Abstract
Although ozone (O3) concentration and nitrogen (N) availability are well known to affect plant physiology, their impacts on the photosynthetic temperature response are poorly understood. We addressed this knowledge gap by exposing seedlings of hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation in a factorial experiment. E-O3 decreased light-saturated net photosynthesis (Asat), mesophyll conductance (gm) and apparent maximum rate of carboxylation (Vcmax, based on intercellular CO2 concentration) but not actual Vcmax (based on chloroplast CO2 concentration) and increased respiration in light (Rd) at 25 °C. Nitrogen fertilization increased Asat, gm, Vcmax and the maximum rate of electron transport (Jmax) and reduced Rd at 25 °C and the activation energy of actual Vcmax. No E-O3 or E-O3 x N interaction effects on the temperature response parameters were detected, simplifying the inclusion of O3 impacts on photosynthesis in vegetation models. gm peaked at 30 °C, apparent Vcmax and Jmax at 32-33 °C, while the optimum temperatures of actual Vcmax and Jmax exceeded the measured temperature range (15-35 °C). Ignoring gm would, thus, have resulted in mistakenly attributing the decrease in Asat at high temperatures to reduced biochemical capacity rather than to greater diffusion limitation.
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Claims 10
Claim · model-written summary
Elevated ozone decreased light-saturated net photosynthesis, mesophyll conductance, and apparent maximum carboxylation rate.
- Treatment
- E-O3e0
- Outcome
- light-saturated net photosynthesis (Asat), mesophyll conductance (gm) and apparent maximum rate of carboxylatione0
- Direction
- decreasede0
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“E-O3 decreased light-saturated net photosynthesis (Asat), mesophyll conductance (gm) and apparent maximum rate of carboxylation (Vcmax, based on intercellular CO2 concentration)”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Elevated ozone did not decrease actual maximum carboxylation rate.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but not actual Vcmax (based on chloroplast CO2 concentration)”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Elevated ozone increased respiration in light at 25 °C.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased respiration in light (Rd) at 25 °C”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Nitrogen fertilization increased photosynthesis, mesophyll conductance, maximum carboxylation, and maximum electron transport.
- Treatment
- Nitrogen fertilizatione0
- Outcome
- Asat, gm, Vcmax and the maximum rate of electron transport (Jmax)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization increased Asat, gm, Vcmax and the maximum rate of electron transport (Jmax)”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Nitrogen fertilization reduced respiration in light at 25 °C and activation energy of actual maximum carboxylation.
- Treatment
- Nitrogen fertilizatione2
- Outcome
- Rd at 25 °C and the activation energy of actual Vcmaxe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced Rd at 25 °C and the activation energy of actual Vcmax”
e2“Nitrogen fertilization increased Asat”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Neither elevated ozone nor ozone by nitrogen interaction affected temperature response parameters detectably.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No E-O3 or E-O3 x N interaction effects on the temperature response parameters were detected”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Mesophyll conductance peaked at 30 °C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gm peaked at 30 °C”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Apparent maximum carboxylation and electron transport peaked at 32-33 °C.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“apparent Vcmax and Jmax at 32-33 °C”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
The optimum temperatures for actual maximum carboxylation and electron transport exceeded the measured 15-35 °C range.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the optimum temperatures of actual Vcmax and Jmax exceeded the measured temperature range (15-35 °C)”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
Claim · model-written summary
Ignoring mesophyll conductance would misattribute the high-temperature photosynthesis decline to biochemical capacity rather than diffusion limitation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ignoring gm would, thus, have resulted in mistakenly attributing the decrease in Asat at high temperatures to reduced biochemical capacity rather than to greater diffusion limitation.”
e1“hybrid poplar clone '107' (Populous euramericana cv. '74/76') to elevated O3 (E-O3) and N availability variation”
The same questions in other papers
ozone · physiology: photosynthesis · Populus (poplar)Results differ
16 papers in the same direction as this paper · 1 in the opposite direction
- negative
- positive
- no effect
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See all 18 papers →fertilization · physiology: photosynthesis · Populus (poplar)Positive and negative results
5 papers in the same direction as this paper · 1 in the opposite direction
- negative
- positive
- positive
3 papers more in this group
See all 7 papers →ozone · physiology: respiration · Populus (poplar)Results agree
2 papers in the same direction as this paper
- negative
- negative
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.