Abstract
In order to investigate the effects, without competition, of CO 2 on germination, growth, physiological response, and reproduction, we focussed on co—occurring species that are prominent members of an annual community in Illinois. Five species of old field annual plants—Abutilon theophrasti (C 3 ), Amaranthus retroflexus (C 4 ), Ambrosia artemisiifolia (C 3 ), Chenopodium album (C 3 ), and Setaria faberii (C 4 )–were grown for their entire life cycle as individuals at CO 2 concentration of 350 @mL/L, 500 @mL/L, and 700@mL/L. Emergence time, growth rate, shoot water status, photosynthesis, conductance, flowering time, nitrogen content, and biomass and reproductive biomass were measured. There was no detectable effect of enhanced CO 2 on timing of emergence in any of the species. Amaranthus relative growth rate (RGR) was always higher at 700 @mL/L CO 2 than at 350 @mL/L. In both Abutilon and Ambrosia, RGR was greater at 700 @mL/L than at 350 @mL/L during the first half of the experimental period, but during the second half of the period the reverse was true. Shoot water potential significantly increased (became less negative) with increasing CO 2 in Amaranthus and Setaria. Similar but statistically nonsignificant trends were found in Chenopodium and Abutilon. Overall rate of photosynthesis increased with CO 2 but there were no significant effects, at the species level, of CO 2 on photosynthetic rates. Stomatal conductance decreased with increased CO 2 at both high and low light levels in C 3 species but only at high light levels in C 4 species. In all species, intercellular CO 2 increased with external CO 2 . Amaranthus flowered significantly earlier at 700 @mL/L than at 350 @mL/L, and Setaria flowered significantly later at 700 @mL/L than at either of the other CO 2 levels. Both Abutilon and Ambrosia showed a trend towards earlier flowering but this was not statistically significant. Of the morphological characters measured at the final harvest only specific leaf area (SLA) showed a consistent response to CO 2 , decreasing with increasing CO 2 . Significant CO 2 x species interactions were also found for leaf area, leaf biomass, biomass of reproductive parts, and seed biomass indicating species—specific responses for these characters. The proportion of nitrogen declined with increasing CO 2 : there was also a significant CO 2 x species interaction caused by the different rates of decline in proportion of nitrogen among the species. The response of most characters had a significant species x CO 2 interaction. However, this was not simply caused by the C 3 /C 4 dichotomy. Reproductive biomass (seed, fruits, and flowers) increased with increasing CO 2 in Amaranthus (C 4 ) and in Chenopodium and Ambrosia (both C 3 ), but there was no change in Setaria (C 4 ), and Abutilon (C 3 ) showed a peak a 500 @mL/L. Species of the same community differed in their response to CO 2 , and these differences may help explain the outcome of competitive interactions among these species above ambient CO 2 levels.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 20
Claim · model-written summary
Enhanced CO 2 had no detectable effect on emergence timing in any species.
Not reportedComparator
Verbatim
e0“There was no detectable effect of enhanced CO 2 on timing of emergence in any of the species.”
e1“Five species of old field annual plants”
Claim · model-written summary
Amaranthus RGR was always higher at 700 than 350 CO 2.
- Taxon
- Amaranthus
_with_green_foliage%2C_photographed_in_Tamil_Nadu%2C_India.jpg?width=60)
Amaranthuse0 - Treatment
- 700 @mL/L CO 2e0
- Outcome
- relative growth rate (RGR)e0
- Direction
- highere0
- Comparator
- 350 @mL/Le0
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“Amaranthus relative growth rate (RGR) was always higher at 700 @mL/L CO 2 than at 350 @mL/L.”
Claim · model-written summary
Abutilon RGR was greater at high CO 2 initially and lower later.
- Treatment
- 700 @mL/Le0
- Outcome
- RGRe0
- Direction
- greatere0
- Qualifier
- during the first half of the experimental period, but during the second half of the period the reverse was truee0
- Comparator
- 350 @mL/Le0
AbutilonOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In both Abutilon and Ambrosia, RGR was greater at 700 @mL/L than at 350 @mL/L during the first half of the experimental period, but during the second half of the period the reverse was true.”
Claim · model-written summary
Ambrosia RGR was greater at high CO 2 initially and lower later.
- Treatment
- 700 @mL/Le0
- Outcome
- RGRe0
- Direction
- greatere0
- Qualifier
- during the first half of the experimental period, but during the second half of the period the reverse was truee0
- Comparator
- 350 @mL/Le0
AmbrosiaOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In both Abutilon and Ambrosia, RGR was greater at 700 @mL/L than at 350 @mL/L during the first half of the experimental period, but during the second half of the period the reverse was true.”
Claim · model-written summary
Shoot water potential increased significantly with CO 2 in Amaranthus.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- increasing CO 2e0
- Outcome
- Shoot water potentiale0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot water potential significantly increased (became less negative) with increasing CO 2 in Amaranthus and Setaria.”
