Exogenous Application Of Melatonin Research Articles

Exogenous melatonin promotes seed germination and osmotic regulation under salt stress in cotton (Gossypium hirsutum L.).

Melatonin (MT; N-acetyI-5-methoxytryptamine) is an amine hormone involved in abiotic stress resistance. Previous studies have confirmed that melatonin can promote seed germination, mediate physiological regulation mechanisms, and stimulate crop growth under stress. However, the osmotic regulation mechanism by which exogenous melatonin mediates salt tolerance in cotton is still largely unknown. To investigate the effect of salt stress on melatonin concentration in germinating cotton seeds, we analyzed melatonin content over time during seed germination under different treatments. Melatonin content reached its minimum at day 6, while cotton germination rates peaked at day 6, indicating melatonin content and seed germination are correlated. Then we investigated the effects of 10-100 μM melatonin treatments on membrane lipid peroxides and osmotic adjustment substances during cotton seed germination under salt stress. Salt stress led to electrolyte leakage (EL) as well as accumulations of hydrogen peroxide (H2O2), malondialdehyde (MDA), organic osmotic substances (i.e., proline, soluble sugars), and inorganic osmotic substances (i.e., Na+, Cl-). Meanwhile, the contents of melatonin, soluble proteins, and K+ as well as the K+/Na+ balance decreased, indicating that salt stress inhibited melatonin synthesis and damaged cellular membranes, seriously affecting seed germination. However, melatonin pretreatment at different concentrations alleviated the adverse effects of salt stress on cotton seeds and reduced EL as well as the contents of H2O2, MDA, Na+, and Cl-. The exogenous application of melatonin also promoted melatonin, soluble sugar, soluble proteins, proline, and K+/Na+ contents under salt stress. These results demonstrate that supplemental melatonin can effectively ameliorate the repression of cotton seed germination by enhancing osmotic regulating substances and adjusting ion homeostasis under salt stress. Thus, melatonin may potentially be used to protect cotton seeds from salt stress, with the 20 μM melatonin treatment most effectively promoting cotton seed germination and improving salt stress tolerance.

Seed Pre-Soaking with Melatonin Improves Wheat Yield by Delaying Leaf Senescence and Promoting Root Development

The effects of exogenous application of melatonin (MEL) on promoting plant growth and alleviating environmental stresses are already known, but the potential value in crop production is still poorly understood. In this study, the effects of seed pre-soaking with MEL on winter wheat (Triticum aestivum L.) growth and yield were investigated in a continuous two-year pot experiment and another year of field experimentation. Results showed that seed pre-soaking with different concentrations of MEL (10, 100 and 500 μM) for 24 h increased grain yields per plant from 29% to 80% in pot experiment and increased grain yield per area from 4–19% in field experiment, compared with the controls. Further analysis showed that the beneficial effects of MEL on improving wheat grain yield can be ascribed to: (1) increased spike number by enhancing tiller number; (2) enhanced carbon assimilation capacity by maintaining large leaf area, high photosynthetic rate and delaying leaf senescence; (3) promoted growth in root system. The result of this study suggests that MEL could be considered as an effective plant growth regulator for improving grain production in winter wheat.

Melatonin treatment improves the shelf-life and postharvest quality of table grape (Vitis labrusca L. cv. ‘Fengzao’)

BACKGROUND: Melatonin (MT) is an endogenous indoleamine that regulates senescence progression and stress response in plants. OBJECTIVE: Here, we investigated the effect of MT on the shelf-life and postharvest quality of table grapes (Vitis labrusca L. cv. ‘Fengzao’). METHODS: After harvesting, ‘Fengzao’ grapes were immersed in MT solution at various concentrations (0 [as control], 0.05, 0.1, 0.5 and 1.0 mM for 2 h and stored at 24±1 for 15 days. Physiological indicators including weight loss rate, firmness, contents of total soluble solids (TSSs), ascorbic acid (AsA), malondialdehyde (MDA), hydrogen peroxide (H2O2), and activities of catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) were investigated. Additionally, the DNA methylation rate of ‘Fengzao’ grapes were measured using the methylation-sensitive amplification polymorphism (MSAP) technique. RESULTS: Application of MT effectively delayed grape senescence in all treatment groups compared with the control, with the longest delay observed in the 0.5 mM treatment. Additionally, the rate of DNA methylation decreased in all the 0.5 mM MT treatment groups, indicating a potential role of MT in demethylation. CONCLUSIONS: Our results suggest that the exogenous application of MT can delay the senescence of grapes during postharvest.

