Effects Of Exogenous Melatonin Research Articles

The effect of exogenous melatonin on waterlogging stress in Clematis.

Clematis is the queen of the vines, being an ornamental plant with high economic value. Waterlogging stress reduces the ornamental value of the plant and limits its application. Melatonin plays an important role in plant resistance to abiotic stresses. In this study, the physiological responses and gene expression levels of two wild species, namely, Clematis tientaiensis and Clematis lanuginosa, and two horticultural varieties, namely, 'Sen-No-Kaze' and 'Viva Polonia,' under waterlogging stress were analyzed to determine the effect of melatonin on waterlogging tolerance. The results showed that the waterlogging tolerances of C. lanuginosa and 'Sen-No-Kaze' were relatively poor, but were significantly improved by concentrations of 100 μmol·L-1 and 50 μmol·L-1 melatonin. C. tientaiensis and 'Viva Polonia' had relatively strong tolerance to waterlogging, and this was significantly improved by 200 μmol·L-1 melatonin. Under waterlogging stress, the relative conductivity and H2O2 content of Clematis increased significantly; the photosynthetic parameters and chlorophyll contents were significantly decreased; photosynthesis was inhibited; the contents of soluble protein and soluble sugars were decreased. Effective improvement of waterlogging tolerance after exogenous melatonin spraying, the relative conductivity was decreased by 4.05%-27.44%; the H2O2 content was decreased by 3.84%-23.28%; the chlorophyll content was increased by 35.59%-103.36%; the photosynthetic efficiency was increased by 25.42%-45.86%; the antioxidant enzyme activities of APX, POD, SOD, and CAT were increased by 28.03%-158.61%; the contents of proline, soluble protein, and soluble sugars were enhanced, and cell homeostasis was improved. Transcription sequencing was performed on wild Clematis with differences in waterlogging tolerance, and nine transcription factors were selected that were highly correlated with melatonin and that had the potential to improve waterlogging tolerance, among which LBD4, and MYB4 were significantly positively correlated with the antioxidant enzyme system, and bHLH36, DOF36, and WRKY4 were significantly negatively correlated. Photosynthetic capacity was positively correlated with DOF36 and WRKY4 while being significantly negatively correlated with MYB4, MOF1, DOF47, REV1 and ABR1. Melatonin could enhance the flooding tolerance of Clematis by improving photosynthetic efficiency and antioxidant enzyme activity. This study provides an important basis and reference for the application of melatonin in waterlogging-resistant breeding of Clematis.

Exogenous melatonin delays leaves senescence and enhances saline and alkaline stress tolerance in grape seedlings

ABSTRACT Saline and alkaline stress is one of the major abiotic stresses facing agricultural production, which severely inhibits the growth and yield of plant. The application of plant growth regulators can effectively prevent crop yield reduction caused by saline and alkaline stress. Exogenous melatonin (MT) can act as a signaling molecule involved in the regulation of a variety of physiological processes in plants, has been found to play a key role in enhancing the improvement of plant tolerance to abiotic stresses. However, the effects of exogenous MT on saline and alkaline tolerance of table grape seedlings and its mechanism have not been clarified. The aim of this study was to investigate the role of exogenous MT on morphological and physiological growth of table grape seedlings ( Vitis vinifera L.) under saline and alkaline stress. The results showed that saline and alkaline stress resulted in yellowing and wilting of grape leaves and a decrease in chlorophyll content, whereas the application of exogenous MT alleviated the degradation of chlorophyll in grape seedling leaves caused by saline and alkaline stress and promoted the accumulation of soluble sugars and proline content. In addition, exogenous MT increased the activity of antioxidant enzymes, which resulted in the scavenging of reactive oxygen species (ROS) generated by saline and alkaline stress. In conclusion, exogenous MT was involved in the tolerance of grape seedlings to saline and alkaline stress, and enhanced the saline and alkaline resistance of grape seedlings to promote the growth and development of the grape industry in saline and alkaline areas.

Exogenous melatonin improves germination rate in buckwheat under high temperature stress by regulating seed physiological and biochemical characteristics.

