Abstract
Abstract A decreased utilization of NADPH for CO 2 fixation as a result of carbohydrate accumulation in chlorotic leaves is generally believed to be associated with an increase in oxidative stress. Molecular oxygen may serve as an alternative electron acceptor of photosynthesis under these conditions. In order to test this hypothesis mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used to study the effect of carbohydrate accumulation on the pigment content and the components of the superoxide dismutase‐ascorbate‐glutathione cycle. During a period of five days the concentration of total soluble carbohydrates increased substantially in leaves supplied with glucose in comparison with control leaves supplied only with water. This increase was accompanied by a twofold decrease in the chlorophyll content. In detached water‐fed leaves the levels of most of the antioxidative components increased, whereas glucose feeding had no or only little additional effect on the activities of the protective enzymes, but caused a 1.6‐ and 4‐fold increase in the contents of glutathione and ascorbate, respectively. In relation to the total foliar ascorbate pool, the amount of reduced ascorbate increased from about 30 % to 60 % upon feeding with glucose. These results do not support the idea that the accumulation carbohydrates per se cause an increased rate of superoxide production which necessitates increased activities of antioxidative enzymes. It rather appears that glucose‐fed leaves have an increased reductive capacity that can be released via glutathione into the ascorbate pool, thereby, regulating the redox state of ascorbate.
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Claims 8
Claim · model-written summary
Glucose feeding substantially increased total soluble carbohydrates in detached tobacco leaves compared with water-fed controls.
- Taxon
- Nicotiana tabacum
Nicotiana tabacume0 - Treatment
- glucosee0
- Outcome
- total soluble carbohydratese1
- Direction
- increasede1
- Comparator
- control leaves supplied only with watere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e1“the concentration of total soluble carbohydrates increased substantially in leaves supplied with glucose in comparison with control leaves supplied only with water”
Claim · model-written summary
Glucose feeding was accompanied by a twofold decrease in chlorophyll content in detached tobacco leaves.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Treatment
- glucosee0
- Outcome
- chlorophyll contente2
- Direction
- decreasee2
- Value
- twofolde2
- Comparator
- control leaves supplied only with watere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e1“the concentration of total soluble carbohydrates increased substantially in leaves supplied with glucose in comparison with control leaves supplied only with water”
e2“This increase was accompanied by a twofold decrease in the chlorophyll content”
Claim · model-written summary
Glucose feeding increased glutathione and ascorbate contents in detached tobacco leaves by 1.6‐ and 4‐fold respectively.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Treatment
- glucosee0
- Outcome
- contents of glutathione and ascorbatee3
- Direction
- increasee3
- Value
- 1.6‐ and 4‐folde3
- Comparator
- control leaves supplied only with watere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e1“the concentration of total soluble carbohydrates increased substantially in leaves supplied with glucose in comparison with control leaves supplied only with water”
e3“caused a 1.6‐ and 4‐fold increase in the contents of glutathione and ascorbate, respectively”
Claim · model-written summary
Feeding with glucose increased the amount of reduced ascorbate from about 30% to 60% of the foliar ascorbate pool.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Treatment
- feeding with glucosee4
- Outcome
- amount of reduced ascorbatee4
- Direction
- increasede4
- Value
- from about 30 % to 60 %e4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e4“the amount of reduced ascorbate increased from about 30 % to 60 % upon feeding with glucose”
Claim · model-written summary
Levels of most antioxidative components increased in detached water-fed tobacco leaves.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Outcome
- levels of most of the antioxidative componentse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e5“In detached water‐fed leaves the levels of most of the antioxidative components increased”
Claim · model-written summary
Glucose feeding had no or only little additional effect on the activities of the protective enzymes in tobacco leaves.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Treatment
- glucosee0
- Outcome
- activities of the protective enzymese6
- Direction
- no_changeinferrede6
- Comparator
- water‐fed leavese5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e5“In detached water‐fed leaves the levels of most of the antioxidative components increased”
e6“glucose feeding had no or only little additional effect on the activities of the protective enzymes”
Claim · model-written summary
The results do not support the idea that carbohydrate accumulation per se causes an increased rate of superoxide production in tobacco leaves.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Treatment
- accumulation carbohydrates per see7
- Outcome
- rate of superoxide productione7
- Direction
- increasede7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e7“These results do not support the idea that the accumulation carbohydrates per se cause an increased rate of superoxide production”
Claim · model-written summary
Glucose-fed leaves have increased reductive capacity released via glutathione into the ascorbate pool, regulating the redox state of ascorbate.
- Taxon
- Nicotiana tabacumNicotiana tabacume0
- Compound
- glutathionee1
- Outcome
- redox state of ascorbatee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mature leaves of tobacco plants ( Nicotiana tabacum ) were detached, fed with glucose (50 mM) via the petiole, and used”
e1“glucose‐fed leaves have an increased reductive capacity that can be released via glutathione into the ascorbate pool, thereby, regulating the redox state of ascorbate”
The same questions in other papers
glucose · physiology: pigments · Nicotiana tabacum (tobacco)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- 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.