Melatonin on hypothyroidism and gonadal development in rats: a review.

We evaluated the evidence in research on the effects of melatonin on hypothyroidism and gonadal development. According to the World Health Organization, thyroid disorders due to iodine deficiency affect about 740 million people worldwide. Hypothyroidism is a thyroid dysfunction characterized by hypometabolism of the gland, with reduced or physiologically normal T3 and T4 serum levels, and high TSH level. This disorder occurs mainly in adult women in the reproductive phase, with a prevalence of 2% among the world's female population, with profound repercussions on gestation and fetal formation. During the gestational period, the thyroid is initially stimulated by high concentrations of human chorionic gonadotrophin; thus, maintaining maternal euthyroidism during pregnancy and lactation is fundamental for fetal growth and development. Besides, the hormones produced by this gland are involved in the formation of various organs, such as the skin, brain and gonads. Hypothyroidism is associated with several menstrual abnormalities, anovulation and hyperprolactinemia, resulting in a high rate of abortions, premature births, placental rupture, and weight-related neonatal deficits. In addition, there are studies showing that hypothyroidism can affect ovarian morphology (number of ovarian follicles) and testicular morphology (changes in the testicular-lumen epithelium). Melatonin is a hormone known to modulate the estrous cycle and pregnancy, and studies show that the exogenous application of melatonin increased T4 levels in female rats and controlled the decrease in T3 serum levels, reverting the sigs of hypothyroidism.

Exogenous melatonin reduces the inhibitory effect of osmotic stress on photosynthesis in soybean.

Understanding the relationship between exogenous melatonin and water deficit stress is crucial for achieving high yields and alleviating the effects of water deficit stress on soybean (Glycine max (L.) Merrill) plants in agriculture. This study investigated the effects of exogenous melatonin on soybean photosynthetic capacity under water deficit stress induced by polyethylene glycol (PEG) 6000. We conducted a potting experiment in 2018 using the soybean (Glycine max L. Merrill) cultivar Suinong 26. We identified the impacts of a concentration of PEG 6000 simulating drought (15%, w/v) and an appropriate melatonin concentration (100 μmol/L) on the growth of soybean seedlings and flowering stages in a preliminary test. We applied exogenous melatonin by foliar spraying and root application to determine the effects on leaf photosynthesis during water deficit stress. Our results indicated that 15% PEG 6000 had an obvious inhibitory effect on the growth of soybean seedlings and flowering stages, causing oxidative stress and damage due to reactive oxygen species (ROS) (H2O2 and O2·-) accumulation and potentially reducing air exchange parameters and photosystem II (PSII) efficiency. The application of exogenous melatonin significantly relieved the inhibitory effects of PEG 6000 stress on seedlings and flowering growth, and gas exchange parameters, potentially improved PSII efficiency, improved the leaf area index (LAI) and the accumulation of dry matter, slowed down oxidative stress and damage to leaves by increasing the activity of antioxidant enzymes (SOD, POD, and CAT), reduced the content of malondialdehyde (MDA), and ultimately improved soybean yield. Overall, the results of this study demonstrated that application of exogenous melatonin at the seedlings and flowering stages of soybean is effective in alleviating plant damage caused by water deficit stress and improving the drought resistance of soybean plants. In addition, the results showed that application of exogenous melatonin by root is superior to foliar spraying.

Melatonin-Nitric Oxide Crosstalk and Their Roles in the Redox Network in Plants.

