Abstract
The correlation between C02 assimilation and nitrate reduction in detached spinach (Spinacia oleracea L.) leaves was examined by measuring light-dependent changes in leaf nitrate levels in response to mild water stress and to artificially imposed CO2 deficiency. The level of extractable nitrate reductase (NR) activity was also measured. The results are: (a) In the light, detached turgid spinach leaves reduced nitrate stored in the vacuoles of mesophyll cells at rates between 3 and 10 micromoles per milligram of chlorophyll per hour. Nitrate fed through the petiole was reduced at similar rates as storage nitrate. Nitrate reduction was accompanied by malate accumulation. (b) Under mild water stress which caused stomatal closure, nitrate reduction was prevented. The inhibition of nitrate reduction observed in water stressed leaves was reversed by external C02 concentrations (10-15%) high enough to overcome stomatal resistance. (c) Nitrate reduction was also inhibited when turgid leaves were kept in C02-free air or at the C02-compensation point or in nitrogen. (d) When leaves were illuminated in C02-free air, activity of NR decreased rapidly. It increased again, when C02 was added back to the system. The half-time for a 50% change in activity was about 30 min. It thus appears that there is a rapid inactivation/activation mechanism of NR in leaves which couples nitrate reductase to net photosynthesis.
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Claims 12
Claim · model-written summary
In the light, detached turgid spinach leaves reduced stored nitrate in mesophyll vacuoles at 3-10 micromoles per milligram of chlorophyll per hour.
- Taxon
- spinach
Spinacia oleraceae0 - Organ / stage
- mesophyll cellse1
- Outcome
- reduced nitrate stored in the vacuoles of mesophyll cellse1
- Value
- 3 and 10 micromoles per milligram of chlorophyll per houre1
- Qualifier
- In the lighte1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e1“In the light, detached turgid spinach leaves reduced nitrate stored in the vacuoles of mesophyll cells at rates between 3 and 10 micromoles per milligram of chlorophyll per hour”
Claim · model-written summary
Nitrate fed through the petiole was reduced at rates similar to stored nitrate.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- Nitrate fed through the petiolee2
- Outcome
- reduced at similar rates as storage nitratee2
- Direction
- similar ratese2
- Comparator
- storage nitratee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e2“Nitrate fed through the petiole was reduced at similar rates as storage nitrate”
Claim · model-written summary
Nitrate reduction in spinach leaves was accompanied by malate accumulation.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- Nitrate reductione3
- Outcome
- malate accumulatione3
- Direction
- accompaniede3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e3“Nitrate reduction was accompanied by malate accumulation”
Claim · model-written summary
Under mild water stress that caused stomatal closure, nitrate reduction in spinach leaves was prevented.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- mild water stresse4
- Outcome
- nitrate reductione4
- Direction
- preventede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e4“Under mild water stress which caused stomatal closure, nitrate reduction was prevented”
Claim · model-written summary
External CO2 concentrations of 10-15% reversed the inhibition of nitrate reduction in water-stressed spinach leaves.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- external C02 concentrations (10-15%)e5
- Outcome
- inhibition of nitrate reductione5
- Direction
- reversede5
- Comparator
- water stressed leavese5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e5“The inhibition of nitrate reduction observed in water stressed leaves was reversed by external C02 concentrations (10-15%) high enough to overcome stomatal resistance”
Claim · model-written summary
Nitrate reduction in turgid spinach leaves was inhibited in C02-free air.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- C02-free aire6
- Outcome
- Nitrate reductione6
- Direction
- inhibitede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e6“Nitrate reduction was also inhibited when turgid leaves were kept in C02-free air or at the C02-compensation point or in nitrogen”
Claim · model-written summary
Nitrate reduction in turgid spinach leaves was inhibited at the CO2 compensation point.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- C02-compensation pointe6
- Outcome
- Nitrate reductione6
- Direction
- inhibitede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e6“Nitrate reduction was also inhibited when turgid leaves were kept in C02-free air or at the C02-compensation point or in nitrogen”
Claim · model-written summary
Nitrate reduction in turgid spinach leaves was inhibited under nitrogen.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- nitrogene6
- Outcome
- Nitrate reductione6
- Direction
- inhibitede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e6“Nitrate reduction was also inhibited when turgid leaves were kept in C02-free air or at the C02-compensation point or in nitrogen”
Claim · model-written summary
Nitrate reductase activity in illuminated spinach leaves decreased rapidly in C02-free air.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- C02-free aire7
- Gene
- NRe7
- Outcome
- activitye7
- Direction
- decreased rapidlye7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e7“When leaves were illuminated in C02-free air, activity of NR decreased rapidly”
Claim · model-written summary
Nitrate reductase activity increased again when CO2 was added back to the system.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- C02 was added back to the systeme1
- Gene
- NRe7
- Outcome
- activitye7
- Direction
- increased againe1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e7“When leaves were illuminated in C02-free air, activity of NR decreased rapidly”
e1“It increased again, when C02 was added back to the system”
Claim · model-written summary
A rapid inactivation/activation mechanism of nitrate reductase couples it to net photosynthesis in spinach leaves.
- Taxon
- spinachSpinacia oleraceae0
- Gene
- NRe2
- Outcome
- couples nitrate reductase to net photosynthesise2
- Qualifier
- rapid inactivation/activation mechanisme2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e2“It thus appears that there is a rapid inactivation/activation mechanism of NR in leaves which couples nitrate reductase to net photosynthesis”
Claim · model-written summary
The half-time for a 50% change in nitrate reductase activity was about 30 min.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- activitye3
- Value
- about 30 mine3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“detached spinach (Spinacia oleracea L.) leaves”
e3“The half-time for a 50% change in activity was about 30 min”
The same questions in other papers
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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.