Abstract
Higher rates of nitrate assimilation are required to support faster growth in enhanced carbon dioxide. To investigate how this is achieved, tobacco plants were grown on high nitrate and high light in ambient and enhanced (700 μ mol mol –1 ) carbon dioxide. Surprisingly, enhanced carbon dioxide did not increase leaf nitrate reductase (NR) activity in the middle of the photoperiod. Possible reasons for this anomalous result were investigated. (a) Measurements of biomass, nitrate, amino acids and glutamine in plants fertilized once and twice daily with 12 mol m –3 nitrate showed that enhanced carbon dioxide did not lead to a nitrate limitation in these plants. (b) Enhanced carbon dioxide modified the diurnal regulation of NR activity in source leaves. The transcript for nia declined during the light period in a similar manner in ambient and enhanced carbon dioxide. The decline of the transcript correlated with a decrease of nitrate in the leaf, and was temporarily reversed after re‐irrigating with nitrate in the second part of the photoperiod. The decline of the transcript was not correlated with changes of sugars or glutamine. NR activity and protein decline in the second part of the photoperiod, and NR is inactivated in the dark in ambient carbon dioxide. The decline of NR activity was smaller and dark inactivation was partially reversed in enhanced carbon dioxide, indicating that post‐transcriptional or post‐translational regulation of NR has been modified. The increased activation and stability of NR in enhanced carbon dioxide was correlated with higher sugars and lower glutamine in the leaves. (c) Enhanced carbon dioxide led to increased levels of the minor amino acids in leaves. (d) Enhanced carbon dioxide led to a large decrease of glycine and a small decrease of serine in leaves of mature plants. The glycine:serine ratio decreased in source leaves of older plants and seedlings. The consequences of a lower rate of photorespiration for the levels of glutamine and the regulation of nitrogen metabolism are discussed. (e) Enhanced carbon dioxide also modified the diurnal regulation of NR in roots. The nia transcript increased after nitrate fertilization in the early and the second part of the photoperiod. The response of the transcript was not accentuated in enhanced carbon dioxide. NR activity declined slightly during the photoperiod in ambient carbon dioxide, whereas it increased 2‐fold in enhanced carbon dioxide. The increase of root NR activity in enhanced carbon dioxide was preceded by a transient increase of sugars, and was followed by a decline of sugars, a faster decrease of nitrate than in ambient carbon dioxide, and an increase of nitrite in the roots. (f) To interpret the physiological significance of these changes in nitrate metabolism, they were compared with the current growth rate of the plants. (g) In 4–5‐week‐old plants, the current rate of growth was similar in ambient and enhanced carbon dioxide (≈ 0·4 g –1 d –1 ). Enhanced carbon dioxide only led to small changes of NR activity, nitrate decreased, and overall amino acids were not significantly increased. (h) Young seedlings had a high growth rate (0·5 g –1 d –1 ) in ambient carbon dioxide, that was increased by another 20% in enhanced carbon dioxide. Enhanced carbon dioxide led to larger increases of NR activity and NR activation, a 2–3‐fold increase of glutamine, a 50% increase of glutamate, and a 2–3‐fold increase in minor amino acids. It also led to a higher nitrate level. It is argued that enhanced carbon dioxide leads to a very effective stimulation of nitrate uptake, nitrate assimilation and amino acid synthesis in seedlings. This will play an important role in allowing faster growth rates in enhanced carbon dioxide at this stage.
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Claims 15
Claim · model-written summary
Enhanced carbon dioxide did not increase leaf nitrate reductase activity in the middle of the photoperiod.
- Taxon
- tobacco
Nicotiana tabacumt0 - Treatment
- enhanced carbon dioxidee1
- Outcome
- leaf nitrate reductase (NR) activitye1
- Direction
- did not increasee1
- Qualifier
- in the middle of the photoperiode1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e1“Surprisingly, enhanced carbon dioxide did not increase leaf nitrate reductase (NR) activity in the middle of the photoperiod”
Claim · model-written summary
Enhanced carbon dioxide gave larger increases of NR activity in young seedlings.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Young seedlingse3
- Treatment
- Enhanced carbon dioxidee2
- Outcome
- NR activitye2
- Direction
- larger increasese2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e2“Enhanced carbon dioxide led to larger increases of NR activity and NR activation, a 2–3‐fold increase of glutamine, a 50% increase of glutamate, and a 2–3‐fold increase in minor amino acids”
e3“Young seedlings had a high growth rate (0·5 g –1 d –1 ) in ambient carbon dioxide, that was increased by another 20% in enhanced carbon dioxide”
Claim · model-written summary
Enhanced carbon dioxide gave a 2–3‐fold increase of glutamine in young seedlings.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Young seedlingse3
- Treatment
- Enhanced carbon dioxidee2
- Outcome
- glutaminee2
- Direction
- increasee2
- Value
- 2–3‐folde2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e2“Enhanced carbon dioxide led to larger increases of NR activity and NR activation, a 2–3‐fold increase of glutamine, a 50% increase of glutamate, and a 2–3‐fold increase in minor amino acids”
e3“Young seedlings had a high growth rate (0·5 g –1 d –1 ) in ambient carbon dioxide, that was increased by another 20% in enhanced carbon dioxide”
Claim · model-written summary
Enhanced carbon dioxide increased the growth rate of young seedlings by another 20%.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Young seedlingse3
- Treatment
- enhanced carbon dioxidee3
- Outcome
- growth ratee3
- Direction
- increasede3
- Value
- 20%e3
- Comparator
- ambient carbon dioxidee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e3“Young seedlings had a high growth rate (0·5 g –1 d –1 ) in ambient carbon dioxide, that was increased by another 20% in enhanced carbon dioxide”
