Search Results (37)

Salinity stress is a primary abiotic constraint limiting global crop productivity, with progressive soil salinization inducing growth inhibition and physiological dysfunction in plants. Although melatonin (MT) has been extensively documented to enhance stress adaptation, the underlying mechanisms through which it mediates salt tolerance by integrating physiological processes remain unclear. This study investigated the effects of varying MT concentrations on photosynthetic performance, plant water relations, water-use efficiency, and stress-responsive physiological parameters in tomatoes, aiming to identify the key physiological pathways for MT-mediated salt stress mitigation. The results showed that salt stress significantly reduced the leaf relative water content and root hydraulic conductivity, suppressed the photosynthetic rate, and ultimately caused significant reductions in the aboveground and root biomass. MT spraying effectively improved leaf water status and root water uptake capacity, enhancing the photosynthetic rate and water-use efficiency, thereby providing material and energy support for plant growth. Furthermore, MT spraying increased the total antioxidant capacity in leaves and promoted the synthesis of phenolic and flavonoid compounds, thereby reducing oxidative damage. Simultaneously, it stimulated the accumulation of osmolytes to enhance cellular osmotic adjustment capacity and optimized ion uptake to maintain cellular ion homeostasis. Among the tested concentrations, 100 μM MT showed the most significant alleviative effects. This concentration comprehensively enhanced the salt tolerance and growth performance of tomato plants by synergistically optimizing water use, photosynthetic function, antioxidant defense, and ion balance. In conclusion, these findings provide experimental evidence for elucidating the physiological mechanisms underlying MT-mediated salt tolerance in tomatoes and offer theoretical references for the rational application of MT in crop production under saline conditions. Full article

Grapevines (Vitis vinifera L.) face significant challenges from abiotic stresses caused by climate change, including drought, salinity, and temperature extremes. This comprehensive review examined the role of beneficial microorganisms in enhancing grapevine tolerance to these stresses, focusing on arbuscular mycorrhizal fungi (AMF), plant growth-promoting rhizobacteria (PGPR), and endophytes. The study analyzes species-specific effects and their molecular mechanisms, highlighting how single and consortium inoculations improve plant resilience. AMF species, particularly Funneliformis mosseae and Rhizophagus irregularis, demonstrated significant enhancement in drought and salinity tolerance through improved nutrient uptake and stress response modulation. The PGPRs, Bacillus and Pseudomonas species, show remarkable abilities to mitigate various abiotic stresses through mechanisms including phytohormone production and antioxidant defense enhancement. Endophytic microorganisms such as Pseudomonas fluorescens RG11 and Serendipita indica play crucial roles in stress mitigation through melatonin production and improved water retention, respectively. The synergistic effects of combined AMF, PGPR, and PGPF applications led to a significant increase in grapevine drought and salinity tolerance, improving nutrient uptake, photosynthesis rates, and antioxidant defense mechanisms. Molecular analysis revealed that these microbial consortia regulate the expression of stress-responsive genes, particularly VvNCED and VvP5CS, enhancing grapevine resilience through improved osmotic adjustment, ROS scavenging, and hormonal regulation. These findings provide valuable insights into the molecular pathways underlying stress tolerance, offering promising strategies for sustainable viticulture under climate change. Full article

Lead (Pb) is a toxic heavy metal that severely impairs plant growth and crop quality. Melatonin, a widely present indoleamine compound, enhances plant stress tolerance, yet its role in tea plant resistance to lead stress remains unclear. This study examined two tea genotypes with distinct anthocyanin levels, Longjing43 (LJ43) and Zijuan (ZJ), comparing their phenotype, antioxidant capacity, secondary metabolite synthesis, and lead transport gene expression under lead stress. Excessive Pb exposure caused severe oxidative stress, reducing PSII efficiency, increasing ROS accumulation, and intensifying lipid peroxidation. ZJ, with higher anthocyanin concentration, exhibited stronger lead stress resistance than LJ43. Under lead stress, melatonin promoted phenylalanine accumulation in ZJ, facilitating its conversion into anthocyanins and catechins via key gene regulation (CsC4H, CsLAR, and CsANS). Moreover, exogenous melatonin significantly reduced Pb concentrations in roots, stems, and leaves, with a more pronounced effect in ZJ (reductions of 20.46%, 53.30%, and 38.17%, respectively), which might be associated with the downregulation of Pb transport genes like CsZIP1 (notably showing a 29-fold decrease). While these results suggest that melatonin might enhance Pb stress tolerance by modulating flavonoid metabolism and restricting Pb uptake, the specific roles of anthocyanins and catechins in this process remains to be fully elucidated. Further studies are necessary to clarify the primary bioactive compounds and mechanisms involved in melatonin-mediated heavy metal stress mitigation. Full article