Melatonin, an amine hormone highly conserved during evolution, has a wide range of physiological functions in animals and plants. It is involved in plant growth, development, maturation, and aging, and also helps ameliorate various types of abiotic and biotic stresses, including salt, drought, heavy metals, and pathogens. Melatonin-related growth and defense responses of plants are complex, and involve many signaling molecules. Among these, the most important one is nitric oxide (NO), a freely diffusing amphiphilic biomolecule that can easily cross the cell membrane, produce rapid signal responses, and participate in a wide variety of physiological reactions. NO-induced S-nitrosylation is also involved in plant defense responses. NO interacts with melatonin as a long-range signaling molecule, and helps regulate plant growth and maintain oxidative homeostasis. Exposure of plants to abiotic stresses causes the increase of endogenous melatonin levels, with the consequent up-regulation of melatonin synthesis genes, and further increase of melatonin content. The application of exogenous melatonin causes an increase in endogenous NO and up-regulation of defense-related transcription factors, resulting in enhanced stress resistance. When plants are infected by pathogenic bacteria, NO acts as a downstream signal to lead to increased melatonin levels, which in turn induces the mitogen-activated protein kinase (MAPK) cascade and associated defense responses. The application of exogenous melatonin can also promote sugar and glycerol production, leading to increased levels of salicylic acid and NO. Melatonin and NO in plants can function cooperatively to promote lateral root growth, delay aging, and ameliorate iron deficiency. Further studies are needed to clarify certain aspects of the melatonin/NO relationship in plant physiology.

Melatonin Is a Potential Target for Improving Post-Harvest Preservation of Fruits and Vegetables.

Melatonin is a ubiquitous molecule distributed in nature and not only plays an important role in animals and humans but also has extensive functions in plants, such as delaying senescence, exerting antioxidant effects, regulating growth and development, and facilitating plant adaption to stress conditions. Endogenous melatonin is widespread in fruits and vegetables and plays prominent roles in the ripening and post-harvest process of fruits and vegetables. Exogenous application of melatonin removes excess reactive oxygen species from post-harvest fruits and vegetables by increasing antioxidant enzymes, non-enzymatic antioxidants, and enzymes related to oxidized protein repair. Moreover, exogenous application of melatonin can increase endogenous melatonin to augment its effects on various physiological processes. Many previous reports have demonstrated that application of exogenous melatonin improves the post-harvest preservation of fruits and vegetables. Although overproduction of melatonin in plants via transgenic approaches could be a potential means for improving the post-harvest preservation of fruits and vegetables, efforts to increase endogenous melatonin in plants are limited. In this review, we summarize the recent progress revealing the role and action mechanisms of melatonin in post-harvest fruits and vegetables and provide future directions for the utilization of melatonin to improve the post-harvest preservation of fruits and vegetables.

Exogenous melatonin confers drought stress by promoting plant growth, photosynthetic capacity and antioxidant defense system of maize seedlings.

Melatonin is an important biologically active hormone that plays a vital role in plant growth and development. In particular, it has been investigated for its roles in abiotic stress management. The current experiment was carried out to investigate the protective role of melatonin in photosynthetic traits and the antioxidant defense system of maize seedling under drought stress. Maize seedlings were subjected to drought stress (40–45% FC) after two weeks of seedling emergence, followed by a foliar spray (0, 25, 50, 75 and 100 µM) and soil drench of melatonin (0, 25, 50, 75 and 100 µM). Our results indicated that drought stress negatively affected maize seedling and decreased plant growth and development, biomass accumulation, reduced chlorophyll, and carotenoid content, and significantly declined photosynthetic rate and stomatal conductance. On the other hand, reactive oxygen species, soluble protein, and proline content increased under drought stress. However, the application of exogenous melatonin reduced the reactive oxygen species burst and enhanced the photosynthetic activity by protecting from damages through activation of various antioxidant enzymes under drought stress. Foliar application of 100 µM and soil drench of 50 µM melatonin was the most effective treatment concentrations under drought stress. Our current findings hereby confirmed the mitigating potential of melatonin application for drought stress by maintaining plant growth, improving the photosynthetic characteristics and activities of antioxidants enzymes.