The germinations of three common buckwheat (Fagopyrum esculentum) varieties and two Tartary buckwheat (Fagopyrum tataricum) varieties seeds are known to be affected by high temperature. However, little is known about the physiological mechanism affecting germination and the effect of melatonin (MT) on buckwheat seed germination under high temperature. This work studied the effects of exogenous MT on buckwheat seed germination under high temperature. MT was sprayed. The parameters, including growth, and physiological factors, were examined. The results showed that exogenous MT significantly increased the germination rate (GR), germination potential (GP), radicle length (RL), and fresh weight (FW) of these buckwheat seeds under high-temperature stress and enhanced the content of osmotic adjustment substances and enzyme activity. Comprehensive analysis revealed that under high-temperature stress during germination, antioxidant enzymes play a predominant role, while osmotic adjustment substances work synergistically to reduce the extent of damage to the membrane structure, serving as the primary key indicators for studying high-temperature resistance. Consequently, our results showed that MT had a positive protective effect on buckwheat seeds exposed to high temperature stress, providing a theoretical basis for improving the ability to adapt to high temperature environments.

Effects of melatonin on lettuce plant growth, antioxidant enzymes and photosynthetic pigments under salinity stress conditions

ABSTRACT Salinity is one of the most important abiotic stresses that significantly decreases the productivity of agricultural crops. Melatonin (MT) acts as an antioxidant and plays a vital role in overcoming oxidative damage. However, previous literature has not provided a clear understanding of the impact of MT on lettuce plants under salinity stress. So, we investigated the effect of exogenous MT at 0 μM, 50 μM, 100 μM and 150 μM on lettuce plants grown under salinity stress (0 mM NaCl, 50 mM NaCl and 100 mM NaCl) with respect to vegetative growth, photosynthetic pigments, relative water content (RWC), electrolyte leakage (EL), malondialdehyde (MDA), H2O2, O2 •- and antioxidants enzymes. Results showed that NaCl stress significantly decreased vegetative growth, RWC and photosynthetic pigments and in contrast enhanced dry matter, EL, MDA, H2O2, O2 •-, Na+, Cl-, peroxidase (POD), superoxide dismutase (SOD) and glutathione reductase (GR) of lettuce plants compared to non-salinized control. The results demonstrated that under salinity conditions, foliar applications of MT significantly alleviated the harmful effects of salinity and increased number of leaves, leaf area, fresh weight, chlorophyll (a), chlorophyll (b), total chlorophyll, carotenoids and RWC in comparison to untreated plants (control). Meanwhile, dry matter, MDA, H2O2, O2 •-, Na+, Cl-, POD, SOD and GR were significantly decreased compared to untreated lettuce plants. In this respect, spraying MT at 150 μM ranked the first, then 100 μM, compared to the lower concentration (50 μM). In conclusion, MT application can be used to alleviate harmful effects of salinity stress.

Effect of exogenous melatonin on postharvest storage quality of passion fruit through antioxidant metabolism

This study investigated the effect of melatonin (MT) on postharvest storage quality of passion fruit. Passion fruits were treated with four different concentrations of MT solutions (100, 200, 300 and 400 μmol/L) for 30 min and stored for 8 days. Compared with the control, the optimal MT concentration (200 μmol/L) treatment significantly reduced the shrinkage index, browning index, weight loss, ethylene production, and respiration rate, and delayed the decline of firmness, total soluble solids (TSS), and color, thus maintaining the quality of postharvest fruits. Exogenous MT enhances antioxidant activity and reduces fruit oxidative damage by inhibiting the increase in pericarp cell membrane permeability, malondialdehyde (MDA) content, maintaining high ascorbic acid (AsA), total phenolics, and flavonoids content, and increasing superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO) activities. These findings suggest that postharvest exogenous application of MT is effective in maintaining passion fruit quality and delaying senescence.

