Abstract
Holm oak (Quercus ilex L.) is native to hot, dry Mediterranean forests where limited water availability often reduces photosynthesis in many species, and forest fires are frequent. Holm oaks resprout after a disturbance, with improved photosynthetic activity and water relations compared with unburned plants. To better understand the role of water availability in this improvement, watering was withheld from container-grown plants, either intact (controls) or resprouts after excision of the shoot, to gradually obtain a wide range of soil water availabilities. At high water availability, gas exchange rates did not differ between controls and resprouts. At moderate soil dryness, net photosynthesis of control plants decreased as a result of increased stomatal limitation, whereas gas exchange rates of resprouts, which had higher midday and predawn leaf water potentials, were unchanged. Under severe drought, resprouts showed a less marked decline in gas exchange than controls and maintained photosystem II integrity, as indicated by chlorophyll fluorescence measurements. Photosynthesis was down-regulated in both plant types in response to reduced CO2 availability caused by high stomatal limitation. Lower non-stomatal limitations in resprouts than in control plants, as evidenced by higher carboxylation velocity and the capacity for ribulose-1,5-bisphosphate regeneration, conferred greater drought resistance under external constraints similar to summer conditions at midday.
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Claims 8
Claim · model-written summary
At high water availability, gas exchange rates were similar in controls and resprouts.
- Taxon
- Quercus ilex
Quercus ilext0 - Outcome
- gas exchange ratese0
- Direction
- did not differe0
- Qualifier
- At high water availabilitye0
- Comparator
- controls and resproutse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At high water availability, gas exchange rates did not differ between controls and resprouts.”
t0“Quercus ilex”
Claim · model-written summary
At moderate soil dryness, control-plant net photosynthesis decreased through increased stomatal limitation.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- control plantse0
- Outcome
- net photosynthesise0
- Direction
- decreasede0
- Qualifier
- increased stomatal limitatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At moderate soil dryness, net photosynthesis of control plants decreased as a result of increased stomatal limitation”
t0“Quercus ilex”
Claim · model-written summary
At moderate soil dryness, resprout gas exchange rates remained unchanged.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- resproutse0
- Outcome
- gas exchange ratese0
- Direction
- unchangede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“gas exchange rates of resprouts, which had higher midday and predawn leaf water potentials, were unchanged.”
t0“Quercus ilex”
Claim · model-written summary
Resprouts had higher midday and predawn leaf water potentials at moderate soil dryness.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- resproutse0
- Outcome
- midday and predawn leaf water potentialse0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“resprouts, which had higher midday and predawn leaf water potentials”
t0“Quercus ilex”
Claim · model-written summary
Under severe drought, gas exchange declined less in resprouts than controls.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- resproutse0
- Outcome
- gas exchangee0
- Direction
- less marked declinee0
- Comparator
- controlse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under severe drought, resprouts showed a less marked decline in gas exchange than controls”
t0“Quercus ilex”
Claim · model-written summary
Under severe drought, resprouts maintained photosystem II integrity.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- resproutse1
- Outcome
- photosystem II integritye0
- Direction
- maintainede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“maintained photosystem II integrity, as indicated by chlorophyll fluorescence measurements.”
e1“Under severe drought, resprouts showed”
t0“Quercus ilex”
Claim · model-written summary
Photosynthesis was down-regulated in both plant types as reduced CO2 availability resulted from high stomatal limitation.
- Taxon
- Quercus ilexQuercus ilext0
- Outcome
- Photosynthesise0
- Direction
- down-regulatede0
- Qualifier
- reduced CO2 availability caused by high stomatal limitatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Photosynthesis was down-regulated in both plant types in response to reduced CO2 availability caused by high stomatal limitation.”
t0“Quercus ilex”
Claim · model-written summary
Resprouts had lower non-stomatal limitations than controls, with greater carboxylation velocity and ribulose-1,5-bisphosphate regeneration capacity.
- Taxon
- Quercus ilexQuercus ilext0
- Material
- resproutse0
- Outcome
- non-stomatal limitationse0
- Direction
- Lowere0
- Qualifier
- higher carboxylation velocity and the capacity for ribulose-1,5-bisphosphate regeneratione0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lower non-stomatal limitations in resprouts than in control plants, as evidenced by higher carboxylation velocity and the capacity for ribulose-1,5-bisphosphate regeneration”
t0“Quercus ilex”