Abstract
Abstract Although many photosynthesis related processes are known to be controlled by the circadian system, consequent changes in photosynthetic activities are poorly understood. Photosynthesis was investigated during the daily cycle by chlorophyll fluorescence using a PAM fluorometer in Pulmonaria vallarsae subsp. apennina , an understory herb. A standard test consists of a light induction pretreatment followed by light response curve (LRC). Comparison of the major diagnostic parameters collected during day and night showed a nocturnal drop of photosynthetic responses, more evident in water-limited plants and consisting of: (i) strong reduction of flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (J max , ETR EM ) and effective PSII quantum yield (Φ PSII ); (ii) strong enhancement of nonphotochemical quenching ( NPQ ) and (iii) little or no change in photochemical quenching qP , maximum quantum yield of linear electron transport ( Φ ), and shape of LRC ( θ ). A remarkable feature of day/night LRCs at moderate to high irradiance was their linear-parallel course in double-reciprocal plots. Photosynthesis was also monitored in plants subjected to 2–3 days of continuous darkness (“long night”). In such conditions, plants exhibited high but declining peaks of photosynthetic activity during subjective days and a low, constant value with elevated NPQ during subjective night tests. The photosynthetic parameters recorded in subjective days in artificial darkness resembled those under natural day conditions. On the basis of the evidence, we suggest a circadian component and a biochemical feedback inhibition to explain the night depression of photosynthesis in P. vallarsae .
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Claims 8
Claim · model-written summary
Night responses showed strong reductions in flash-induced fluorescence peaks, maximum electron transport rate and effective PSII yield, especially under water limitation.
- Taxon
- Pulmonaria vallarsae subsp. apennina
Pulmonaria vallarsaee1 - Outcome
- flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (J max , ETR EM ) and effective PSII quantum yield (Φ PSII )e0
- Direction
- reductione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“strong reduction of flash-induced fluorescence peaks (FIP), maximum linear electron transport rate (J max , ETR EM ) and effective PSII quantum yield (Φ PSII )”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
Night responses strongly enhanced nonphotochemical quenching.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- nonphotochemical quenching ( NPQ )e0
- Direction
- enhancemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“strong enhancement of nonphotochemical quenching ( NPQ )”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
Photochemical quenching, maximum quantum yield and light-response-curve shape changed little or not at night.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- photochemical quenching qP , maximum quantum yield of linear electron transport ( Φ ), and shape of LRC ( θ )e0
- Direction
- little or no changee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“little or no change in photochemical quenching qP , maximum quantum yield of linear electron transport ( Φ ), and shape of LRC ( θ )”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
Day-night light-response curves were linear and parallel in double-reciprocal plots at moderate to high irradiance.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- linear-parallel course in double-reciprocal plotse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A remarkable feature of day/night LRCs at moderate to high irradiance was their linear-parallel course in double-reciprocal plots”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
During continuous darkness, subjective-day photosynthetic peaks were high but declining.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- peaks of photosynthetic activitye0
- Direction
- declininge0
- Qualifier
- subjective dayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“plants exhibited high but declining peaks of photosynthetic activity during subjective days”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
During continuous darkness, subjective-night photosynthetic activity stayed low and constant with elevated NPQ.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- low, constant value with elevated NPQe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a low, constant value with elevated NPQ during subjective night tests”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
Subjective-day parameters in continuous darkness resembled natural-day parameters.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- photosynthetic parameterse0
- Comparator
- natural day conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The photosynthetic parameters recorded in subjective days in artificial darkness resembled those under natural day conditions”
e1“Pulmonaria vallarsae subsp. apennina”
Claim · model-written summary
Authors propose circadian regulation and biochemical feedback inhibition for night depression of photosynthesis.
- Taxon
- Pulmonaria vallarsae subsp. apenninaPulmonaria vallarsaee1
- Outcome
- night depression of photosynthesise0
- Qualifier
- a circadian component and a biochemical feedback inhibitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we suggest a circadian component and a biochemical feedback inhibition to explain the night depression of photosynthesis”
e1“Pulmonaria vallarsae subsp. apennina”