Effects of Exogenous Melatonin on the Growth and Physiological Characteristics of Ginkgo biloba L. under Salinity Stress Conditions

Ginkgo (Ginkgo biloba L.) is a cherished relic among plants, commonly planted as a street tree. However, it faces cultivation challenges due to escalating soil salinization and widespread snowmelt application. Therefore, this study used 4-year-old Ginkgo seedlings to investigate how exogenous melatonin at varying concentrations affects seedling growth and physiology under salinity stress. The results revealed that appropriate melatonin concentrations (0.02, 0.1 mmol·L−1) significantly mitigated leaf yellowing under different NaCl stress levels. Furthermore, they increased ground diameter, current-year branch growth, relative water concentration, free proline, and soluble sugars in leaves. Melatonin also reduced electrolyte exudation rates, flavonoids, and malonic dialdehyde concentration, while enhancing peroxidase and superoxide dismutase activities. This led to reduced chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate, stabilizing intercellular CO2 concentration, preserving photosynthetic structures, and enhancing photosynthetic rates. Additionally, the decline in the photosynthetic electron transport rate, the effective photochemical quantum yield of PSII, and the potential efficiency of primary conversion of light energy of PSII was alleviated. Minimal fluorescence and the non-photochemical quenching coefficient also improved. However, high melatonin concentration (0.5 mmol·L−1) exacerbated salinity stress. After analyzing composite scores, the 0.02 mmol·L−1 melatonin treatment was most effective in alleviating NaCl stress, while the 0.5 mmol·L−1 treatment intensified physiological stress under 200 mmol·L−1 NaCl stress. Principal component analysis and correlation analysis identified seven physiological indicators (photosynthetic rate, transpiration rate, photosynthetic electron transport rate, minimal fluorescence, superoxide dismutase, free proline, and chlorophyll a) and three growth indicators (ground diameter, branch length, and current-year branch thickness) as key markers for rapid salinity stress assessment in Ginkgo. These findings are crucial for addressing challenges associated with snowmelt’s impact on roadside Ginkgo trees, expanding planting areas, and breeding exceptional salt-tolerant Ginkgo varieties.

Melatonin Promotes Iron Reactivation and Reutilization in Peach Plants under Iron Deficiency.

The yellowing of leaves due to iron deficiency is a prevalent issue in peach production. Although the capacity of exogenous melatonin (MT) to promote iron uptake in peach plants has been demonstrated, its underlying mechanism remains ambiguous. This investigation was carried out to further study the effects of exogenous MT on the iron absorption and transport mechanisms of peach (Prunus persica) plants under iron-deficient conditions through transcriptome sequencing. Under both iron-deficient and iron-supplied conditions, MT increased the content of photosynthetic pigments in peach leaves and decreased the concentrations of pectin, hemicellulose, cell wall iron, pectin iron, and hemicellulose iron in peach plants to a certain extent. These effects stemmed from the inhibitory effect of MT on the polygalacturonase (PG), cellulase (Cx), phenylalanine ammonia-lyase (PAL), and cinnamoyl-coenzyme A reductase (CCR) activities, as well as the promotional effect of MT on the cinnamic acid-4-hydroxylase (C4H) activity, facilitating the reactivation of cell wall component iron. Additionally, MT increased the ferric-chelate reductase (FCR) activity and the contents of total and active iron in various organs of peach plants under iron-deficient and iron-supplied conditions. Transcriptome analysis revealed that the differentially expressed genes (DEGs) linked to iron metabolism in MT-treated peach plants were primarily enriched in the aminoacyl-tRNA biosynthesis pathway under iron-deficient conditions. Furthermore, MT influenced the expression levels of these DEGs, regulating cell wall metabolism, lignin metabolism, and iron translocation within peach plants. Overall, the application of exogenous MT promotes the reactivation and reutilization of iron in peach plants.

Effect of exogenous melatonin on metabolic profile and reproductive performance in undernourished suckling Merino ewes in the early postpartum period

Effect of exogenous melatonin on metabolic profile and reproductive performance in undernourished suckling Merino ewes in the early postpartum period

Effects of exogenous melatonin on sugar and organic acid metabolism in early-ripening peach fruits.

To evaluated the effects melatonin (MT) on the sugar and acid metabolism of early-ripening peach fruits, the concentration of 150 μmol/L MT was sprayed on the leaves of peach trees. MT increased the contents of total soluble sugar and sucrose in peach fruits during the whole ripening period, and increased the contents of glucose and sorbitol at the mature stage. During the whole ripening period, MT also increased the activities of sucrose synthase, sucrose phosphate synthase, neutral invertase, and acidic invertase and the relative expression levels of sucrose synthase, sucrose phosphate synthase, neutral invertase, and acidic invertase genes, while decreased the activity of sorbitol oxidase and the relative expression level of sorbitol dehydrogenase to some extent. Moreover, MT decreased the contents of total organic acid, malic acid, and citric acid at mature stage. At mature stage, MT decreased the activities of citrate synthetase and phosphoenolpyruvate carboxylase and the relative expression levels of citrate synthetase and phosphoenolpyruvate carboxylase genes, while increased the relative expression levels of Nicotinamide adenine dinucleotide phosphate (NADP+)-malic enzyme, malate dehydrogenase, and aconitase genes. Therefore, MT promotes the sugar accumulation and organic acid degradation in early-ripening peach fruits.