Application of melatonin promotes anthocyanin accumulation in crabapple leaves

Anthocyanins are a class of compounds that are widespread in plants, where they provide protection against stresses, and are also beneficial to human health as dietary components. Melatonin application is known to affect anthocyanin production, but the relationship between anthocyanin and melatonin is still unclear. In this study, we analyzed anthocyanin contents and the expression levels of anthocyanin biosynthetic and regulatory genes in tissue cultured plantlets of two Malus crabapple cultivars following various exogenous melatonin treatments under light and dark conditions. The application of exogenous melatonin not only promoted anthocyanin accumulation in leaves, but also increased the contents of flavonols and proanthocyanins (PAs), via a process that was not dependent on light. Quantitative real time PCR (qRT-PCR) analyses indicated that the expression of flavonoid biosynthetic genes, flavonoid related transcription factors and melatonin biosynthetic genes was induced by melatonin. We propose that anthocyanin biosynthesis is regulated by melatonin in crabapple leaves via the expression of flavonoid related transcription factors. This study provides insight into the mechanism of melatonin induction of anthocyanin biosynthesis in woody plants, and suggests that pretreatment with melatonin may represent a cultivation strategy to increase the flavonoid contents of plants.

Exogenous application of melatonin improves plant resistance to virus infection

In this study, melatonin (MEL)‐mediated plant resistance to tobacco mosaic virus (TMV) was examined to study local infection in Nicotiana glutinosa and systemic infection in Solanum lycopersicum. Exogenous application of 100 µm MEL increased anti‐virus infection activity to 37.4% in virus‐infected N. glutinosa plants. The same treatment significantly reduced relative levels of virus RNA analysed by qRT‐PCR and virus titres measured by dot‐ELISA, and increased the relative expression levels of the PR1 and PR5 genes analysed by qRT‐PCR, in virus‐infected S. lycopersicum. MEL treatment induced considerable accumulations of salicylic acid (SA) and nitric oxide (NO) but did not significantly affect production of hydrogen peroxide (H2O2) in the virus‐infected S. lycopersicum plants. Transgenic nahG N. tabacum was used to determine whether MEL‐induced TMV resistance was dependent on the SA pathway. The results showed that the relative RNA level of the TMV analysed by qRT‐PCR and virus titres analysed by dot‐ELISA were not reduced by the MEL treatment in the nahG transgenic N. tabacum seedlings treated twice with 100 µm MEL. The increased relative expression levels of PR1 and PR5 were greatly reduced when cPTIO, an NO scavenger, was included in the MEL treatment. A working model of MEL‐mediated plant resistance to TMV is proposed. MEL‐mediated plant resistance to viruses provides a new avenue to control plant viral diseases.

The Evaluation of Exogenous Melatonin Administration in Supraspinatus Overuse Tendinopathy in an Experimental Rat Model.

BackgroundIncreased oxidative stress and inflammation play a critical role in the etiopathogenesis of chronic tendinopathy. Melatonin is an endogenous molecule that exhibits antioxidant and anti-inflammatory activity. The aim of this study was to evaluate the biochemical and histopathological effects of exogenous melatonin administrations in supraspinatus overuse tendinopathy.MethodsFifty rats were divided into the following four groups: cage activity, melatonin treatment, corticosteriod therapy, and control. Melatonin (10 mg/kg, intraperitoneal; twice a day) and triamcinolone (0.3 mg/kg, subacromial; weekly) were administered to the treatment groups after the overuse period. Biochemical and histopathological evaluations were performed on serum samples and biopsies obtained from rats. Plasma inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels were evaluated biochemically.ResultsThe TAS, TOS, OSI, iNOS, and VEGF values were significantly lower than the pre-treatment levels in rats receiving exogenous melatonin treatment (3 or 6 weeks) (p<0.05). TOS, iNOS, VEGF, and OSI values after 3 weeks of triamcinolone administration, and TOS, VEGF, and OSI levels after 6 weeks of triamcinolone application, were significantly lower than the pre-treatment levels (p<0.05).ConclusionsExogenous melatonin application in overuse tendinopathy reduces oxidative stress and inflammation. Melatonin might be an alternative potential molecule to corticosteroids in the treatment of chronic tendinopathy.

