Abstract
Many of the studies analysing the CO2 effect on plant development have been conducted in optimal growth conditions. Furthermore, although some of those studies suggest that legumes might show a steady productivity increase with rising CO2, the role of nodule activity on the plant responsiveness to predicted atmospheric CO2 enhancement is not well understood. In this study, C (metabolism and allocation) and N (nodule activity) interaction between the plant and the bacterial symbiont during the photosynthetic acclimation of N2-fixing alfalfa (Medicago sativa L. cv. Aragón) plants exposed to elevated CO2 and temperature conditions was analysed. The plants were grown in temperature gradient greenhouses (TGG) where, in the case of elevated CO2 treatments, the isotopic 13C/12C composition (d13C) inside the TGG was modified. Compared with the corresponding temperature treatment, exposure to 700 µmol mol–1 CO2 enhanced dry mass (DM) of plants in elevated temperature treatments (26%), whereas no significant effect was detected in ambient temperature treatments. The d13C data revealed that although all the carbon corresponding to leaf total organic matter (TOM) came from newly assimilated C, plants exposed to elevated CO2 did not develop strong sink activity (especially in ambient temperature conditions). Leaf carbohydrate build-up induced reduction in the Rubisco (E.C. 4.1.1.39) carboxylation capacity of plants. Despite this reduction in Rubisco content, plants exposed to elevated CO2 conditions maintained (at ambient temperature) or increased (at elevated temperature) photosynthetic rates (measured at growth conditions) by increasing N use efficiency. The larger C sink strength of nodules in plants grown at elevated CO2 and temperature conditions did not contribute towards overcoming photosynthetic acclimation. Further, the inhibitory effect of CO2 on nodule total activity was caused by a large depletion in total soluble protein (TSP) of nodules. Depletion of leaf N demand, together with the reduction in nodule carbohydrate availability (as reflected by the nodule starch concentration), negatively affected the nodule TSP content and enzymatic activity.
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Claims 11
Claim · model-written summary
Elevated CO2 increased plant dry mass by 26% at elevated temperature.
- Taxon
- Medicago sativa
Medicago sativat0 - Treatment
- 700 µmol mol–1 CO2e0
- Outcome
- dry mass (DM)e0
- Direction
- enhancede0
- Value
- 26%e0
- Comparator
- elevated temperature treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exposure to 700 µmol mol–1 CO2 enhanced dry mass (DM) of plants in elevated temperature treatments (26%)”
t0“Medicago sativa”
Claim · model-written summary
Elevated CO2 had no significant dry mass effect at ambient temperature.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- CO2e2
- Outcome
- dry mass (DM)e1
- Direction
- no significant effecte0
- Comparator
- ambient temperature treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas no significant effect was detected in ambient temperature treatments”
e1“dry mass (DM) of plants”
e2“exposure to 700 µmol mol–1 CO2”
t0“Medicago sativa”
Claim · model-written summary
All leaf total organic matter carbon came from newly assimilated carbon.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- leafe0
- Outcome
- all the carbon corresponding to leaf total organic matter (TOM) came from newly assimilated Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“all the carbon corresponding to leaf total organic matter (TOM) came from newly assimilated C”
t0“Medicago sativa”
Claim · model-written summary
Elevated CO2 plants did not develop strong sink activity, especially at ambient temperature.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- elevated CO2e0
- Outcome
- sink activitye0
- Direction
- did not develop stronge0
- Qualifier
- especially in ambient temperature conditionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants exposed to elevated CO2 did not develop strong sink activity (especially in ambient temperature conditions)”
t0“Medicago sativa”
Claim · model-written summary
Leaf carbohydrate buildup reduced Rubisco carboxylation capacity.
- Taxon
- Medicago sativaMedicago sativat0
- Gene
- Rubisco (E.C. 4.1.1.39)e0
- Outcome
- Rubisco (E.C. 4.1.1.39) carboxylation capacitye0
- Direction
- reductione0
- Qualifier
- Leaf carbohydrate build-upe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf carbohydrate build-up induced reduction in the Rubisco (E.C. 4.1.1.39) carboxylation capacity of plants”
t0“Medicago sativa”
Claim · model-written summary
At ambient temperature, elevated CO2 plants maintained photosynthetic rates through increased nitrogen use efficiency.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- elevated CO2e0
- Outcome
- photosynthetic ratese0
- Direction
- maintainede0
- Qualifier
- increasing N use efficiencye0
- Setting
- ambient temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants exposed to elevated CO2 conditions maintained (at ambient temperature) or increased (at elevated temperature) photosynthetic rates (measured at growth conditions) by increasing N use efficiency”
t0“Medicago sativa”
Claim · model-written summary
At elevated temperature, elevated CO2 plants increased photosynthetic rates through increased nitrogen use efficiency.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- elevated CO2e0
- Outcome
- photosynthetic ratese0
- Direction
- increasede0
- Qualifier
- increasing N use efficiencye0
- Setting
- elevated temperaturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants exposed to elevated CO2 conditions maintained (at ambient temperature) or increased (at elevated temperature) photosynthetic rates (measured at growth conditions) by increasing N use efficiency”
t0“Medicago sativa”
Claim · model-written summary
Greater nodule carbon sink strength under elevated CO2 and temperature did not overcome photosynthetic acclimation.
- Taxon
- Medicago sativaMedicago sativat0
- Organ / stage
- nodulese0
- Treatment
- elevated CO2 and temperature conditionse0
- Outcome
- did not contribute towards overcoming photosynthetic acclimatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The larger C sink strength of nodules in plants grown at elevated CO2 and temperature conditions did not contribute towards overcoming photosynthetic acclimation”
t0“Medicago sativa”
Claim · model-written summary
CO2 inhibited total nodule activity through depletion of nodule total soluble protein.
- Taxon
- Medicago sativaMedicago sativat0
- Treatment
- CO2e0
- Outcome
- nodule total activitye0
- Direction
- inhibitorye0
- Qualifier
- large depletion in total soluble protein (TSP) of nodulese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inhibitory effect of CO2 on nodule total activity was caused by a large depletion in total soluble protein (TSP) of nodules”
t0“Medicago sativa”
Claim · model-written summary
Reduced leaf nitrogen demand and nodule carbohydrate availability negatively affected nodule total soluble protein content.
- Taxon
- Medicago sativaMedicago sativat0
- Outcome
- nodule TSP contente0
- Direction
- negatively affectede0
- Qualifier
- Depletion of leaf N demand, together with the reduction in nodule carbohydrate availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Depletion of leaf N demand, together with the reduction in nodule carbohydrate availability (as reflected by the nodule starch concentration), negatively affected the nodule TSP content and enzymatic activity”
t0“Medicago sativa”
Claim · model-written summary
Reduced leaf nitrogen demand and nodule carbohydrate availability negatively affected nodule enzymatic activity.
- Taxon
- Medicago sativaMedicago sativat0
- Outcome
- enzymatic activitye0
- Direction
- negatively affectede0
- Qualifier
- Depletion of leaf N demand, together with the reduction in nodule carbohydrate availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Depletion of leaf N demand, together with the reduction in nodule carbohydrate availability (as reflected by the nodule starch concentration), negatively affected the nodule TSP content and enzymatic activity”
t0“Medicago sativa”
The same questions in other papers
co2 · growth · Medicago sativa (alfalfa)Positive and negative results
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