Abstract
The effects of elevated CO2 were studied on the photosynthetic gas exchange behaviour and leaf physiology of two contrasting poplar (Populus) hybrids grown and treated in open top chambers (OTCs in Antwerp, Belgium) and in closed glasshouse cabinets (GHCs in Sussex, UK). The CO2 concentrations used in the OTCs were ambient and ambient +350 μmol mol−1 while in the GHCs they were c. 360 μmol mol−1 versus 719 μmol mol−1. Measurements of photosynthetic gas exchange were made for euramerican and interamerican poplar hybrids in combination with measurements of dark respiration rate and Rubisco activity. Significant differences in the leaf anatomy and structure (leaf mass per area and chlorophyll content) were observed between the leaves grown in the OTCs and those grown in the GHCs. Elevated CO2 stimulated net photosynthesis in the poplar hybrids after 1 month in the GHCs and after 4 months in the OTCs, and there was no evidence of downward acclimation (or down-regulation) of photosynthesis when the plants in the two treatments were measured in their growth CO2 concentration. There was also no evidence of down-regulation of Rubisco activity and there were even examples of increases in Rubisco activity. Rubisco exerted a strong control over the light-saturated rate of photosynthesis, which was demonstrated by the close agreement between observed net photosynthetic rates and those that were predicted from Rubisco activities and Michaelis-Menten kinetics. After 17 months in elevated CO2 in the OTCs there was a significant loss of Rubisco activity for one of the hybrid clones, i.e. Beaupré, but not for clone Robusta. The effect of the CO2 measurement concentration (i.e. the short-term treatment effect) on net photosynthesis was always larger than the effect of the growth concentration in both the OTCs or GHCs (i.e. the longterm growth CO2 effect), with one exception. For the interamerican hybrid Beaupré dark respiration rates in the OTCs were not significantly affected by the elevated CO2 concentrations. The results suggest that for rapidly growing tree species, such as poplars, there is little evidence for downward acclimation of photosynthesis when plants are exposed to elevated CO2 for up to 4 months; longer term exposure reveals loss of Rubisco activity.
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Claims 10
Claim · model-written summary
Leaf anatomy and structure (leaf mass per area and chlorophyll content) differed significantly between poplar leaves grown in OTCs and those grown in GHCs.
- Outcome
- leaf anatomy and structure (leaf mass per area and chlorophyll content)e0
- Comparator
- those grown in the GHCse0
PopulusNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“Significant differences in the leaf anatomy and structure (leaf mass per area and chlorophyll content) were observed between the leaves grown in the OTCs and those grown in the GHCs”
Claim · model-written summary
Elevated CO2 stimulated net photosynthesis in the poplar hybrids after 1 month in GHCs and after 4 months in OTCs.
Not reportedComparator
Verbatim
e0“Elevated CO2 stimulated net photosynthesis in the poplar hybrids after 1 month in the GHCs and after 4 months in the OTCs”
Claim · model-written summary
There was no evidence of downward acclimation of photosynthesis in poplar when plants were measured at their growth CO2 concentration.
- Outcome
- downward acclimation (or down-regulation) of photosynthesise0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“there was no evidence of downward acclimation (or down-regulation) of photosynthesis when the plants in the two treatments were measured in their growth CO2 concentration”
Claim · model-written summary
There was no evidence of down-regulation of Rubisco activity in the poplar hybrids under elevated CO2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“There was also no evidence of down-regulation of Rubisco activity and there were even examples of increases in Rubisco activity”
Claim · model-written summary
There were examples of increased Rubisco activity in the poplar hybrids under elevated CO2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“There was also no evidence of down-regulation of Rubisco activity and there were even examples of increases in Rubisco activity”
Claim · model-written summary
Rubisco exerted strong control over the light-saturated rate of photosynthesis in poplar, shown by close agreement between observed net photosynthetic rates and rates predicted from Rubisco activities and Michaelis-Menten kinetics.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“Rubisco exerted a strong control over the light-saturated rate of photosynthesis, which was demonstrated by the close agreement between observed net photosynthetic rates and those that were predicted from Rubisco activities and Michaelis-Menten kinetics”
Claim · model-written summary
After 17 months in elevated CO2 in OTCs, poplar clone Beaupre showed a significant loss of Rubisco activity.
- Material
- Beauprée0
- Treatment
- elevated CO2e0
- Gene
- Rubiscoe0
- Outcome
- Rubisco activitye0
- Direction
- losse0
- Qualifier
- After 17 monthse0
- Setting
- OTCse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“After 17 months in elevated CO2 in the OTCs there was a significant loss of Rubisco activity for one of the hybrid clones, i.e. Beaupré”
Claim · model-written summary
After 17 months in elevated CO2 in OTCs, poplar clone Robusta did not show a loss of Rubisco activity.
- Material
- Robustae0
- Treatment
- elevated CO2e0
- Gene
- Rubiscoe0
- Outcome
- Rubisco activitye0
- Direction
- no_changeinferrede0
- Qualifier
- After 17 monthse0
- Setting
- OTCse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“After 17 months in elevated CO2 in the OTCs there was a significant loss of Rubisco activity for one of the hybrid clones, i.e. Beaupré, but not for clone Robusta”
Claim · model-written summary
The short-term effect of the CO2 measurement concentration on net photosynthesis was always larger than the long-term effect of the growth CO2 concentration in both OTCs and GHCs, with one exception.
- Treatment
- CO2 measurement concentratione0
- Outcome
- net photosynthesise0
- Direction
- largere0
- Qualifier
- with one exceptione0
- Comparator
- growth concentratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“The effect of the CO2 measurement concentration (i.e. the short-term treatment effect) on net photosynthesis was always larger than the effect of the growth concentration in both the OTCs or GHCs (i.e. the longterm growth CO2 effect), with one exception”
Claim · model-written summary
In OTCs, dark respiration rates of the interamerican hybrid Beaupre were not significantly affected by elevated CO2.
- Material
- Beauprée0
- Treatment
- elevated CO2 concentrationse0
- Outcome
- dark respiration ratese0
- Direction
- not significantly affectede0
- Setting
- OTCse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“poplar”
e0“For the interamerican hybrid Beaupré dark respiration rates in the OTCs were not significantly affected by the elevated CO2 concentrations”
The same questions in other papers
co2 · physiology: photosynthesis · Populus (poplar)Positive and negative results
9 papers in the same direction as this paper · 1 in the opposite direction
- positive
- negative
- positive
7 papers more in this group
See all 11 papers →co2 · physiology: respiration · Populus (poplar)Results agree
1 paper in the same direction as this paper
- no effect
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.