Claim · model-written summary
Shoot water potential increased significantly with CO 2 in Setaria.
SetariaNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot water potential significantly increased (became less negative) with increasing CO 2 in Amaranthus and Setaria.”
Claim · model-written summary
Chenopodium showed a nonsignificant water-potential trend.
- Taxon
- Chenopodium
Chenopodiume0e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar but statistically nonsignificant trends were found in Chenopodium and Abutilon.”
e1“Shoot water potential significantly increased (became less negative) with increasing CO 2 in Amaranthus and Setaria.”
Claim · model-written summary
Abutilon showed a nonsignificant water-potential trend.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar but statistically nonsignificant trends were found in Chenopodium and Abutilon.”
e1“Shoot water potential significantly increased (became less negative) with increasing CO 2 in Amaranthus and Setaria.”
Claim · model-written summary
Photosynthesis increased overall with CO 2, without significant species-level effects.
Not reportedComparator
Verbatim
e0“Overall rate of photosynthesis increased with CO 2 but there were no significant effects, at the species level, of CO 2 on photosynthetic rates.”
e1“Five species of old field annual plants”
Claim · model-written summary
Stomatal conductance declined with CO 2 in C 3 species at both light levels.
- Taxon
- C 3 speciese0
- Treatment
- increased CO 2e0
- Outcome
- Stomatal conductancee0
- Direction
- decreasede0
- Qualifier
- at both high and low light levelse0
Not reportedComparator
Verbatim
e0“Stomatal conductance decreased with increased CO 2 at both high and low light levels in C 3 species but only at high light levels in C 4 species.”
Claim · model-written summary
Stomatal conductance declined with CO 2 in C 4 species at high light.
- Taxon
- C 4 speciese0
- Treatment
- increased CO 2e0
- Outcome
- Stomatal conductancee0
- Direction
- decreasede0
- Qualifier
- only at high light levelse0
Not reportedComparator
Verbatim
e0“Stomatal conductance decreased with increased CO 2 at both high and low light levels in C 3 species but only at high light levels in C 4 species.”
Claim · model-written summary
Intercellular CO 2 rose with external CO 2 in all species.
Not reportedComparator
Verbatim
e0“In all species, intercellular CO 2 increased with external CO 2 .”
e1“Five species of old field annual plants”
Claim · model-written summary
Amaranthus flowered earlier at 700 than 350 CO 2.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- 700 @mL/Le0
- Outcome
- flowerede0
- Direction
- earliere0
- Comparator
- 350 @mL/Le0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Amaranthus flowered significantly earlier at 700 @mL/L than at 350 @mL/L”
Claim · model-written summary
Setaria flowered later at 700 than other CO 2 levels.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Setaria flowered significantly later at 700 @mL/L than at either of the other CO 2 levels.”
Claim · model-written summary
Abutilon tended to flower earlier without statistical significance.
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both Abutilon and Ambrosia showed a trend towards earlier flowering but this was not statistically significant.”
Claim · model-written summary
Ambrosia tended to flower earlier without statistical significance.
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both Abutilon and Ambrosia showed a trend towards earlier flowering but this was not statistically significant.”
Claim · model-written summary
Specific leaf area decreased consistently as CO 2 increased.
Not reportedComparator
Verbatim
e0“only specific leaf area (SLA) showed a consistent response to CO 2 , decreasing with increasing CO 2”
e1“Five species of old field annual plants”
Claim · model-written summary
CO 2 by species interactions occurred for leaf area, leaf biomass, reproductive-part biomass and seed biomass.
Not reportedDirection
Verbatim
e0“Significant CO 2 x species interactions were also found for leaf area, leaf biomass, biomass of reproductive parts, and seed biomass”
e1“Five species of old field annual plants”
Claim · model-written summary
Nitrogen proportion declined with CO 2 and its decline varied by species.
Not reportedComparator
Verbatim
e0“The proportion of nitrogen declined with increasing CO 2 : there was also a significant CO 2 x species interaction caused by the different rates of decline in proportion of nitrogen among the species.”
e1“Five species of old field annual plants”
Claim · model-written summary
Reproductive biomass responses to CO 2 differed among species, increasing in three species, unchanged in Setaria and peaking at intermediate CO 2 in Abutilon.
- Taxon
- AmaranthusAmaranthuse0
- Treatment
- increasing CO 2e0
- Outcome
- Reproductive biomass (seed, fruits, and flowers)e0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reproductive biomass (seed, fruits, and flowers) increased with increasing CO 2 in Amaranthus (C 4 ) and in Chenopodium and Ambrosia (both C 3 ), but there was no change in Setaria (C 4 ), and Abutilon (C 3 ) showed a peak a 500 @mL/L.”
The same questions in other papers
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.