Abstract
Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.). In the present study, an O 3 -sensitive cultivar, 'Apica', and an O 3 -tolerant cultivar, 'Team', of alfalfa were exposed to multiple levels of ambient O 3 concentrations (i.e., 0x, 1x, 1.5x, and 3x) using open-top chambers. The objectives were to characterize O 3 sensitivities at the leaf level and to determine whether stomatal or mesophyll conductance could account for the differences in O 3 sensitivity. Differences in photoassimilate allocation were also determined using 14 CO 2 . Effects of O 3 exposures on leaf characteristics such as leaf area and dry matter; leaf concentrations of chlorophyll, starch, proteins, amino acids, and nutrients; and stomatal density were evaluated. Gas exchange measurements were also performed. Results showed that O 3 exposures produced a greater decline in leaf biomass, chlorophyll concentration, and net assimilation rate for 'Apica' compared with 'Team'. For O 3 concentrations of 20-40 nL ·L -1 , a 7-15% reduction in net assimilation rate was observed for 'Apica' only. With an increase in O 3 concentrations, stomatal limitation did not increase correspondingly, and a strong correlation between net assimilation rate, stomatal conductance, and carboxylation efficiency was observed, suggesting a physiological coordination of the O 3 stress response at the leaf level. Possibly the decrease in assimilation rate induced by O 3 could be associated with the O 3 effects at the mesophyll level. For both cultivars, O 3 increased the CO 2 compensation point of the leaves, and some effects were also noted in terms of leaf mineral concentrations. O 3 did not alter photoassimilate allocation between shoots and roots but stimulated their retention in leaves compared with stems. These results suggest that O 3 has a major impact on the carbon metabolism of leaves, which could explain differences in O 3 sensitivities.Key words: gas exchange, ozone tolerance, alfalfa cultivars, stomata, photoassimilate allocation.
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Claims 8
Claim · model-written summary
Ozone produced a greater decline in leaf biomass, chlorophyll concentration and net assimilation rate in the sensitive cultivar Apica than in the tolerant cultivar Team.
- Taxon
- alfalfa
Medicago sativae0 - Material
- Apicae2
- Treatment
- O 3 exposurese2
- Outcome
- leaf biomass, chlorophyll concentration, and net assimilation ratee2
- Direction
- greater declinee2
- Comparator
- Teame2
- Setting
- open-top chamberse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“an O 3 -sensitive cultivar, 'Apica', and an O 3 -tolerant cultivar, 'Team', of alfalfa were exposed to multiple levels of ambient O 3 concentrations (i.e., 0x, 1x, 1.5x, and 3x) using open-top chambers”
e2“Results showed that O 3 exposures produced a greater decline in leaf biomass, chlorophyll concentration, and net assimilation rate for 'Apica' compared with 'Team'”
Claim · model-written summary
In cultivar Apica only, ozone at 20-40 nL ·L -1 reduced net assimilation rate by 7-15%.
- Taxon
- alfalfaMedicago sativae0
- Material
- Apicae1
- Treatment
- O 3 concentrations of 20-40 nL ·L -1e1
- Outcome
- net assimilation ratee1
- Direction
- reductione1
- Value
- 7-15%e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“For O 3 concentrations of 20-40 nL ·L -1 , a 7-15% reduction in net assimilation rate was observed for 'Apica' only”
Claim · model-written summary
With increasing ozone concentration, stomatal limitation did not increase correspondingly.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- an increase in O 3 concentrationse1
- Outcome
- stomatal limitatione1
- Direction
- did not increase correspondinglye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“With an increase in O 3 concentrations, stomatal limitation did not increase correspondingly, and a strong correlation between net assimilation rate, stomatal conductance, and carboxylation efficiency was observed”
Claim · model-written summary
Net assimilation rate, stomatal conductance and carboxylation efficiency were strongly correlated in alfalfa under ozone.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- With an increase in O 3 concentrationse1
- Outcome
- net assimilation rate, stomatal conductance, and carboxylation efficiencye1
- Qualifier
- strong correlatione1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“With an increase in O 3 concentrations, stomatal limitation did not increase correspondingly, and a strong correlation between net assimilation rate, stomatal conductance, and carboxylation efficiency was observed”
Claim · model-written summary
Ozone increased the CO2 compensation point of alfalfa leaves in both cultivars.
- Taxon
- alfalfaMedicago sativae0
- Organ / stage
- leavese1
- Treatment
- O 3e1
- Outcome
- CO 2 compensation pointe1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“For both cultivars, O 3 increased the CO 2 compensation point of the leaves, and some effects were also noted in terms of leaf mineral concentrations”
Claim · model-written summary
Ozone had some effects on leaf mineral concentrations in alfalfa; the direction is not stated.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- O 3e1
- Outcome
- leaf mineral concentrationse1
- Qualifier
- some effects were also notede1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“For both cultivars, O 3 increased the CO 2 compensation point of the leaves, and some effects were also noted in terms of leaf mineral concentrations”
Claim · model-written summary
Ozone did not alter photoassimilate allocation between shoots and roots in alfalfa.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- O 3e1
- Outcome
- photoassimilate allocation between shoots and rootse1
- Direction
- did not altere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“O 3 did not alter photoassimilate allocation between shoots and roots but stimulated their retention in leaves compared with stems”
Claim · model-written summary
Ozone stimulated photoassimilate retention in leaves compared with stems in alfalfa.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- O 3e1
- Outcome
- retention in leavese1
- Direction
- stimulatede1
- Comparator
- stemse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ozone (O 3 ) is a major air pollutant that has been reported to affect growth of alfalfa (Medicago sativa L.)”
e1“O 3 did not alter photoassimilate allocation between shoots and roots but stimulated their retention in leaves compared with stems”
The same questions in other papers
ozone · growth · Medicago sativa (alfalfa)Positive and negative results
4 papers in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
- no effect
2 papers more in this group
See all 6 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.