Abstract
Down-regulation of photosynthesis is among the most common responses observed in C3 plants grown under elevated atmospheric CO2 concentration ([CO2]). Down-regulation is often attributed to an insufficient capacity of sink organs to use or store the increased carbohydrate production that results from the stimulation of photosynthesis by elevated [CO2]. Down-regulation can be accentuated by inadequate nitrogen (N) supply, which may limit sink development. While there is strong evidence for down-regulation of photosynthesis at elevated [CO2] in enclosure studies most often involving potted plants, there is little evidence for this when [CO2] is elevated fully under open-air field treatment conditions. To assess the importance of sink strength on the down-regulation of photosynthesis and on the potential of N to mitigate this down-regulation under agriculturally relevant field conditions, two tobacco cultivars of strongly contrasting ability to produce the major sink of this crop, leaves, (Nicotiana tabacum L. cv. Petit Havana; cv. Mammoth) were grown under ambient and elevated [CO2] and with two different N additions in a free air [CO2] (FACE) facility. Photosynthetic down-regulation at elevated [CO2] reached only 9% in cv. Mammoth late in the season likely reflecting sustained sink strength of the rapidly growing plant whereas down-regulation in cv. Petit Havana reached 25%. Increased N supply partially mitigated down-regulation of photosynthesis in cv. Petit Havana and this mitigation was dependent on plant developmental stage. Overall, these field results were consistent with the hypothesis that sustained sink strength, that is the ability to utilize photosynthate, and adequate N supply will allow C3 crops in the field to maintain enhanced photosynthesis and therefore productivity as [CO2] continues to rise.
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Claims 5
Claim · model-written summary
At elevated CO2, photosynthetic down-regulation reached 9% late in the season in cv. Mammoth.
- Taxon
- Nicotiana tabacum L.
Nicotiana tabacumt0 - Material
- cv. Mammothe0
- Treatment
- elevated [CO2]e0
- Outcome
- Photosynthetic down-regulatione0
- Direction
- down-regulatione0
- Value
- 9%e0
- Qualifier
- late in the seasone0
- Comparator
- ambiente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum L.”
e0“Photosynthetic down-regulation at elevated [CO2] reached only 9% in cv. Mammoth late in the season”
e1“ambient and elevated [CO2]”
Claim · model-written summary
At elevated CO2, photosynthetic down-regulation reached 25% in cv. Petit Havana.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacumt0
- Material
- cv. Petit Havanae0
- Treatment
- elevated [CO2]e1
- Outcome
- down-regulatione0
- Direction
- down-regulatione0
- Value
- 25%e0
- Comparator
- ambiente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum L.”
e0“down-regulation in cv. Petit Havana reached 25%”
e1“ambient and elevated [CO2]”
Claim · model-written summary
Increased nitrogen partially mitigated photosynthetic down-regulation in cv. Petit Havana.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacumt0
- Material
- cv. Petit Havanae0
- Treatment
- Increased N supplye0
- Outcome
- down-regulation of photosynthesise0
- Direction
- mitigatede0
- Qualifier
- partiallye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum L.”
e0“Increased N supply partially mitigated down-regulation of photosynthesis in cv. Petit Havana”
Claim · model-written summary
Nitrogen mitigation of photosynthetic down-regulation depended on plant developmental stage.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacumt0
- Organ / stage
- plant developmental stagee0
- Treatment
- Increased N supplye1
- Outcome
- mitigatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum L.”
e0“this mitigation was dependent on plant developmental stage”
e1“Increased N supply partially mitigated down-regulation of photosynthesis in cv. Petit Havana”
Claim · model-written summary
Field results were consistent with sustained sink strength and adequate nitrogen allowing C3 crops to maintain enhanced photosynthesis as CO2 rises.
- Taxon
- Nicotiana tabacum L.Nicotiana tabacumt0
- Outcome
- enhanced photosynthesise0
- Qualifier
- sustained sink strengthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum L.”
e0“field results were consistent with the hypothesis that sustained sink strength, that is the ability to utilize photosynthate, and adequate N supply will allow C3 crops in the field to maintain enhanced photosynthesis”
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See all 5 papers →nitrogen · molecular: expression · Nicotiana tabacum (tobacco)Positive and negative results
4 papers in the same direction as this paper · 3 in the opposite direction · 1 reporting no difference from an alternative
- negative
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See all 9 papers →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.