Abstract
Increasing tropospheric ozone (O3) is well-known to decrease leaf photosynthesis under steady-state light through reductions in biochemical capacity. However, the effects of O3 on photosynthetic induction and its biochemical limitations in response to fluctuating light remain unclear, despite the rapid fluctuations of light intensity occurring under field conditions. In this study, two hybrid poplar clones with different O3 sensitivities were exposed to elevated O3. Dynamic photosynthetic CO2 response measurements were conducted to quantify the impact of elevated O3 and exposure duration on biochemical limitations during photosynthetic induction. We found that elevated O3 significantly reduced the steady-state light-saturated photosynthetic rate, the maximum rate of carboxylation (Vcmax) and Rubisco content. In addition, elevated O3 significantly decreased the time constants for slow phases and weighting of the fast phase of the Vcmax induction in poplar clone '546' but not in clone '107'. However, elevated O3 did not affect the time, it took to reach a given percentage of full Vcmax activation or photosynthetic induction in either clone. Overall, photosynthetic induction was primarily limited by the activity of Rubisco rather than the regeneration of ribulose-1,5-biphosphate regardless of O3 concentration and exposure duration. The lack of O3-induced effects on the activation of Rubisco observed here would simplify the simulation of impacts of O3 on nonsteady-state photosynthesis in dynamic photosynthetic models.
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Claims 9
Claim · model-written summary
Elevated ozone significantly reduced steady-state light-saturated photosynthetic rate.
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 significantly reduced the steady-state light-saturated photosynthetic rate”
t0“poplar”
Claim · model-written summary
Elevated ozone significantly reduced maximum carboxylation rate.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 significantly reduced the steady-state light-saturated photosynthetic rate, the maximum rate of carboxylation (Vcmax) and Rubisco content”
t0“poplar”
Claim · model-written summary
Elevated ozone significantly reduced Rubisco content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 significantly reduced the steady-state light-saturated photosynthetic rate, the maximum rate of carboxylation (Vcmax) and Rubisco content”
t0“poplar”
Claim · model-written summary
Elevated ozone decreased slow-phase Vcmax induction time constants in clone 546 but not 107.
- Material
- clone '546'e0
- Treatment
- elevated O3e0
- Outcome
- time constants for slow phasese0
- Direction
- decreasede0
- Comparator
- clone '107'e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 significantly decreased the time constants for slow phases and weighting of the fast phase of the Vcmax induction in poplar clone '546' but not in clone '107'”
Claim · model-written summary
Elevated ozone decreased fast-phase weighting of Vcmax induction in clone 546 but not 107.
- Material
- clone '546'e0
- Treatment
- elevated O3e0
- Outcome
- weighting of the fast phase of the Vcmax inductione0
- Direction
- decreasede0
- Comparator
- clone '107'e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 significantly decreased the time constants for slow phases and weighting of the fast phase of the Vcmax induction in poplar clone '546' but not in clone '107'”
Claim · model-written summary
Elevated ozone did not affect time to a given percentage of full Vcmax activation.
- Treatment
- elevated O3e0
- Outcome
- time, it took to reach a given percentage of full Vcmax activatione0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 did not affect the time, it took to reach a given percentage of full Vcmax activation or photosynthetic induction in either clone”
t0“poplar”
Claim · model-written summary
Elevated ozone did not affect photosynthetic induction time in either clone.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated O3 did not affect the time, it took to reach a given percentage of full Vcmax activation or photosynthetic induction in either clone”
t0“poplar”
Claim · model-written summary
Rubisco activity primarily limited photosynthetic induction.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic induction was primarily limited by the activity of Rubisco rather than the regeneration of ribulose-1,5-biphosphate”
t0“poplar”
Claim · model-written summary
The observed lack of ozone effect on Rubisco activation could simplify dynamic photosynthesis models.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lack of O3-induced effects on the activation of Rubisco observed here would simplify the simulation of impacts of O3 on nonsteady-state photosynthesis in dynamic photosynthetic models.”
t0“poplar”
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See all 8 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.