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High soil salinity represents a critical environmental constraint to crop production. In order to ameliorate the effects of salinity, a plethora of molecules have been applied and promising outcomes have been noted. The beneficial effects of chitosan (CTS) and melatonin (Mel) application, separately, have been previously recorded with respect to plant growth and productivity, leading to the hypothesis that their conjugation in the form of chitosan-melatonin nanoparticles (CTS-HPMC-Mel NPs) could lead to further enhanced performance of plants under control and stress conditions. In this regard, novel CTS-HPMC-Mel NPs were synthesized, characterized and then employed as a chemical priming agent in spearmint (Mentha spicata L.) plants 24 h prior to salinity stress imposition. As expected, salt stress negatively affected morphophysiological attributes such as plant height, leaf number, leaf fresh weight, leaf dry weight, photosynthetic pigments, Fv/Fo, and Fv/Fm. On the other hand, stress-related attributes, such as content of proline, MDA and H2O2, as well as activity of APX and GP enzymes were increased in response to salt stress. However, adverse effects of salt stress were ameliorated with Mel and CTS-HPMC-Mel NP treatments by enhancing morphological traits, proline, antioxidant enzymatic activities, as well as content of dominant constituents of essential oil profile. It is worth noting that conjugated form of Mel with chitosan, in comparison with solo treatment of Mel, was more effective in combating stress effects. To our knowledge, this is the first report to demonstrate that engineered CTS-HPMC-Mel NPs could be applied as an innovative protective agent to mitigate the effects of salinity in crop plants.

Background:‘Xynisteri’is the reference Cypriot white cultivar that, despite its significant societal and economic impact, ispoorly characterized regarding its qualitative properties, while scarce information exists regarding its aroma profile. In the cur-rent study, the effect of leaf removal during fruit set (BBCH 71) on 6-year cordon-trained, spur-pruned grapevines was assessedand an array of physiological, biochemical, and qualitative indices were monitored during successive developmental stages(BBCH 75, BBCH 85, BBCH 87, and BBCH 89). Grapes were additionally monitored for the volatile organic compounds (VOCs)profile during the advanced on-vine developmental stages (BBCH 85–BBCH 89) with the employment of gaschromatography–mass spectrometry (GC–MS), Fourier-transform near infrared (FT-NIR) spectra and electronic nose (E-nose)techniques.Results: Grape berries from the vines subjected to leaf removal were characterized by higher solid soluble sugars (SSC), titrat-able acidity (TA), tartaric acid, and ammonium nitrogen contents, while this was not the case for assimilable amino nitrogen(primary amino nitrogen). A total of 75 compounds were identified and quantified, including aliphatic alcohols, benzenic com-pounds, phenols, vanillins, monoterpenes, and C13-norisoprenoids. Leaf removal led to enhanced amounts of glycosylatedaroma compounds, mainly monoterpenes, and C13-norisoprenoids. Chemometric analysis, used through FT-NIR and E-nose,showed that the aromatic patterns detected were well associated to the grape ripening trend and differences between leafremoval-treated and control grapes were detectable during fully ripe stage.Conclusion: Leaf removal at fruit set resulted in an overall induction of secondary metabolism, with special reference to glyco-sylated aroma compounds, namely monoterpenes and C13-norisoprenoids

Due to their sessile nature, plant cannot escape from stress factors in their growing environment, in either biotic or abiotic nature. Amid the abiotic stress factors; high levels of soil cadmium (Cd) impose heavy metal stress on plants, resulting in critical injuries and reduced agronomic performance. In order to buffer the adverse effects of Cd stress, novel nanoparticles (NP) have been applied and notable improvements have been reported. According to the literature, the protective roles of polyamines (e.g., Putrescine; Put) and carbon quantum dots (CQD) have been reported with respect to the plant productivity under either stress or non-stress conditions. Those reports led us to hypothesize that the conjugation of Put and CQD (Put-CQD NPs) might lead to further augmented performance of plants under stress and non-stress conditions. In this regard, we successfully synthesized a novel nanomaterial Put-CQD NPs. In this respect, Put (50 mg L−1), CQD (50 mg L−1) and Put-CQD NPs (25 and 50 mg L−1) were sprayed in ‘Sultana’ grapevines under Cd stress (10 mg kg−1). As expected, upon stress, Cd content in leaf and root tissues increased by 103.40% and 65.15%, respectively (p < 0.05). The high uptake and accumulation of Cd in plant tissues were manifested in significant alterations of physiological and biochemical attributes of the plant. Concerning stress markers, Cd stress caused increases in content of induced MDA, H2O2, and proline as well as electrolyte leakage rate. As expected, Cd stress caused critical reductions in fresh and dry leaf weight by 21.31% and 42.34%, respectively (p < 0.05). On the other hand, both Put-CQD NPs increased fresh and dry leaf weigh up to approximately 30%. The Cd-mediated disturbances in photosynthetic pigments and chlorophyll fluorescence were buffered with Put-CQD NPs. Of the defence system, enzymatic (SOD, APX, GP) as well as anthocyanin and phenolics were induced by both Cd stress and Put-CQD NPs (p < 0.05). On the other hand, Cd stress reduced content of polyamines (putrescine (Put), spermine (Spm) and spermidine (Spd) by 39.28%, 53.36%, and 39.26%, respectively (p < 0.05). However, the reduction levels were buffered by the treatments. Considering the effectiveness of both NP concentrations, the lower dose (25 mg L−1) could be considered as an optimal concentration. To our knowledge, this is the first report of its kind as a potential agent to reduce the adverse effects of Cd stress in grapevines.

Salt stress is of the most detrimental abiotic stress factors on either crop or non-crop species. Of the strategies employed to boost the performance of the plants against harmful impacts of salt stress; application of novel nano-engineered particles have recently gained great attention as a promising tool. Octa-aminopropyl polyhedral oligomeric silsesquioxanes nanoparticles (OA-POSS NPs) were synthesized and then a foliar-application of OA-POSS NPs were carried out on sweet basil plants subjected to the salt stress. In that context, interactive effects of OA-POSS NPs (25, 50 and 100 mg L-1) and salinity stress (50 and 100 mM NaCl) were assayed by estimating a series of agronomic, physiological, biochemical and analytical parameters. OA-POSS NPs decreased the harmful effects of salinity by increasing photosynthetic pigment content, adjusting chlorophyll fluorescence, and triggering non-enzymatic (phenolic content) and enzymatic antioxidant components. The findings suggested that 25 mg L-1 OA-POSS NPs is the optimum concentration for sweet basil grown under salt stress. Considering the essential oil profile, estragole was the predominant compound with a percentage higher than 50% depending on the treatment. In comparison to the control group, 50 mM NaCl did not significantly affect estragole content, whilst 100 mM NaCl caused a substantial increase in estragole content. Regarding OA-POSS NPs treatments, increments by 16.8%, 11.8% and 17.5% were observed following application with 25, 50 and 100 mg L-1, respectively. Taken together, the current study provides evidence that POSS NPs can be employed as novel, 'green' growth promoting agents in combating salt stress in sweet basil.

