Abstract
Many of the most troublesome weeds in agricultural systems are C4 plants. As atmospheric CO2 increases it is conceivable that competitive ability of these weeds could be reduced relative to C3 crops such as rice. At the International Rice Research Institute (IRRI) in the Philippines, rice (IR72) and one of its associated C4 weeds, Echinochloa glabrescens, were grown from seeding to maturity using replacement series mixtures (100:0, 75:25, 50:50, 25:75, and 0:100, % rice:%weed) at two different CO2 concentrations (393 and 594 μL L-1) in naturally sunlit glasshouses. Since increasing CO2 may also result in elevated growth temperatures, the response of rice to each CO2 concentration was also examined at daylnight temperatures of 27/21 and 37/29ºC. At 27/21ºC, increasing the CO2 concentration resulted in a significant increase in above ground biomass (+47%) and seed yield (+55%) of rice when averaged over all mixtures. For E. glabrescens, the C4 species, no significant effect of CO2 concentration on biomass or yield was observed. When grown in mixture, the proportion of rice biomass increased significantly relative to that of the C4 weed at all mixtures at elevated CO2. Evaluation of changes in competitiveness (by calculation of plant relative yield (PRY) and replacement series diagrams) of the two species demonstrated that, at elevated CO2, the competitiveness of rice was increased relative to that of E. glabrescens. However, at the higher growth temperature (37/29ºC), growth and reproductive stimulation of rice by elevated CO2 was reduced compared to the lower growth temperature. This resulted in a reduction in the proportion of rice:weed biomass present in all mixtures relative to 27/21ºC and a greater reduction in PRY in rice relative to E. glabrescens. Data from this experiment suggest that competitiveness could be enhanced in a C3 crop (rice) relative to a C4 weed (E. glabrescens) with elevated CO2 alone, but that simultaneous increases in CO2 and temperature could still favour a C4 species.
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Claims 9
Claim · model-written summary
Increasing CO2 raised rice above-ground biomass by 47% at 27/21ºC across mixtures.
- Taxon
- rice
Oryza sativae0 - Treatment
- increasing the CO2 concentratione0
- Outcome
- above ground biomasse0
- Direction
- increasee0
- Value
- +47%e0
- Qualifier
- 27/21ºCe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 27/21ºC, increasing the CO2 concentration resulted in a significant increase in above ground biomass (+47%) and seed yield (+55%) of rice when averaged over all mixtures.”
Claim · model-written summary
Increasing CO2 raised rice seed yield by 55% at 27/21ºC across mixtures.
- Taxon
- riceOryza sativae0
- Treatment
- increasing the CO2 concentratione0
- Outcome
- seed yielde0
- Direction
- increasee0
- Value
- +55%e0
- Qualifier
- 27/21ºCe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 27/21ºC, increasing the CO2 concentration resulted in a significant increase in above ground biomass (+47%) and seed yield (+55%) of rice when averaged over all mixtures.”
Claim · model-written summary
CO2 concentration had no significant effect on E. glabrescens biomass or yield.
- Taxon
- E. glabrescensEchinochloa glabrescense0
- Treatment
- CO2 concentratione0
- Outcome
- biomass or yielde0
- Direction
- no significant effecte0
Not reportedComparator
Verbatim
e0“For E. glabrescens, the C4 species, no significant effect of CO2 concentration on biomass or yield was observed.”
Claim · model-written summary
Elevated CO2 increased the proportion of rice biomass relative to the C4 weed in all mixtures.
- Taxon
- riceOryza sativae0
- Treatment
- elevated CO2e0
- Interactor
- C4 weede0weed
- Outcome
- proportion of rice biomasse0
- Direction
- increasede0
- Comparator
- C4 weede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When grown in mixture, the proportion of rice biomass increased significantly relative to that of the C4 weed at all mixtures at elevated CO2.”
Claim · model-written summary
Elevated CO2 increased rice competitiveness relative to E. glabrescens.
- Taxon
- riceOryza sativae0
- Treatment
- elevated CO2e0
- Interactor
- E. glabrescensEchinochloa glabrescense0weed
- Outcome
- competitiveness of ricee0
- Direction
- increasede0
- Comparator
- E. glabrescense0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at elevated CO2, the competitiveness of rice was increased relative to that of E. glabrescens.”
Claim · model-written summary
At 37/29ºC, elevated CO2 stimulated rice growth and reproduction less than at lower temperature.
- Taxon
- riceOryza sativae0
- Treatment
- higher growth temperature (37/29ºC)e0
- Outcome
- growth and reproductive stimulatione0
- Direction
- reducede0
- Comparator
- lower growth temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at the higher growth temperature (37/29ºC), growth and reproductive stimulation of rice by elevated CO2 was reduced compared to the lower growth temperature.”
Claim · model-written summary
Higher temperature reduced the rice-to-weed biomass proportion across mixtures relative to 27/21ºC.
- Taxon
- riceOryza sativae0
- Interactor
- weede0weed
- Outcome
- proportion of rice:weed biomasse0
- Direction
- reductione0
- Comparator
- 27/21ºCe0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This resulted in a reduction in the proportion of rice:weed biomass present in all mixtures relative to 27/21ºC and a greater reduction in PRY in rice relative to E. glabrescens.”
Claim · model-written summary
Higher temperature reduced rice PRY more than E. glabrescens PRY.
- Taxon
- riceOryza sativae0
- Interactor
- E. glabrescensEchinochloa glabrescense0weed
- Outcome
- PRY in ricee0
- Direction
- reductione0
- Comparator
- E. glabrescense0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This resulted in a reduction in the proportion of rice:weed biomass present in all mixtures relative to 27/21ºC and a greater reduction in PRY in rice relative to E. glabrescens.”
Claim · model-written summary
The authors infer that combined CO2 and temperature increases could favor a C4 species.
Verbatim
e0“simultaneous increases in CO2 and temperature could still favour a C4 species.”
The same questions in other papers
co2 · growth · Oryza sativa (rice)Positive and negative results
99 papers in the same direction as this paper · 23 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- no effect
- no effect
120 papers more in this group
See all 124 papers →co2 · yield · Oryza sativa (rice)Positive and negative results
130 papers in the same direction as this paper · 28 in the opposite direction
- negative
- negative
- negative
155 papers more in this group
See all 159 papers →co2 · Echinochloa glabrescens · Oryza sativa (rice)Results agree
1 paper in the same direction as this paper
- 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.