In response to evolving climatic conditions, plants frequently confront multiple abiotic stresses, necessitating robust adaptive mechanisms. This study focuses on the responses of Selenicereus undatus L. to both individual stresses (cadmium; Cd, salt; S, and drought; D) and their combined applications, with an emphasis on evaluating the mitigating effects of (M) melatonin. Through transcriptome analysis, this study identifies significant gene expression changes and regulatory network activations. The results show that stress decreases pitaya growth rates by 30%, reduces stem and cladode development by 40%, and increases Cd uptake under single and combined stresses by 50% and 70%, respectively. Under stress conditions, enhanced activities of H₂O₂, POD, CAT, APX, and SOD and elevated proline content indicate strong antioxidant defenses. We identified 141 common DEGs related to stress tolerance, most of which were related to AtCBP, ALA, and CBP pathways. Interestingly, the production of genes related to signal transduction and hormones, including abscisic acid and auxin, was also significantly induced. Several calcium-dependent protein kinase genes were regulated during M and stress treatments. Functional enrichment analysis showed that most of the DEGs were enriched during metabolism, MAPK signaling, and photosynthesis. In addition, weighted gene co-expression network analysis (WGCNA) identified critical transcription factors (WRKYs, MYBs, bZIPs, bHLHs, and NACs) associated with antioxidant activities, particularly within the salmon module. This study provides morpho-physiological and transcriptome insights into pitaya’s stress responses and suggests molecular breeding techniques with which to enhance plant resistance. Full article

An excess of selenium (Se) can cause toxicity to plants. Treatment with melatonin (MT) can alleviate the stress conditions in plants. Limited research exists on the impact of MT on Se stress and uptake in fruit trees. To address Se stress and enhance Se accumulation in Cyphomandra betacea Sendt. (Solanum betaceum Cav.), the effects of exogenous MT (50–200 µmol L⁻¹) on C. betacea growth and Se accumulation under Se stress were studied. MT increased the biomass, photosynthetic pigments levels, and peroxidase activity of C. betacea under Se stress. Only at concentrations of 150 and 200 µmol L⁻¹ did MT increase superoxide dismutase and catalase activities, as well as soluble protein content in C. betacea leaves. MT treatment also boosted the Se content and bioconcentration factor of C. betacea under Se stress while reducing the translocation factor. The dose of MT was directly related to the Se content, and the highest levels of Se in roots and shoots were observed at 150 µmol L⁻¹, which was an increase of 114% and 60%, respectively, compared with the control. In addition, correlation, principal component, cluster, grey, and path analyses revealed a strong correlation between root Se content and shoot biomass with the shoot Se content. Therefore, MT treatment can mitigate Se stress and enhance Se uptake in C. betacea, and the most effective dose of MT is 150 µmol L⁻¹. Full article

Envenomation by the Hypnale hypnale in the Western Ghats of India (particularly in the Malabar region of Kerala) and the subcontinent island nation of Sri Lanka is known to inflict devastating mortality and morbidity. Currently, H. hypnale bites in India are devoid of anti-venom regimens. A detailed characterization of the venom is essential to stress the need for therapeutic anti-venom. Notably, the deleterious effects of this venom on human blood cells have largely remained less explored. Therefore, in continuation of our previous study, in the present study, we envisioned investigating the effect of venom on the morphological and physiological properties of red blood cells (RBCs). The venom readily induced deleterious morphological changes and, finally, the aggregation of washed RBCs. The aggregation process was independent of the ROS and the intracellular Ca²⁺ ion concentration. Confocal and scanning electron microscopy (SEM) images revealed the loss of biconcave morphology and massive cytoskeletal disarray. Crenation or serrated plasma membrane projections were evenly distributed on the surface of the RBCs. The venom did not cause the formation of methemoglobin in washed RBCs but was significantly induced in whole blood. Venom did not affect glucose uptake and Na⁺/K⁺ -ATPase activity but inhibited glucose 6 phosphate dehydrogenase activity and decreased the fluidity of the plasma membrane. Venom-induced RBC aggregates exhibited pro-coagulant activity but without affecting platelet aggregation. In pre-incubation or co-treatment studies, none of the bioactive compounds, such as melatonin, curcumin, fisetin, berberine, and quercetin, sugars such as mannose and galactose, and therapeutic polyvalent anti-venoms (Bharat and VINS) were inhibited, whereas only N-acetylcysteine and H. hypnale monovalent anti-venom could inhibit venom-induced deleterious morphological changes and aggregation of RBCs. In post-treatment studies, paradoxically, none of the bioactives and anti-venoms, including N-acetylcysteine and H. hypnale monovalent anti-venom, reversed the venom-induced RBC aggregates. Full article

