Abstract
The fundamental cause of down-regulation of photosynthesis at elevated carbon dioxide concentration (EC) is thought to be a slower rate of utilization of saccharides than their stimulated rate of production, but there are few studies directly supporting this idea under field conditions. We hypothesized that within Brassica oleracea, down-regulation would not occur in kohlrabi because it has a large sink for saccharides in an enlarged stem, but would occur in collards, which lack this sink. Field tests were consistent with this hypothesis. In collards, the degree of down-regulation of photosynthesis in plants grown at EC varied depending on the daily integral of photosynthetically active radiation (PAR) of the day prior to the measurement of photosynthetic capacity, as did leaf saccharide content. However, EC did not result in lower leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylase, or nitrate in collards, nor was there any evidence of a triose phosphate utilization rate limiting photosynthesis. Experiments in controlled environment chambers confirmed that there was a threshold response for the down-regulation of photosynthesis in collards at EC to the PAR of the previous day, with down-regulation only occurring above a minimum daily integral of PAR. Down-regulation of photosynthesis could be induced in plants grown at ambient carbon dioxide by a single night at low temperature or by a single day with high PAR and EC. In the controlled environment study, the degree of down-regulation of photosynthesis was highly correlated with leaf glucose, fructose, and sucrose contents, and less well correlated with starch content. Hence down-regulation of photosynthesis at EC in collards in the field represented feedback inhibition from the accumulation of soluble saccharides and day-to-day variation in its occurrence was predictable from the weather.
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Claims 13
Claim · model-written summary
Field tests supported absence of down-regulation in kohlrabi with its enlarged stem sink at elevated CO2.
- Taxon
- Brassica oleracea
Brassica oleraceae0 - Material
- kohlrabie0
- Outcome
- down-regulatione0
- Direction
- would not occure0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We hypothesized that within Brassica oleracea, down-regulation would not occur in kohlrabi because it has a large sink for saccharides in an enlarged stem, but would occur in collards, which lack this sink. Field tests were consistent with this hypothesis.”
Claim · model-written summary
Field tests supported photosynthetic down-regulation in collards at elevated CO2.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- ECe1
- Outcome
- down-regulation of photosynthesise1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“down-regulation would not occur in kohlrabi because it has a large sink for saccharides in an enlarged stem, but would occur in collards, which lack this sink. Field tests were consistent with this hypothesis.”
t0“Brassica oleracea”
e1“In collards, the degree of down-regulation of photosynthesis in plants grown at EC”
Claim · model-written summary
In field collards at elevated CO2, photosynthetic down-regulation varied with the previous day's PAR integral.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- daily integral of photosynthetically active radiation (PAR)e0
- Outcome
- degree of down-regulation of photosynthesise0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In collards, the degree of down-regulation of photosynthesis in plants grown at EC varied depending on the daily integral of photosynthetically active radiation (PAR) of the day prior to the measurement of photosynthetic capacity, as did leaf saccharide content.”
t0“Brassica oleracea”
Claim · model-written summary
Collard leaf saccharide content varied with the previous day's PAR integral at elevated CO2.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- daily integral of photosynthetically active radiation (PAR)e0
- Outcome
- leaf saccharide contente0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In collards, the degree of down-regulation of photosynthesis in plants grown at EC varied depending on the daily integral of photosynthetically active radiation (PAR) of the day prior to the measurement of photosynthetic capacity, as did leaf saccharide content.”
t0“Brassica oleracea”
Claim · model-written summary
Elevated CO2 did not lower collard leaf chlorophyll, soluble protein or ribulose-1,5-bisphosphate carboxylase contents.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- ECe0
- Outcome
- leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylasee0
- Direction
- did not result in lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“EC did not result in lower leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylase, or nitrate in collards”
t0“Brassica oleracea”
Claim · model-written summary
Elevated CO2 did not lower collard leaf nitrate content.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- ECe0
- Outcome
- nitratee0
- Direction
- did not result in lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“EC did not result in lower leaf contents of chlorophyll, soluble protein, ribulose-1,5-bisphosphate carboxylase, or nitrate in collards”
t0“Brassica oleracea”
Claim · model-written summary
There was no evidence that triose phosphate utilization limited collard photosynthesis.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Outcome
- triose phosphate utilization rate limiting photosynthesise0
- Qualifier
- nor was there any evidencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nor was there any evidence of a triose phosphate utilization rate limiting photosynthesis”
t0“Brassica oleracea”
Claim · model-written summary
Chamber-grown collards at elevated CO2 down-regulated photosynthesis only above a minimum previous-day PAR integral.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Treatment
- PAR of the previous daye0
- Outcome
- down-regulation of photosynthesise0
- Qualifier
- only occurring above a minimum daily integral of PARe0
- Setting
- controlled environment chamberse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Experiments in controlled environment chambers confirmed that there was a threshold response for the down-regulation of photosynthesis in collards at EC to the PAR of the previous day, with down-regulation only occurring above a minimum daily integral of PAR.”
t0“Brassica oleracea”
Claim · model-written summary
A single low-temperature night induced photosynthetic down-regulation in plants grown at ambient CO2.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Treatment
- a single night at low temperaturee0
- Outcome
- Down-regulation of photosynthesise0
- Direction
- Down-regulatione0
- Qualifier
- grown at ambient carbon dioxidee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Down-regulation of photosynthesis could be induced in plants grown at ambient carbon dioxide by a single night at low temperature or by a single day with high PAR and EC.”
t0“Brassica oleracea”
Claim · model-written summary
A single day of high PAR and elevated CO2 induced photosynthetic down-regulation in plants grown at ambient CO2.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Treatment
- a single day with high PAR and ECe0
- Outcome
- Down-regulation of photosynthesise0
- Direction
- Down-regulatione0
- Qualifier
- grown at ambient carbon dioxidee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Down-regulation of photosynthesis could be induced in plants grown at ambient carbon dioxide by a single night at low temperature or by a single day with high PAR and EC.”
t0“Brassica oleracea”
Claim · model-written summary
Chamber photosynthetic down-regulation correlated highly with glucose, fructose and sucrose contents.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Compound
- glucose, fructose, and sucrosee0
- Outcome
- degree of down-regulation of photosynthesise0
- Qualifier
- highly correlatede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the controlled environment study, the degree of down-regulation of photosynthesis was highly correlated with leaf glucose, fructose, and sucrose contents, and less well correlated with starch content.”
t0“Brassica oleracea”
Claim · model-written summary
Photosynthetic down-regulation correlated less well with starch content.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Compound
- starche0
- Outcome
- degree of down-regulation of photosynthesise0
- Qualifier
- less well correlatede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the controlled environment study, the degree of down-regulation of photosynthesis was highly correlated with leaf glucose, fructose, and sucrose contents, and less well correlated with starch content.”
t0“Brassica oleracea”
Claim · model-written summary
Field collard photosynthetic down-regulation represents feedback inhibition from soluble saccharide accumulation, with daily occurrence predictable from weather.
- Taxon
- Brassica oleraceaBrassica oleraceat0
- Material
- collardse0
- Compound
- soluble saccharidese0
- Outcome
- down-regulation of photosynthesise0
- Qualifier
- day-to-day variation in its occurrence was predictable from the weathere0
- Setting
- fielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hence down-regulation of photosynthesis at EC in collards in the field represented feedback inhibition from the accumulation of soluble saccharides and day-to-day variation in its occurrence was predictable from the weather.”
t0“Brassica oleracea”
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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.