The effect of exogenous melatonin on root growth and lifespan and seed cotton yield under drought stress

Drought stress is the major environmental factor that inhibits the growth and reduces the yield of cotton (Gossypium hirsutum L.). The exogenous application of melatonin has been shown to alleviate drought stress damage, but it is unclear whether melatonin mediates the alleviation by preventing the drought-induced inhibition of root growth. To address this gap, we subjected cotton plants grown in RhizoPotsto treatments of thorough watering, drought stress treatment, and drought stress supplemented with exogenous melatonin. Melatonin promoted the aboveground growth compared with the non-melatonin treatment under drought stress, and increased the plant height, stem diameter, leaf area, SPAD value, and net photosynthetic rate. The application of melatonin significantly prevented the drought-induced yield losses by increasing the boll weight. The drought stress+melatonin treatment significantly increased the root length, root surface area, root volume, and specific root length by 18.36%, 25.46%, 26.07%, and 18.53%, respectively, compared with the drought stress treatment. Under drought stress, melatonin increased the root length by increasing its maximum and average rates of accumulation and increased the taproot diameter by increasing its maximum and average rates of accumulation. The drought stress+melatonin treatment significantly increased the lifespan of lateral roots and root hairs compared with the drought stress treatment. In conclusion, this study indicated that exogenous melatonin could improve the drought resistance and yield of cotton by promoting root growth and delaying root senescence.

Overview of Melatonin’s Impact on Postharvest Physiology and Quality of Fruits

Fruits are important horticultural commodities because they provide nutrients that help human health. Fruits are mostly consumed as fresh products; however, there are challenges in retaining the freshness, such as the rapid ripening process that triggers fruit deterioration and reduces fruit quality and nutrient content. The postharvest quality of horticultural crops is affected by pre-and postharvest treatment. Most farmers use chemical compounds and fungicides to prevent postharvest damage; however, this results in health hazards and environmental pollution. Melatonin can be used for maintaining and improving postharvest horticultural crops such as fruits. Melatonin is a new bioactive compound that is a potent free radical scavenger and antioxidant. It has been studied as an alternative to harmful chemicals used commercially in the postharvest management of fresh products. For human health, melatonin plays a regulatory role in circadian and seasonal rhythms, sleep, retinal functions, and the immune system. In plants, melatonin regulates many biological processes, particularly when plants have experienced abiotic stress, germination, aging, and growth. The effect of exogenous melatonin on fruit ripening has focused primarily on the relationship between melatonin and ethylene plant hormones. Many studies in recent years have discussed melatonin’s role in plants, particularly in delaying plant aging as an alternative way of increasing fruit shelf life. This review provides a comprehensive overview of melatonin biosynthesis in plants, factors that affect the content of melatonin in fruit, melatonin mechanisms in fruit ripening, the impact of melatonin on postharvest fruit quality, the effect of melatonin on postharvest quality, and the change in metabolite content of horticultural products, particularly fruits.

Exogenous melatonin ameliorates heat damages by regulating growth, photosynthetic efficiency and leaf ultrastructure of carnation

