Abstract
Plants grown in an environment of elevated CO 2 and temperature often show reduced CO 2 assimilation capacity, providing evidence of photosynthetic downregulation. The aim of this study was to analyse the downregulation of photosynthesis in elevated CO 2 (700 µmol mol −1 ) in nodulated alfalfa plants grown at different temperatures (ambient and ambient + 4°C) and water availability regimes in temperature gradient tunnels. When the measurements were taken in growth conditions, a combination of elevated CO 2 and temperature enhanced the photosynthetic rate; however, when they were carried out at the same CO 2 concentration (350 and 700 µmol mol −1 ), elevated CO 2 induced photosynthetic downregulation, regardless of temperature and drought. Intercellular CO 2 concentration measurements revealed that photosynthetic acclimation could not be accounted for by stomatal limitations. Downregulation of plants grown in elevated CO 2 was a consequence of decreased carboxylation efficiency as a result of reduced rubisco activity and protein content; in plants grown at ambient temperature, downregulation was also induced by decreased quantum efficiency. The decrease in rubisco activity was associated with carbohydrate accumulation and depleted nitrogen availability. The root nodules were not sufficiently effective to balance the source–sink relation in elevated CO 2 treatments and to provide the required nitrogen to counteract photosynthetic acclimation.
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Claims 7
Claim · model-written summary
Combined elevated CO2 and temperature enhanced photosynthesis measured under growth conditions.
- Taxon
- alfalfa
Medicago sativat0 - Treatment
- a combination of elevated CO 2 and temperaturee0
- Outcome
- photosynthetic ratee0
- Direction
- enhancede0
- Qualifier
- measurements were taken in growth conditionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the measurements were taken in growth conditions, a combination of elevated CO 2 and temperature enhanced the photosynthetic rate”
t0“alfalfa”
Claim · model-written summary
Elevated CO2 induced photosynthetic downregulation at common measurement CO2 concentrations irrespective of temperature and drought.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- elevated CO 2e0
- Outcome
- photosynthetic downregulatione0
- Qualifier
- regardless of temperature and droughte0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when they were carried out at the same CO 2 concentration (350 and 700 µmol mol −1 ), elevated CO 2 induced photosynthetic downregulation, regardless of temperature and drought.”
t0“alfalfa”
Claim · model-written summary
Stomatal limitations could not explain photosynthetic acclimation.
- Taxon
- alfalfaMedicago sativat0
- Outcome
- photosynthetic acclimatione0
- Qualifier
- could not be accounted for by stomatal limitationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Intercellular CO 2 concentration measurements revealed that photosynthetic acclimation could not be accounted for by stomatal limitations.”
t0“alfalfa”
Claim · model-written summary
Downregulation under elevated CO2 resulted from reduced carboxylation efficiency due to reduced rubisco activity and protein content.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- elevated CO 2e0
- Gene
- rubiscoe0
- Outcome
- Downregulatione0
- Qualifier
- decreased carboxylation efficiency as a result of reduced rubisco activity and protein contente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Downregulation of plants grown in elevated CO 2 was a consequence of decreased carboxylation efficiency as a result of reduced rubisco activity and protein content”
t0“alfalfa”
Claim · model-written summary
At ambient temperature decreased quantum efficiency also induced downregulation.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- ambient temperaturee0
- Outcome
- downregulatione0
- Qualifier
- decreased quantum efficiencye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in plants grown at ambient temperature, downregulation was also induced by decreased quantum efficiency.”
t0“alfalfa”
Claim · model-written summary
Reduced rubisco activity was associated with carbohydrate accumulation and depleted nitrogen availability.
- Taxon
- alfalfaMedicago sativat0
- Compound
- carbohydratee0
- Outcome
- rubisco activitye0
- Direction
- decreasee0
- Qualifier
- carbohydrate accumulation and depleted nitrogen availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease in rubisco activity was associated with carbohydrate accumulation and depleted nitrogen availability.”
t0“alfalfa”
Claim · model-written summary
Root nodules were insufficient to balance source and sink and supply nitrogen to counteract acclimation under elevated CO2.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- root nodulese0
- Treatment
- elevated CO 2 treatmentse0
- Outcome
- photosynthetic acclimatione0
- Qualifier
- not sufficiently effective to balance the source–sink relatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The root nodules were not sufficiently effective to balance the source–sink relation in elevated CO 2 treatments and to provide the required nitrogen to counteract photosynthetic acclimation.”
t0“alfalfa”
The same questions in other papers
co2 · physiology: photosynthesis · Medicago sativa (alfalfa)Results differ
6 papers in the same direction as this paper · 3 in the opposite direction
- negative
- positive
- positive
6 papers more in this group
See all 10 papers →co2 · molecular: expression · Medicago sativa (alfalfa)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- negative
- 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.