Abstract
Rooted cuttings from three aspen (Populus tremuloides Michx.) clones (216, 271 and 259, classified as high, intermediate and low in O(3) tolerance, respectively) were exposed to either diurnal O(3) profiles simulating those of Michigan's Lower Peninsula (episodic treatments), or diurnal square-wave O(3) treatments in open-top chambers in northern Michigan, USA. Ozone was dispensed in chambers ventilated with charcoal-filtered (CF) air. In addition, seedlings were compared to rooted cuttings in their response to episodic O(3) treatments. Early in the season, O(3) caused decreased photosynthetic rates in mature leaves of all clones, whereas only the photosynthetic rates of recently mature leaves of the O(3)-sensitive Clone 259 decreased in response to O(3) exposure. During midseason, O(3) caused decreased photosynthetic rates of both recently mature and mature leaves of the O(3)-sensitive Clone 259, but it had no effect on the photosynthetic rate of recently mature leaves of the O(3)-tolerant Clone 216. Late in the season, however, photosynthetic rates of both recently mature and mature leaves of Clone 216 were lower than those of the control plants maintained in CF air. Ozone decreased the photosynthetic rate of mature leaves of Clone 271, but it increased or had no effect on the photosynthetic rate of recently mature leaves. Photosynthetic response patterns of seedlings to O(3) treatment were similar to those of the clones, but total magnitude of the response was less, perhaps reflecting the diverse genotypes of the seedling population. Early leaf abscission was observed in all clones exposed to O(3); however, Clones 216 and 259 lost more leaf area than Clone 271. By late August, leaf area in the highest O(3) treatment had decreased relative to the controls by 26, 24 and 9% for Clones 216, 259 and 271, respectively. Ozone decreased whole-tree photosynthesis in all clones, and the decrease was consistently less in Clone 271 (23%) than in Clones 216 (56%) and 259 (56%), and was accompanied by declines in total biomass of 19, 28 and 47%, respectively. The relationship between biomass and whole-tree photosynthesis indicates that the negative impact of O(3) on biomass in the clones was determined largely by lower photosynthetic productivity of the foliage, rather than by potential changes in the carbon relations of other plant organs.
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Claims 20
Claim · model-written summary
Early-season ozone lowered mature-leaf photosynthesis in all clones.
- Taxon
- aspent0
- Organ / stage
- mature leavese0
- Treatment
- O(3)e0
- Outcome
- photosynthetic rates in mature leavese0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“Early in the season, O(3) caused decreased photosynthetic rates in mature leaves of all clones”
t0“aspen”
Claim · model-written summary
Early-season ozone lowered photosynthesis in recently mature leaves only in sensitive Clone 259.
- Taxon
- aspent0
- Material
- Clone 259e0
- Treatment
- O(3) exposuree0
- Outcome
- photosynthetic rates of recently mature leavese0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“only the photosynthetic rates of recently mature leaves of the O(3)-sensitive Clone 259 decreased in response to O(3) exposure”
t0“aspen”
Claim · model-written summary
Midseason ozone lowered photosynthesis in recently mature and mature leaves of sensitive Clone 259.
- Taxon
- aspent0
- Material
- Clone 259e0
- Treatment
- O(3)e0
- Outcome
- photosynthetic rates of both recently mature and mature leavese0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“During midseason, O(3) caused decreased photosynthetic rates of both recently mature and mature leaves of the O(3)-sensitive Clone 259”
t0“aspen”
Claim · model-written summary
Midseason ozone had no effect on recently mature leaf photosynthesis of tolerant Clone 216.
- Taxon
- aspent0
- Material
- Clone 216e0
- Treatment
- O(3)e0
- Outcome
- photosynthetic rate of recently mature leavese0
- Direction
- no effecte0
Not reportedComparator
Verbatim
e0“it had no effect on the photosynthetic rate of recently mature leaves of the O(3)-tolerant Clone 216”
t0“aspen”
Claim · model-written summary
Late-season photosynthesis in both leaf ages of Clone 216 was lower than in filtered-air controls.
- Taxon
- aspent0
- Material
- Clone 216e0
- Outcome
- photosynthetic rates of both recently mature and mature leavese0
- Direction
- lowere0
- Comparator
- control plants maintained in CF aire0
Not reportedTreatment
Verbatim
e0“photosynthetic rates of both recently mature and mature leaves of Clone 216 were lower than those of the control plants maintained in CF air”
t0“aspen”
Claim · model-written summary
Ozone decreased mature-leaf photosynthesis in Clone 271.
- Taxon
- aspent0
- Material
- Clone 271e0
- Treatment
- Ozonee0
- Outcome
- photosynthetic rate of mature leavese0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“Ozone decreased the photosynthetic rate of mature leaves of Clone 271”
t0“aspen”
Claim · model-written summary
Ozone increased or did not affect recently mature-leaf photosynthesis in Clone 271.