Carnation (Dianthus caryophyllus L.) is a floral crop that is highly valuable commercially. However, high temperatures adversely affect its growth and the quality of its cut flowers. Melatonin (MT) is a indole substance that can mitigate plant damage under heat stress. In this study, the leaves of carnation seedlings were sprayed with different concentrations of MT before exposure to high temperature. The indices of growth, physiological and chlorophyll fluorescence were measured and analyzed by the membership function method. The results showed that treatment with 100 μM MT was the most effective at ameliorating damage on carnation. We then analyzed the effects of 100 μM MT pretreatment on carnation at different time points of heat stress and found that this concentration of MT ameliorated the damage caused by heat stress, increased the content of photosynthetic pigments, enhanced the performance of photosystem II and improved photosynthesis. In addition, MT also reduced cell damage and lipid peroxidation, increased the activities of antioxidant enzymes and regulated the accumulation of osmotic substances in carnation. Moreover, MT increased the fresh/dry weight of stems and roots, promoted the opening of stomata, and protected the integrity of chloroplast structure of carnation. Compared with heat stress, pre-spraying with MT significantly down-regulated the transcription of a chlorophyll degradation gene and up-regulated the transcription of stress-related genes. Overall, this study provides a theoretical foundation for the mitigation of the adverse effects of exogenous MT under heat stress and proposes beneficial implications for the management of other plants subjected to global warming.

Exogenous Application of Melatonin Alleviates Drought Stress in Ranunculus asiaticus by Improving Its Morphophysiological and Biochemical Attributes

Melatonin (MT) controls various physiological functions and enhances plant drought tolerance. This study aimed to evaluate the effect of exogenous MT on the morpho-physiological and biochemical attributes of Ranunculus asiaticus under normal and drought conditions. A completely randomized design was used with two factors, drought stress and MT concentration (0, 50, 100, and 200 μM), to assess the effect of foliar application of MT on R. asiaticus seedlings. The experiment was conducted with a total of two groups: the drought stress group and the control group. The foliar application of MT was carried out four times during the study period. The drought stress group exhibited considerably decreased shoot length by 26.0%, leaf number by 31.03%, leaf area by 62.2%, fresh and dry vegetative weights by 34.5% and 52.9%, respectively, total chlorophyll and carotenoid contents by 68.29% and 51.72%, respectively, and relative water content by 7.1%; early emergence of flower stalks was observed within 29 days; increased relative electrolyte leakage by 20.5% compared to well-watered plants. Conversely, the foliar application of MT notably increased growth parameters compared with their no-treatment counterparts. Foliar treatment with 200 µM MT resulted in the most significant growth response in R. asiaticus under normal and drought stress conditions. Moreover, under stressful conditions compared with no treatment, exogenously applied MT induced the appearance of flower buds 21 days early and increased relative water content by 6.4%, proline contents by 32%, and peroxidase activity by 58% while reducing electrolyte leakage by 14.3%. Regarding tolerance index percentages, higher peroxidase and proline contents indicated their suitability for use as markers for drought tolerance, supporting the effective role of exogenous MT in enhancing the adaptability of Ranunculus to drought stress.

Melatonin Promotes the Development of Secondary Hair Follicles in Adult Cashmere Goats by Activating the Keap1-Nrf2 Signaling Pathway and Inhibiting the Inflammatory Transcription Factors NFκB and AP-1.

Exogenous melatonin (MT) has been used to promote the growth of secondary hair follicles and improve cashmere fiber quality, but the specific cellular-level mechanisms involved are unclear. This study was carried out to investigate the effect of MT on the development of secondary hair follicles and on cashmere fiber quality in cashmere goats. The results showed that MT improved secondary follicle numbers and function as well as enhanced cashmere fiber quality and yield. The MT-treated goat groups had high secondary-to-primary ratios (S:P) for hair follicles, greater in the elderly group (p < 0.05). Antioxidant capacities of secondary hair follicles improved fiber quality and yield in comparison with control groups (p < 0.05/0.01). Levels of reactive oxygen and nitrogen species (ROS, RNS) and malondialdehyde (MDA) were lowered (p < 0.05/0.01) by MT. There was significant upregulation of antioxidant genes (for SOD-3; GPX-1; NFE2L2) and the protein of nuclear factor (Nrf2), and downregulation of the Keap1 protein. There were significant differences in the expression of genes for secretory senescence-associated phenotype (SASP) cytokines (IL-1β, IL-6, MMP-9, MMP-27, CCL-21, CXCL-12, CXCL-14, TIMP-1,2,3) plus their protein of key transcription factors, nuclear factor kappa B (NFκB) and activator protein-1 (AP-1), in comparison with the controls. We concluded that MT could enhance antioxidant capacity and reduce ROS and RNS levels of secondary hair follicles through the Keap1-Nrf2 pathway in adult cashmere goats. Furthermore, MT reduced the expression of the SASP cytokines genes by inhibiting the protein of NFκB and AP-1 in the secondary hair follicles in older cashmere goats, thus delaying skin aging, improving follicle survival, and increasing the number of secondary hair follicles. Collectively, these effects of exogenous MT enhanced the quality and yield of cashmere fibers, especially at 5-7 years old.