Melatonin improves the multiple stress tolerance in pepper (Capsicum annuum)

Plants are often simultaneously exposed to various abiotic stress factors such as herbicide and drought at agricultural areas. The aim of this study is to investigate the effects of pendimethaline (Pend) on pepper, which is a culture plant, to determine interaction of multiple stresses when Pend and drought stresses are applied simultaneously on pepper and also to establish how exogenous melatonin (MEL) application affects multiple stress interaction and antioxidant responses in pepper. The results of the study show that for peppers exposed to 10% polyethylene glycol (PEG) and Pend at different concentrations (8, 16 and 32 mM) both separately and simultaneously, total chlorophyll content and relative water content decreased while carotenoid, proline, glutathione, endogenous MEL and malondialdehyde contents, ascorbate peroxidase, glutathine S-transferase and glutathine reductase activities as well as mRNA levels increased. These changes were found to be more significant statistically for (Pend + PEG) groups treated with stress simultaneously. While malondialdehyde content decreased, compared to untreated plants, for plants pre-treated with 50 μM MEL; relative water content, chlorophyll, carotenoid, proline, glutathione and endogenous MEL contents as well as mRNA levels and activities of antioxidant enzymes (ascorbate peroxidase, glutathine S-transferase and glutathine reductase) increased. Our findings show that both Pend and PEG created some phytotoxic responses on pepper plant and multiple stress treatment induced these responses. However, exogenous MEL application alleviated negative effects of herbicide and drought stresses by inducing antioxidant defense responses of pepper.

Exogenous application of melatonin mitigates the adverse effects of drought stress on morpho-physiological traits and secondary metabolites in Moldavian balm (Dracocephalum moldavica).

Melatonin has emerged as an important signaling molecule that regulates plant responses to environmental stresses. In this research, melatonin was used to alleviate the adverse effects of oxidative stress induced by water deficit in Moldavian balm (Dracocephalum moldavica) plants and morpho-physiological traits were investigated. This experiment was conducted as a factorial arrangement based on completely randomized design with four replications. Treatments included foliar melatonin application at four levels 0 (distilled water), 50, 100 and 150μM and drought stress 100 (control), 80, 60 and 40% of field capacity(FC). Higher levels of drought stress at 60% and 40% FC, caused the reduction of plant height, shoot fresh and dry weight, root length, root fresh and dry weight, photosynthetic pigments and protein content. Increased amount of soluble sugar content, malondialdehyde content and lipoxygenase activity, non-enzyme antioxidants (including flavonoid, polyphenol compounds and anthocyanin), phenylalanine ammonia-lyase and polyphenol oxidase enzymes activities were also observed at 60% and 40% FC. Melatonin at 100µM improved morphological parameters, photosynthetic pigments and protein content under moderate and severe drought stress. The obtained results suggested that foliar application of 100μM melatonin also alleviated oxidative burst and malondialdehyde production in Moldavian balm plant under moderate and severe drought stress probably through regulation of secondary metabolism and the enzymes activity of phenylalanine ammonia-lyase and polyphenol oxidase.

Exogenous melatonin-mediated modulation of arsenic tolerance with improved accretion of secondary metabolite production, activating antioxidant capacity and improved chloroplast ultrastructure in rosemary herb

