abutilon theophrastiAbutilon theophrastie1
- Treatment
- high CO2e0
- Outcome
- optimum LAIe0
- Direction
- did not increasee0
- Qualifier
- N availability was limitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the optimum LAI did not increase at high CO2 when N availability was limited.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
The authors suggest elevated CO2 increases leaf absorptance and thereby lowers optimal LAI through nitrogen limitation.
- Taxon
- Abutilon theophrastiAbutilon theophrastie1
- Treatment
- elevated CO2e0
- Outcome
- optimal LAIe0
- Direction
- lowerse0
- Qualifier
- more N limitede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher φabs of plants grown in elevated CO2, which makes leaves in the canopy more N limited, favors higher NL and thus lowers optimal LAI.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
Claim · model-written summary
The authors suggest elevated CO2 raises respiration and light compensation points, lowering optimal LAI.
- Taxon
- Abutilon theophrastiAbutilon theophrastie1
- Treatment
- elevated CO2e0
- Outcome
- optimal LAIe0
- Direction
- lowerse0
- Qualifier
- higher light compensation pointse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher Rd in elevated CO2, which leads to higher light compensation points, and lowers optimal LAI.”
e1“annual species Abutilon theophrasti and Ambrosia artemisiifolia”
The same questions in other papers
co2 · growth · Abutilon theophrasti (velvetleaf)Positive and negative results
1 paper in the same direction as this paper · 4 in the opposite direction
- positive
- positive
- positive
2 papers more in this group
See all 6 papers →altitude · physiology: photosynthesis · Abutilon theophrasti (velvetleaf)Results agree
1 paper in the same direction as this paper
- positive
co2 · physiology: photosynthesis · Ambrosia artemisiifolia (common ragweed)Results agree
1 paper in the same direction as this paper
- positive
altitude · physiology: photosynthesis · Ambrosia artemisiifolia (common ragweed)Results agree
1 paper in the same direction as this paper
- positive
co2 · physiology: photosynthesis · Abutilon theophrasti (velvetleaf)Results agree
2 papers in the same direction as this paper
- positive
- positive
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.