Abstract
Summary Interactive effects of CO 2 and water availability have been predicted to alter the competitive relationships between C3 and C4 species over geological and contemporary time scales. We tested the effects of drought and CO 2 partial pressures ( p CO 2 ) ranging from values of the Pleistocene to those predicted for the future on the physiology and growth of model C3 and C4 species. We grew co‐occurring Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture at 18 (Pleistocene), 27 (preindustrial), 35 (current), and 70 (future) Pa CO 2 under conditions of high light and nutrient availability. After 27 days of growth, water was withheld from randomly chosen plants of each species until visible wilting occurred. Under well‐watered conditions, low p CO 2 that occurred during the Pleistocene was highly limiting to C3 photosynthesis and growth, and C3 plants showed increased photosynthesis and growth with increasing p CO 2 between the Pleistocene and future CO 2 values. Well‐watered C4 plants exhibited increased photosynthesis in response to increasing p CO 2 , but total mass and leaf area were unaffected by p CO 2 . In response to drought, C3 plants dropped a large amount of leaf area and maintained relatively high leaf water potential in remaining leaves, whereas C4 plants retained greater leaf area, but at a lower leaf water potential. Furthermore, drought‐treated C3 plants grown at 18 Pa CO 2 retained relatively greater leaf area than C3 plants grown at higher p CO 2 and exhibited a delay in the reduction of stomatal conductance that may have occurred in response to severe carbon limitations. The C4 plants grown at 70 Pa CO 2 showed lower relative reductions in net photosynthesis by the end of the drought compared to plants at lower p CO 2 , indicating that CO 2 enrichment may alleviate drought effects in C4 plants. At the Pleistocene p CO 2 , C3 and C4 plants showed similar relative recovery from drought for leaf area and biomass production, whereas C4 plants showed higher recovery than C3 plants at current and elevated p CO 2 . Based on these model systems, we conclude that C3 species may not have been at a disadvantage relative to C4 species in response to low CO 2 and severe drought during the Pleistocene. Furthermore, C4 species may have an advantage over C3 species in response to increasing atmospheric CO 2 and more frequent and severe droughts.
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Claims 13
Claim · model-written summary
Well-watered C3 plants increased photosynthesis and growth as CO2 partial pressure rose from Pleistocene to future values.
- Taxon
- Abutilon theophrasti
Abutilon theophrastie0 - Treatment
- increasing p CO 2e1
- Outcome
- photosynthesis and growthe1
- Direction
- increasede1
- Comparator
- Pleistocenee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“C3 plants showed increased photosynthesis and growth with increasing p CO 2 between the Pleistocene and future CO 2 values”
Claim · model-written summary
Low CO2 partial pressure of the Pleistocene was highly limiting to C3 photosynthesis and growth.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- low p CO 2e2
- Outcome
- C3 photosynthesis and growthe2
- Direction
- highly limitinge2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e2“low p CO 2 that occurred during the Pleistocene was highly limiting to C3 photosynthesis and growth”
Claim · model-written summary
Well-watered C4 plants increased photosynthesis as CO2 partial pressure increased.
