Abstract
The interaction between nitrogen storage and translocation, senescence, and late phase photosynthesis is critical to the post-anthesis grain fill period in wheat, but ozone's effect on nitrogen dynamics within the wheat plant is not well understood. This study used solardomes to expose a widely grown elite spring wheat cultivar, cv. Skyfall, to four levels of ozone (30 ppb, 45 ppb, 70 ppb, 85 ppb) for 11 weeks, with two levels of nitrogen fertilization, 140 kg ha−1 and 160 kg ha−1, the higher rate including an additional 20 kg N ha−1 at anthesis. Chronic ozone exposure triggered earlier senescence in the 4th, 3rd and 2nd leaves but not the flag leaf, with a similar pattern of reduced chlorophyll content in the lower, older leaf cohorts, which started before senescence became visible. At anthesis there was no evidence of any effect of ozone on nitrogen storage in upper plant parts. However, high ozone increased levels of residual nitrogen found within plant parts at harvest, with concomitant reductions in C:N ratios and Nitrogen Remobilization Efficiency. Extra nitrogen fertilization applied at anthesis appeared to ameliorate the effect of ozone on nitrogen content and nitrogen translocation. The application of 15N ammonium nitrate at anthesis confirmed that the majority of post-anthesis nitrogen uptake had been translocated to the ear/grain by harvest, with no effect of ozone on the translocation of nitrogen around the plant. These data can inform future modelling of ozone's effect on nitrogen dynamics and global wheat yields.
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Claims 10
Claim · model-written summary
Chronic ozone caused earlier senescence in the fourth, third and second wheat leaves.
- Taxon
- wheat
Triticum aestivumt0 - Treatment
- Chronic ozone exposuree0
- Outcome
- senescence in the 4th, 3rd and 2nd leavese0
- Direction
- earliere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chronic ozone exposure triggered earlier senescence in the 4th, 3rd and 2nd leaves but not the flag leaf”
t0“wheat”
Claim · model-written summary
Ozone did not trigger earlier senescence in the flag leaf.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Chronic ozone exposuree0
- Outcome
- flag leafe0
- Direction
- note0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Chronic ozone exposure triggered earlier senescence in the 4th, 3rd and 2nd leaves but not the flag leaf”
t0“wheat”
Claim · model-written summary
Chlorophyll declined in older lower leaf cohorts before visible senescence.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- lower, older leaf cohortse0
- Outcome
- chlorophyll contente0
- Direction
- reducede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced chlorophyll content in the lower, older leaf cohorts, which started before senescence became visible”
t0“wheat”
Claim · model-written summary
At anthesis, ozone showed no evidence of affecting nitrogen storage in upper plant parts.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- anthesise0
- Treatment
- ozonee0
- Outcome
- nitrogen storage in upper plant partse0
- Direction
- no evidence of any effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At anthesis there was no evidence of any effect of ozone on nitrogen storage in upper plant parts.”
t0“wheat”
Claim · model-written summary
High ozone increased residual nitrogen at harvest.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high ozonee0
- Outcome
- levels of residual nitrogene0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high ozone increased levels of residual nitrogen found within plant parts at harvest”
t0“wheat”
Claim · model-written summary
High ozone reduced C:N ratios.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high ozonee0
- Outcome
- C:N ratiose0
- Direction
- reductionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high ozone increased levels of residual nitrogen found within plant parts at harvest, with concomitant reductions in C:N ratios and Nitrogen Remobilization Efficiency.”
t0“wheat”
Claim · model-written summary
High ozone reduced nitrogen remobilization efficiency.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- high ozonee0
- Outcome
- Nitrogen Remobilization Efficiencye0
- Direction
- reductionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high ozone increased levels of residual nitrogen found within plant parts at harvest, with concomitant reductions in C:N ratios and Nitrogen Remobilization Efficiency.”
t0“wheat”
Claim · model-written summary
Additional nitrogen at anthesis appeared to lessen ozone effects on nitrogen content and translocation.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Extra nitrogen fertilization applied at anthesise0
- Outcome
- nitrogen content and nitrogen translocatione0
- Direction
- amelioratee0
- Qualifier
- appearede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Extra nitrogen fertilization applied at anthesis appeared to ameliorate the effect of ozone on nitrogen content and nitrogen translocation.”
t0“wheat”
Claim · model-written summary
Most post-anthesis nitrogen uptake was translocated to the ear or grain by harvest.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- post-anthesis nitrogen uptake had been translocated to the ear/grain by harveste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the majority of post-anthesis nitrogen uptake had been translocated to the ear/grain by harvest”
t0“wheat”
Claim · model-written summary
Ozone had no effect on translocation of nitrogen around the plant.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- ozonee0
- Outcome
- translocation of nitrogen around the plante0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with no effect of ozone on the translocation of nitrogen around the plant”
t0“wheat”
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