Abstract
Rising atmospheric CO₂ concentrations will probably increase rice (Oryza sativa L.) yield but decrease grain nitrogen (GN) concentration. Grains attached to different positions in the panicles differ greatly in weight and quality, but their responses to elevated CO₂ (e[CO₂]) are poorly understood, which limits our understanding of the mechanisms of yield enhancement and quality degradation. Thus a free-air CO₂ enrichment experiment was conducted to examine the effects of e[CO₂] on grain mass (GM), grain carbon (GC), and GN accumulation in the spikelets attached to the upper primary rachis branch (superior spikelets; SS) and those attached to the lower secondary rachis (inferior spikelets; IS). e[CO₂] stimulated the rice yield by 13% but decreased the N concentration in the panicle by 7% when averaged over two levels of N fertilizations (P < 0.01). The responses of SS and IS to e[CO₂] were different particularly under higher N supply. For SS, e[CO₂] decreased GN by 24% (P < 0.01) but did not affect GM. For IS, e[CO₂] increased GM by 13% (P < 0.05) but GN was not affected. The reduction of GN due to e[CO₂] started to appear at the beginning of grain filling. These results suggest that future [CO₂] levels probably stimulate the grain growth of IS, most of which are not marketable due to limited size, at the expense of GN reduction in SS. Translocation of N from SS to IS may be a possible mechanism for reduction in GN of SS. This may degrade the grain quality of marketable rice under e[CO₂].
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Claims 10
Claim · model-written summary
Elevated CO2 stimulated rice yield by 13%.
- Taxon
- rice
Oryza sativae0 - Treatment
- e[CO₂]e1
- Outcome
- rice yielde1
- Direction
- stimulatede1
- Value
- 13%e1
- Qualifier
- averaged over two levels of N fertilizationse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e1“e[CO₂] stimulated the rice yield by 13% but decreased the N concentration in the panicle by 7% when averaged over two levels of N fertilizations (P < 0.01)”
Claim · model-written summary
Elevated CO2 decreased the N concentration in the rice panicle by 7%.
- Taxon
- riceOryza sativae0
- Organ / stage
- paniclee1
- Treatment
- e[CO₂]e1
- Outcome
- N concentration in the paniclee1
- Direction
- decreasede1
- Value
- 7%e1
- Qualifier
- averaged over two levels of N fertilizationse1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e1“e[CO₂] stimulated the rice yield by 13% but decreased the N concentration in the panicle by 7% when averaged over two levels of N fertilizations (P < 0.01)”
Claim · model-written summary
Elevated CO2 decreased grain nitrogen by 24% in superior spikelets.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e2“For SS, e[CO₂] decreased GN by 24% (P < 0.01) but did not affect GM”
Claim · model-written summary
Elevated CO2 did not affect grain mass in superior spikelets.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e2“For SS, e[CO₂] decreased GN by 24% (P < 0.01) but did not affect GM”
Claim · model-written summary
Elevated CO2 increased grain mass by 13% in inferior spikelets.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e3“For IS, e[CO₂] increased GM by 13% (P < 0.05) but GN was not affected”
Claim · model-written summary
Elevated CO2 did not affect grain nitrogen in inferior spikelets.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e3“For IS, e[CO₂] increased GM by 13% (P < 0.05) but GN was not affected”
Claim · model-written summary
The reduction of grain nitrogen under elevated CO2 started to appear at the beginning of grain filling.
- Taxon
- riceOryza sativae0
- Treatment
- e[CO₂]e4
- Outcome
- reduction of GNe4
- Qualifier
- started to appear at the beginning of grain fillinge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e4“The reduction of GN due to e[CO₂] started to appear at the beginning of grain filling”
Claim · model-written summary
Future CO2 levels probably stimulate grain growth of inferior spikelets at the expense of grain nitrogen in superior spikelets.
- Taxon
- riceOryza sativae0
- Treatment
- future [CO₂] levelse5
- Outcome
- grain growth of ISe5
- Direction
- increaseinferrede5
- Qualifier
- at the expense of GN reduction in SSe5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e5“These results suggest that future [CO₂] levels probably stimulate the grain growth of IS, most of which are not marketable due to limited size, at the expense of GN reduction in SS”
Claim · model-written summary
Translocation of N from superior to inferior spikelets may explain the reduction of grain nitrogen in superior spikelets.
- Taxon
- riceOryza sativae0
- Outcome
- reduction in GN of SSe6
- Qualifier
- Translocation of N from SS to ISe6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e6“Translocation of N from SS to IS may be a possible mechanism for reduction in GN of SS”
Claim · model-written summary
Elevated CO2 may degrade the grain quality of marketable rice.
- Taxon
- riceOryza sativae0
- Treatment
- e[CO₂]e7
- Outcome
- grain quality of marketable ricee7
- Direction
- decreaseinferrede7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice (Oryza sativa L.) yield”
e7“This may degrade the grain quality of marketable rice under e[CO₂]”
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