Water stress may greatly limit plant functionality and growth. Stomatal closure and consequently reduced transpiration are considered as early and sensitive plant responses to drought and salinity stress. An important consequence of stomatal closure under water stress is the rise of leaf temperature (Tleaf ), yet Tleaf is not only fluctuating with stomatal closure. It is regulated by several plant parameters and environmental factors. Thermal imaging and different stress indices, incorporating actual leaf/crop temperature and reference temperatures, were developed in previous studies toward normalizing for effects unassociated to water stress on Tleaf , aiming at a more efficient water stress assessment. The concept of stress indices has not been extensively studied on the model plant Arabidopsis thaliana. Therefore, the aim of this study was to examine the different indices employed in previous studies in assessing rosette transpiration rate (E) in Arabidopsis plants grown under two different light environments and subjected to salinity. After salinity imposition, E was gravimetrically quantified, and thermal imaging was employed to quantify rosette (Trosette ) and artificial reference temperature (Twet, Tdry ). Trosette and several water stress indices were tested for their relation to E. Among the microclimatic growth conditions tested, RWSI1 ([Trosette - Twet ]/[Tdry - Twet ]) and RWSI2 ([Tdry - Trosette ]/[Tdry - Twet ]) were well linearly-related to E, irrespective of the light environment, while the sole use of either Twet or Tdry in different combinations with Trosette returned less accurate results. This study provides evidence that selected combinations of Trosette , Tdry , and Twet can be utilized to assess E under water stress irrespective of the light environment.

Climate change gives rise to numerous environmental stresses, including soil salinity. Salinity/salt stress is the second biggest abiotic factor affecting agricultural productivity worldwide by damaging numerous physiological, biochemical, and molecular processes. In particular, salinity affects plant growth, development, and productivity. Salinity responses include modulation of ion homeostasis, antioxidant defense system induction, and biosynthesis of numerous phytohormones and osmoprotectants to protect plants from osmotic stress by decreasing ion toxicity and augmented reactive oxygen species scavenging. As most crop plants are sensitive to salinity, improving salt tolerance is crucial in sustaining global agricultural productivity. In response to salinity, plants trigger stress-related genes, proteins, and the accumulation of metabolites to cope with the adverse consequence of salinity. Therefore, this review presents an overview of salinity stress in crop plants. We highlight advances in modern biotechnological tools, such as omics (genomics, transcriptomics, proteomics, and metabolomics) approaches and different genome editing tools (ZFN, TALEN, and CRISPR/Cas system) for improving salinity tolerance in plants and accomplish the goal of “zero hunger,” a worldwide sustainable development goal proposed by the FAO.

Accumulating evidence suggests that the biphasic phenomenon of hormesis may provide the means for ensuring agricultural sustainability in changing climate scenarios. The adaptive responses induced in plants exposed to hormetic, low doses of various stressors can result in enhanced tolerance upon their subsequent exposure to adverse environmental stimuli. Hormesis-based priming is highly generalizable, as it can be induced by a series of effectors applied at different growth stages in a plethora of plant species. This review aims at highlighting the most promising hormesis-based priming approaches, based on natural as well as artificial environmental factors, including chemicals, radiation, and nanomaterials. Furthermore, we discuss research gaps, future perspectives and recommended actions for reaching specific milestones in the roadmap for achieving the target of commercializing the benefits of this platform, in order to secure agricultural sustainability.

Background Melatonin is a multi-functional molecule widely employed in order to mitigate abiotic stress factors, in general and salt stress in particular. Even though previous reports revealed that melatonin could exhibit roles in promoting seed germination and protecting plants during various developmental stages of several plant species under salt stress, no reports are available with respect to the regulatory acts of melatonin on the physiological and biochemical status as well as the expression levels of defense- and secondary metabolism-related related transcripts in bitter melon subjected to the salt stress. Results Herewith the present study, we performed a comprehensive analysis of the physiological and ion balance, antioxidant system, as well as transcript analysis of defense-related genes (WRKY1, SOS1, PM H+-ATPase, SKOR, Mc5PTase7, and SOAR1) and secondary metabolism-related gene expression (MAP30, α-MMC, polypeptide-P, and PAL) in salt-stressed bitter melon (Momordica charantia L.) plants in response to melatonin treatment. In this regard, different levels of melatonin (0, 75 and 150 µM) were applied to mitigate salinity stress (0, 50 and 100 mM NaCl) in bitter melon. Accordingly, present findings revealed that 100 mM salinity stress decreased growth and photosynthesis parameters (SPAD, Fv/Fo, Y(II)), RWC, and some nutrient elements (K+, Ca2+, and P), while it increased Y(NO), Y(NPQ), proline, Na+, Cl−, H2O2, MDA, antioxidant enzyme activity, and lead to the induction of the examined genes. However, prsiming with 150 µM melatonin increased SPAD, Fv/Fo, Y(II)), RWC, and K+, Ca2+, and P concentration while decreased Y(NO), Y(NPQ), Na+, Cl−, H2O2, and MDA under salt stress. In addition, the antioxidant system and gene expression levels were increased by melatonin (150 µM). Conclusions Overall, it can be postulated that the application of melatonin (150 µM) has effective roles in alleviating the adverse impacts of salinity through critical modifications in plant metabolism.

Heavy metals are the cause of one of the most significant biosphere contamination problems worldwide, as they can be highly reactive and toxic according to their oxidation levels. Their toxic effects are correlated with the elevated production of reactive oxygen species (ROS) and oxidative cellular damage occurring in plants. The aim of the present study was the investigation of the effects of three heavy metals (Ni, Cu, Zn) applied to the soil in biochemical defense-related responses and allergen production in the aromatic plant oregano (Origanum vulgare L.) from the Lamiaceae family. The concentrations of the three heavy metals used, were based on the 2002 Regulation of the Polish Ministry of the Environment on Soil Quality Standards [(i) agricultural land (group B): Ni 100 ppm, Ni 210 ppm, Cu 200 ppm, Cu 500 ppm, Zn 720 ppm and (ii) industrial land (group C): Ni 500 ppm, Cu 1000 ppm, Zn 1500 ppm, Zn 3000 ppm]. The investigated plants accumulated heavy metal ions in aerial parts to a variable extent. For plants grown in soil contaminated with Zn, phenotypic representation of the growth and development were strongly limited and dependent on zinc concentration. Phenotypic representation of plants grown in soil contaminated with Ni and Cu were characterized by normal growth, slightly lower or equal to that of the control plants. All tested metals (Ni, Cu, Zn) caused a concentration-dependent decrease in photosynthetic pigments especially in total chlorophyll content. Highest cellular damage levels were observed in plants treated with Cu and Zn. Increasing concentration of these metals (especially Zn) caused a further increase in cellular damage. 3000 ppm Zn caused highest increase in the concentration of proline compared with control plants, suggesting osmotic stress imposition. Treatment with 1000 ppm Cu led to increased concentration of the allergenic protein profilin in relation to control plants by profilin ELISA analysis, while increasing concentrations of Cu and Zn led to a decrease in the concentration of phenolic compounds and total antioxidant capacity. On the basis of these findings, Ni stress in oregano plants appears to be less damaging (in relation to Cu and Zn) and with lower allergenic potential, compared with 1000 ppm Cu. The present study provides novel biochemical insight in the defense and allergenic response of aromatic plants to metal ions present in the rhizosphere; however, more comprehensive research under realistic field conditions is needed to fully decipher this interaction.

Melatonin functions in multiple aspects of plant growth, development, and stress response. Nonetheless, the mechanism of melatonin in plant carbon metabolism remains largely unknown. In this study, we investigated the influence of melatonin on the degradation of starch in tomato leaves. Results showed that exogenous melatonin attenuated carbon starvation-induced chlorophyll degradation and leaf senescence. In addition, melatonin delayed leaf starch degradation and inhibited the transcription of starch-degrading enzymes after sunset. Interestingly, melatonin-alleviated symptoms of leaf senescence and starch degradation were compromised when the first key gene for starch degradation, α-glucan water dikinase (GWD), was overexpressed. Furthermore, exogenous melatonin significantly upregulated the transcript levels of several microRNAs, including miR171b. Crucially, the GWD gene was identified as a target of miR171b, and the overexpression of miR171b ameliorated the carbon starvation-induced degradation of chlorophyll and starch, and inhibited the expression of the GWD gene. Taken together, these results demonstrate that melatonin promotes plant tolerance against carbon starvation by upregulating the expression of miR171b, which can directly inhibit GWD expression in tomato leaves.

