Abstract
Abstract Melatonin can mitigate the adverse effects of salt stress in plants, but the combined effects of it and bacterial bio-stimulants on enhancing plant resilience to salinity remain poorly understood. To fill in such a knowledge gap, we investigated the interaction between melatonin and bacterial bio-stimulants on the growth, productivity, and physiological characteristics of Calendula officinalis seedlings under salt stress. Using a pot-sand culture method, we tested various concentrations of exogenous melatonin (distilled water, 50, 100 µM) combined with a bacterial mixture (5 ml/pot at 10 8 CFU/ml) of Azotobacter chroococcum , Bacillus megaterium , and Pseudomonas fluorescens . The seedlings were subjected to different saline irrigation levels with NaCl (tap water, 42.8, 85.6, and 128.3 mM) over two growing seasons in 2023 and 2024. The experiment was designed as a factorial study using a randomized complete block design with three replicates. NaCl concentrations of 85.6 mM and 128.3 mM negatively affected seedling growth and yield. Foliar application of 100 µM melatonin combined with bacterial inoculation significantly enhanced leaf area and shoot dry weight. Inflorescence parameters improved notably, with increases in total carotenoids and flavonoids in petals. Total chlorophyll content, mineral percentages (N, P, K), and proline increased significantly, while sodium and chloride levels decreased. The activities of polyphenol oxidase and peroxidase increased significantly and also improved relative water content and reduced electrolyte leakage. Our findings suggest that the combination of exogenous melatonin and bacterial inoculation can effectively mitigate the adverse effects of salt stress on Calendula seedlings.
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Claims 9
Claim · model-written summary
High NaCl concentrations reduced seedling growth and yield.
- Taxon
- calendula officinalis
Calendula officinalist0 - Treatment
- NaCl concentrations of 85.6 mM and 128.3 mMe0
- Outcome
- seedling growth and yielde0
- Direction
- negatively affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NaCl concentrations of 85.6 mM and 128.3 mM negatively affected seedling growth and yield.”
t0“calendula officinalis”
Claim · model-written summary
Melatonin plus bacterial inoculation enhanced leaf area and shoot dry weight.
- Taxon
- calendula officinalisCalendula officinalist0
- Treatment
- Foliar application of 100 µM melatonin combined with bacterial inoculatione0
- Outcome
- leaf area and shoot dry weighte0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Foliar application of 100 µM melatonin combined with bacterial inoculation significantly enhanced leaf area and shoot dry weight.”
t0“calendula officinalis”
Claim · model-written summary
The combined treatments improved inflorescence parameters.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- Inflorescence parameterse0
- Direction
- improvede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inflorescence parameters improved notably, with increases in total carotenoids and flavonoids in petals.”
t0“calendula officinalis”
Claim · model-written summary
The treatments increased petal carotenoids and flavonoids.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- total carotenoids and flavonoids in petalse0
- Direction
- increasese0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inflorescence parameters improved notably, with increases in total carotenoids and flavonoids in petals.”
t0“calendula officinalis”
Claim · model-written summary
The treatments increased chlorophyll content, N, P, K and proline.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- Total chlorophyll content, mineral percentages (N, P, K), and prolinee0
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total chlorophyll content, mineral percentages (N, P, K), and proline increased significantly”
t0“calendula officinalis”
Claim · model-written summary
The treatments decreased sodium and chloride levels.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- sodium and chloride levelse0
- Direction
- decreasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sodium and chloride levels decreased.”
t0“calendula officinalis”
Claim · model-written summary
Polyphenol oxidase and peroxidase activities increased.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- activities of polyphenol oxidase and peroxidasee0
- Direction
- increasede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The activities of polyphenol oxidase and peroxidase increased significantly”
t0“calendula officinalis”
Claim · model-written summary
Relative water content improved.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- relative water contente0
- Direction
- improvede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“improved relative water content and reduced electrolyte leakage.”
t0“calendula officinalis”
Claim · model-written summary
Electrolyte leakage decreased.
- Taxon
- calendula officinalisCalendula officinalist0
- Outcome
- electrolyte leakagee0
- Direction
- reducede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced electrolyte leakage.”
t0“calendula officinalis”
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