Obituary: Stuart Maxwell Armstrong (1945-2022).

Professor Stuart M. Armstrong, best known in the field of chronobiology and pineal research for his pioneering studies on the effects of exogenous melatonin on rat circadian rhythms, left this mortal coil on June 3, 2022, in Cairns, Queensland, Australia. This article is protected by copyright. All rights reserved.

Effects of exogenous melatonin on body mass and thermogenesis in red-backed vole (Eothenomys miletus) between Kunming and Dali regions.

Melatonin (MEL) is an indole hormone synthesized and secreted by the pineal gland at night, which is involved in the regulation of body mass and thermogenesis in small mammals. To test the effects of exogenous MEL on body mass and thermogenic ability in two different red-backed vole (Eothenomys miletus) populations from two different regions (Kunming [KM] and Dali [DL]) with different annual variation in climatic variables, such as temperature, sunshine and rainfall. we traced the changes of energy balance in E. miletus from KMand DL, which were placed at 25 ± 1°C with photoperiod of 12 L:12 D, intraperitoneal injection of MEL was performed daily for 28 days. The results showed that body mass and food intake were significantly decreased, while resting metabolic rate (RMR) and nonshivering thermogenesis (NST) were significantly increased after MEL injection; Contents of total protein, mitochondrial protein, the activities of cytochrome C oxidase (COX) and α-glycerophosphate oxidase (α-PGO) in liver and brown adipose tissue (BAT) were enhanced; the activity of thyroxin 5'-deiodinase (T4 5'-DII) and uncoupling protein 1 (UCP1) in BAT were also increased. Serum leptin, triiodothyronine (T3 ) levels and T3 /T4 ratio were significantly increased, thyroxine (T4 ) levels was significantly decreased. Moreover, body mass and food intake in E. miletus from KM were higher than those from DL, but RMR and NST were lower than those from DL. Changes of body mass, food intake and thermogenic activity of KM were higher than those of DL when exposed to injection of MEL, indicating that E. miletus in KM were more sensitive to MEL. Furthermore, MEL was involved in the regulation of body mass and thermogenesis in E. miletus between KM and DL.

Effects of Exogenous Melatonin on Chrysanthemum Physiological Characteristics and Photosynthesis under Drought Stress

Melatonin has been confirmed to relieve drought stress in various plant species. However, the mechanism in garden chrysanthemums remains to be elucidated. Here, we examined the putative role of exogenous melatonin application in improving drought-stress tolerance in Chrysanthemum seedlings. Treatment with melatonin (100 µM) significantly mitigated the negative effects of drought stress on the seedling photosynthetic parameters and physiological and biochemical indexes. The increased tolerance conferred by exogenous melatonin was attributable to increased photosynthetic activity, which alleviates drought-induced oxidative damage by reducing malondialdehyde accumulation. In other words, the combined application of MT and PEG was better than their individual applications, as it prevented heat-induced membrane damages by declining the hydrogen peroxide (28%), malondialdehyde contents (38%), and relative electrical conductivity (19%) as compared to PEG. Interestingly, the melatonin application stimulated the activity of major antioxidant enzymes such as superoxide dismutase (21%), catalase (26%) and polyphenol oxidase (35%). In addition, exogenous melatonin promoted photosynthesis. Compared with the PEG drought-stress treatment, the melatonin treatment significantly increased the net photosynthetic rate (39%), stomatal conductance (27%), and transpiration rates (18%), while decreasing the intercellular CO2 concentration (10%). The photochemical quenching coefficient (46%), photosystem II (PSII) maximum photochemical quantum yield (22%), apparent electron transfer rate (37%), and PSII potential photochemical efficiency (18%) showed an upward trend. In summary, exogenous spraying of MT can effectively improve drought tolerance and mitigate the damage caused by drought stress in the “Xuanqiu ninghong” Chrysanthemum.

Effect of exogenous melatonin on improvement of chlorophyll content and photochemical efficiency of PSII in mallow plants (Malva parviflora L.) treated with cadmium.