- Taxon
- aspent0
- Material
- Clone 271e1
- Treatment
- Ozonee1
- Outcome
- photosynthetic rate of recently mature leavese0
- Direction
- increased or had no effecte0
Not reportedComparator
Verbatim
e0“it increased or had no effect on the photosynthetic rate of recently mature leaves”
e1“Ozone decreased the photosynthetic rate of mature leaves of Clone 271”
t0“aspen”
Claim · model-written summary
Seedling ozone response patterns resembled clone patterns but were smaller in magnitude.
Verbatim
e0“Photosynthetic response patterns of seedlings to O(3) treatment were similar to those of the clones, but total magnitude of the response was less”
t0“aspen”
Claim · model-written summary
Ozone exposed clones showed early leaf abscission.
Not reportedDirection
Verbatim
e0“Early leaf abscission was observed in all clones exposed to O(3)”
t0“aspen”
Claim · model-written summary
Clones 216 and 259 lost more leaf area than Clone 271.
Verbatim
e0“Clones 216 and 259 lost more leaf area than Clone 271”
t0“aspen”
Claim · model-written summary
At the highest ozone treatment, Clone 216 leaf area was 26% below controls by late August.
Verbatim
e0“By late August, leaf area in the highest O(3) treatment had decreased relative to the controls by 26, 24 and 9% for Clones 216, 259 and 271, respectively”
t0“aspen”
Claim · model-written summary
At the highest ozone treatment, Clone 259 leaf area was 24% below controls by late August.
Verbatim
e0“By late August, leaf area in the highest O(3) treatment had decreased relative to the controls by 26, 24 and 9% for Clones 216, 259 and 271, respectively”
t0“aspen”
Claim · model-written summary
At the highest ozone treatment, Clone 271 leaf area was 9% below controls by late August.
Verbatim
e0“By late August, leaf area in the highest O(3) treatment had decreased relative to the controls by 26, 24 and 9% for Clones 216, 259 and 271, respectively”
t0“aspen”
Claim · model-written summary
Ozone reduced whole-tree photosynthesis by 23% in Clone 271.
- Taxon
- aspent0
- Material
- Clone 271e0
- Treatment
- Ozonee0
- Outcome
- whole-tree photosynthesise0
- Direction
- decreasede0
- Value
- 23%e0
Not reportedComparator
Verbatim
e0“Ozone decreased whole-tree photosynthesis in all clones, and the decrease was consistently less in Clone 271 (23%) than in Clones 216 (56%) and 259 (56%)”
t0“aspen”
Claim · model-written summary
Ozone reduced whole-tree photosynthesis by 56% in Clone 216.
- Taxon
- aspent0
- Material
- Clones 216e0
- Treatment
- Ozonee0
- Outcome
- whole-tree photosynthesise0
- Direction
- decreasede0
- Value
- 56%e0
Not reportedComparator
Verbatim
e0“Ozone decreased whole-tree photosynthesis in all clones, and the decrease was consistently less in Clone 271 (23%) than in Clones 216 (56%) and 259 (56%)”
t0“aspen”
Claim · model-written summary
Ozone reduced whole-tree photosynthesis by 56% in Clone 259.
- Taxon
- aspent0
- Material
- 259e0
- Treatment
- Ozonee0
- Outcome
- whole-tree photosynthesise0
- Direction
- decreasede0
- Value
- 56%e0
Not reportedComparator
Verbatim
e0“Ozone decreased whole-tree photosynthesis in all clones, and the decrease was consistently less in Clone 271 (23%) than in Clones 216 (56%) and 259 (56%)”
t0“aspen”
Claim · model-written summary
Ozone accompanied a 19% biomass decline in Clone 271.
Not reportedComparator
Verbatim
e0“was accompanied by declines in total biomass of 19, 28 and 47%, respectively”
e1“Clone 271 (23%) than in Clones 216 (56%) and 259 (56%)”
e2“Ozone decreased whole-tree photosynthesis”
t0“aspen”
Claim · model-written summary
Ozone accompanied a 28% biomass decline in Clone 216.
Not reportedComparator
Verbatim
e0“was accompanied by declines in total biomass of 19, 28 and 47%, respectively”
e1“Clones 216 (56%) and 259 (56%)”
e2“Ozone decreased whole-tree photosynthesis”
t0“aspen”
Claim · model-written summary
Ozone accompanied a 47% biomass decline in Clone 259.
Not reportedComparator
Verbatim
e0“was accompanied by declines in total biomass of 19, 28 and 47%, respectively”
e1“259 (56%)”
e2“Ozone decreased whole-tree photosynthesis”
t0“aspen”
Claim · model-written summary
Reduced foliage photosynthetic productivity largely determined the ozone impact on biomass.
Verbatim
e0“the negative impact of O(3) on biomass in the clones was determined largely by lower photosynthetic productivity of the foliage”
t0“aspen”