Horticultural crops play a vital role in global food production, nutrition, and the economy. Horticultural crops are highly vulnerable to abiotic stresses. These abiotic stresses hinder plant growth and development by affecting seed germination, impairing photosynthetic activity, and damaging root development, thus leading to a decrease in fruit yield, quality, and productivity. Scientists have conducted extensive research to investigate the mechanisms of resilience and the ability to cope with environmental stresses. In contrast, the use of phytohormones to alleviate the detrimental impacts of abiotic stresses on horticulture plants has been generally recognized as an effective method. Among phytohormones, melatonin (MT) is a novel plant hormone that regulates various plants’ physiological functions such as seedling development, root system architecture, photosynthetic efficiency, balanced redox homeostasis, secondary metabolites production, accumulation of mineral nutrient uptake, and activated antioxidant defense system. Importantly, MT application significantly restricted heavy metals (HMs) uptake and increased mineral nutrient accumulation by modifying the root architecture system. In addition, MT is a naturally occurring, multifunctional, nontoxic biomolecule having antioxidant properties. Furthermore, this review described the hormonal interaction between MT and other signaling molecules in order to enhance abiotic stress tolerance in horticulture crops. This review focuses on current research advancements and prospective approaches for enhancing crop tolerance to abiotic stress. Full article

This study aimed to develop a biostimulant formulation using humic acid (HA), silicon, and biochar alone or in combination to alleviate the lethality induced by combined heavy metals (HM-C; As, Cd, and Pb), drought stress (DS; 30–40% soil moisture), and salt stress (SS; 150 mM NaCl) in rice. The results showed that HA, Si, and biochar application alone or in combination improved plant growth under normal, DS, and SS conditions significantly. However, HA increased the lethality of rice by increasing the As, Cd, and Pb uptake significantly, thereby elevating lipid peroxidation. Co-application reduced abscisic acid, elevated salicylic acid, and optimized the Ca²⁺ and Si uptake. This subsequently elevated the K⁺/Na⁺ influx and efflux by regulating the metal ion regulators (Si: Lsi1 and Lsi2; K⁺/Na⁺: OsNHX1) and increased the expressions of the stress-response genes OsMTP1 and OsNramp in the rice shoots. Melatonin synthesis was significantly elevated by HM-C (130%), which was reduced by 50% with the HA + Si + biochar treatment. However, in the SS- and DS-induced crops, the melatonin content showed only minor differences. These findings suggest that the biostimulant formulation could be used to mitigate SS and DS, and precautions should be taken when using HA for heavy metal detoxification. Full article

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. Full article

There have been concerns about the potential health risks posed by microplastics (MP). The detection of MP in a variety of food products revealed that humans are ingesting MP. Nevertheless, there is a paucity of data about their impacts, as well as their uptake, on intestinal barrier integrity. This study examined the toxic effects of oral administration of two doses of polyethylene microplastics (PE-MP) (3.75 or 15 mg/kg/day for 5 weeks; mean particle size: 4.0–6.0 µm) on the intestinal barrier integrity in rats. Moreover, the effect of melatonin treatment with MP exposure was also assessed. The PE-MP particle uptake, histopathological changes, Alcian blue staining, Muc2 mRNA, proinflammatory cytokines (IL-1β and TNF-α), and cleaved caspase-3, as well as tight junction proteins (claudin-1, myosin light-chain kinase (MLCK), occludin, and zonula occludens-1 (ZO-1)) were assessed. Oral administration of PE-MP resulted in apparent jejunal histopathological alterations; significantly decreased mucin secretion, occludin, ZO-1, and claudin-1 expression; and significantly upregulated MLCK mRNA, IL-1β concentration, and cleaved caspase-3 expression. Melatonin reversed these altered parameters and improved the PE-MP-induced histopathological and ultrastructure changes. This study highlighted the PE-MP’s toxic effect on intestinal barrier integrity and revealed the protective effect of melatonin. Full article