The positive effects of biochar applied as soil conditioner for boosting soil fertility and thus plant growth are sufficiently documented, mostly through in-situ experimentation. This field study evaluated the effects of soil amendment (5% v/v) with distinct types of biochar (biosolids-derived biochar, BDB; cattle manure-derived biochar, MDB; spent coffee grounds-derived biochar, SCGDB) on the growth, physiology and quality attributes of lettuce (Lactuca sativa L.) plants grown in sandy clay loam-textured soil, under temperate climatic conditions. Peat moss (PM) was also used, to serve as internal control due to its wide use. Plants grown on MDB-amended soil showed a significant increase of biomass production rate, evident through elevated mean fresh and dry weight values compared with all other treatments. Increased growth was also found in BDB treatment, though failed to reach significance. None of the treatments impacted the photosynthetic pigment content, however they did reduce the nitrates content in leaves. Leaves sampled from BDB and MDB treatments showed reduced soluble solids content (SSC) and titratable acidity (TA), and increased sucrose content. MDB-treated plants showed increased fructose content while BDB-treated plants showed increased total soluble sugar and total phenolics content. Moreover, plants grown in MDB- and BDB-amended soil showed increased total antioxidant capacity, despite maintaining ascorbic acid content in values similar to control. SCGDB and PM treatment did not affect any of the parameters tested. Overall, results showed that BDB and MDB applied as soil amendments may serve as means for enhancing the growth, and partially the nutritional value of lettuce plants.

Under the era of climate change, plants are forced to survive under increasingly adverse conditions. Application of biostimulants in plants is shown to mitigate the deleterious effects of abiotic stresses including salinity, enhancing plant tolerance and performance. The present study focuses on the effects of five biostimulants based on biocompost and biofertilizer compounds that have been applied to tomato plants grown in the presence (salt-stressed plants) or absence of salt stress (control plants). To study the beneficial effects of the biostimulants in tomato plants, a series of analyses were performed, including phenotypic and agronomic observations, physiological, biochemical and enzymatic activity measurements, as well as gene expression analysis (RT-qPCR) including genes involved in antioxidant defense (SlCu/ZnSOD, SlFeSOD, SlCAT1, SlcAPX), nitrogen (SlNR, SlNiR, SlGTS1) and proline metabolism (p5CS), potassium transporters (HKT1.1, HKT1.2), and stress-inducible TFs (SlWRKY8, SlWRKY31). Among all the biostimulant solutions applied to the plants, the composition of 70% biofertilizer and 30% biocompost (Bf70/Bc30) as well as 70% biocompost and 30% biofertilizer (Bc70/Bf30) formulations garnered interest, since the former showed growth promoting features while the latter displayed better defense responses at the time of harvesting compared with the other treatments and controls. Taken together, current findings provide new insight into the beneficial effects of biostimulants, encouraging future field studies to further evaluate the biostimulant effects in plants under a real environment which is compromised by a combination of abiotic and biotic stresses.

High levels of soil salinity can cause substantial decline in growth and productivity of crops worldwide, thus representing a major threat to global agriculture. In recent years, engineered nanoparticles (NPs) have been deemed as a promising alternative in combating abiotic stress factors, such as salinity. In this context, the present study was designed to explore the potential of cerium oxide nanoparticles (CeO2NPs) in alleviating salt stress in grapevine (Vitis vinifera L. cv. Flame Seedless) cuttings. Specifically, the interaction between CeO2 NPs (25, 50 and 100 mg L−1) and salinity (25 and 75 mM NaCl) was evaluated by assaying an array of agronomic, physiological, analytical and biochemical parameters. Treatments with CeO2 NPs, in general, alleviated the adverse impacts of salt stress (75 mM NaCl) significantly improving relevant agronomic traits of grapevine. CeO2 NPs significantly ameliorated chlorophyll damage under high levels of salinity. Furthermore, the presence of CeO2 NPs attenuated salinity-induced damages in grapevine as indicated by lower levels of proline, MDA and EL; however, H2O2 content was not ameliorated by the presence of CeO2 NPs under salt stress. Additionally, salinity caused substantial increases in enzymatic activities of GP, APX and SOD, compared with control plants. Similar to stress conditions, all concentrations of CeO2 NPs triggered APX activity, while the highest concentration of CeO2 NPs significantly increased GP activity. However, CeO2 NPs did not significantly modify SOD activity. Considering mineral nutrient profile, salinity increased Na and Cl content as well as Na/K ratio, while it decreased K, P and Ca contents. Nevertheless, the presence of CeO2 NPs did not lead to significant alterations in Na, K and P content of salt-stressed plants. Taken together, current findings suggest that CeO2 NPs could be employed as promising salt-stress alleviating agents in grapevine.

During the last years, a great effort has been dedicated at the development and employment of diverse approaches for achieving more stress-tolerant and climate-flexible crops and sustainable yield increases to meet the food and energy demands of the future. The ongoing climate change is in fact leading to more frequent extreme events with a negative impact on food production, such as increased temperatures, drought, soil salinization as well as invasive arthropod pests and diseases. In this review, diverse "green strategies" (e.g., chemical priming, root-associated microorganisms), and advanced technologies (e.g., genome editing, high-throughput phenotyping) are described on the basis of the most recent research evidence. Particularly, attention has been focused on the potential use in a context of sustainable and climate-smart agriculture (the so called "next agriculture generation") to improve plant tolerance and resilience to abiotic and biotic stresses. In addition, the gap between the results obtained in controlled experiments and those from application of these technologies in real field conditions (lab to field step) is also discussed. This article is protected by copyright. All rights reserved.

Salinity has destructive impacts in plant production; therefore, application of new approaches such as nanotechnology and plant priming is attracting increasing attention as an innovative means to ameliorate salt stress effects. Considering the unique properties and recorded beneficial influence of carbon quantum dots (CQDs) and proline in plant growth and physiological parameters when applied individually, their conjugation in the form of carbon quantum dot nanoparticles functionalized by proline (Pro-CQDs NPs) could lead to synergistic effects. Accordingly, an experiment was conducted to evaluate the impact of this advanced nanomaterial (Pro-CQDs NPs) as a chemical priming agent, in grapevine plants cv. 'Rasha'. For this purpose, proline, CQDs, and Pro-CQDs NPs at three concentrations (0, 50, and 100 mg L-1) were applied exogenously 48 h prior to salinity stress (0 and 100 mM NaCl) that was imposed for a month. Three days after imposing salt stress, an array of biochemical measurements was recorded, while agronomic and some physiological parameters were noted at the end of the stress period. Results revealed that proline treatment at both concentrations, as well as CQDs and Pro-CQDs NPs at low concentration, positively affected grapevine plants under both non-stress and stress conditions. Specifically, the application of proline at 100 mg L-1 and Pro-CQDs NPs at 50 mg L-1 resulted in optimal performance identifying 50 mg L-1 Pro-CQDs NPs as the optimal treatment. Proline treatment at 100 mg L-1 increased leaf fresh weight (FW) and dry weight (DW); chl a, b, and proline content; SOD activity under both non-stress and stress conditions; Y (II) under salinity and carotenoid content; and CAT activity under control conditions. Pro-CQDs NP treatment at 50 mg L-1 enhanced total phenol, anthocyanin, and Fv/Fo, as well as APX and GP activities under both conditions, while increasing carotenoid, Y (II), Fv/Fo, and CAT activity under salinity. Furthermore, it decreased MDA and H2O2 contents at both conditions and EL and Y (NO) under salt stress. Overall, conjugation of CQDs with proline at 50 mg L-1 resulted in further improving the protective effect of proline application at 100 mg L-1. Therefore, functionalization of NPs with chemical priming agents appears to be an effective means of optimizing plant-priming approaches towards efficient amelioration of abiotic stress-related damage in plants.

