Abstract
Abstract The effect of withholding water on the specific activities of pyruvate, orthophosphate dikinase (PPDK EC 2.7.9.1.) and phosphoenol pyruvate carboxylase (PEPC, EC 4.1.1.31) was studied in two cultivars of Sorghum bicolor L. different in their sensitivity to water deficit. The drought sensitive cultivar ICSV 1063 and the more resistant cultivar MIGSOR were subjected to water deficit in controlled conditions. The results showed a decrease in both enzyme specific activities, higher for drought sensitive cultivar ICSV 1063, when leaf water potential (Ψ) was lowered to ‐2.3 MPa. Following rewatering, enzyme specific activities increased in both cultivars, with the increase being more significant in MIGSOR. Relative water content (RWC) decreased significantly for water‐stressed ICSV 1063 cultivar, lower for MIGSOR and returned quickly to that of control plants upon rehydration. Net photosynthesis showed a decrease for water‐stressed plants, higher for ICSV 1063. At minimal Ψ, net photosynthesis was completely inhibited, with the stomata being closed After rehydration, MIGSOR showed a better recovery in photosynthesis but never reached the initial values of day 0. Water stress had a striking effect, both on net photosynthesis by regulation of stomatal aperture and on PPDK and PEPC activities, although the enzymes were still active when photosynthesis ceased. Therefore the level of PPDK and PEPC activities may contribute to the limitation of photosynthetic carbon dioxide fixation.
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Claims 9
Claim · model-written summary
Water deficit decreased both enzyme activities, more in ICSV 1063 at -2.3 MPa.
- Taxon
- Sorghum bicolor L.
Sorghum bicolort0 - Material
- ICSV 1063e0
- Treatment
- leaf water potential (Ψ) was lowered to ‐2.3 MPae0
- Outcome
- both enzyme specific activitiese0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a decrease in both enzyme specific activities, higher for drought sensitive cultivar ICSV 1063, when leaf water potential (Ψ) was lowered to ‐2.3 MPa”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
Rewatering increased both enzyme activities, more significantly in MIGSOR.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Material
- MIGSORe0
- Treatment
- rewateringe0
- Outcome
- enzyme specific activitiese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Following rewatering, enzyme specific activities increased in both cultivars, with the increase being more significant in MIGSOR”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
Water stress significantly reduced relative water content in ICSV 1063, less in MIGSOR.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Material
- ICSV 1063e0
- Treatment
- water‐stressede0
- Outcome
- Relative water content (RWC)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative water content (RWC) decreased significantly for water‐stressed ICSV 1063 cultivar, lower for MIGSOR”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
Relative water content quickly recovered after rehydration.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Treatment
- rehydratione0
- Outcome
- Relative water content (RWC)e1
- Direction
- returnede0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“returned quickly to that of control plants upon rehydration”
e1“Relative water content (RWC)”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
Water stress decreased net photosynthesis, more in ICSV 1063.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Material
- ICSV 1063e0
- Treatment
- water‐stressede0
- Outcome
- Net photosynthesise0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Net photosynthesis showed a decrease for water‐stressed plants, higher for ICSV 1063”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
At minimal water potential, photosynthesis was completely inhibited and stomata closed.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Outcome
- net photosynthesis was completely inhibited, with the stomata being closede0
- Qualifier
- minimal Ψe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At minimal Ψ, net photosynthesis was completely inhibited, with the stomata being closed”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
MIGSOR photosynthesis recovered better after rehydration but stayed below day-zero values.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Material
- MIGSORe0
- Treatment
- rehydratione0
- Outcome
- recovery in photosynthesise0
- Direction
- bettere0
- Comparator
- initial values of day 0e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After rehydration, MIGSOR showed a better recovery in photosynthesis but never reached the initial values of day 0”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
PPDK and PEPC remained active when photosynthesis ceased.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Gene
- PPDK and PEPCe1
- Outcome
- enzymes were still active when photosynthesis ceasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the enzymes were still active when photosynthesis ceased”
e1“on PPDK and PEPC activities”
t0“Sorghum (Sorghum bicolor L.)”
Claim · model-written summary
Authors suggest PPDK and PEPC activity may limit carbon dioxide fixation.
- Taxon
- Sorghum bicolor L.Sorghum bicolort0
- Gene
- PPDK and PEPCe0
- Outcome
- limitation of photosynthetic carbon dioxide fixatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of PPDK and PEPC activities may contribute to the limitation of photosynthetic carbon dioxide fixation”
t0“Sorghum (Sorghum bicolor L.)”
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