Abstract
BACKGROUND AND AIMS: Climate change poses significant challenges to the enhancement of crop productivity in pace with the increasing world population. Intraspecific variability in ryegrass responses to elevated CO2 can be exploited to screen for high-producing genotypes under future atmospheres and has been used to identify targets for breeding high CO2-ready cultivars. The present study expands on this approach by investigating the responses of multiple perennial and annual ryegrass genotypes to projected future atmospheric/climatic conditions. METHODS: Ten ryegrass genotypes of diverse origin were grown under ambient and elevated CO2 and higher temperature conditions (HTC), consistent with an intermediate IPCC scenario (RCP6.0). Morphometric measurements, gas analysis and CN analysis were used to assess the responses of their biomass production and allocation, photosynthetic physiology and carbon/nitrogen elemental composition to simulated future conditions. Genotypic variability in these responses was subsequently used to identify traits and trait responses that correlate strongly with increased productivity under elevated CO2 and higher temperature. RESULTS: Biomass responses to future conditions varied significantly across genotypes, spanning a 32% reduction to a 62% enhancement, but were unrelated to corresponding changes in leaf photosynthetic rates. Although plant productivity showed a significant positive relationship with estimates of the whole-plant carbon assimilation rate, there were clear signs of sink limitation under ambient and HTC, since this correlated strongly with the leaf C:N ratio and the biomass allocation to sink tissues, especially stems. Stem biomass allocation under future conditions increased significantly and scaled positively with the corresponding plant productivity responses. No similar trend was observed for root biomass allocation, which showed no significant differences between treatments. CONCLUSIONS: Increased biomass allocation to the stem carbon sink is a key characteristic to exploit under future climate change conditions, and this would also maximize any benefits associated with an increase in leaf area on whole-plant carbon gain.
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Claims 9
Claim · model-written summary
Genotype biomass responses ranged from a 32% reduction to a 62% enhancement.
LoliumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Biomass responses to future conditions varied significantly across genotypes, spanning a 32% reduction to a 62% enhancement”
t0“ryegrass”
Claim · model-written summary
Biomass response was unrelated to changes in leaf photosynthetic rates.
- Organ / stage
- leafe0
- Outcome
- Biomass responsese0
- Direction
- unrelatede0
- Qualifier
- changes in leaf photosynthetic ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Biomass responses to future conditions varied significantly across genotypes, spanning a 32% reduction to a 62% enhancement, but were unrelated to corresponding changes in leaf photosynthetic rates.”
t0“ryegrass”
Claim · model-written summary
Plant productivity had a significant positive relationship with whole plant carbon assimilation.
- Outcome
- plant productivitye0
- Direction
- positive relationshipe0
- Qualifier
- whole-plant carbon assimilation ratee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plant productivity showed a significant positive relationship with estimates of the whole-plant carbon assimilation rate”
t0“ryegrass”
Claim · model-written summary
Carbon assimilation correlated strongly with leaf C:N ratio.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Although plant productivity showed a significant positive relationship with estimates of the whole-plant carbon assimilation rate, there were clear signs of sink limitation under ambient and HTC, since this correlated strongly with the leaf C:N ratio and the biomass allocation to sink tissues, especially stems.”
t0“ryegrass”
Claim · model-written summary
Carbon assimilation correlated strongly with allocation to sink tissues, especially stems.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this correlated strongly with the leaf C:N ratio and the biomass allocation to sink tissues, especially stems.”
t0“ryegrass”
Claim · model-written summary
Stem allocation increased significantly under future conditions.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stem biomass allocation under future conditions increased significantly”
t0“ryegrass”
Claim · model-written summary
Stem allocation scaled positively with productivity responses.
- Organ / stage
- Steme0
- Outcome
- Stem biomass allocatione0
- Direction
- positivelye0
- Qualifier
- plant productivity responsese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stem biomass allocation under future conditions increased significantly and scaled positively with the corresponding plant productivity responses.”
t0“ryegrass”
Claim · model-written summary
Root allocation had no significant treatment difference.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root biomass allocation, which showed no significant differences between treatments.”
t0“ryegrass”
Claim · model-written summary
Authors identify increased stem carbon sink allocation as a useful breeding trait.
- Outcome
- Increased biomass allocation to the stem carbon sinke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased biomass allocation to the stem carbon sink is a key characteristic to exploit under future climate change conditions”
t0“ryegrass”