Transgenerationally acquired information equips offspring with tools essential for enhancing their physiological functioning, reproduction, survival, and tolerance to a plethora of environmental stressors. To provide a perspective for a better understanding of the effects of contaminants, organismal stress biology, and their implications to environmental and agricultural health, this report presents an overview of evidence of transgenerational hormesis induced by various environmental stressors in animals, plants, and microbes. Transgenerational effects of stress are analyzed within a dose-response framework, dissecting subNOAEL (no-observed-adverse-effect-level) effects from sublethal, superNOAEL effects. SubNOAEL effects can lead to beneficial effects in both parents and offspring. Conversely, in the case of sublethal, superNOAEL stress, parents may sacrifice their own health and survival for the benefit of offspring and their species. In this case, offspring often exhibit enhanced growth, reproduction, survival, and tolerance to stress; however, important risks exist, with effects alternating between inhibition and stimulation across generations. Results are discussed within a mechanistic framework.

Global food security for a growing population with finite resources is often challenged by multiple, simultaneously occurring on-farm abiotic stresses (i.e., drought, salinity, low and high temperature, waterlogging, metal toxicity, etc.) due to climatic uncertainties and variability. Breeding for multiple stress tolerance is a long-term solution, though developing multiple-stress-tolerant crop varieties is still a challenge. Generation of reactive oxygen species in plant cells is a common response under diverse multiple abiotic stresses which play dual role of signaling molecules or damaging agents depending on concentration. Thus, a delicate balance of reactive oxygen species generation under stress may improve crop health, which depends on the natural antioxidant defense system of the plants. Biostimulants represent a promising type of environment-friendly formulation based on natural products that are frequently used exogenously to enhance abiotic stress tolerance. In this review, we illustrate the potential of diverse biostimulants on the activity of the antioxidant defense system of major crop plants under stress conditions and their other roles in the management of abiotic stresses. Biostimulants have the potential to overcome oxidative stress, though their wider applicability is tightly regulated by dose, crop growth stage, variety and type of biostimulants. However, these limitations can be overcome with the understanding of biostimulants’ interaction with ROS signaling and the antioxidant defense system of the plants.

Melatonin is produced by plants, algae, and animals. Worldwide studies show diverse positive effects of exogenous melatonin on plants, edible plant products, and algae, but the potential of melatonin to enhance food and feed systems through these positive effects remains largely unexplored. Through a meta-analysis of about 25,000 observations, we show for the first time that exogenous application of melatonin significantly increases crop productivity and yields, and enhances the nutritional and nutraceutical value of edible plant products and algae by regulating diverse biological functions. We demonstrate that melatonin can improve plants, edible plant products, and algae under various current climate change scenarios, environmental pollution factors, and other stresses by about 7% to nearly 30%, on average, depending on the stressor. We also analyze various technical/methodological factors influencing the desired outcomes and identify conditions that offer optimal enhancement. We show that the positive effect of melatonin on plants and edible plant products varies among species, genera, and families, and strongly depends on the concentration of melatonin and treatment duration. The effect of melatonin is slightly lower on the monocot clade Commelinids than on the eudicot clades Asterids and Rosids. We also show that its stimulatory effect on plants depends on cultivation system, with a larger effect obtained in hydroponic systems. However, it does not depend on application stage (seed or vegetative), application route (foliage, roots, or seed), and whether the cultivation system is ex vivo or in vivo. This is the first meta-analysis examining the effects of melatonin on plants, edible plant products, and algae, and offers a scientific and technical roadmap facilitating sustainable food and feed production through the application of exogenous melatonin.

Lycopene is a naturally occurring chemical compound that gives fruits and vegetables a red/orange color. As an intermediate metabolite of β-carotene biosynthesis, lycopene represents one of the major carotenoids. This work studies the gene expression pattern of lycopene biosynthesis/catabolism transcripts and the accumulation pattern of lycopene/β-carotene/chlorophyll contents at three developmental stages and three tissues in five widely consumed, commercial tomato cultivars (cvs. ‘Cherry Ninolino F1’, ‘Elpida F1’, ‘Daphne F1’, ‘Eliseo Plum F1’, and ‘Oxheart’). These contents were correlated with in vitro antioxidant activity. Higher levels of lycopene were observed in the peel than other tissues and in the fully ripe stage, with ‘Oxheart’ displaying the highest content. Differential regulation of lycopene biosynthetic genes (SlZDS and SlCRTISO) was demonstrated in all cultivars. Interestingly, a gene implicated in lycopene catabolism (SlLCYB) demonstrated a general induction in the tested tissues. High lycopene content correlates with significant induction of both SlZDS and SlCRTISO in ‘Oxheart’. Significantly increased antioxidant activity was observed in the peel of ‘Cherry Ninolino F1’ and ‘Elpida F1’ cultivars compared with other tested tissues across all cultivars. The exploration of lycopene activity in different cultivars and the consumption of ripe tomatoes including the peel could be useful for the protection of human health.

Background Salinity is an important global problem with destructive impacts on plants leading to different biochemical and metabolic changes in plants through induced oxidative stress that disturbs metabolism, growth, performance and productivity of plants. Given that putrescine (Put) and carbon quantum dots (CQDs), individually, have promising effects in different plant processes, the idea of their combination in a nano-structure “Put-CQD” lead to its synthesis to evaluate the potential exertion of synergistic effects. The current study aimed to investigate the application of newly-synthesized nanoparticles (NPs) consisting of CQDs and Put in grapevine (Vitis vinifera cv. ‘Sultana’) under salinity stress conditions. For this purpose, Put, CQDs and Put-CQD NPs at 5 and 10 mg L− 1 concentrations were applied as chemical priming agents in ‘Sultana’ grapevine 48 h prior salinity stress imposition (0 and 100 mM NaCl). Results Salinity significantly decreased (P ≤ 0.05) morphological parameters, photosynthetic pigments, chlorophyll fluorescence parameters and membrane stability index. In addition, salinity enhanced MDA, H2O2, proline content and antioxidant enzyme activity. Results revealed that Put-CQD NPs, particularly at 10 mg L− 1 concentration, alleviated the destructive impacts of salinity stress by improving leaf fresh and dry weights, K+ content, photosynthetic pigments, chlorophyll fluorescence and SPAD parameters, proline content, total phenolics and antioxidant enzymatic activities (CAT, APX, GP and SOD), while decreasing Na+ content, EL, MDA and H2O2 levels. Conclusion To conclude, Put-CQD NPs represent an innovative priming treatment that could be effectively applied on grapevine to improve plant performance under salinity stress conditions.

Graphical abstract, Highlight • Τhe response of different Medicago truncatula genotypes to salt stress was examined. • Systems biology revealed tissue-specific metabolic and transcriptional signatures. • RFO metabolites linked with tolerance were identified. • Several genes belonging to the TIR-NBS-LRR class were linked with hyper-sensitivity., Salt stress is an important factor limiting plant productivity by affecting plant physiology and metabolism. To explore salt tolerance adaptive mechanisms in the model legume Medicago truncatula, we used three genotypes with differential salt-sensitivity: TN6.18 (highly sensitive), Jemalong A17 (moderately sensitive), and TN1.11 (tolerant). Cellular damage was monitored in roots and leaves 48 h after 200 mM NaCl treatment by measuring lipid peroxidation, nitric oxide, and hydrogen peroxide contents, further supported by leaf stomatal conductance and chlorophyll readings. The salt-tolerant genotype TN1.11 displayed the lowest level of oxidative damage, in contrast to the salt sensitive TN6.18, which showed the highest responses. Metabolite profiling was employed to explore the differential genotype-related responses to stress at the molecular level. The metabolic data in the salt tolerant TN1.11 roots revealed an accumulation of metabolites related to the raffinose pathway. To further investigate the sensitivity to salinity, global transcriptomic profiling using microarray analysis was carried out on the salt-stressed sensitive genotypes. In TN6.18, the transcriptomic analysis identified a lower expression of many genes related to stress signalling, not previously linked to salinity, and corresponding to the TIR-NBS-LRR gene class. Overall, this global approach contributes to gaining significant new insights into the complexity of stress adaptive mechanisms and to the identification of potential targets for crop improvement.

