Abstract
In the phytotron experiment, the effect of elevated atmospheric CO2 (EC, 750 μmol mol-1) on the drought tolerance was studied in two winter varieties (Mv Mambo, tolerant; Mv Regiment, moderately tolerant) and in one spring variety of wheat (Lona, sensitive to drought). Changes in net photosynthetic rate (P N), stomatal conductance, transpiration, wateruse efficiency, effective quantum yield of photosystem II, and activities of glutathione reductase (GR), glutathione-Stransferase (GST), guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were monitored during water withdrawal. Drought caused a faster decline of P N at EC, leading to the lower assimilation rates under severe drought compared with ambient CO2 (NC). In the sensitive variety, P N remained high for a longer period at EC. The growth at EC resulted in a more relaxed activation level of the antioxidant enzyme system in all three varieties, with very low activities of GR, GST, APX, and POD. The similar, low values were due to decreases in the varieties which had higher ambient values. A parallel increase of CAT was, however, recorded in two varieties. As the decline in P N was faster at EC under drought but there was no change in the rate of electron transport compared to NC values, a higher level of oxidative stress was induced. This triggered a more pronounced, general response in the antioxidant enzyme system at EC, leading to very high activities of APX, CAT, and GST in all three varieties. The results indicated that EC had generally favourable effects on the development and stress tolerance of plants, although bigger foliage made the plants more prone to the water loss. The relaxation of the defence mechanisms increased potentially the risk of damage due to the higher level of oxidative stress at EC under severe drought compared with NC.
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Claims 10
Claim · model-written summary
Under drought, elevated CO2 caused faster photosynthetic decline and lower assimilation under severe drought than ambient CO2.
- Taxon
- wheat
Triticum aestivumt0 - Treatment
- ECe0
- Outcome
- P Ne0
- Direction
- faster declinee0
- Qualifier
- under severe droughte0
- Comparator
- ambient CO2 (NC)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought caused a faster decline of P N at EC, leading to the lower assimilation rates under severe drought compared with ambient CO2 (NC).”
t0“wheat”
Claim · model-written summary
In the sensitive variety, photosynthetic rate stayed high longer at elevated CO2.
- Taxon
- wheatTriticum aestivumt0
- Material
- sensitive varietye0
- Treatment
- ECe0
- Outcome
- P Ne0
- Direction
- remained high for a longer periode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the sensitive variety, P N remained high for a longer period at EC.”
t0“wheat”
Claim · model-written summary
Elevated CO2 lowered GR, GST, APX and POD activity in all three wheat varieties.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- ECe0
- Outcome
- activities of GR, GST, APX, and PODe0
- Direction
- very lowe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The growth at EC resulted in a more relaxed activation level of the antioxidant enzyme system in all three varieties, with very low activities of GR, GST, APX, and POD.”
t0“wheat”
Claim · model-written summary
CAT activity increased in two varieties at elevated CO2.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A parallel increase of CAT was, however, recorded in two varieties.”
t0“wheat”
Claim · model-written summary
Electron transport rate did not change at elevated CO2 under drought versus ambient CO2.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated atmospheric CO2t1
- Outcome
- rate of electron transporte0
- Direction
- no changee0
- Comparator
- NC valuese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no change in the rate of electron transport compared to NC values”
t0“wheat”
t1“elevated atmospheric CO2”
Claim · model-written summary
Elevated CO2 under drought induced a higher level of oxidative stress.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- elevated atmospheric CO2t1
- Outcome
- oxidative stresse0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a higher level of oxidative stress was induced.”
t0“wheat”
t1“elevated atmospheric CO2”
Claim · model-written summary
Under drought, elevated CO2 produced very high APX, CAT and GST activities in all three varieties.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- activities of APX, CAT, and GSTe0
- Direction
- very highe0
- Qualifier
- all three varietiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leading to very high activities of APX, CAT, and GST in all three varieties.”
t0“wheat”
Claim · model-written summary
Elevated CO2 generally favored plant development and stress tolerance.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- ECe0
- Outcome
- development and stress tolerancee0
- Direction
- favourable effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“EC had generally favourable effects on the development and stress tolerance of plants”
t0“wheat”
Claim · model-written summary
Larger foliage at elevated CO2 increased susceptibility to water loss.
- Taxon
- wheatTriticum aestivumt0
- Organ / stage
- foliagee0
- Outcome
- water losse0
- Direction
- more pronee0
- Qualifier
- bigger foliagee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“bigger foliage made the plants more prone to the water loss.”
t0“wheat”
Claim · model-written summary
Relaxed defenses could increase oxidative damage risk under severe drought at elevated CO2.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- EC under severe droughte0
- Outcome
- risk of damagee0
- Direction
- increased potentiallye0
- Qualifier
- relaxation of the defence mechanismse0
- Comparator
- NCe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The relaxation of the defence mechanisms increased potentially the risk of damage due to the higher level of oxidative stress at EC under severe drought compared with NC.”
t0“wheat”
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