Abstract
Melatonin, a natural agent, has multiple functions in animals as well as in plants. However, its possible roles in plants under abiotic stress are not clear. Nowadays, soil salinity is a major threat to global agriculture because a high soil salt content causes multiple stresses (hyperosmotic, ionic, and oxidative). Therefore, the aim of the present study was to explore: (1) the involvement of melatonin in biosynthesis of photosynthetic pigments and in regulation of photosynthetic enzymes, such as carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco); (2) the role of melatonin in osmoregulation by proline and carbohydrate metabolism; and (3) the function of melatonin in the antioxidant defense system under salinity. Outcomes of the study reveal that under non-saline conditions, application of melatonin (20 and 50 µM) improved plant growth, viz. shoot length, root length, shoot fresh weight (FW), root FW, shoot dry weight (DW), root DW and leaf area and physio-biochemical parameters [chlorophyll (Chl) a and b, proline (Pro) and total soluble carbohydrates (TSC) content, and increased the activity of CA and Rubisco]. However, tomato seedlings treated with NaCl exhibited enhanced Chl degradation, electrolyte leakage (EL), malondialdehyde (MDA) and reactive oxygen species (ROS; superoxide and hydrogen peroxide). ROS were detected in leaf and root. Interestingly, application of melatonin improved plant growth and reduced EL, MDA and ROS levels through upregulation of photosynthesis enzymes (CA, Rubisco), antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and ascorbate reductase) and levels of non-enzymatic antioxidants [ascorbate (ASC) and reduced glutathione (GSH)], as well as by affecting the ASC—GSH cycle. Additionally, exogenous melatonin also improved osmoregulation by increasing the content of TSC, Pro and Δ1-pyrroline-5-carboxylate synthetase activity. These results suggest that melatonin has beneficial effects on tomato seedlings growth under both stress and non-stress conditions. Melatonin’s role in tolerance to salt stress may be associated with the regulation of enzymes involved in photosynthesis, the antioxidant system, metabolism of proline and carbohydrate, and the ASC—GSH cycle. Also, melatonin could be responsible for maintaining the high ratios of GSH/GSSG and ASC/DHA.
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Claims 13
Claim · model-written summary
Melatonin improved tomato seedling shoot and root length and leaf area without salt.
- Taxon
- tomato seedlings
Solanum lycopersicume0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under non-saline conditions, application of melatonin (20 and 50 µM) improved plant growth, viz. shoot length, root length, shoot fresh weight (FW), root FW, shoot dry weight (DW), root DW and leaf area”
e1“However, tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin improved tomato shoot and root fresh and dry weights without salt.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under non-saline conditions, application of melatonin (20 and 50 µM) improved plant growth, viz. shoot length, root length, shoot fresh weight (FW), root FW, shoot dry weight (DW), root DW and leaf area”
e1“However, tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin improved chlorophyll, proline and soluble carbohydrate content without salt.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“chlorophyll (Chl) a and b, proline (Pro) and total soluble carbohydrates (TSC) content, and increased the activity of CA and Rubisco”
e1“under non-saline conditions, application of melatonin (20 and 50 µM) improved plant growth”
e2“However, tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin increased CA and Rubisco activity without salt.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased the activity of CA and Rubisco”
e1“under non-saline conditions, application of melatonin (20 and 50 µM) improved plant growth”
e2“However, tomato seedlings treated with NaCl”
Claim · model-written summary
NaCl enhanced chlorophyll degradation and electrolyte leakage in tomato seedlings.
- Taxon
- tomato seedlingsSolanum lycopersicume0
- Treatment
- NaCle0
- Outcome
- Chl degradation, electrolyte leakage (EL)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tomato seedlings treated with NaCl exhibited enhanced Chl degradation, electrolyte leakage (EL)”
Claim · model-written summary
NaCl enhanced MDA and reactive oxygen species in tomato seedlings.
- Taxon
- tomato seedlingsSolanum lycopersicume0
- Treatment
- NaCle0
- Outcome
- malondialdehyde (MDA) and reactive oxygen species (ROS; superoxide and hydrogen peroxide)e0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tomato seedlings treated with NaCl exhibited enhanced Chl degradation, electrolyte leakage (EL), malondialdehyde (MDA) and reactive oxygen species (ROS; superoxide and hydrogen peroxide)”
Claim · model-written summary
Melatonin improved tomato growth under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“application of melatonin improved plant growth and reduced EL, MDA and ROS levels”
e1“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin reduced electrolyte leakage, MDA and ROS levels under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“application of melatonin improved plant growth and reduced EL, MDA and ROS levels”
e1“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin upregulated CA and Rubisco under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upregulation of photosynthesis enzymes (CA, Rubisco)”
e1“application of melatonin improved plant growth”
e2“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin upregulated antioxidant enzymes under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1e2e3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase and ascorbate reductase)”
e1“through upregulation of photosynthesis enzymes (CA, Rubisco), antioxidant enzymes”
e2“application of melatonin improved plant growth”
e3“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin increased nonenzymatic antioxidant levels under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1e2e3
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“levels of non-enzymatic antioxidants [ascorbate (ASC) and reduced glutathione (GSH)]”
e1“through upregulation of photosynthesis enzymes (CA, Rubisco), antioxidant enzymes”
e2“application of melatonin improved plant growth”
e3“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin increased TSC, proline and P5CS activity under salt stress.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exogenous melatonin also improved osmoregulation by increasing the content of TSC, Pro and Δ1-pyrroline-5-carboxylate synthetase activity”
e1“tomato seedlings treated with NaCl”
Claim · model-written summary
Melatonin may help maintain high GSH/GSSG and ASC/DHA ratios.
- Taxon
- tomato seedlingsSolanum lycopersicume0e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“melatonin could be responsible for maintaining the high ratios of GSH/GSSG and ASC/DHA”
e1“These results suggest that melatonin has beneficial effects on tomato seedlings growth”
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