Chromium has been proven to be extremely phytotoxic. This study explored the impacts of increasing Cr(VI) exposure (up to 10 mg L−1 K2Cr2O7) on the growth and development of alfalfa plants and adaptation responses employed, in an environmentally relevant context. The threshold concentration of K2Cr2O7 in irrigation water beyond which stress responses are initiated is 1 mg L−1. Lower Cr(VI) exposure (0.5 mg L−1 K2Cr2O7) induced hormesis, evident through increased biomass and larger leaves, likely mediated by increased NO content (supported by elevated NR enzymatic activity and overexpression of NR and ndh genes). Elevated Cr(VI) exposure (5 and 10 mg L−1 K2Cr2O7) resulted in reduced biomass and smaller leaves, and lower levels of photosynthetic pigment (10 mg L−1 K2Cr2O7). Higher levels of lipid peroxidation, H2O2 and NO contents in these plants suggested nitro-oxidative stress. Stress responses included increased SOD and CAT enzymatic activities, further supported to some extent by MnSOD, FeSOD, Cu/ZnSOD and CAT transcripts levels. GST7 and GST17 gene expression patterns, as well as proline content, P5CS enzymatic activity and corresponding P5CS and P5CR gene expression levels emphasized the role of proline and GSTs in the adaptation responses. Results highlight the importance of managing Cr(VI) levels in irrigation water.

International audience; Sustainable production of high-quality food is one of today's major challenges of agriculture. To achieve this goal, a better understanding of plant physiological processes and a more integrated approach with respect to current agronomical practices are needed. In this review, various examples of cooperation between integrative plant physiology and agronomy are discussed, and this demonstrates the complexity of these interrelations. The examples are meant to stimulate discussions on how both research areas can deliver solutions to avoid looming food crises due to population growth and climate change. In the last decades, unprecedented progress has been made in the understanding of how plants grow and develop in a variety of environments and in response to biotic stresses, but appropriate management and interpretation of the resulting complex datasets remains challenging. After providing an historical overview of integrative plant physiology, we discuss possible avenues of integration, involving advances in integrative plant physiology, to sustain plant production in the current post-omics era. Finally, recommendations are provided on how to practice the transdisciplinary mindset required, emphasising a broader approach to sustainable production of high-quality food in the future, whereby all those who are involved are made partners in knowledge generation processes through transdisciplinary cooperation.

Plants exposed to toxic Cr(VI) concentrations show reduced biomass production and yield. The present study examined (1) the impacts of increasing Cr(VI) exposure (0.05, 0.5, 1, 5 and 10 mg L−1 K2Cr2O7 in irrigation water) on the growth and development, yield, and stress physiology of two important crop species, such as wheat (Triticum aestivum L.) and lettuce (Lactuca sativa L.), and (2) the associated human health risks due to the consumption of these commodities. Plants in all Cr(VI) treatments preserved similar growth rates and phenotypes with control, untreated plants, with no remarkable modulations in biomass yield (fresh/dry weight, plant height, straw/grain weight). Grains harvested from plants exposed to all Cr(VI) treatments had increased size and 1000 grain weight, partially suggesting hormetic effect. Elevated K2Cr2O7 concentrations (5 and 10 mg L−1) resulted in increased photosynthetic pigments’ levels in lettuce leaves. Lipid peroxidation and H2O2 content also revealed the absence of oxidative stress in lettuce plants. Non-carcinogenic (target hazard quotient) and carcinogenic risks from the consumption of these commodities grown under the conditions described in this study were found de minimis. However, more studies are needed in order to obtain more solid information on the safety of Cr(VI)-contaminated water irrigation.

Trigonella foenum-graecum (fenugreek) is a leguminous plant that produces secondary metabolites frequently used in medicinal and food preparation. Here, the role of an arbuscular mycorrhizal (AM) fungal inoculum, alone or in combination with methyl jasmonate (MeJA) chemical treatment, was evaluated on the production of trigonelline and diosgenin in fenugreek plants grown under mild water limitation. After inoculation, fenugreek plants were subjected to several combined treatments, i.e. well-watered (NS) and water-stressed (WS), both treated with different MeJA concentrations (0, 50, 100, 200 mL/L). At the end of the experiment, in addition to trigonelline and diosgenin content, an array of plant growth parameters (i.e. fruit, stem and root dry weights, fruit number) and biochemical stress markers (i.e. proline, nitric oxide, hydrogen peroxide, MDA) were examined. Results mainly showed a significant increase in production of the considered secondary metabolites, although they are differentially influenced by the individual factors (Stress, SYM, MeJA) and their interactions. SYM treatment was more effective on the production of trigonelline, independently from growth conditions, while diosgenin biosynthesis was influenced by the presence of root symbioses only in combination with MeJA treatment. A differential impact, depending on the applied treatment (inoculum, MeJA treatments, water deficit), on plant growth and on production of the considered bioactive molecules was revealed, providing new information on the effect of biological and chemical priming treatments.

V.F. would like to acknowledge support by the Cyprus University of Technology Open Access Author Fund. Global climate change and associated adverse abiotic stress conditions, such as drought, salinity, heavy metals, waterlogging, extreme temperatures, oxygen deprivation, etc., greatly influence plant growth and development, ultimately affecting crop yield and quality, as well as agricultural sustainability in general. Plant cells produce oxygen radicals and their derivatives, so-called reactive oxygen species (ROS), during various processes associated with abiotic stress. Moreover, the generation of ROS is a fundamental process in higher plants and employs to transmit cellular signaling information in response to the changing environmental conditions. One of the most crucial consequences of abiotic stress is the disturbance of the equilibrium between the generation of ROS and antioxidant defense systems triggering the excessive accumulation of ROS and inducing oxidative stress in plants. Notably, the equilibrium between the detoxification and generation of ROS is maintained by both enzymatic and nonenzymatic antioxidant defense systems under harsh environmental stresses. Although this field of research has attracted massive interest, it largely remains unexplored, and our understanding of ROS signaling remains poorly understood. In this review, we have documented the recent advancement illustrating the harmful effects of ROS, antioxidant defense system involved in ROS detoxification under different abiotic stresses, and molecular cross-talk with other important signal molecules such as reactive nitrogen, sulfur, and carbonyl species. In addition, state-of-the-art molecular approaches of ROS-mediated improvement in plant antioxidant defense during the acclimation process against abiotic stresses have also been discussed.

The article was funded by the “CUT Open Access Author Fund” The extension of commercial life and the reduction of postharvest losses of perishable fruits is mainly based on storage at low temperatures alone or in combination with modified atmospheres (MAs) and controlled atmospheres (CAs), directed primarily at reducing their overall metabolism thus delaying ripening and senescence. Fruits react to postharvest conditions with desirable changes if appropriate protocols are applied, but otherwise can develop negative and unacceptable traits due to the onset of physiological disorders. Extended cold storage periods and/or inappropriate temperatures can result in development of chilling injuries (CIs). The etiology, incidence, and severity of such symptoms vary even within cultivars of the same species, indicating the genotype significance. Carbohydrates and amino acids have protective/regulating roles in CI development. MA/CA storage protocols involve storage under hypoxic conditions and high carbon dioxide concentrations that can maximize quality over extended storage periods but are also affected by the cultivar, exposure time, and storage temperatures. Pyruvate metabolism is highly reactive to changes in oxygen concentration and is greatly affected by the shift from aerobic to anaerobic metabolism. Ethylene-induced changes in fruits can also have deleterious effects under cold storage and MA/CA conditions, affecting susceptibility to chilling and carbon dioxide injuries. The availability of the inhibitor of ethylene perception 1-methylcyclopropene (1-MCP) has not only resulted in development of a new technology but has also been used to increase understanding of the role of ethylene in ripening of both non-climacteric and climacteric fruits. Temperature, MA/CA, and 1-MCP alter fruit physiology and biochemistry, resulting in compositional changes in carbon- and nitrogen-related metabolisms and compounds. Successful application of these storage technologies to fruits must consider their effects on the metabolism of carbohydrates, organic acids, amino acids and lipids.

