Abstract
The effect of temporary droughts on photosynthesis, total conductance to water vapour, intercellular CO2 concentration, CO2 compensation point, light-response curves, photorespiration, dark respiration, chlorophyll content, and ribulose 1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) activity has been examined in nodulated alfalfa plants (Medicago saliva cv. Aragón). Plants were subjected to moderate (S1/RS1) or severe (S2/RS2) cycles of drought (drought/recovery). Photosynthetic light-response curves showed decreased light-saturated photosynthetic capacity and decreased apparent quantum yield. Upon rewatering, photosynthesis did not recover whereas conductance did in moderately stressed plants. Calculated electron transport rate also declined in drought-stressed plants, but upon rewatering, moderately stressed plants exhibited a total recovery. Comparison of photosynthetic intercellular CO2 response curves in well-watered and stressed leaves led to the assertion that effects in chloroplast metabolism contribute significantly to photosynthetic inhibition. Although the validity of this entire line of research has been questioned by some recent studies because the occurrence of heterogeneous stomatal closure would affect these curves, in our case, the effect of water stress was investigated in experimental systems where stomata had been removed. Measurements of in vitro RuBP carboxylase activity and protein content showed a strong decline during drought treatments and upon rewatering no recovery was observed. Therefore, our results suggest the major implication of non-stomatal factors in the decline of photosynthesis in alfalfa plants under cyclic drought conditions.
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Claims 9
Claim · model-written summary
Drought decreased light-saturated photosynthetic capacity and apparent quantum yield.
- Taxon
- Alfalfa Plants
Medicago sativat0 - Treatment
- Droughtst0
- Outcome
- light-saturated photosynthetic capacity and decreased apparent quantum yielde0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Photosynthetic light-response curves showed decreased light-saturated photosynthetic capacity and decreased apparent quantum yield.”
t0“Temporary Droughts on Photosynthesis of Alfalfa Plants”
Claim · model-written summary
Photosynthesis failed to recover after rewatering moderately stressed plants.
- Taxon
- plantsViridiplantaee0
- Treatment
- rewateringe0
- Outcome
- photosynthesise0
- Direction
- did not recovere0
- Qualifier
- moderately stressed plantse0
Not reportedComparator
Verbatim
e0“Upon rewatering, photosynthesis did not recover whereas conductance did in moderately stressed plants.”
Claim · model-written summary
Conductance recovered after rewatering moderately stressed plants.
- Taxon
- plantsViridiplantaee0
- Treatment
- rewateringe0
- Outcome
- conductancee0
- Direction
- dide0
- Qualifier
- moderately stressed plantse0
Not reportedComparator
Verbatim
e0“Upon rewatering, photosynthesis did not recover whereas conductance did in moderately stressed plants.”
Claim · model-written summary
Calculated electron transport rate declined under drought.
- Taxon
- plantsViridiplantaee0
- Treatment
- drought-stressede0
- Outcome
- Calculated electron transport ratee0
- Direction
- declinede0
Not reportedComparator
Verbatim
e0“Calculated electron transport rate also declined in drought-stressed plants”
Claim · model-written summary
Calculated electron transport rate recovered fully after rewatering in moderately stressed plants.
- Taxon
- plantsViridiplantaee0
- Treatment
- rewateringe0
- Outcome
- total recoverye0
- Direction
- total recoverye0
- Qualifier
- moderately stressed plantse0
Not reportedComparator
Verbatim
e0“but upon rewatering, moderately stressed plants exhibited a total recovery.”
Claim · model-written summary
Chloroplast metabolic effects contribute significantly to drought-induced photosynthetic inhibition.
- Taxon
- alfalfa plantsMedicago sativat0
- Outcome
- photosynthetic inhibitione0
- Qualifier
- effects in chloroplast metabolisme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“effects in chloroplast metabolism contribute significantly to photosynthetic inhibition.”
t0“Alfalfa Plants”
Claim · model-written summary
RuBP carboxylase activity declined strongly during drought and did not recover on rewatering.
- Taxon
- alfalfa plantsMedicago sativat0
- Treatment
- drought treatmentse0
- Gene
- RuBP carboxylasee0
- Outcome
- RuBP carboxylase activitye0
- Direction
- strong declinee0
- Qualifier
- upon rewatering no recovery was observede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Measurements of in vitro RuBP carboxylase activity and protein content showed a strong decline during drought treatments and upon rewatering no recovery was observed.”
t0“Alfalfa Plants”
Claim · model-written summary
Protein content declined strongly during drought and did not recover on rewatering.
- Taxon
- alfalfa plantsMedicago sativat0
- Treatment
- drought treatmentse0
- Outcome
- protein contente0
- Direction
- strong declinee0
- Qualifier
- upon rewatering no recovery was observede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Measurements of in vitro RuBP carboxylase activity and protein content showed a strong decline during drought treatments and upon rewatering no recovery was observed.”
t0“Alfalfa Plants”
Claim · model-written summary
Non-stomatal factors appear to be the major contributors to photosynthetic decline under cyclic drought.
- Taxon
- alfalfa plantsMedicago sativae0
- Treatment
- cyclic drought conditionse0
- Outcome
- decline of photosynthesise0
- Qualifier
- non-stomatal factorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“major implication of non-stomatal factors in the decline of photosynthesis in alfalfa plants under cyclic drought conditions.”
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