The thyroid gland is the primary site of sodium/iodide symporter (NIS), an intrinsic plasma membrane protein responsible for the active uptake of iodine, which is indispensable for thyroid hormone synthesis. Since exposure of the thyroid to NIS inhibitors can potentially have harmful effects on the entire organism, it is important to investigate the potential protective effects of known antioxidants, such as melatonin and indole-3-propionic acid (IPA), against pro-oxidative action of classic NIS inhibitors. The study aimed to check if and to what extent melatonin and IPA interact with some confirmed NIS inhibitors regarding their effects on oxidative damage to membrane lipids in the thyroid. For comparison with the thyroid gland, in which NIS is typically present, the liver tissue—not possessing NIS—was applied in the present study. Thyroid and liver homogenates were incubated in the presence of tested NIS inhibitors (i.e., NaClO₃, NH₄SCN, KSeCN, KNO₃, NaF, KClO₄, and BPA) in different ranges of concentrations with/without melatonin (5 mM) or IPA (5 mM). The malondialdehyde+4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. NaClO₃ increased LPO in the thyroid and in the liver, but these pro-oxidative effects were not prevented by either melatonin or IPA. Instead, pro-oxidative effects of NH₄SCN observed in both tissues were prevented by both indole substances. KSeCN and NaF increased LPO only in the thyroid, and these pro-oxidative effects were prevented by melatonin and IPA. KNO₃, KClO₄, and BPA did not increase LPO, which can be due to their low concentrations resulting from restricted solubility. In conclusion, as melatonin prevented oxidative damage to membrane lipids in the thyroid caused by some sodium/iodide symporter inhibitors, this indoleamine shoud be considered as a potential protective agent when produced appropriately in living organisms but also as an exogenous substance recommended to individuals overexposed to NIS inhibitors. Full article

Melatonin, a hormone known for its role in regulating sleep–wake cycles in mammals, has been found to have diverse functions in horticultural plants. In recent years, research has revealed the involvement of melatonin in various physiological processes in plants, like regulation of growth and development, stress tolerance, and antioxidant defense. Melatonin can augment seed germination, roots, shoot growth, and biomass accumulation in horticultural crops. It also performs a vital role in regulating vegetative and reproductive growth stages, floral transition, and leaf senescence. Melatonin improves stress tolerance in crops by regulating root architecture, nutrient uptake, and ion transport. Additionally, melatonin works like a broad-spectrum antioxidant by scavenging reactive oxygen species and enhancing antioxidant activity. The mechanism of action of melatonin in horticultural plants involves gene expressions, hormone signaling pathways, and antioxidant defense pathways. Melatonin also interacts with other plant growth regulators (PGRs), comprising auxins, cytokinins, and abscisic acid to coordinate various physiological processes in plants. Melatonin has evolved as a versatile chemical entity with diverse functions in horticultural plants, and its potential applications in crop production and stress management are increasingly being explored. This review aims to provide a comprehensive insight into the present state of knowledge about melatonin and its role in horticulturally important plants and identify avenues for further research and practical applications. Further study must be conducted to fully elucidate the mechanisms of melatonin action in crops and to outline effective strategies for its practical use in horticultural practices. Full article

Nitric oxide (NO) plays an important role in plant stress responses. However, the mechanisms underlying NO-induced stress resistance to cadmium (Cd) stress in rice remain elusive. In this study, rat neuron NO synthase (nNOS)-overexpressing rice plants with higher endogenous NO level showed higher cadmium stress tolerance than the wild-type plants. The results showed that nNOS-overexpressing rice plants accumulated less cadmium in the roots and shoots by downregulating the expression of Cd uptake and transport related genes including OsCAL1, OsIRT2, OsNramp5, and OsCd1. Moreover, nNOS-overexpressing rice plants accumulated less hydrogen peroxide (H₂O₂), accompanying with higher expression of antioxidant enzyme genes (OsCATA, OsCATB, and OsPOX1) and corresponding higher enzyme activities under cadmium stress. Furthermore, the transcription of melatonin biosynthetic genes, including OsASMT1, OsTDC1, OsTDC3, and OsSNAT2, was also upregulated in nNOS-overexpressing plants, resulting in increased content of melatonin under cadmium treatment compared with the wild-type controls. Taken together, this study indicates that nNOS overexpression improves Cd tolerance of rice seedlings through decreasing cadmium accumulation and enhancing the antioxidant capacity and melatonin biosynthesis of the plants. Full article

