Abstract
We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O(2) electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO(2) saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O(2) per mole photons) was slightly, if at all, affected by mild water stress (>-1.5 megapascals). (c) Severe water stress (<-1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (F(v)/F(m)) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred.
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Claims 9
Claim · model-written summary
The CO(2) saturated photosynthetic rate at high light was the most water stress sensitive measured parameter.
- Taxon
- Xanthium strumarium and Helianthus annuus
Helianthus annuus
Xanthium strumariumt0 - Outcome
- CO(2) saturated rate of photosynthesis at high lighte0
- Direction
- most water stress sensitivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The CO(2) saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured.”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Mild water stress affected apparent quantum yield only slightly, if at all.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- mild water stress (>-1.5 megapascals)e0
- Outcome
- apparent quantum yielde0
- Qualifier
- slightly, if at alle0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The apparent quantum yield (moles O(2) per mole photons) was slightly, if at all, affected by mild water stress (>-1.5 megapascals).”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Severe water stress reduced photosynthetic quantum yield in sun and shade.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- Severe water stress (<-1.5 megapascals)e0
- Outcome
- quantum yield of photosynthesise0
- Direction
- reducede0
- Qualifier
- sun or shadee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Severe water stress (<-1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade.”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
The light independent quantum yield reduction was not associated with reduced 77 K fluorescence.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Outcome
- reduction of quantum yielde0
- Comparator
- 77 K fluorescence (F(v)/F(m))e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (F(v)/F(m))”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Water stressed sun leaves had a greatly exaggerated diel fluctuation in 77 K fluorescence relative to controls.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- water stressed leavese0
- Outcome
- diel fluctuation in 77 K fluorescencee0
- Direction
- greatly exaggeratede0
- Qualifier
- enhanced decline in 77 K fluorescence in the morninge0
- Comparator
- sun-exposed control leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning.”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Fluorescence recovery rate was similar in control and water stressed leaves.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- water stressed leavese0
- Outcome
- rate of recoverye0
- Direction
- similare0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The rate of recovery was similar in both control and water stressed leaves.”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Shaded leaves showed no change in 77 K fluorescence whether water stressed or not.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- water stresse0
- Outcome
- 77 K fluorescencee0
- Direction
- no changee0
- Qualifier
- Shaded leavese0
- Comparator
- note0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not.”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Plants did not recover after acute water stress severe enough to reduce quantum yield.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- acute water stresse0
- Outcome
- did not recovere0
- Qualifier
- severe enough to reduce the quantum yielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not recover from acute water stress severe enough to reduce the quantum yield”
t0“Xanthium strumarium and Helianthus annuus”
Claim · model-written summary
Plants did not recover after chronic stress lasting until light dependent primary photochemical damage occurred.
- Taxon
- Xanthium strumarium and Helianthus annuusHelianthus annuusXanthium strumariumt0
- Treatment
- chronic water stresse0
- Outcome
- did not recovere0
- Qualifier
- light dependent damage to primary photochemistry occurrede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred.”
t0“Xanthium strumarium and Helianthus annuus”
The same questions in other papers
drought · physiology: photosynthesis · Helianthus annuus (common sunflower)Positive and negative results
21 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- no effect
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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.