Abstract
Photosynthetic responses of sunflower plants grown for 52 d in ambient and elevated CO(2) (A=350 or E=700 micromol mol(-1), respectively) and subjected to no (control), mild or severe water deficits after 45 d were analysed to determine if E modifies responses to water deficiency. Relative water content, leaf water potential (Psi(w)) and osmotic potential decreased with water deficiency, but there were no effects of E. Growth in E decreased stomatal conductance (g(s)) and thereby transpiration, but increased net CO(2) assimilation rate (P(n), short-term measurements); therefore, water-use efficiency increased by 230% (control plants) and 380% (severe stress). Growth in E did not affect the response of P(n) to intercellular CO(2) concentration, despite a reduction of 25% in Rubisco content, because this was compensated by a 32% increase in Rubisco activity. Analysis of chlorophyll a fluorescence showed that changes in energy metabolism associated with E were small, despite the decreased Rubisco content. Water deficits decreased g(s) and P(n): metabolic limitation was greater than stomatal at mild and severe deficit and was not overcome by elevated CO(2). The decrease in P(n) with water deficiency was related to lower Rubisco activity rather than to ATP and RuBP contents. Thus, there were no important interactions between CO(2) during growth and water deficit with respect to photosynthetic metabolism. Elevated CO(2 )will benefit sunflower growing under water deficit by marginally increasing P(n), and by slowing transpiration, which will decrease the rate and severity of water deficits, with limited effects on metabolism.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 13
Claim · model-written summary
Water deficit lowered sunflower relative water content, leaf water potential and osmotic potential.
- Taxon
- sunflower
Helianthus annuust0 - Treatment
- water deficiencye0
- Outcome
- Relative water content, leaf water potential (Psi(w)) and osmotic potentiale0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Relative water content, leaf water potential (Psi(w)) and osmotic potential decreased with water deficiency”
t0“sunflower”
Claim · model-written summary
Elevated CO2 did not affect these sunflower water status measures.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- Ee0
- Outcome
- effectse0
- Direction
- no effectse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but there were no effects of E”
t0“sunflower”
Claim · model-written summary
Elevated CO2 decreased sunflower stomatal conductance and transpiration.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- Ee0
- Outcome
- stomatal conductance (g(s)) and thereby transpiratione0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth in E decreased stomatal conductance (g(s)) and thereby transpiration”
t0“sunflower”
Claim · model-written summary
Elevated CO2 increased sunflower net CO2 assimilation rate.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- net CO(2) assimilation ratee0
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but increased net CO(2) assimilation rate (P(n), short-term measurements)”
t0“sunflower”
Claim · model-written summary
Elevated CO2 increased sunflower water-use efficiency by 230% in controls.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- water-use efficiencye0
- Direction
- increasede0
- Value
- 230%e0
- Qualifier
- control plantse0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“water-use efficiency increased by 230% (control plants)”
t0“sunflower”
Claim · model-written summary
Elevated CO2 increased sunflower water-use efficiency by 380% under severe stress.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- water-use efficiencye0
- Direction
- increasede0
- Value
- 380%e0
- Qualifier
- severe stresse0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“water-use efficiency increased by 230% (control plants) and 380% (severe stress)”
t0“sunflower”
Claim · model-written summary
Elevated CO2 reduced sunflower Rubisco content by 25%.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- Rubisco contente0
- Direction
- reductione0
- Value
- 25%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a reduction of 25% in Rubisco content”
t0“sunflower”
Claim · model-written summary
Elevated CO2 increased sunflower Rubisco activity by 32%.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- Rubisco activitye0
- Direction
- increasee0
- Value
- 32%e0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a 32% increase in Rubisco activity”
t0“sunflower”
Claim · model-written summary
Water deficits decreased sunflower stomatal conductance and assimilation.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- Water deficitse0
- Outcome
- g(s) and P(n)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Water deficits decreased g(s) and P(n)”
t0“sunflower”
Claim · model-written summary
Metabolic limitation of sunflower photosynthesis exceeded stomatal limitation at mild and severe deficit.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- metabolic limitatione0
- Direction
- greater thane0
- Comparator
- stomatale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“metabolic limitation was greater than stomatal at mild and severe deficit”
t0“sunflower”
Claim · model-written summary
Elevated CO2 did not overcome the metabolic limitation under water deficit.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- elevated CO(2)e0
- Outcome
- metabolic limitatione0
- Direction
- not overcomee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“metabolic limitation was greater than stomatal at mild and severe deficit and was not overcome by elevated CO(2)”
t0“sunflower”
Claim · model-written summary
Reduced assimilation under water deficiency was linked to lower Rubisco activity.
- Taxon
- sunflowerHelianthus annuust0
- Gene
- Rubiscoe0
- Outcome
- P(n)e0
- Direction
- decreasee0
- Qualifier
- lower Rubisco activitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease in P(n) with water deficiency was related to lower Rubisco activity rather than to ATP and RuBP contents”
t0“sunflower”
Claim · model-written summary
Elevated CO2 is expected to benefit deficit-stressed sunflower by slowing transpiration and marginally increasing assimilation.
- Taxon
- sunflowerHelianthus annuuse0
- Outcome
- benefit sunflower growing under water deficite0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated CO(2 )will benefit sunflower growing under water deficit by marginally increasing P(n), and by slowing transpiration”
The same questions in other papers
drought · physiology: water · Helianthus annuus (common sunflower)Results differ
20 papers in the same direction as this paper · 8 in the opposite direction
- positive
- negative
- positive
25 papers more in this group
See all 29 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.