Abstract
BACKGROUND AND AIMS: Nitrogen (N) is a major factor affecting yield gain of crops under elevated atmospheric carbon dioxide concentrations [CO(2)]. It is well established that elevated [CO(2)] increases root mass, but there are inconsistent reports on the effects on N uptake capacity per root mass. In the present study, it was hypothesized that the responses of N uptake capacity would change with the duration of exposure to elevated [CO(2)]. METHODS: The hypothesis was tested by measuring N uptake capacity in rice plants exposed to long-term and short-term [CO(2)] treatments at different growth stages in plants grown under non-limiting N conditions in hydroponic culture. Seasonal changes in photosynthesis rate and transpiration rate were also measured. KEY RESULTS: In the long-term [CO(2)] study, leaf photosynthetic responses to intercellular CO(2) concentration (Ci) were not affected by elevated [CO(2)] before the heading stage, but the initial slope in this response was decreased by elevated [CO(2)] at the grain-filling stage. Nitrate and ammonium uptake capacities per root dry weight were not affected by elevated [CO(2)] at panicle initiation, but thereafter they were reduced by elevated [CO(2)] by 31-41 % at the full heading and mid-ripening growth stages. In the short-term study (24 h exposures), elevated [CO(2)] enhanced nitrate and ammonium uptake capacities at the early vegetative growth stage, but elevated [CO(2)] decreased the uptake capacities at the mid-reproductive stage. CONCLUSIONS: This study showed that N uptake capacity was downregulated under long-term exposure to elevated [CO(2)] and its response to elevated [CO(2)] varied greatly with growth stage.
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Claims 6
Claim · model-written summary
Long-term elevated CO2 did not affect leaf photosynthetic response before heading.
- Taxon
- rice
Oryza sativat0 - Organ / stage
- before the heading stagee0
- Treatment
- elevated [CO(2)]e0
- Outcome
- leaf photosynthetic responsese0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf photosynthetic responses to intercellular CO(2) concentration (Ci) were not affected by elevated [CO(2)] before the heading stage”
t0“rice”
Claim · model-written summary
Elevated CO2 decreased the initial slope of leaf photosynthetic response at grain filling.
- Taxon
- riceOryza sativat0
- Organ / stage
- grain-filling stagee0
- Treatment
- elevated [CO(2)]e0
- Outcome
- initial slope in this responsee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the initial slope in this response was decreased by elevated [CO(2)] at the grain-filling stage”
e1“leaf photosynthetic responses to intercellular CO(2) concentration (Ci)”
t0“rice”
Claim · model-written summary
Elevated CO2 did not affect nitrate and ammonium uptake per root dry weight at panicle initiation.
- Taxon
- riceOryza sativat0
- Organ / stage
- panicle initiatione0
- Treatment
- elevated [CO(2)]e0
- Outcome
- Nitrate and ammonium uptake capacities per root dry weighte0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate and ammonium uptake capacities per root dry weight were not affected by elevated [CO(2)] at panicle initiation”
t0“rice”
Claim · model-written summary
Long-term elevated CO2 reduced nitrate and ammonium uptake capacities 31-41% at full heading and mid-ripening.
- Taxon
- riceOryza sativat0
- Organ / stage
- full heading and mid-ripening growth stagese0
- Treatment
- elevated [CO(2)]e0
- Outcome
- Nitrate and ammonium uptake capacities per root dry weighte1
- Direction
- reducede0
- Value
- 31-41 %e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they were reduced by elevated [CO(2)] by 31-41 % at the full heading and mid-ripening growth stages”
e1“Nitrate and ammonium uptake capacities per root dry weight”
t0“rice”
Claim · model-written summary
A 24-hour exposure to elevated CO2 enhanced nitrate and ammonium uptake capacities at early vegetative growth.
- Taxon
- riceOryza sativat0
- Organ / stage
- early vegetative growth stagee0
- Treatment
- elevated [CO(2)]e0
- Outcome
- nitrate and ammonium uptake capacitiese0
- Direction
- enhancede0
- Qualifier
- 24 h exposurese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“short-term study (24 h exposures), elevated [CO(2)] enhanced nitrate and ammonium uptake capacities at the early vegetative growth stage”
t0“rice”
Claim · model-written summary
A 24-hour exposure to elevated CO2 decreased uptake capacities at mid-reproductive growth.
- Taxon
- riceOryza sativat0
- Organ / stage
- mid-reproductive stagee0
- Treatment
- elevated [CO(2)]e0
- Outcome
- uptake capacitiese0
- Direction
- decreasede0
- Qualifier
- 24 h exposurese1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated [CO(2)] decreased the uptake capacities at the mid-reproductive stage”
e1“short-term study (24 h exposures)”
t0“rice”
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