In the past decade, hydrogen sulfide (H2S) and nitricoxide (NO) have emerged as major signaling moleculeswhich are involved in most life cycle processes in plants,i.e. from seed germination to plant death. H2S and NO-regulated development of plants requires integration ofcomplex signaling networks and also involves other sig-naling pathways. Moreover, to re-establish cellular redoxhomeostasis under stress conditions, regulation of geneexpression takes place, which helps in achieving anappropriate plant response. In this context, the most sig-nificant controls occur at the transcriptional, post-transcriptional and post-translational levels which helpin acquiring adaptive changes in stress-challengedplants. Although various studies have demonstrated therole of H2S and NO in regulating a plethora of plantgrowth and development processes under stressed/non-stressed conditions, much remains to be elucidatedregarding their roles in plant biology. Therefore, this spe-cial issue was organized to collect state-of-the-art plantresearch involving H2S and NO under changing environ-mental conditions. This special issue has collected sevenreviews and 11 original research articles aimed at com-piling a comprehensive status quo on the implication ofH2S and NO signaling in plant biology.

Considering titanium dioxide nanoparticles (TiO2 NPs) role in plant growth and especially in plant tolerance against abiotic stress, a greenhouse experiment was carried out to evaluate TiO2 NPs effects (0, 50, 100 and 200 mg L−1) on agronomic traits of Moldavian balm (Dracocephalum moldavica L.) plants grown under different salinity levels (0, 50 and 100 mM NaCl). Results demonstrated that all agronomic traits were negatively affected under all salinity levels but application of 100 mg L−1 TiO2 NPs mitigated these negative effects. TiO2 NPs application on Moldavian balm grown under salt stress conditions improved all agronomic traits and increased antioxidant enzyme activity compared with plants grown under salinity without TiO2 NP treatment. The application of TiO2 NPs significantly lowered H2O2 concentration. In addition, highest essential oil content (1.19%) was obtained in 100 mg L−1 TiO2 NP-treated plants under control conditions. Comprehensive GC/MS analysis of essential oils showed that geranial, z-citral, geranyl acetate and geraniol were the dominant essential oil components. The highest amounts for geranial, geraniol and z-citral were obtained in 100 mg L−1 TiO2 NP-treated plants under control conditions. In conclusion, application of 100 mg L−1 TiO2 NPs could significantly ameliorate the salinity effects in Moldavian balm.

Tobacco is an economically important crop with leaves that are a significant source of aromatic, bioactive compounds such as phenolics and alkaloids. In the present study un-biased transcriptomics and metabolomics approaches were employed to identify and quantify individual changes in transcript and metabolite profiles in leaves of three oriental tobacco varieties. Based on next generation sequencing (NGS) and gas chromatography mass spectrometry (GC–MS) technologies, a wide variety of transcripts and metabolites was detected and the metabolic diversity among varieties was determined. Genes with largest expression differences were identified in the leaves of the three varieties; among them three were commonly over-expressed in two varieties in comparison with the third variety. Notably, significant expression differences were recorded in phenylalanine ammonia lyase (PAL) genes that are key genes of phenylpropanoid biosynthesis. Following transcriptomics, metabolomics analysis has shown that polyphenolic compounds varied widely among the three varieties. Furthermore, statistically significant differences in soluble sugars, alcohols, organic acids, amino acids and other metabolites were also revealed. The integration of the two -omics datasets in determining diversity of tobacco varieties offers important readouts for the genetic control of metabolite production and constitutes a resource for future studies in the area of plant biotechnology for improving tobacco specific traits.

Land plants are continuously exposed to multiple abiotic stress factors like drought, heat, and salinity. Nitric oxide (NO) and hydrogen sulfide (H2S) are two well-examined signaling molecules that act as priming agents, regulating the response of plants to stressful conditions. Several chemical donors exist that provide plants with NO and H2S separately. NOSH is a remarkable novel donor as it can donate NO and H2S simultaneously to plants, while NOSH-aspirin additionally provides the pharmaceutical molecule acetylsalicylic acid. The current study aimed to investigate the potential synergistic effect of these molecules in drought-stressed Medicago sativa L. plants by following a pharmacological approach. Plants were initially pre-treated with both donors (NOSH and NOSH-aspirin) via foliar spraying, and were then subsequently exposed to a moderate water deficit while NO and H2S inhibitors (cPTIO and HA, respectively) were also employed. Phenotypic and physiological data showed that pre-treatment with NOSH synthetic compounds induced acclimation to subsequent drought stress and improved the recovery following rewatering. This was accompanied by modified reactive-oxygen and nitrogen-species signaling and metabolism, as well as attenuation of cellular damage, as evidenced by altered lipid peroxidation and proline accumulation levels. Furthermore, real-time RT-qPCR analysis revealed the differential regulation of multiple defense-related transcripts, including antioxidant enzymes. Overall, the present study proposed a novel role for NOSH compounds as efficient plant priming agents against environmental constraints through the coordinated regulation of multiple defense components, thus opening new horizons in the field of chemical priming research toward the use of target-selected compounds for stress tolerance enhancement.

Fruits and vegetables contain vitamins, dietary fibre and phytochemicals, which promote human health. Specifically vitamins are major bioactive compounds. In plant raw materials there are water-soluble (vitamins B and C) and lipid-soluble (vitamins A, E and K) ones, having strong antioxidant potential and limiting several diseases, including cancer and cardio-vascular diseases. Furthermore, vitamins play a key role in plant protection against abiotic and biotic stress factors. Vitamin E is a group of eight fat-soluble compounds known as tocochromanols, which are synthesized exclusively by photosynthetic organisms. Tocochromanols are categorised into two groups – tocopherols and tocotrienols. Each group contains four forms identified by prefixes α-, β-, γ- and δ-, yielding a total of eight forms. Vitamin E is an essential, lipid-soluble antioxidant in the human diet, protecting from cancer, diabetes, cardiovascular and neurological diseases. This review summarizes the recent developments in the understanding the variety of roles of vitamin E as well as its major genetic regulatory pathways in plants. In addition, a comprehensive mapping of vitamin E occurrence is presented in different plant tissues, organelles and horticultural crop species, as well as throughout different stages of fruit development and after postharvest.

Drought represents one of the major constraints on agricultural productivity and food security and in future is destined to spread widely as a consequence of climate change. Research efforts are focused on developing strategies to make crops more resilient and to mitigate the effects of stress on crop production. In this context, the use of root-associated microbial communities and chemical priming strategies able to improve plant tolerance to abiotic stresses, including drought, have attracted increasing attention in recent years. The current review offers an overview of recent research aimed at verifying the role of arbuscular mycorrhizal fungi and chemical agents to improve plant tolerance to drought and to highlight the mechanisms involved in this improvement. Attention will be devoted mainly to current knowledge on the mechanisms involved in water transport.

