Abstract
In the halophytic species Mesembryanthemum crystallinum, the induction of crassulacean acid metabolism (CAM) by salinity requires a substantial investment of resources in storage carbohydrates to provide substrate for nocturnal CO(2) uptake. Acclimation to salinity also requires the synthesis and accumulation of cyclitols as compatible solutes, maintenance of root respiration, and nitrate assimilation. This study assessed the hierarchy and coordination of sinks for carbohydrate in leaves and roots during acclimation to salinity in M. crystallinum. By comparing wild type and a CAM-/starch-deficient mutant of this species, it was sought to determine if other metabolic sinks could compensate for a curtailment in CAM and enable acclimation to salinity. Under salinity, CAM deficiency reduced 24 h photosynthetic carbon gain by >50%. Cyclitols were accumulated to comparable levels in leaves and roots of both the wild type and mutant, but represented only 5% of 24 h carbon balance. Dark respiration of leaves and roots was a stronger sink for carbohydrate in the mutant compared with the wild type and implied higher maintenance costs for the metabolic processes underpinning acclimation to salinity when CAM was curtailed. CAM required the nocturnal mobilization of >70% of primary carbohydrate in the wild type and >85% of carbohydrate in the mutant. The substantial allocation of carbohydrate to CAM limited the export of sugars to roots, and the root:shoot ratio declined under salinity. The data suggest a key role for the vacuole in regulating the supply and demand for carbohydrate over the day/night cycle in the starch-/CAM-deficient mutant.
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Claims 9
Claim · model-written summary
Under salinity, CAM deficiency reduced daily photosynthetic carbon gain by more than 50%.
- Taxon
- Mesembryanthemum crystallinum
Mesembryanthemum crystallinumt0 - Treatment
- CAM deficiencye0
- Outcome
- 24 h photosynthetic carbon gaine0
- Direction
- reducede0
- Value
- >50%e0
- Qualifier
- Under salinitye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under salinity, CAM deficiency reduced 24 h photosynthetic carbon gain by >50%”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
Cyclitols accumulated to comparable levels in mutant and wild type leaves and roots.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Material
- mutante0
- Organ / stage
- leaves and rootse0
- Outcome
- Cyclitolse0
- Direction
- comparable levelse0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cyclitols were accumulated to comparable levels in leaves and roots of both the wild type and mutant”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
Cyclitols represented only 5% of daily carbon balance.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Outcome
- 24 h carbon balancee0
- Value
- 5%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“represented only 5% of 24 h carbon balance”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
Leaf and root dark respiration was a stronger carbohydrate sink in the mutant.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Material
- mutante0
- Outcome
- Dark respiration of leaves and rootse0
- Direction
- strongere0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dark respiration of leaves and roots was a stronger sink for carbohydrate in the mutant compared with the wild type”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
CAM required nocturnal mobilization of over 70% of primary carbohydrate in wild type.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Material
- wild typee0
- Outcome
- nocturnal mobilizatione0
- Value
- >70%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAM required the nocturnal mobilization of >70% of primary carbohydrate in the wild type”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
CAM required nocturnal mobilization of over 85% of carbohydrate in the mutant.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Material
- mutante0
- Outcome
- carbohydratee0
- Value
- >85%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“>85% of carbohydrate in the mutant”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
Carbohydrate allocation to CAM limited sugar export to roots.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Outcome
- export of sugars to rootse0
- Qualifier
- allocation of carbohydrate to CAMe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The substantial allocation of carbohydrate to CAM limited the export of sugars to roots”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
Root to shoot ratio declined under salinity.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Treatment
- salinitye0
- Outcome
- root:shoot ratioe0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the root:shoot ratio declined under salinity”
t0“Mesembryanthemum crystallinum”
Claim · model-written summary
The vacuole was suggested to regulate carbohydrate supply and demand across the day and night cycle.
- Taxon
- Mesembryanthemum crystallinumMesembryanthemum crystallinumt0
- Material
- starch-/CAM-deficient mutante0
- Outcome
- supply and demand for carbohydratee0
- Qualifier
- vacuolee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a key role for the vacuole in regulating the supply and demand for carbohydrate over the day/night cycle in the starch-/CAM-deficient mutant”
t0“Mesembryanthemum crystallinum”
The same questions in other papers
salinity · growth · Mesembryanthemum crystallinum (common iceplant)Results agree
2 papers in the same direction as this paper
- negative
- 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.