Melatonin is a growth regulator that improves the growth and chlorophyll (chl) content in plants. This study aims to investigate the effect of melatonin pretreatment on chl synthesis and fluorescence parameters in Malva parviflora exposed to cadmium (Cd). The 42-day-old plants were transferred to nutrient solutions containing 50μM melatonin. After two days, some plants were exposed to 50μM Cd. Eight days after Cd treatment, some indicators related to chl fluorescence and some biochemical parameters were measured. In this study, melatonin increased chl content and chl a/pheophytin a (pheo a) ratio, chlorophyllide a (chlide a), porphyrin compounds, and 5-aminolevulinic acid (5-ALA) in the presence of Cd. However, it decreased chl a/chlide a ratio under these conditions. Whereas Cd treatment resulted in significant reductions in photochemical activity and electron transfer rate in PSII, melatonin improved photochemical efficiency of PSII by reducing the toxic effect of Cd on the activity of the oxygen evolving complex (OEC) on the electron donor site and reducing non-photochemical quenching (NPQ). Based on the results, it appears that melatonin can maintain the chl content of plants exposed to Cd by increasing the precursors of the chl biosynthesis pathway and reducing its degradation rate. These results may, at least in our experimental conditions, partly explain the reason for the improved yield and growth of Cd-exposed plants when pretreated with melatonin.

Protective Effect (Safener) of Melatonin on Vigna Radiata L. Seedlings in the Presence of the Fungicide Copper Oxychloride

Melatonin (N-acetyl-5-methoxytriptamine) is a novel plant regulatory molecule currently under study. Its role as a biostimulator and protector against abiotic and biotic stressors, through the regulation of the redox network and change in the expression of many elements of primary and secondary metabolism, is of great interest. The possible protective effect of melatonin in mungbean seedlings, previously primed seed treated with the fungicide copper oxychloride, was studied. The effect of melatonin and fungicide in growth of seedlings and photosynthetic pigments, leakage membranes, lipid peroxidation, antioxidant activity, and phytomelatonin content was studied. Also, the effect of exogenous melatonin on endogenous plant hormones indoleacetic acid, gibberellins, cytokinins, abscisic acid, salicylic acid, and jasmonic acid levels, in the absence and presence of fungicide, was analyzed. Melatonin improved growth of roots and aerial parts in the presence of fungicide; chlorophyll and carotenoid contents were protected by melatonin in the presence of melatonin and in melatonin-fungicide co-treatments. Membrane damage due to fungicide was lessened by melatonin. The hormonal profile (auxin, gibberellins, cytokinins, abscisic acid, ethylene precursor, salicylic acid, and jasmonic acid) in roots and leaves was greatly affected by copper fungicide and melatonin treatments. In general, an increasing in plant tolerance response has been detected, proposing melatonin as a natural safener molecule of plants in the presence of copper fungicide.

МОРФОФУНКЦИОНАЛЬНЫЕ ИЗМЕНЕНИЯ СЕМЕННИКОВ КРЫСПРИ ПРЕЖДЕВРЕМЕННОМ СТАРЕНИИ, ВЫЗВАННОМ ТЕМНОВОЙ ДЕПРИВАЦИЕЙ

The rapid development of technology has a significant impact on the daily life of a person. Light, sound, information pollution leads to sleep disturbance, which has a negative impact on the physical condition. Even short-term sleep disturbance caused by dark deprivation leads to a decrease in serum testosterone levels. The imbalance of male sex hormones, the synthesis of which is under the control of the hypothalamic-pituitary system, negatively affects the morphofunctional state of the testes. The effect of exogenous melatonin on the morphological and functional state of the spermatogenic epithelium of the testes, Leydig cells in white outbred male rats of 4 months of age was studied on the model of premature aging caused by 30-day dark deprivation, and the Klotho protein level in blood serum was assessed by enzyme immunoassay. It was found that the morphological changes in the testes were characterized by a decrease in the thickness of the spermatogenic epithelium by 30 days after darkdeprivation and a decrease in the level of the Klotho protein, which is a marker of premature aging. The introduction of exogenous melatonin had a protective effect on the morphological and functional status of the testes of animals, accompanied by the restorationof the spermatogenic epithelium, an increase in the Klotho protein to the level of thenegative control group