The effect of preharvest foliar spray applications at fruit colour breaker stage with acetylsalicylic acid (synthetic salicylate), spermidine (polyamine), their combination and a commercial calcium supplement on loquat (Eriobotrya japonica Lindl cv. ‘Karantoki’) fruit at successive harvests and subsequently during maintenance at room temperature (shelf-life) for 3 and 6 days respectively, were investigated. Yield efficiency, qualitative attributes, textural properties and the incidence of physiological disorders, namely purple spot and fruit cracking, were determined. Loquat fruit quality parameters were affected by spraying treatments, harvesting day and shelf-life periods applied. Acetylsalicylic acid is recommended as an efficient and cost-effective treatment that needs to be further explored towards production of loquat fruit with enhanced quality properties. However, spermidine application alone, or in combination with acetylsalicylic acid, did not show any beneficial and/or synergistic effect on loquat fruit quality parameters to justify its application. All foliar applications did not affect fruit growth and yield efficiency. The current study shed some light on the potential use of foliar spraying with acetylsalicylic acid, alone or in combination with a calcium supplement, towards enhancement of fruit quality properties of an added value product as loquat. To this aim, further studies need to be implemented to test their efficacy under different environmental conditions that may accelerate the incidence of physiological disorders and/or multiple applications over the growing season.

Cr(VI) is known to induce hormesis in plants. Nevertheless, its effects on the quality of agricultural produce are poorly studied. In the present study, tomato (Solanum lycopersicum L.) plants were exposed to incremental Cr(VI) concentrations through irrigation with water containing K2Cr2O7 in escalating concentrations (0.05, 0.5, 1, 5 and 10 mg L−1), aiming at investigating potential mediated effects on (1) yield, (2) stress responses in leaves, (3) the biosafety of fruits and (4) the mediated alterations in tomato fruit quality attributes. Plants in all Cr(VI) treatments displayed similar phenotype, with no modulations in fruit setting. Plants irrigated with water containing 10 mg L-1 K2Cr2O7 had lower photosynthetic pigment concentration and suffered from oxidative stress in their leaves (evidenced by increased MDA and H2O2 content). Elevated Cr(VI) treatments (5 or 10 mg L-1 K2Cr2O7) resulted in the production of fruits with lower weight and smaller size, along with increased ripening index and soluble solids, lycopene, β-carotene and soluble carbohydrate (fructose, sucrose, total sugars) content. Alterations in fruit quality attributes were at least in part corroborated by the abundance of transcripts related to sucrose (SlSuSys, SlLin5, SlLin6, SlLin7) and carotenoid (SlZDS, SlCRTISO, SlbLCY) biosynthesis. The concentration of total Cr in all fruit samples was far below the maximum permissible limits, thus indicating safety for human consumption. Overall, results presented herein provide novel evidence that Cr(VI) can exert significant effects on the quality of agricultural produce at the biochemical and molecular level, indicating that Cr(VI)-contaminated water should be cautiously used after rigorous investigation.

20 p.-3 fig., Although epigenetic modifications have been intensely investigated over the last decade due to their role in crop adaptation to rapid climate change, it is unclear which epigenetic changes are heritable and therefore transmitted to their progeny. The identification of epigenetic marks that are transmitted to the next generations is of primary importance for their use in breeding and for the development of new cultivars with a broad-spectrum of tolerance/resistance to abiotic and biotic stresses. In this review, we discuss general aspects of plant responses to environmental stresses and provide an overview of recent findings on the role of transgenerational epigenetic modifications in crops. In addition, we take the opportunity to describe the aims of EPI-CATCH, an international COST action consortium composed by researchers from 28 countries. The aim of this COST action launched in 2020 is: (1) to define standardized pipelines and methods used in the study of epigenetic mechanisms in plants, (2) update, share, and exchange findings in epigenetic responses to environmental stresses in plants, (3) develop new concepts and frontiers in plant epigenetics and epigenomics, (4) enhance dissemination, communication, and transfer of knowledge in plant epigenetics and epigenomics, This finalization of the review was funded by COST Action CA19125—EPIgenetic mechanisms of Crop Adaptation to Climate cHange.

The aim of this study was to understand the antioxidant metabolic changes of peach (cvs. ‘Royal Glory’, ‘Red Haven’ and ‘Sun Cloud’) and nectarine fruits (cv. ‘Big Top’) exposed to different combinations of low-temperature storage (0, 2, 4 weeks storage at 0 °C, 90% R.H.) and additional ripening at room temperature (1, 3 and 5 d, shelf life, 20 °C) with an array of analytical, biochemical and molecular approaches. Initially, harvested fruit of the examined cultivars were segregated non-destructively at advanced and less pronounced maturity stages and qualitative traits, physiological parameters, phytochemical composition and antioxidant capacity were determined. ‘Big Top’ and ‘Royal Glory’ fruits were characterized by slower softening rate and less pronounced ripening-related alterations. The coupling of HPLC fingerprints, consisted of 7 phenolic compounds (chlorogenic, neochlorogenic acid, catechin, epicatechin, rutin, quecetin-3-O-glucoside, procyanidin B1) and spectrophotometric methods disclosed a great impact of genotype on peach bioactive composition, with ‘Sun Cloud’ generally displaying the highest contents. Maturity stage at harvest did not seem to affect fruit phenolic composition and no general guidelines for the impact of cold storage and shelf-life on individual phenolic compounds can be extrapolated. Subsequently, fruit of less pronounced maturity at harvest were used for further molecular analysis. ‘Sun Cloud’ was proven efficient in protecting plasmid pBR322 DNA against ROO[rad] attack throughout the experimental period and against HO[rad] attack after 2 and 4 weeks of cold storage. Interestingly, a general down-regulation of key genes implicated in the antioxidant apparatus with the prolongation of storage period was recorded; this was more evident for CAT, cAPX, Cu/ZnSOD2, perAPX3 and GPX8 genes. Higher antioxidant capacity of ‘Sun Cloud’ fruit could potentially be linked with compounds other than enzymatic antioxidants that further regulate peach fruit ripening.

Fruits and vegetables are the main source of health promoting phytonutrients, including vitamins, dietary fibers and phytochemicals. Vitamins are key bioactive compounds with strong antioxidant potential including both water-soluble (vitamins B and C) and lipid-soluble (vitamins A, E and K) compounds, and are thought to limit the risk of several chronic diseases such as cancers and cardio-vascular diseases. This chapter review recent advances in the understanding of the multiple roles of vitamins, as well as their major genetic regulatory pathways within plant kingdom. Further, it discusses vitamin occurrence and diversity in different plant tissues, organelles, and horticultural species, as well as throughout fruit development and at postharvest.

Salinity constitutes one of the most important causes leading to severe reduction in plant yield. Several reports correlate the accumulation of polyamines in plants with tolerance to abiotic stress cues. The present study examined three Medicago truncatula genotypes with differing sensitivities to salinity (TN1.11, tolerant; Jemalong A17, moderately sensitive; TN6.18, sensitive), with the aim of examining the genotype-specific involvement of the polyamine metabolic pathway in plant response to salinity. The study was carried out with leaves harvested 48 h after watering plants with 200 mM NaCl. A comprehensive profile of free polyamines was determined using high performance liquid chromatography. All genotypes showed spermidine and spermine as the most abundant polyamines under control conditions. In salinity conditions, spermine levels increased at the expense of putrescine and spermidine, indicating a drift of polyamine metabolism towards the synthesis of increasing polycationic forms as a stress response. The increasing balance between high and low polycationic forms was clearly diminished in the salt-sensitive genotype TN6.18, showing a clear correlation with its sensitive phenotype. The polyamine metabolic profile was then supported by molecular evidence through the examination of polyamine metabolism transcript levels by RT-qPCR. General suppression of genes that are involved upstream in the PA biosynthetic pathway was determined. Contrarily, an induction in the expression of genes involved in the biosynthesis of spermine and spermidine was observed, in agreement with the metabolic analysis. A significant induction in diamino oxidase expression, involved in the catabolism of putrescine, was specifically found in the sensitive genotype ΤΝ6.18, indicating a distinct metabolic response to stress. Present findings highlight the involvement of polyamines in the defense response of Medicago genotypes showing sensitivity to salt stress.