Drought is one of the most detrimental factors that causes significant effects on crop development and yield. However, the negative effects of drought stress may be alleviated with the aid of exogenous melatonin (MET) and the use of plant-growth-promoting bacteria (PGPB). The present investigation aimed to validate the effects of co-inoculation of MET and Lysinibacillus fusiformis on hormonal, antioxidant, and physio-molecular regulation in soybean plants to reduce the effects of drought stress. Therefore, ten randomly selected isolates were subjected to various plant-growth-promoting rhizobacteria (PGPR) traits and a polyethylene-glycol (PEG)-resistance test. Among these, PLT16 tested positive for the production of exopolysaccharide (EPS), siderophore, and indole-3-acetic acid (IAA), along with higher PEG tolerance, in vitro IAA, and organic-acid production. Therefore, PLT16 was further used in combination with MET to visualize the role in drought-stress mitigation in soybean plant. Furthermore, drought stress significantly damages photosynthesis, enhances ROS production, and reduces water stats, hormonal signaling and antioxidant enzymes, and plant growth and development. However, the co-application of MET and PLT16 enhanced plant growth and development and improved photosynthesis pigments (chlorophyll a and b and carotenoids) under both normal conditions and drought stress. This may be because hydrogen-peroxide (H₂O₂), superoxide-anion (O²⁻), and malondialdehyde (MDA) levels were reduced and antioxidant activities were enhanced to maintain redox homeostasis and reduce the abscisic-acid (ABA) level and its biosynthesis gene NCED3 while improving the synthesis of jasmonic acid (JA) and salicylic acid (SA) to mitigate drought stress and balance the stomata activity to maintain the relative water states. This may be possible due to a significant increase in endo-melatonin content, regulation of organic acids, and enhancement of nutrient uptake (calcium, potassium, and magnesium) by co-inoculated PLT16 and MET under normal conditions and drought stress. In addition, co-inoculated PLT16 and MET modulated the relative expression of DREB2 and TFs bZIP while enhancing the expression level of ERD1 under drought stress. In conclusion, the current study found that the combined application of melatonin and Lysinibacillus fusiformis inoculation increased plant growth and could be used to regulate plant function during drought stress as an eco-friendly and low-cost approach. Full article

Amending Pb-affected soil with biochar (BH) and magnesium potassium phosphate cement (MKC) reduces Pb uptake in plants. Moreover, foliar applications of melatonin and proline are also known to reduce plant oxidative stress and Pb uptake. However, little is known about combining both techniques, i.e., adding a combo immobilizing dose (CIA = mixture of BH and MKC at 50:50 ratio) in Pb-polluted soil and foliar application of proline and melatonin for reducing Pb uptake and oxidative stress in spinach. Control, proline, melatonin, CIA, CIA+proline, and CIA+melatonin were the treatments utilized in this pot study to see their effects on reducing plant oxidative stress, Pb uptake, and improving spinach quality in Pb-polluted soil. Moreover, Pb bioavailability, enzymatic activities, and numbers of bacteria, fungi, and actinomycetes in the soil were also evaluated. The effect of CIA on reducing Pb in the soil-plant system and improving soil enzymes and microbial numbers was more pronounced than melatonin alone. The most effective treatment was CIA+melatonin reducing Pb availability in soil (77%), shoots (95%), and roots (84%), alleviating oxidative stress, and improving plant biomass (98%) and nutrients. Soil enzymatic activities and the number of microorganisms in the rhizosphere were also highest with CIA+melatonin. Results highlight the significance of CIA+melatonin, as an inexpensive approach, in remediating Pb-polluted soil and improving spinach quality. However, further research is needed to understand the significance of CIA+melatonin on different crops and various soil Pb concentrations before employing this technique commercially in agriculture and environment sectors. Full article