Abstract
ABSTRACT A spring wheat crop was grown at ambient and elevated (550 μmol mol −1 ) CO 2 concentrations under free‐air CO 2 enrichment (FACE) in the field. Four experimental blocks, each comprising 21‐m‐diameter FACE and control experimental areas, were used. CO 2 elevation was maintained day and night from crop emergence to final grain harvest. This experiment provided a unique opportunity to examine the hypothesis that CO 2 elevation in the field would lead to acclimatory changes within the photosynthetic apparatus under open field conditions and lo assess whether acclimation was affected by crop developmental stage, leaf ontogeny and leaf age. Change in the photosynthetic apparatus was assessed by measuring changes in the composition of total leaf and thylakoid polypeptides separated by SDS‐PAGE. For leaves at completion of emergence of the blade, growth at the elevated CO 2 concentration had no apparent effect on the amount of any of the major proteins of the photosynthetic apparatus regardless of the leaf examined. Leaf 5 on the main stem was in full sunlight at emergence, but then became shaded progressively as 3–4 further leaves formed above with continued development of the crop. By 35 d following completion of blade emergence, leaf 5 was in shade. At this point, the chlorophyll alb ratio had declined by 26% both in plants grown at the control CO 2 concentration and in those grown at the elevated CO 2 concentration, which is indicative of shade acclimation. The ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) content declined by 45% in the control leaves, but by 60% in the leaves grown at the elevated CO 2 concentration. The light‐ harvesting complex of photosystcm II (LHCII) and the chlorophyll content showed no decrease and no difference between treatments, indicating that the decrease in Rubisco was not an effect of earlier senescence in the leaves at the elevated CO 2 concentration. Following completion of the emergence of the flag‐leaf blade, the elevated‐CO 2 treatment inhibited the further accumulation of Rubisco which was apparent in control leaves over the subsequent 14 d. From this point onwards, the flag leaves from both treatments showed a loss of Rubisco, which was far more pronounced in the elevated‐CO 2 treatment, so that by 36 d the Rubisco content of these leaves was just 70% of that of the controls and by 52 d it was only 20%. At 36 d, there was no decline in chlorophyll, LHCII or the chloroplast ATPase coupling factor (CFI) in the elevated CO 2 concentration treatment relative to the control. By 52 d, all of these proteins showed a significant decline relative to the control. This indicates that the decreased concentration of Rubisco at this final stage probably reflected earlier senescence in the elevated‐CO 2 treatment, but that this was preceded by a CO 2 ‐concentration‐dependent decline in Rubisco.
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Claims 13
Claim · model-written summary
Elevated CO2 had no apparent effect on major photosynthetic protein amounts at blade emergence.
- Taxon
- wheat
Triticum aestivumt0 - Treatment
- elevated CO 2 concentratione0
- Outcome
- amount of any of the major proteins of the photosynthetic apparatuse0
- Direction
- no apparent effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“growth at the elevated CO 2 concentration had no apparent effect on the amount of any of the major proteins of the photosynthetic apparatus regardless of the leaf examined”
Claim · model-written summary
Leaf 5 became shaded by 35 days after blade emergence.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- leaf 5e0
- Outcome
- leaf 5 was in shadee0
- Qualifier
- 35 d following completion of blade emergencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“By 35 d following completion of blade emergence, leaf 5 was in shade”
Claim · model-written summary
At 35 days, leaf 5 chlorophyll alb ratio declined by 26% in both CO2 treatments.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- chlorophyll alb ratioe0
- Direction
- declinede0
- Value
- 26%e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“the chlorophyll alb ratio had declined by 26% both in plants grown at the control CO 2 concentration and in those grown at the elevated CO 2 concentration”
Claim · model-written summary
Rubisco content in control leaf 5 declined by 45%.
- Taxon
- wheatTriticum aestivumt0
- Gene
- ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco)e0
- Outcome
- Rubisco) contente0
- Direction
- declinede0
- Value
- 45%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“The ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) content declined by 45% in the control leaves”
Claim · model-written summary
Rubisco content in elevated CO2 leaves declined by 60%.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated CO 2 concentratione0
- Outcome
- Rubisco) contente1
- Direction
- declinede1
- Value
- 60%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“but by 60% in the leaves grown at the elevated CO 2 concentration”
e1“The ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) content declined by 45% in the control leaves”
Claim · model-written summary
LHCII and chlorophyll content showed no decrease or treatment difference at this point.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- light‐ harvesting complex of photosystcm II (LHCII) and the chlorophyll contente0
- Direction
- no differencee0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“The light‐ harvesting complex of photosystcm II (LHCII) and the chlorophyll content showed no decrease and no difference between treatments”
Claim · model-written summary
Elevated CO2 inhibited further Rubisco accumulation in flag leaves during the 14 days after emergence.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated‐CO 2 treatmente0
- Outcome
- further accumulation of Rubiscoe0
- Direction
- inhibitede0
- Qualifier
- subsequent 14 de0
- Comparator
- control leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“the elevated‐CO 2 treatment inhibited the further accumulation of Rubisco which was apparent in control leaves over the subsequent 14 d”
Claim · model-written summary
Flag leaves in both treatments subsequently lost Rubisco, more strongly under elevated CO2.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- flag leavese0
- Treatment
- elevated‐CO 2 treatmente0
- Outcome
- loss of Rubiscoe0
- Direction
- far more pronouncede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“the flag leaves from both treatments showed a loss of Rubisco, which was far more pronounced in the elevated‐CO 2 treatment”
Claim · model-written summary
At 36 days, elevated CO2 flag leaves had 70% of control Rubisco content.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- Rubisco contente0
- Direction
- lowerinferrede0
- Value
- 70%e0
- Qualifier
- 36 de0
- Comparator
- controlse0
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“by 36 d the Rubisco content of these leaves was just 70% of that of the controls”
Claim · model-written summary
At 52 days, elevated CO2 flag leaves had only 20% of control Rubisco content.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- Rubisco contente1
- Direction
- lowerinferrede0
- Value
- 20%e0
- Qualifier
- 52 de0
- Comparator
- controlse1
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“by 52 d it was only 20%”
e1“by 36 d the Rubisco content of these leaves was just 70% of that of the controls”
Claim · model-written summary
At 36 days, elevated CO2 produced no decline in chlorophyll, LHCII or CFI relative to controls.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated CO 2 concentration treatmente0
- Outcome
- chlorophyll, LHCII or the chloroplast ATPase coupling factor (CFI)e0
- Direction
- no declinee0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“At 36 d, there was no decline in chlorophyll, LHCII or the chloroplast ATPase coupling factor (CFI) in the elevated CO 2 concentration treatment relative to the control”
Claim · model-written summary
At 52 days, chlorophyll, LHCII and CFI declined significantly under elevated CO2 relative to controls.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated CO 2 concentration treatmente1
- Outcome
- chlorophyll, LHCII or the chloroplast ATPase coupling factor (CFI)e1
- Direction
- declinee0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“By 52 d, all of these proteins showed a significant decline relative to the control”
e1“chlorophyll, LHCII or the chloroplast ATPase coupling factor (CFI) in the elevated CO 2 concentration treatment”
Claim · model-written summary
The late Rubisco decline probably reflected earlier senescence under elevated CO2.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated‐CO 2 treatmente0
- Outcome
- decreased concentration of Rubiscoe0
- Qualifier
- probably reflected earlier senescencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e0“the decreased concentration of Rubisco at this final stage probably reflected earlier senescence in the elevated‐CO 2 treatment”
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