Abstract
We examined how CO 2 concentrations and temperature interacted to affect growth, resource acquisition, and resource allocation of two annual plants that were supplied with a single pulse of nutrients. Physiological and growth measurements were made on individuals of Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 ) grown in environments with atmospheric CO 2 levels of 400 or 700 @mL/L and with light/dark temperatures of 28°/22° or 38°/31°C. Elevated CO 2 and temperature treatments had significant independent and interactive effects on plant growth, resource allocation, and resource acquisition (i.e., photosynthesis and nitrogen uptake), and the strength and direction of these affects were often dependent on plant species. For example, final biomass of Amaranthus was enhanced by elevated CO 2 at 28° but was depressed at 38°. For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°, and had no significant effects on final biomass at either temperature. These results are interpreted in light of the interactive effects of CO 2 and temperature on the rates of net leaf area production and loss, and on net whole—plant nitrogen retention. At 28°, elevated CO 2 stimulated the initial production of leaf area in both species, which led to an initial stimulation of biomass accumulation at the higher CO 2 level. However, in elevated CO 2 at 28°, the rate of net leaf area loss for Abutilon increased while that of Amaranthus decreased. Furthermore, high CO 2 apparently enhanced the ability of Amaranthus to retain nitrogen at this temperature, which may have helped to enhance photosynthesis, whereas nitrogen retention was unaffected in Abutilon. Thus, at 28°, final biomass of Abutilon was not simulated in a high CO 2 environment whereas the final biomass of Amaranthus was. At 38°, Abutilon had slightly reduced peak leaf areas under elevated CO 2 in comparison to ambient CO 2 grown plants, but increased rates of photosynthesis per unit leaf area early in the experiment apparently compensated for reduced leaf area. For Amaranthus at 38°, peak leaf area production was not affected by CO 2 treatment, but the rate of net leaf area loss hastened under elevated CO 2 conditions and was accompanied by substantial reductions of whole—plant nitrogen content and leaf photosynthesis. This may have led to the reduced biomass accumulation of high CO 2 grown plants that we observed during the last 30 d of growth. Plants of both species grown in elevated CO 2 exhibited reduced tissue—specific rates of nitrogen absorption, increased plant photosynthetic rate per unit of conductance, and increased initial allocation of biomass to roots, irrespective of temperature. Plants of both species grown under an elevated temperature regime had substantially decreased reproductive allocation, increased allocation to stem biomass, and increased plant water flux at both CO 2 treatments. The age of plants also affected our interpretations of plant responses to CO 2 and temperature treatments. For example, significant effects of CO 2 treatment on the growth of Abutilon were evident early, prior to the initiation of flowering, when nitrogen availability would have been highest and pot space would not have been limited. Nevertheless, the opposite was true for Amaranthus, in which significant effects of CO 2 treatment on plant growth were not detectable until the final 30 d of the experiment. Elevated CO 2 interacted with temperature to affect plant productivity in different ways than would have been predicted from plant responses to elevated CO 2 alone. Furthermore, a majority of the interactive effects of CO 2 concentration and temperature on plant growth could be interpreted in light of their effects on the rates of net leaf area production and loss, nitrogen retention, and, to a lesser degree, photosynthesis and resource partitioning.
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Claims 16
Claim · model-written summary
Elevated CO2 enhanced final Amaranthus biomass at 28°.
- Taxon
- Amaranthus
_with_green_foliage%2C_photographed_in_Tamil_Nadu%2C_India.jpg?width=60)
Amaranthuse0 - Treatment
- elevated CO 2e0
- Outcome
- final biomasse0
- Direction
- enhancede0
- Qualifier
- 28°e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_with_green_foliage%2C_photographed_in_Tamil_Nadu%2C_India.jpg?width=500)
Verbatim
e0“final biomass of Amaranthus was enhanced by elevated CO 2 at 28°”
Claim · model-written summary
Elevated CO2 depressed final Amaranthus biomass at 38°.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- elevated CO 2e0
- Outcome
- final biomasse0
- Direction
- depressede0
- Qualifier
- 38°e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“final biomass of Amaranthus was enhanced by elevated CO 2 at 28° but was depressed at 38°”
Claim · model-written summary
Elevated CO2 increased initial relative growth rate of Abutilon at 28°.
- Treatment
- elevated CO 2e0
- Outcome
- initial plant relative growth ratese0
- Direction
- increasede0
- Qualifier
- 28°e0
AbutilonNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°”
Claim · model-written summary
Elevated CO2 had no significant effect on final Abutilon biomass.