- Taxon
- Amaranthus retroflexus
Amaranthus retroflexuse0 - Treatment
- increasing p CO 2e3
- Outcome
- photosynthesise3
- Direction
- increasede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e3“exhibited increased photosynthesis in response to increasing p CO 2”
Claim · model-written summary
Total mass and leaf area of C4 plants were unaffected by CO2 partial pressure.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse0
- Treatment
- p CO 2e4
- Outcome
- total mass and leaf areae4
- Direction
- unaffectede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e4“total mass and leaf area were unaffected by p CO 2”
Claim · model-written summary
Under drought, C3 plants dropped a large amount of leaf area.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- droughte5
- Outcome
- leaf areae5
- Direction
- droppede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e5“In response to drought, C3 plants dropped a large amount of leaf area”
Claim · model-written summary
Under drought, C3 plants maintained relatively high leaf water potential in remaining leaves.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- droughte5
- Outcome
- leaf water potentiale6
- Direction
- maintainede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e5“In response to drought, C3 plants dropped a large amount of leaf area”
e6“maintained relatively high leaf water potential in remaining leaves”
Claim · model-written summary
Under drought, C4 plants retained greater leaf area than C3 plants.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse0
- Treatment
- droughte5
- Outcome
- leaf areae7
- Direction
- retained greatere7
- Comparator
- C3 plantse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e5“In response to drought, C3 plants dropped a large amount of leaf area”
e7“whereas C4 plants retained greater leaf area, but at a lower leaf water potential”
Claim · model-written summary
Under drought, C4 plants had a lower leaf water potential than C3 plants.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse0
- Treatment
- droughte5
- Outcome
- leaf water potentiale7
- Direction
- lowere7
- Comparator
- C3 plantse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e5“In response to drought, C3 plants dropped a large amount of leaf area”
e7“whereas C4 plants retained greater leaf area, but at a lower leaf water potential”
Claim · model-written summary
Drought-treated C3 plants grown at 18 Pa CO2 retained relatively greater leaf area than C3 plants grown at higher CO2.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- 18 Pa CO 2e1
- Outcome
- leaf areae1
- Direction
- retained relatively greatere1
- Comparator
- higher p CO 2e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“C3 plants grown at 18 Pa CO 2 retained relatively greater leaf area than C3 plants grown at higher p CO 2”
Claim · model-written summary
Drought-treated C3 plants grown at 18 Pa CO2 showed a delay in the reduction of stomatal conductance.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- 18 Pa CO 2e1
- Outcome
- stomatal conductancee2
- Direction
- delay in the reductione2
- Comparator
- higher p CO 2e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“C3 plants grown at 18 Pa CO 2 retained relatively greater leaf area than C3 plants grown at higher p CO 2”
e2“exhibited a delay in the reduction of stomatal conductance that may have occurred in response to severe carbon limitations”
Claim · model-written summary
C4 plants grown at 70 Pa CO2 showed lower relative reductions in net photosynthesis by the end of drought than at lower CO2.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse0
- Treatment
- 70 Pa CO 2e1
- Outcome
- net photosynthesise1
- Direction
- lower relative reductionse1
- Comparator
- lower p CO 2e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“The C4 plants grown at 70 Pa CO 2 showed lower relative reductions in net photosynthesis by the end of the drought compared to plants at lower p CO 2”
Claim · model-written summary
At the Pleistocene CO2 partial pressure, C3 and C4 plants showed similar relative recovery from drought for leaf area and biomass.
- Taxon
- Abutilon theophrastiAbutilon theophrastie0
- Treatment
- Pleistocene p CO 2e1
- Outcome
- relative recovery from drought for leaf area and biomass productione1
- Direction
- similare1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“At the Pleistocene p CO 2 , C3 and C4 plants showed similar relative recovery from drought for leaf area and biomass production”
Claim · model-written summary
At current and elevated CO2, C4 plants showed higher recovery from drought than C3 plants.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse0
- Treatment
- current and elevated p CO 2e1
- Outcome
- recoverye1
- Direction
- highere1
- Comparator
- C3 plantse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) in monoculture”
e1“whereas C4 plants showed higher recovery than C3 plants at current and elevated p CO 2”
The same questions in other papers
co2 · physiology: photosynthesis · Amaranthus retroflexus (redroot amaranth)Positive and negative results
1 in the opposite direction
- negative
co2 · yield · Abutilon theophrasti (velvetleaf)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
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drought · growth · Amaranthus retroflexus (redroot amaranth)Positive and negative results
1 paper in the same direction as this paper · 3 in the opposite direction
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1 paper more in this group
See all 5 papers →co2 · growth · Abutilon theophrasti (velvetleaf)Positive and negative results
3 papers in the same direction as this paper · 2 in the opposite direction
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See all 6 papers →co2 · growth · Amaranthus retroflexus (redroot amaranth)Positive and negative results
4 papers in the same direction as this paper · 2 in the opposite direction
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See all 7 papers →co2 · physiology: photosynthesis · Abutilon theophrasti (velvetleaf)Results agree
2 papers in the same direction as this paper
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drought · growth · Abutilon theophrasti (velvetleaf)Results agree
2 papers in the same direction as this paper
- negative
- negative
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.