Abstract
While nitrogen (N) derived from ammonium would be energetically less expensive than nitrate-derived N, the use of ammonium-based fertilizer is limited by the potential for toxicity symptoms. Nevertheless, previous studies have shown that exposure to elevated CO2 favors ammonium assimilation in plants. However, little is known about the impact of different forms of N fertilizer on stomatal opening and their consequent effects on CO2 and H2O diffusion in wheat plants exposed to ambient and elevated CO2. In this paper we have examined the response of the photosynthetic machinery of durum wheat (Triticum durum, var. Amilcar) grown with different types of N fertilizer (NO3-, NH4+ and NH4NO3) at 400 versus 700 ppm of CO2. Alongside gas exchange and photochemical parameters, the expression of genes involved in CO2 (PIP1.1 and PIP2.3) and H2O (TIP1) diffusion as well as key C and N primary metabolism enzymes and metabolites were studied. Our results show that at 400 ppm CO2, wheat plants fertilized with ammonium as the N source had oxidative stress symptoms and a strong reduction in stomatal conductance, which negatively affected photosynthetic rates. The higher levels of PIP1.1 and PIP 2.3 expression in ammonium-fertilized plants at 400 ppm CO2 might reflect the need to overcome limitations to the CO2 supply to chloroplasts due to restrictions in stomatal conductance. This stomatal limitation might be associated with a strategy to reduce ammonium transport toward leaves. On the other hand, ammonium-fertilized plants at elevated CO2 did not show stress symptoms and no differences were detected in stomatal opening or water use efficiency (WUE). Moreover, similar gene expression of the aquaporins TIP1, PIP1.1 and PIP2.3 in ammonium-fertilized plants grown at 700 ppm compared to nitrate- and ammonium nitrate-plants would suggest that an adjustment in CO2 and H2O diffusion is not required. Therefore, in the absence of a stress context triggered by elevated CO2, ammonium- and ammonium nitrate-fertilized plants were able to increase their photosynthetic rates, which was translated eventually into higher leaf protein content.
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Claims 12
Claim · model-written summary
Ammonium fertilization at 400 ppm CO2 produced oxidative stress symptoms.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- ammonium as the N sourcee0
- Outcome
- oxidative stress symptomse0
- Setting
- 400 ppm CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at 400 ppm CO2, wheat plants fertilized with ammonium as the N source had oxidative stress symptoms”
Claim · model-written summary
Ammonium fertilization at 400 ppm CO2 strongly reduced stomatal conductance.
- Taxon
- wheatTriticum aestivume0
- Treatment
- ammonium as the N sourcee0
- Outcome
- stomatal conductancee0
- Direction
- reductione0
- Setting
- 400 ppm CO2e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at 400 ppm CO2, wheat plants fertilized with ammonium as the N source had oxidative stress symptoms and a strong reduction in stomatal conductance”
Claim · model-written summary
Reduced stomatal conductance negatively affected photosynthetic rates.
- Taxon
- durum wheat
Triticum turgidum subsp. durumt0 - Outcome
- photosynthetic ratese0
- Qualifier
- reduction in stomatal conductancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a strong reduction in stomatal conductance, which negatively affected photosynthetic rates”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Ammonium fertilization at 400 ppm CO2 was associated with higher PIP1.1 and PIP 2.3 expression.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium-fertilizede0
- Gene
- PIP1.1 and PIP 2.3e0
- Outcome
- PIP1.1 and PIP 2.3 expressione0
- Direction
- highere0
- Setting
- 400 ppm CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The higher levels of PIP1.1 and PIP 2.3 expression in ammonium-fertilized plants at 400 ppm CO2”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Higher PIP expression might compensate for restricted CO2 delivery to chloroplasts.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Outcome
- CO2 supply to chloroplastse0
- Qualifier
- restrictions in stomatal conductancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“might reflect the need to overcome limitations to the CO2 supply to chloroplasts due to restrictions in stomatal conductance”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Stomatal limitation might reduce ammonium transport toward leaves.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Organ / stage
- leavese0
- Outcome
- ammonium transport toward leavese0
- Qualifier
- stomatal limitatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This stomatal limitation might be associated with a strategy to reduce ammonium transport toward leaves”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Ammonium-fertilized plants at elevated CO2 showed no stress symptoms.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium-fertilizede0
- Outcome
- stress symptomse0
- Setting
- elevated CO2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium-fertilized plants at elevated CO2 did not show stress symptoms”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
At elevated CO2, ammonium-fertilized plants showed no difference in stomatal opening.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium-fertilizede0
- Outcome
- stomatal openinge0
- Direction
- no differencese0
- Setting
- elevated CO2e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium-fertilized plants at elevated CO2 did not show stress symptoms and no differences were detected in stomatal opening or water use efficiency (WUE)”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
At elevated CO2, ammonium-fertilized plants showed no difference in water use efficiency.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium-fertilizede0
- Outcome
- water use efficiency (WUE)e0
- Direction
- no differencese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium-fertilized plants at elevated CO2 did not show stress symptoms and no differences were detected in stomatal opening or water use efficiency (WUE)”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
At 700 ppm CO2, aquaporin gene expression was similar under ammonium, nitrate, and ammonium nitrate fertilization.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium-fertilizede0
- Gene
- TIP1, PIP1.1 and PIP2.3e0
- Outcome
- gene expressione0
- Direction
- similare0
- Comparator
- nitrate- and ammonium nitrate-plantse0
- Setting
- 700 ppme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“similar gene expression of the aquaporins TIP1, PIP1.1 and PIP2.3 in ammonium-fertilized plants grown at 700 ppm compared to nitrate- and ammonium nitrate-plants”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Ammonium and ammonium nitrate fertilization increased photosynthetic rates under elevated CO2.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Treatment
- ammonium- and ammonium nitrate-fertilizede0
- Outcome
- photosynthetic ratese0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ammonium- and ammonium nitrate-fertilized plants were able to increase their photosynthetic rates”
t0“durum wheat (Triticum durum, var. Amilcar)”
Claim · model-written summary
Increased photosynthesis under elevated CO2 translated into higher leaf protein content.
- Taxon
- durum wheatTriticum turgidum subsp. durumt0
- Organ / stage
- leafe0
- Outcome
- leaf protein contente0
- Qualifier
- photosynthetic ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increase their photosynthetic rates, which was translated eventually into higher leaf protein content”
t0“durum wheat (Triticum durum, var. Amilcar)”
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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.