- Treatment
- elevated CO 2e0
- Outcome
- final biomasse0
- Direction
- no significant effectse0
- Qualifier
- at either temperaturee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°, and had no significant effects on final biomass at either temperature.”
Claim · model-written summary
Elevated CO2 stimulated initial leaf area production at 28° in both species.
- Treatment
- elevated CO 2e0
- Outcome
- initial production of leaf areae0
- Direction
- stimulatede0
- Qualifier
- At 28°e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 28°, elevated CO 2 stimulated the initial production of leaf area in both species”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°”
Claim · model-written summary
Elevated CO2 increased net leaf area loss in Abutilon at 28°.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in elevated CO 2 at 28°, the rate of net leaf area loss for Abutilon increased”
Claim · model-written summary
Elevated CO2 decreased net leaf area loss in Amaranthus at 28°.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- elevated CO 2e0
- Outcome
- rate of net leaf area losse0
- Direction
- decreasede0
- Qualifier
- 28°e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in elevated CO 2 at 28°, the rate of net leaf area loss for Abutilon increased while that of Amaranthus decreased”
Claim · model-written summary
High CO2 enhanced Amaranthus nitrogen retention at 28°.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- high CO 2e0
- Outcome
- retain nitrogene0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high CO 2 apparently enhanced the ability of Amaranthus to retain nitrogen at this temperature”
Claim · model-written summary
Nitrogen retention in Abutilon was unaffected.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nitrogen retention was unaffected in Abutilon”
Claim · model-written summary
Elevated CO2 slightly reduced Abutilon peak leaf area at 38°.
- Treatment
- elevated CO 2e0
- Outcome
- peak leaf arease0
- Direction
- reducede0
- Qualifier
- At 38°e0
- Comparator
- ambient CO 2 grown plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 38°, Abutilon had slightly reduced peak leaf areas under elevated CO 2 in comparison to ambient CO 2 grown plants”
Claim · model-written summary
Elevated CO2 hastened Amaranthus net leaf area loss at 38°.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- elevated CO 2e0
- Outcome
- rate of net leaf area losse0
- Direction
- hastenede0
- Qualifier
- 38°e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For Amaranthus at 38°, peak leaf area production was not affected by CO 2 treatment, but the rate of net leaf area loss hastened under elevated CO 2 conditions”
Claim · model-written summary
Elevated CO2 at 38° reduced Amaranthus whole-plant nitrogen and photosynthesis.
- Taxon
- AmaranthusAmaranthuse1
- Treatment
- elevated CO 2e0
- Outcome
- whole—plant nitrogen content and leaf photosynthesise0
- Direction
- reductionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under elevated CO 2 conditions and was accompanied by substantial reductions of whole—plant nitrogen content and leaf photosynthesis”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“final biomass of Amaranthus was enhanced by elevated CO 2 at 28°”
Claim · model-written summary
Both species under elevated CO2 had reduced tissue-specific nitrogen absorption.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants of both species grown in elevated CO 2 exhibited reduced tissue—specific rates of nitrogen absorption”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°”
Claim · model-written summary
Elevated CO2 increased photosynthesis per unit conductance and initial root allocation in both species.
- Taxon
- AmaranthusAmaranthuse1
- Outcome
- plant photosynthetic rate per unit of conductancee0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased plant photosynthetic rate per unit of conductance, and increased initial allocation of biomass to roots”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“final biomass of Amaranthus was enhanced by elevated CO 2 at 28°”
Claim · model-written summary
Elevated temperature decreased reproductive allocation in both species.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants of both species grown under an elevated temperature regime had substantially decreased reproductive allocation”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“For Abutilon, elevated CO 2 increased initial plant relative growth rates at 28° but not at 38°”
Claim · model-written summary
Elevated temperature increased stem allocation and water flux in both species.
- Taxon
- AmaranthusAmaranthuse1
- Outcome
- allocation to stem biomass, and increased plant water fluxe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased allocation to stem biomass, and increased plant water flux at both CO 2 treatments”
t0“Co‐Occurring C_3 and C_4 Annuals”
e1“final biomass of Amaranthus was enhanced by elevated CO 2 at 28°”
The same questions in other papers
co2 · growth · AbutilonPositive and negative results
1 in the opposite direction
- no effect
co2 · growth · AmaranthusResults 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.