Abstract
The correlation between CO(2) 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 CO(2) 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 CO(2) concentrations (10-15%) high enough to overcome stomatal resistance. (c) Nitrate reduction was also inhibited when turgid leaves were kept in CO(2)-free air or at the CO(2)-compensation point or in nitrogen. (d) When leaves were illuminated in CO(2)-free air, activity of NR decreased rapidly. It increased again, when CO(2) 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
Turgid spinach leaves reduced stored nitrate at 3 to 10 micromoles per milligram chlorophyll per hour in light.
- Taxon
- spinach
Spinacia oleraceae0 - Organ / stage
- leavese0
- Outcome
- reduced nitrate stored in the vacuoles of mesophyll cellse0
- Value
- 3 and 10 micromoles per milligram of chlorophyll per houre0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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
Petiole fed nitrate was reduced at rates similar to stored nitrate.
- Taxon
- spinachSpinacia oleraceae1
- Outcome
- Nitrate fed through the petiole was reducede0
- Direction
- similar ratese0
- Comparator
- storage nitratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate fed through the petiole was reduced at similar rates as storage nitrate”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Nitrate reduction was accompanied by malate accumulation.
- Taxon
- spinachSpinacia oleraceae1
- Compound
- malatee0
- Outcome
- Nitrate reductione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate reduction was accompanied by malate accumulation”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Mild water stress with stomatal closure prevented nitrate reduction.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- mild water stresse0
- Outcome
- nitrate reductione0
- Direction
- preventede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under mild water stress which caused stomatal closure, nitrate reduction was prevented”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
External CO2 at 10-15% reversed nitrate reduction inhibition in water stressed leaves.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- external CO(2) concentrations (10-15%)e0
- Outcome
- inhibition of nitrate reductione0
- Direction
- reversede0
- Value
- 10-15%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The inhibition of nitrate reduction observed in water stressed leaves was reversed by external CO(2) concentrations (10-15%) high enough to overcome stomatal resistance”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
CO2 free air inhibited nitrate reduction in turgid leaves.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- CO(2)-free aire0
- Outcome
- Nitrate reductione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate reduction was also inhibited when turgid leaves were kept in CO(2)-free air”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
CO2 compensation point conditions inhibited nitrate reduction.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- CO(2)-compensation pointe0
- Outcome
- Nitrate reductione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate reduction was also inhibited when turgid leaves were kept in CO(2)-free air or at the CO(2)-compensation point or in nitrogen”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Nitrogen atmosphere inhibited nitrate reduction.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- nitrogene0
- Outcome
- Nitrate reductione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate reduction was also inhibited when turgid leaves were kept in CO(2)-free air or at the CO(2)-compensation point or in nitrogen”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Nitrate reductase activity decreased rapidly under light in CO2 free air.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- CO(2)-free aire0
- Gene
- NRe0
- Outcome
- activity of NRe0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When leaves were illuminated in CO(2)-free air, activity of NR decreased rapidly”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Nitrate reductase activity increased again when CO2 was restored.
- Taxon
- spinachSpinacia oleraceae1
- Treatment
- CO(2) was added backe0
- Outcome
- activity of NRe2
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It increased again, when CO(2) was added back to the system”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
e2“activity of NR decreased rapidly”
Claim · model-written summary
Nitrate reductase activity changed by 50% with an approximately 30 minute half-time.
- Taxon
- spinachSpinacia oleraceae1
- Outcome
- change in activitye0
- Value
- 30 mine0
- Qualifier
- 50%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The half-time for a 50% change in activity was about 30 min”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
Claim · model-written summary
Rapid nitrate reductase activation and inactivation couples the enzyme to net photosynthesis.
- Taxon
- spinachSpinacia oleraceae1
- Gene
- NRe0
- Outcome
- couples nitrate reductase to net photosynthesise0
- Qualifier
- rapid inactivation/activation mechanisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there is a rapid inactivation/activation mechanism of NR in leaves which couples nitrate reductase to net photosynthesis”
t0“Leaves”
e1“detached spinach (Spinacia oleracea L.) leaves”
The same questions in other papers
co2 · disease · Spinacia oleracea (spinach)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
nitrogen · nutrient: content · Spinacia oleracea (spinach)Positive and negative results
13 papers in the same direction as this paper · 21 in the opposite direction
- positive
- positive
- positive
31 papers more in this group
See all 35 papers →drought · nutrient: content · Spinacia oleracea (spinach)Results agree
2 papers in the same direction as this paper
- negative
- negative
co2 · nutrient: content · Spinacia oleracea (spinach)Results agree
3 papers in the same direction as this paper
- negative
- negative
- negative
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.