Abstract
Summary In order to separate the net effect of growth at elevated [CO 2 ] on stomatal conductance ( g s ) into direct and acclimatory responses, mid‐day values of g s were measured for plants grown in field plots in open‐topped chambers at the current ambient [CO 2 ], which averaged 350 μmol mol −1 in the daytime, and at ambient + 350 μmol mol −1 [CO 2 ] for winter wheat, winter barley, potato and sorghum. The acclimatory response was determined by comparing g s measured at 700 μmol mol −1 [CO 2 ] for plants grown at the two [CO 2 ]. The direct effect of increasing [CO 2 ] from 350 to 700 μmol mol −1 was determined for plants grown at the lower concentration. Photosynthetic rates were measured concurrently with g s . For all species, growth at the higher [CO 2 ] significantly reduced g s measured at 700 μmol mol −1 [CO 2 ]. The reduction in g s caused by growth at the higher [CO 2 ] was larger for all species on days with low leaf to air water vapour pressure difference for a given temperature, which coincided with highest conductances and also the smallest direct effects of increased [CO 2 ] on conductance. For barley, there was no other evidence for stomatal acclimation, despite consistent down‐regulation of photosynthetic rate in plants grown at the higher [CO 2 ]. In wheat and potato, in addition to the vapour pressure difference interaction, the magnitude of stomatal acclimation varied directly in proportion to the magnitude of down‐regulation of photosynthetic rate through the season. In sorghum, g s consistently exhibited acclimation, but there was no down‐regulation of photosynthetic rate. In none of the species except barley was the direct effect the larger component of the net reduction in g s when averaged over measurement dates. The net effect of growth at elevated [CO 2 ] on mid‐day g s resulted from unique combinations of direct and acclimatory responses in the various species.
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Claims 10
Claim · model-written summary
Elevated carbon dioxide growth significantly reduced wheat stomatal conductance.
- Taxon
- winter wheat
Triticum aestivume1 - Treatment
- higher [CO 2 ]e0
- Outcome
- g se0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For all species, growth at the higher [CO 2 ] significantly reduced g s measured at 700 μmol mol −1 [CO 2 ]”
e1“winter wheat, winter barley, potato and sorghum”
Claim · model-written summary
Elevated carbon dioxide growth significantly reduced barley stomatal conductance.
- Taxon
- winter barley
.jpg?width=60)
Hordeum vulgaree1 - Treatment
- higher [CO 2 ]e0
- Outcome
- g se0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“For all species, growth at the higher [CO 2 ] significantly reduced g s measured at 700 μmol mol −1 [CO 2 ]”
e1“winter wheat, winter barley, potato and sorghum”
Claim · model-written summary
Elevated carbon dioxide growth significantly reduced potato stomatal conductance.
- Taxon
- potato
Solanum tuberosume1 - Treatment
- higher [CO 2 ]e0
- Outcome
- g se0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For all species, growth at the higher [CO 2 ] significantly reduced g s measured at 700 μmol mol −1 [CO 2 ]”
e1“winter wheat, winter barley, potato and sorghum”
Claim · model-written summary
Elevated carbon dioxide growth significantly reduced sorghum stomatal conductance.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For all species, growth at the higher [CO 2 ] significantly reduced g s measured at 700 μmol mol −1 [CO 2 ]”
e1“winter wheat, winter barley, potato and sorghum”
Claim · model-written summary
Acclimatory conductance reduction was larger on low vapour pressure difference days for all four crops.
- Taxon
- winter wheat, winter barley, potato and sorghumSolanum tuberosumHordeum vulgare
SorghumTriticum aestivume1 - Outcome
- reduction in g se0
- Direction
- largere0
- Setting
- days with low leaf to air water vapour pressure differencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The reduction in g s caused by growth at the higher [CO 2 ] was larger for all species on days with low leaf to air water vapour pressure difference for a given temperature”
e1“winter wheat, winter barley, potato and sorghum”
Claim · model-written summary
Barley photosynthetic rate was consistently downregulated at higher carbon dioxide.
- Taxon
- barleyHordeum vulgaree0
- Treatment
- higher [CO 2 ]e0
- Outcome
- photosynthetic ratee0
- Direction
- down‐regulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For barley, there was no other evidence for stomatal acclimation, despite consistent down‐regulation of photosynthetic rate in plants grown at the higher [CO 2 ]”
Claim · model-written summary
Wheat stomatal acclimation magnitude tracked photosynthetic downregulation through the season.
- Taxon
- wheatTriticum aestivume0
- Outcome
- magnitude of stomatal acclimatione0
- Direction
- varied directly in proportione0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In wheat and potato, in addition to the vapour pressure difference interaction, the magnitude of stomatal acclimation varied directly in proportion to the magnitude of down‐regulation of photosynthetic rate through the season”
Claim · model-written summary
Potato stomatal acclimation magnitude tracked photosynthetic downregulation through the season.
- Taxon
- potatoSolanum tuberosume0
- Outcome
- magnitude of stomatal acclimatione0
- Direction
- varied directly in proportione0
- Setting
- through the seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In wheat and potato, in addition to the vapour pressure difference interaction, the magnitude of stomatal acclimation varied directly in proportion to the magnitude of down‐regulation of photosynthetic rate through the season”
Claim · model-written summary
Sorghum conductance acclimated while photosynthetic rate did not downregulate.
- Outcome
- g s consistently exhibited acclimation, but there was no down‐regulation of photosynthetic ratee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In sorghum, g s consistently exhibited acclimation, but there was no down‐regulation of photosynthetic rate”
Claim · model-written summary
Only barley had a larger direct than acclimatory component of net conductance reduction averaged over dates.
- Taxon
- barleyHordeum vulgaree0
- Outcome
- direct effecte0
- Direction
- largere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In none of the species except barley was the direct effect the larger component of the net reduction in g s when averaged over measurement dates”
The same questions in other papers
co2 · physiology: photosynthesis · Hordeum vulgare (barley)Positive and negative results
7 papers in the same direction as this paper · 5 in the opposite direction
- positive
- positive
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9 papers more in this group
See all 13 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.