Arsenic (As) recognized as a group I human carcinogen additionally poses a threat to plants which limit growth, metabolic activity, and productivity. Melatonin (MEL) is a naturally occurring compound in plants that have been recognized to mediate numerous morphological, physiological and molecular processes. Conversely, the role of MEL in inducing As-tolerance remains inexpressible and the plausible mechanisms in inducing As tolerance have remained largely unknown. The present investigation was designed to understand the protective role of MEL concentrations in rosemary herbs cultivated under As contamination.Arsenic evoked a deleterious decline on herb productivity, photosynthetic pigment, ion concentration, water status, ascorbic acid, essential oil (EO) yield and induced malformation of the chloroplast. Alternatively, increased organic osmolytes, oxidative impairment criteria, additionally antioxidant enzymes, phenol, flavonoid, anthocyanin, and EO%. Exogenous application of MEL with or without As, considerably increased growth, photosynthetic pigment, ion concentration, organic osmolytes as well as EO yield regarding polluted or non-polluted treatment respectively. Moreover, MEL treatment stabilized the cell membrane integrity, suppressed oxidative impairment criteria, and enhanced antioxidant capacity, additionally upregulation antioxidant enzymes.Plant treated with As showed a significant increase in As contamination and a bioconcentration factor in both root and shoot system. MEL supplementation under normal or As concentration, reduced As accumulation and bioconcentration factors, in either shoot or root systems. Additionally As decrease transfer factor, however, supplementation of MEL further decreased it.Application of 50 μM MEL might help the herbs to withstand As stress by strengthening their antioxidant machinery and osmoregulation capacity.

Melatonin increases the performance of Malus hupehensis after UV-B exposure

Melatonin, an evolutionarily conserved molecule, is implicated in numerous physiological processes in plants. To explore the potential roles of melatonin in response to UV-B radiation, we examined the influence of exogenous melatonin on Malus hupehensis Rehd. seedlings under two levels of UV-B radiation. Under UV-B stress, seedlings showed significant reduction in plant growth, biomass production, and root system development. However, 1 μM melatonin solution markedly alleviated these effects, especially at the higher dosage of UV-B radiation. The inhibitory effects of UV-B radiation on photosynthetic parameters, chlorophyll fluorescence parameters, stomatal apertures, chlorophyll levels and leaf membrane damages were also markedly alleviated with melatonin application. Melatonin treatment was also associated with higher activity and expression of genes encoding antioxidant enzymes (ascorbate peroxidase, catalase and peroxidase) and greater decline of H2O2 content in leaves exposed to UV-B. Moreover, exogenous melatonin treatment and UV-B stress increased the concentration of endogenous melatonin. The content of several phenolic compounds, including chlorogenic acid, phloridzin and quercetin-3-galactoside, also increased under UV-B stress, and these were further elevated significantly with melatonin addition. This study provides insight into the role(s) of endogenous melatonin in response to UV-B stress, and will facilitate application of exogenous melatonin in agriculture.

Melatonin delays leaf senescence of Chinese flowering cabbage by suppressing ABFs-mediated abscisic acid biosynthesis and chlorophyll degradation.

Melatonin and abscisic acid (ABA) play contrasting roles in regulating leaf senescence in plants. The molecular mechanism underlying the interaction between melatonin and ABA involved in leaf senescence, however, remains poorly defined. Herein, we found that exogenous application of melatonin delayed the senescence of Chinese flowering cabbage, accompanied by reduced expression of chlorophyll catabolic and ABA biosynthetic genes, and a lower endogenous ABA level. Significantly, three nucleus-localized transcriptional activators BrABF1, BrABF4, and BrABI5 were identified, and their expressions were repressed by melatonin. In vitro and in vivo binding experiments revealed that BrABF1, BrABF4, and BrABI5 activated the transcription of a series of ABA biosynthetic and chlorophyll catabolic genes by physically binding to their promoters. Moreover, transient over-expression of BrABF1, BrABF4, and BrABI5 in tobacco leaves induced ABA accumulation and promoted chlorophyll degradation by upregulating tobacco ABA biosynthetic and chlorophyll catabolic genes, resulting in the accelerated leaf senescence. These effects were significantly attenuated by melatonin treatment. Our findings suggest that melatonin-mediated inhibition of leaf senescence involves suppression of ABFs-mediated ABA biosynthesis and chlorophyll degradation. Unraveling of the molecular regulatory mechanism of leaf senescence controlled by ABA and melatonin expands our understanding of the regulation of this phenomenon and offers potentially more effective molecular breeding strategies for extending the shelf-life of Chinese flowering cabbage.

