Abstract
The influence of long-term water deficit on photosynthesis, electron transport and carbon metabolism of sunflower leaves has been examined. Water deficit was imposed from flower bud formation up to the stage of full flowering in the field on two sunflower hybrids with different drought tolerance. CO2 assimilation and stomatal conductance of the intact leaves, determined at atmospheric CO2 and full sunlight (1500-2000 mu mol quanta m(-2) s(-1)), decreased with water deficit, Maximum quantum efficiency of PSII (F-v/F-m) and relative quantum yield of PSII (Phi(II)) determined under similar experimental conditions, did not change significantly in severely stressed leaves. The strong inhibition of the plateau region of the light response curve, determined at high CO2 (5%) in water-deficient sunflower leaves, indicates that photosynthesis is also limited by non-stomatal factors. The decreased slope and the plateau of the CO2 response curves show that the capacity of carboxylation and RuBP regeneration decreased in severely stressed intact leaves. Rubisco specific activity decreased in severely stressed leaves, but Rubisco content increased under prolonged drought. The increase of Rubisco content was significantly higher in leaves of the drought-tolerant sunflower hybrid indicating that a higher Rubisco content could be one factor in conferring better acclimation and higher drought tolerance.
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Claims 9
Claim · model-written summary
Water deficit decreased CO2 assimilation and stomatal conductance in sunflower leaves.
- Taxon
- sunflower
Helianthus annuust0 - Organ / stage
- intact leavese0
- Treatment
- water deficite0
- Outcome
- CO2 assimilation and stomatal conductancee0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO2 assimilation and stomatal conductance of the intact leaves, determined at atmospheric CO2 and full sunlight (1500-2000 mu mol quanta m(-2) s(-1)), decreased with water deficit”
t0“sunflower”
Claim · model-written summary
Severe water stress did not significantly change maximum PSII quantum efficiency or relative PSII quantum yield.
- Taxon
- sunflowerHelianthus annuust0
- Organ / stage
- leavese0
- Treatment
- severely stressede0
- Outcome
- Maximum quantum efficiency of PSII (F-v/F-m) and relative quantum yield of PSII (Phi(II))e0
- Direction
- did not changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Maximum quantum efficiency of PSII (F-v/F-m) and relative quantum yield of PSII (Phi(II)) determined under similar experimental conditions, did not change significantly in severely stressed leaves.”
t0“sunflower”
Claim · model-written summary
The high CO2 light-response plateau was strongly inhibited in water-deficient sunflower leaves.
- Taxon
- sunflowerHelianthus annuuse0
- Organ / stage
- leavese0
- Treatment
- water-deficiente0
- Outcome
- plateau region of the light response curvee0
- Direction
- inhibitione0
- Qualifier
- high CO2 (5%)e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The strong inhibition of the plateau region of the light response curve, determined at high CO2 (5%) in water-deficient sunflower leaves”
Claim · model-written summary
Carboxylation capacity decreased in severely stressed intact leaves.
- Taxon
- sunflowerHelianthus annuust0
- Organ / stage
- intact leavese0
- Treatment
- severely stressede0
- Outcome
- capacity of carboxylatione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the capacity of carboxylation and RuBP regeneration decreased in severely stressed intact leaves.”
t0“sunflower”
Claim · model-written summary
RuBP regeneration decreased in severely stressed intact leaves.
- Taxon
- sunflowerHelianthus annuust0
- Organ / stage
- intact leavese0
- Treatment
- severely stressede0
- Outcome
- RuBP regeneratione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the capacity of carboxylation and RuBP regeneration decreased in severely stressed intact leaves.”
t0“sunflower”
Claim · model-written summary
Rubisco specific activity decreased in severely stressed leaves.
- Taxon
- sunflowerHelianthus annuust0
- Organ / stage
- leavese0
- Treatment
- severely stressede0
- Gene
- Rubiscoe0
- Outcome
- Rubisco specific activitye0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rubisco specific activity decreased in severely stressed leaves”
t0“sunflower”
Claim · model-written summary
Rubisco content increased under prolonged drought.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- prolonged droughte0
- Gene
- Rubiscoe0
- Outcome
- Rubisco contente0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rubisco content increased under prolonged drought.”
t0“sunflower”
Claim · model-written summary
Rubisco content increased significantly more in drought-tolerant sunflower hybrid leaves.
- Taxon
- sunflowerHelianthus annuuse0
- Material
- drought-tolerant sunflower hybride0
- Organ / stage
- leavese0
- Outcome
- Rubisco contente0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increase of Rubisco content was significantly higher in leaves of the drought-tolerant sunflower hybrid”
Claim · model-written summary
Higher Rubisco content could contribute to better acclimation and drought tolerance.
- Taxon
- sunflowerHelianthus annuust0
- Gene
- Rubiscoe0
- Outcome
- better acclimation and higher drought tolerancee0
- Qualifier
- could be one factore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a higher Rubisco content could be one factor in conferring better acclimation and higher drought tolerance.”
t0“sunflower”
The same questions in other papers
drought · physiology: photosynthesis · Helianthus annuus (common sunflower)Positive and negative results
2 papers in the same direction as this paper · 22 in the opposite direction
- negative
- negative
- negative
21 papers more in this group
See all 25 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.