Abstract
Drought is a major environmental constraint that disrupts photosynthetic processes. This study investigated the effects of foliar-applied commercial humic acid (HA) at different concentrations (1, 3 and 5 mg/mL) on the photosynthetic apparatus of sweet basil (Ocimum basilicum L. Italiano classico) under PEG-induced stress. The responses of the photosynthetic machinery were evaluated using chlorophyll a fluorescence analyses (JIP-test and PAM), leaf pigment composition, and assessments of membrane integrity. Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired QA− reoxidation, reduced open PSII reaction centers (qP), diminished electron transport (ETo/RC, REo/RC), and substantial declines in performance indices (PIABS, PItotal). Energy dissipation increased (DI0/RC), with regulated energy losses (ΦNPQ) rising more strongly than non-regulated losses (ΦNO). Drought also elevated oxidative stress markers (MDA and H2O2), leading to enhanced membrane injury. Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress. This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides and increased the proportion of open reaction centers (qP). Improved PSII photochemistry corresponded with more efficient QA− reoxidation, facilitated its interaction with plastoquinone, and caused the overall stabilization of photosynthetic functions under drought. The protective effects of HA were also evident for both PSI subpopulations. The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC). In contrast, lower HA concentrations (1 and 3 mg/mL) provided insufficient protection. This study clearly demonstrates that HA enhances drought tolerance in basil in a concentration-dependent manner by protecting the structural and functional integrity of the photosynthetic apparatus, supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions.
Abstract from the paper’s OpenAlex record; open copy licensed cc-by. 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 20
Claim · model-written summary
Drought impaired PSII donor and acceptor function, including QA− reoxidation.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)
Ocimum basilicume1 - Treatment
- Drought stresse0
- Outcome
- QA− reoxidatione0
- Direction
- impairede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired QA− reoxidation”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Drought reduced open PSII centers.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- Drought stresse2
- Outcome
- open PSII reaction centers (qP)e0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced open PSII reaction centers (qP)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
e2“Drought stress caused pronounced alterations”
Claim · model-written summary
Drought diminished electron transport.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- Drought stresse2
- Outcome
- electron transport (ETo/RC, REo/RC)e0
- Direction
- diminishede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“diminished electron transport (ETo/RC, REo/RC)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
e2“Drought stress caused pronounced alterations”
Claim · model-written summary
Drought reduced PSII performance indices.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- Drought stresse2
- Outcome
- performance indices (PIABS, PItotal)e0
- Direction
- declinese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“substantial declines in performance indices (PIABS, PItotal)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
e2“Drought stress caused pronounced alterations”
Claim · model-written summary
Drought increased energy dissipation.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Outcome
- Energy dissipatione0
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Energy dissipation increased (DI0/RC)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Regulated energy losses rose more strongly than non-regulated losses.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Outcome
- regulated energy losses (ΦNPQ)e0
- Direction
- rising more stronglye0
- Comparator
- non-regulated losses (ΦNO)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“regulated energy losses (ΦNPQ) rising more strongly than non-regulated losses (ΦNO)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Drought elevated MDA and H2O2 oxidative-stress markers.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- Droughte0
- Outcome
- oxidative stress markers (MDA and H2O2)e0
- Direction
- elevatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought also elevated oxidative stress markers (MDA and H2O2)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Drought enhanced membrane injury.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- Droughte2
- Outcome
- membrane injurye0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leading to enhanced membrane injury”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
e2“Drought also elevated oxidative stress markers”
Claim · model-written summary
5 mg/mL humic acid provided the strongest drought protection.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- 5 mg/mL HAe0
- Outcome
- protection against drought stresse0
- Direction
- most effectivee0
- Comparator
- tested concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
5 mg/mL humic acid mitigated drought injury to PSII donor and acceptor sides.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume2
- Treatment
- 5 mg/mL HAe1
- Outcome
- PEG-induced damage on both PSII donor and acceptor sidese0
- Direction
- mitigatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides”
e1“5 mg/mL HA”
e2“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
5 mg/mL humic acid increased open reaction centers.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume2
- Treatment
- 5 mg/mL HAe1
- Outcome
- proportion of open reaction centers (qP)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased the proportion of open reaction centers (qP)”
e1“5 mg/mL HA”
e2“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Improved PSII photochemistry accompanied more efficient QA− reoxidation.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- 5 mg/mL HAe2
- Outcome
- QA− reoxidatione0
- Direction
- more efficiente0
- Qualifier
- Improved PSII photochemistrye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Improved PSII photochemistry corresponded with more efficient QA− reoxidation”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
e2“5 mg/mL HA”
Claim · model-written summary
Improved PSII photochemistry facilitated QA− interaction with plastoquinone.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume2
- Outcome
- interaction with plastoquinonee0
- Qualifier
- Improved PSII photochemistrye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“facilitated its interaction with plastoquinone”
e1“Improved PSII photochemistry corresponded with more efficient QA− reoxidation”
e2“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Improved PSII photochemistry stabilized photosynthetic function under drought.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume2
- Outcome
- stabilization of photosynthetic functions under droughte0
- Qualifier
- Improved PSII photochemistrye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“caused the overall stabilization of photosynthetic functions under drought”
e1“Improved PSII photochemistry”
e2“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Humic acid protected both PSI subpopulations.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- HAe0
- Outcome
- protective effectse0
- Direction
- protectivee0
- Qualifier
- both PSI subpopulationse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The protective effects of HA were also evident for both PSI subpopulations”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Enhanced tolerance was associated with CAT, SOD, and APX antioxidant enzyme activation.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Gene
- antioxidant enzymes (CAT, SOD, APX)e0
- Outcome
- enhanced tolerancee0
- Direction
- enhancede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Enhanced tolerance was associated with increased anthocyanin and phenolic content.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Compound
- anthocyaninse0
- Outcome
- enhanced tolerancee0
- Direction
- enhancede0
- Qualifier
- increased levels of anthocyanins and total phenolic content (TPC)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC)”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
The 1 mg/mL humic acid dose provided insufficient drought protection.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- 1e0
- Outcome
- insufficient protectione0
- Direction
- insufficiente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower HA concentrations (1 and 3 mg/mL) provided insufficient protection”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
The 3 mg/mL humic acid dose provided insufficient drought protection.
- Taxon
- sweet basil (Ocimum basilicum L. Italiano classico)Ocimum basilicume1
- Treatment
- 3 mg/mLe0
- Outcome
- insufficient protectione0
- Direction
- insufficiente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower HA concentrations (1 and 3 mg/mL) provided insufficient protection”
e1“sweet basil (Ocimum basilicum L. Italiano classico)”
Claim · model-written summary
Authors propose foliar humic acid to improve basil resilience under water limitation.
- Taxon
- basilOcimum basilicume1
- Outcome
- potential use as a foliar treatment to improve crop resilience under water-limited conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions”
e1“enhances drought tolerance in basil”
The same questions in other papers
other · physiology: photosynthesis · Ocimum basilicum (basil)Results agree
2 papers in the same direction as this paper
- positive
- positive
other · control · Ocimum basilicum (basil)Results agree
2 papers in the same direction as this paper
- positive
- positive
drought · physiology: oxidative · Ocimum basilicum (basil)Results agree
4 papers in the same direction as this paper
- negative
- negative
- negative
1 paper more in this group
See all 5 papers →drought · physiology: photosynthesis · Ocimum basilicum (basil)Results agree
6 papers in the same direction as this paper
- negative
- negative
- negative
3 papers more in this group
See all 7 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.