Exogenous application of melatonin improves eradication of apple stem grooving virus from the infected in vitro shoots by shoot tip culture

Production and maintenance of virus‐free planting materials is pivotal for the control of viral diseases. The present study attempted to test exogenous application of melatonin for eradication of apple stem grooving virus (ASGV) from virus‐infected in vitro shoots of apple cultivar Gala. Exogenous application of 15 μm melatonin to the shoot proliferation medium significantly increased the number of shoots and shoot length. The level of endogenous indole‐3‐acetic acid (IAA) was the highest in the shoots proliferating on the shoot proliferation medium containing 15 μm melatonin. Shoot regrowth levels were significantly higher in shoot tips of the virus‐infected shoots cultured for 4 weeks on this medium than the control. In addition, culture of shoot tips of the virus‐infected in vitro shoots proliferated for 4 weeks on this medium resulted in 95% of shoots being virus‐free, while no virus‐free shoots were obtained in shoot tips of the virus‐infected shoots cultured without melatonin. Analyses by microtissue direct RT‐PCR and RT‐qPCR showed that ASGV concentration decreased in shoot tips of the virus‐infected shoots proliferating on the medium containing 15 μm melatonin for 4 weeks. Virus localization showed that exogenous application of melatonin enlarged the virus‐free area in the virus‐infected shoot tips. These data provide explanations as to why exogenous application of melatonin can efficiently eradicate ASGV. Exogenous application of melatonin provides an alternative means for plant virus eradication and has the potential to produce virus‐free plants.

Impact of Exogenous Melatonin Application on Chilling Injury in Tomato Fruits During Cold Storage

In this study, the mechanism recruited by exogenous melatonin application at 100 μM for alleviating chilling injury in tomato fruits during cold storage was investigated. Alleviating chilling injury in tomato fruits in response to exogenous melatonin application at 100 μM may ascribe to providing sufficient intracellular ATP occur by higher H-ATPase, Ca-ATPase, cytochrome c oxidase (CCO), and succinate dehydrogenase (SDH) enzymes activity during cold storage. Also, higher unsaturated/saturated fatty acids (unSFA/SFA) ratio owing to higher linoleic and linolenic acids accumulation coincides with lower palmitic, stearic and oleic acids accumulation may be responsible for alleviating chilling injury in tomato fruits in response to exogenous melatonin application at 100 μM, which may occur by higher fatty acid desaturase 3 and 7 (FAD3 and FAD7) genes expression accompanying by lower phospholipase D (PLD) and lipoxygenase (LOX) genes expression and enzymes activity, in addition to providing sufficient intracellular ATP. Therefore, exogenous melatonin application may be a beneficial postharvest procedure for alleviating chilling injury in tomato fruits during cold storage.

Effects of Exogenous Application of Melatonin on Quality and Sugar Metabolism in ‘Zaosu’ Pear Fruit

Melatonin (MT) modulates a wide range of physiological functions with pleiotropic effects in plants. In this study, we studied the effect of exogenous applications of MT to pear trees on indicators of pear fruit quality. The results showed that MT increased the size of pear fruit by improving the net photosynthetic rate and maximal quantum efficiency of photosystem II photochemistry during the late stage of pear fruit development. Overall, MT increased fruit weight by 47.85% compared to the control. During the period of fruit maturation, MT increased the content of soluble sugars, particularly sucrose and sorbitol, likely as a result of improved starch accumulation. Expression levels of the invertase gene Pbinvertase 1/2 were lower in MT-treated fruit that resulted in lower enzyme activity, whereas activity of sucrose phosphate synthase was greater due to enhanced levels of expression of PbSPS1/2/3. Thus, application of melatonin improved sucrose content. This study shows that the application of MT to pear trees may be utilized for the production of larger and sweeter fruit of higher economic value.

Enhancing salt tolerance in melon by application of exogenous melatonin and Ca2+

Enhancing salt tolerance in melon by application of exogenous melatonin and Ca2+