Claim · model-written summary
Enhanced carbon dioxide increased root NR activity by 2-fold during the photoperiod, while it declined slightly in ambient carbon dioxide.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- enhanced carbon dioxidee4
- Outcome
- NR activitye4
- Direction
- increasede4
- Value
- 2‐folde4
- Comparator
- ambient carbon dioxidee4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e4“NR activity declined slightly during the photoperiod in ambient carbon dioxide, whereas it increased 2‐fold in enhanced carbon dioxide”
Claim · model-written summary
Enhanced carbon dioxide led to a large decrease of glycine in leaves of mature plants.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leaves of mature plantse5
- Treatment
- Enhanced carbon dioxidee5
- Outcome
- glycinee5
- Direction
- large decreasee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e5“Enhanced carbon dioxide led to a large decrease of glycine and a small decrease of serine in leaves of mature plants”
Claim · model-written summary
Enhanced carbon dioxide led to a small decrease of serine in leaves of mature plants.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leaves of mature plantse5
- Treatment
- Enhanced carbon dioxidee5
- Outcome
- serinee5
- Direction
- small decreasee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e5“Enhanced carbon dioxide led to a large decrease of glycine and a small decrease of serine in leaves of mature plants”
Claim · model-written summary
The glycine:serine ratio decreased in source leaves of older plants and seedlings.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- source leaves of older plants and seedlingse6
- Outcome
- glycine:serine ratioe6
- Direction
- decreasede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e6“The glycine:serine ratio decreased in source leaves of older plants and seedlings”
Claim · model-written summary
Enhanced carbon dioxide increased the levels of minor amino acids in leaves.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leavese6
- Treatment
- Enhanced carbon dioxidee6
- Outcome
- levels of the minor amino acidse6
- Direction
- increasede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e6“Enhanced carbon dioxide led to increased levels of the minor amino acids in leaves”
Claim · model-written summary
In 4–5‐week‐old plants, the current growth rate was similar in ambient and enhanced carbon dioxide.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- 4–5‐week‐old plantse7
- Treatment
- enhanced carbon dioxidee7
- Outcome
- current rate of growthe7
- Direction
- similare7
- Value
- ≈ 0·4 g –1 d –1e7
- Comparator
- ambiente7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e7“In 4–5‐week‐old plants, the current rate of growth was similar in ambient and enhanced carbon dioxide (≈ 0·4 g –1 d –1 )”
Claim · model-written summary
In 4–5‐week‐old plants, enhanced carbon dioxide decreased nitrate.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- 4–5‐week‐old plantse7
- Treatment
- Enhanced carbon dioxidee0
- Outcome
- nitratee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e7“In 4–5‐week‐old plants, the current rate of growth was similar in ambient and enhanced carbon dioxide (≈ 0·4 g –1 d –1 )”
e0“Enhanced carbon dioxide only led to small changes of NR activity, nitrate decreased, and overall amino acids were not significantly increased”
Claim · model-written summary
In 4–5‐week‐old plants, enhanced carbon dioxide produced only small changes in NR activity and no significant increase in overall amino acids.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- 4–5‐week‐old plantse7
- Treatment
- Enhanced carbon dioxidee0
- Outcome
- overall amino acidse0
- Direction
- not significantly increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e7“In 4–5‐week‐old plants, the current rate of growth was similar in ambient and enhanced carbon dioxide (≈ 0·4 g –1 d –1 )”
e0“Enhanced carbon dioxide only led to small changes of NR activity, nitrate decreased, and overall amino acids were not significantly increased”
Claim · model-written summary
Enhanced carbon dioxide raised the nitrate level in seedlings.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- Young seedlingse3
- Treatment
- Enhanced carbon dioxidee2
- Outcome
- nitrate levele1
- Direction
- highere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e2“Enhanced carbon dioxide led to larger increases of NR activity and NR activation, a 2–3‐fold increase of glutamine, a 50% increase of glutamate, and a 2–3‐fold increase in minor amino acids”
e1“It also led to a higher nitrate level”
e3“Young seedlings had a high growth rate (0·5 g –1 d –1 ) in ambient carbon dioxide, that was increased by another 20% in enhanced carbon dioxide”
Claim · model-written summary
Nitrate decreased faster in enhanced than in ambient carbon dioxide in roots, while nitrite increased.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- rootse5
- Outcome
- nitratee5
- Direction
- faster decreasee5
- Comparator
- ambient carbon dioxidee5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e5“a faster decrease of nitrate than in ambient carbon dioxide, and an increase of nitrite in the roots”
Claim · model-written summary
Enhanced carbon dioxide may stimulate nitrate uptake, nitrate assimilation and amino acid synthesis in seedlings, which may support faster growth.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- seedlingse4
- Outcome
- nitrate uptake, nitrate assimilation and amino acid synthesise4
- Qualifier
- a very effective stimulatione4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“young tobacco plants”
e4“enhanced carbon dioxide leads to a very effective stimulation of nitrate uptake, nitrate assimilation and amino acid synthesis in seedlings”
The same questions in other papers
co2 · molecular: metabolites · Nicotiana tabacum (tobacco)Results differ
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- positive
- no effect
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11 papers in the same direction as this paper · 6 in the opposite direction
- no effect
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See all 18 papers →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.