Abstract
Abstract Two Japanese rice cultivars with different heat-tolerance, Hinohikari (sensitive) and Nikomaru (tolerant), were grown in pots inside open-top chambers and exposed to ambient CO 2 (400 µmol mol −1 ) or elevated CO 2 (550 µmol mol −1 ) from the beginning of the tillering stage to maturity. The study was conducted in Nagasaki, in the Kyushu region of Japan, where heat stress on rice has become increasingly evident. Although elevated CO 2 significantly improved the net photosynthesis and whole-plant growth of the cultivars, there were no significant effects on grain yield, which in turn reduced harvest index. In both cultivars, adverse effects occurred with elevated CO 2 , such as reductions in spikelet fertility and grain appearance quality, which are typical manifestations of heat stress in rice. During the flowering period, the air temperature was high that spikelet fertility was reduced even under ambient CO 2 conditions for both cultivars. These results suggest that, under high-temperature conditions, elevated CO 2 could induce or exacerbate the manifestations of heat stress in rice. Because transpiration rate in the flag leaf was significantly reduced by the exposure to elevated CO 2 , it is possible that elevated CO 2 increased plant temperature via a reduction in transpiration during flowering period, although we did not detect significance of the increase in leaf and panicle temperature. To ensure a more confident conclusion, further studies focusing on the effects of elevated CO 2 on the determinants of spikelet fertility and grain appearance quality with other cultivars in different year are required.
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Claims 9
Claim · model-written summary
Elevated CO2 significantly improved net photosynthesis.
- Taxon
- Oryza sativa L.
Oryza sativat0 - Treatment
- elevated CO 2e0
- Outcome
- net photosynthesise0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“elevated CO 2 significantly improved the net photosynthesis and whole-plant growth of the cultivars”
Claim · model-written summary
Elevated CO2 significantly improved whole-plant growth.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- whole-plant growthe0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“elevated CO 2 significantly improved the net photosynthesis and whole-plant growth of the cultivars”
Claim · model-written summary
Elevated CO2 had no significant grain yield effect.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- grain yielde0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“Although elevated CO 2 significantly improved the net photosynthesis and whole-plant growth of the cultivars, there were no significant effects on grain yield”
Claim · model-written summary
Elevated CO2 reduced harvest index.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- harvest indexe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“Although elevated CO 2 significantly improved the net photosynthesis and whole-plant growth of the cultivars, there were no significant effects on grain yield, which in turn reduced harvest index.”
Claim · model-written summary
Elevated CO2 reduced spikelet fertility in both cultivars.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- spikelet fertilitye0
- Direction
- reductionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“In both cultivars, adverse effects occurred with elevated CO 2 , such as reductions in spikelet fertility and grain appearance quality”
Claim · model-written summary
Elevated CO2 reduced grain appearance quality in both cultivars.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- grain appearance qualitye0
- Direction
- reductionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“In both cultivars, adverse effects occurred with elevated CO 2 , such as reductions in spikelet fertility and grain appearance quality”
Claim · model-written summary
High flowering-period temperature reduced spikelet fertility even at ambient CO2.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- air temperature was highe0
- Outcome
- spikelet fertilitye0
- Direction
- reducede0
- Qualifier
- ambient CO 2 conditionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“During the flowering period, the air temperature was high that spikelet fertility was reduced even under ambient CO 2 conditions for both cultivars.”
Claim · model-written summary
Elevated CO2 significantly reduced flag-leaf transpiration.
- Taxon
- Oryza sativa L.Oryza sativat0
- Organ / stage
- flag leafe0
- Treatment
- elevated CO 2e0
- Outcome
- transpiration ratee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“transpiration rate in the flag leaf was significantly reduced by the exposure to elevated CO 2”
Claim · model-written summary
The increase in leaf and panicle temperature was not statistically significant.
- Taxon
- Oryza sativa L.Oryza sativat0
- Treatment
- elevated CO 2e0
- Outcome
- leaf and panicle temperaturee0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice(Oryza sativa L.)”
e0“it is possible that elevated CO 2 increased plant temperature via a reduction in transpiration during flowering period, although we did not detect significance of the increase in leaf and panicle temperature.”
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