Abstract
Relationships between photosynthetic acclimation and changes in the balance between source-sink supply and demand of carbon (C) and nitrogen (N) were tested using rice (Oryza sativa L. cv. Akitakomachi). Plants were field-grown in northern Japan at ambient CO2 partial pressure [p(CO2)] or free air CO2 enrichment (FACE; p(CO2) ~ 26-32 Pa above ambient) with low, medium or high N supplies. Leaf CO2 assimilation rates (A) and biochemical parameters were measured at 32-36 (eighth leaf) and 76-80 (flag leaf) d after transplanting, representing stages with a contrasting balance between C and N supply and demand in sources and sinks. Acclimation due to FACE was pronounced in flag leaves at each N supply. This was not fully accounted for by reductions in leaf N concentrations, because A/N and Vcmax/N were lower in FACE-grown flag leaves. Acclimation did not occur in the eighth leaf, and A/N and Vcmax/N was not significantly increased in FACE-grown leaves. Soluble protein / sucrose and amino acid / sucrose concentrations decreased under FACE, whereas sucrose phosphate synthase protein levels increased. At flag leaf stage, there was a discrepancy between the demand and supply of N, which was resolved by enhanced leaf N remobilization, associated with the lower Rubisco concentrations under FACE. In contrast to the early growth stage, enhanced growth of rice plants was accompanied by increased plant N uptake in FACE. We conclude that photosynthetic acclimation in flag leaves occurs under FACE because there is a large demand for N for reproductive development, relative to supply of N from root uptake and remobilization from leaves.
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Claims 12
Claim · model-written summary
FACE produced pronounced photosynthetic acclimation in flag leaves at each nitrogen supply.
- Taxon
- rice
Oryza sativat0 - Organ / stage
- flag leavese0
- Treatment
- FACEe0
- Outcome
- Acclimatione0
- Direction
- pronouncede0
- Qualifier
- at each N supplye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Acclimation due to FACE was pronounced in flag leaves at each N supply.”
t0“rice”
Claim · model-written summary
Flag-leaf A/N and Vcmax/N were lower under FACE.
- Taxon
- riceOryza sativat0
- Organ / stage
- flag leavese0
- Treatment
- FACE-growne0
- Outcome
- A/N and Vcmax/Ne0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A/N and Vcmax/N were lower in FACE-grown flag leaves.”
t0“rice”
Claim · model-written summary
The eighth leaf showed no photosynthetic acclimation under FACE.
- Taxon
- riceOryza sativat0
- Organ / stage
- eighth leafe0
- Treatment
- FACEt0
- Outcome
- Acclimatione0
- Direction
- did not occure0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Acclimation did not occur in the eighth leaf”
t0“rice to free air CO 2 enrichment (FACE)”
Claim · model-written summary
A/N and Vcmax/N were not significantly increased in FACE-grown eighth leaves.
- Taxon
- riceOryza sativat0
- Treatment
- FACE-growne0
- Outcome
- A/N and Vcmax/Ne0
- Direction
- not significantly increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A/N and Vcmax/N was not significantly increased in FACE-grown leaves.”
t0“rice”
Claim · model-written summary
Soluble protein to sucrose and amino acid to sucrose ratios decreased under FACE.
- Taxon
- riceOryza sativat0
- Treatment
- FACEe0
- Outcome
- Soluble protein / sucrose and amino acid / sucrose concentrationse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soluble protein / sucrose and amino acid / sucrose concentrations decreased under FACE”
t0“rice”
Claim · model-written summary
Sucrose phosphate synthase protein levels increased under FACE.
- Taxon
- riceOryza sativat0
- Treatment
- FACEt0
- Gene
- sucrose phosphate synthasee0
- Outcome
- sucrose phosphate synthase protein levelse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas sucrose phosphate synthase protein levels increased.”
t0“rice to free air CO 2 enrichment (FACE)”
Claim · model-written summary
At flag-leaf stage, nitrogen demand and supply were discrepant.
- Taxon
- riceOryza sativat0
- Organ / stage
- flag leaf stagee0
- Outcome
- discrepancy between the demand and supply of Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At flag leaf stage, there was a discrepancy between the demand and supply of N”
t0“rice”
Claim · model-written summary
Leaf nitrogen remobilization was enhanced at the flag-leaf stage.
- Taxon
- riceOryza sativat0
- Outcome
- leaf N remobilizatione0
- Direction
- enhancede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which was resolved by enhanced leaf N remobilization”
t0“rice”
Claim · model-written summary
Lower Rubisco concentrations were associated with enhanced leaf nitrogen remobilization under FACE.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“associated with the lower Rubisco concentrations under FACE.”
t0“rice”
Claim · model-written summary
FACE was accompanied by enhanced rice growth at a later stage.
- Taxon
- riceOryza sativae0
- Treatment
- FACEe0
- Outcome
- growth of rice plantse0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced growth of rice plants was accompanied by increased plant N uptake in FACE.”
t0“rice”
Claim · model-written summary
Rice nitrogen uptake increased under FACE at a later stage.
- Taxon
- riceOryza sativat0
- Treatment
- FACEe0
- Outcome
- plant N uptakee0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased plant N uptake in FACE.”
t0“rice”
Claim · model-written summary
The authors attribute flag-leaf photosynthetic acclimation under FACE to reproductive nitrogen demand exceeding supply.
- Taxon
- riceOryza sativat0
- Treatment
- FACEe0
- Outcome
- photosynthetic acclimation in flag leavese0
- Qualifier
- large demand for N for reproductive development, relative to supply of N from root uptake and remobilization from leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic acclimation in flag leaves occurs under FACE because there is a large demand for N for reproductive development, relative to supply of N from root uptake and remobilization from leaves.”
t0“rice”
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