Highlight The fungicide kresoxim-methyl displays novel priming properties against key abiotic stress factors (drought and salinity) by modifying reactive oxygen and nitrogen species signalling, inducing osmoprotection through increased proline biosynthesis and suppressing proteolysis., Biotic and abiotic stresses, such as fungal infection and drought, cause major yield losses in modern agriculture. Kresoxim-methyl (KM) belongs to the strobilurins, one of the most important classes of agricultural fungicides displaying a direct effect on several plant physiological and developmental processes. However, the impact of KM treatment on salt and drought stress tolerance is unknown. In this study we demonstrate that KM pre-treatment of Medicago truncatula plants results in increased protection to drought and salt stress. Foliar application with KM prior to stress imposition resulted in improvement of physiological parameters compared with stressed-only plants. This protective effect was further supported by increased proline biosynthesis, modified reactive oxygen and nitrogen species signalling, and attenuation of cellular damage. In addition, comprehensive transcriptome analysis identified a number of transcripts that are differentially accumulating in drought- and salinity-stressed plants (646 and 57, respectively) after KM pre-treatment compared with stressed plants with no KM pre-treatment. Metabolomic analysis suggests that the priming role of KM in drought- and to a lesser extent in salinity-stressed plants can be attributed to the regulation of key metabolites (including sugars and amino acids) resulting in protection against abiotic stress factors. Overall, the present study highlights the potential use of this commonly used fungicide as a priming agent against key abiotic stress conditions.

© 2020 Elsevier B.V. Global agricultural production is suffering substantial losses due to climate change-related phenomena such as drought and salinity, which lead to tissue damage and, ultimate, major yield losses. The development of sustainable, ‘green’ technologies is therefore becoming increasingly important. Nanotechnology provides invaluable tools to a variety of industrial sectors. Recent focus has been given to the development and optimization of nanomaterials for application in the agricultural industry towards improved growth, plant protection and overall performance based on their small size, high surface to volume ratio and unique optical properties. The present review provides an up-to-date description of advanced nanoparticles and polymers applied at plant and seed level, covering technical, biological and socioeconomical aspects of this promising approach. This technology offers an attractive alternative to established approaches such as conventional breeding and genetic modification with key advantages, representing a characteristic example of integrative plant physiology where multiple disciplines such as materials science, agriculture and analytical chemistry join forces to develop exciting new tools in modern agriculture.

Pharmaceutically active compounds (PhACs) entering agroecosystems as a result of various human activities may be taken up by and accumulated within crop plants, with potential human health implications. Despite their extensive metabolism by a sophisticated enzyme-based detoxification system in plant cells, PhACs and their transformation products (TPs) may result in adverse effects on plants' physiology. PhACs–mediated phytotoxic effects, as well as plants' defense responses have been depicted on plants exposed to individual or low number of PhACs under controlled conditions. We highlight the need to consider the cocktails effects and synergistic interactions of PhACs present in mixtures in actual agroecosystems, towards phytotoxicity and agricultural sustainability in general. Considering PhACs as emerging plant stressors will better facilitate the understanding of their phytotoxic effects. Keywords: Antibiotics, Cocktail effects, Oxidative stress, Plant physiology, Phytotoxicity, Reclaimed wastewater irrigation

Glutathione- s -transferases (GSTs) and nitric oxide (NO) have both been implicated in the response of plants to salinity stress. However, their interplay and underlying mechanisms are relatively unknown. The present study attempts to provide new insight into the time course effects of NO application on GST biosynthesis regulation in Glycine max L. leaves under salt stress. A 150 μM concentration of sodium nitroprusside (SNP), a widely used NO donor, was sprayed on soybean seedlings for two days at 24 h intervals, followed by application of 200 mM NaCl. The relative water content (RWC), total chlorophyll content (CHL), stomatal conductance ( g s ), ABA content, malondialdehyde (MDA), hydrogen peroxide content (H 2 O 2 ), along with GST enzyme and isoenzyme activities and GST1 and GST4 transcript levels were determined at 0 h, 6 h and 12 h after stress imposition. The results indicated that salt treatment alone did not alter MDA, H 2 O 2 or ABA content and stomatal conductance in soybean leaves, most likely due to short-term (6 h and 12 h) application, although lower RWC and CHL were recorded. SNP treatment alone increased ABA content and reduced stomatal conductance, but did not change RWC, CHL, MDA (except at 12 h) and H 2 O 2. However, exogenous SNP application protected soybean leaves from salt stress by increasing RWC, CHL and ABA content, as well as by lowering stomatal conductance in order to maintain water balance. A significant increase in GST activity was recorded under salt stress alone at 6 h. Conversely, SNP application lowered GST activity in soybean leaves at 0 h and 12 h, while it increased at 6 h, supported by GST isoenzyme activities. Thus, it could be suggested that exogenous NO application induced GST activity in an ABA-dependent manner, while GST activity could also be induced by salt stress independent of ABA. In addition, SNP pre-treatment in salt-stressed seedlings lowered GST activity at 6 h and 12 h, in line with the GST isoenzyme expression profile. Finally, GST1 and GST4 transcript levels were significantly induced in both salt-stressed and SNP pre-treated and subsequently stressed samples at 6 h and 12 h, while a more variable regulation pattern was observed in plants treated only with SNP. Overall, our findings suggest that both NO and salt stress act as potent regulators of GST gene and enzyme expression through both ABA-dependent and independent pathways.

Reactive oxygen, nitrogen and sulfur species are key signalling molecules involved in multiple physiological processes that can be examined in qualitative and quantitative manners. Here, we describe simple spectrophotometric assays that allow the quantification of hydrogen peroxide, nitrite-derived nitric oxide and hydrogen sulphide from plant tissues.

AM symbiosis did not strongly affect Arundo donax performances under salt stress, although differences in the plants inoculated with two different fungi were recorded. The mechanisms at the basis of the improved tolerance to abiotic stresses by arbuscular mycorrhizal (AM) fungi have been investigated mainly focusing on food crops. In this work, the potential impact of AM symbiosis on the performance of a bioenergy crop, Arundo donax, under saline conditions was considered. Specifically, we tried to understand whether AM symbiosis helps this fast-growing plant, often widespread in marginal soils, withstand salt. A combined approach, involving eco-physiological, morphometric and biochemical measurements, was used and the effects of two different AM fungal species (Funneliformis mosseae and Rhizophagus irregularis) were compared. Results indicate that potted A. donax plants do not suffer permanent damage induced by salt stress, but photosynthesis and growth are considerably reduced. Since A. donax is a high-yield biomass crop, reduction of biomass might be a serious agronomical problem in saline conditions. At least under the presently experienced growth conditions, and plant–AM combinations, the negative effect of salt on plant performance was not rescued by AM fungal colonization. However, some changes in plant metabolisms were observed following AM-inoculation, including a significant increase in proline accumulation and a trend toward higher isoprene emission and higher H2O2, especially in plants colonized by R. irregularis. This suggests that AM fungal symbiosis influences plant metabolism, and plant–AM fungus combination is an important factor for improving plant performance and productivity, in presence or absence of stress conditions.

Recent reports have uncovered the multifunctional role of melatonin in plant physiological responses under optimal and suboptimal environmental conditions. In this study, we explored whether melatonin pretreatment could provoke priming effects in alfalfa (Medicago sativa L.) plants subsequently exposed to prolonged drought stress (7 days), by withholding watering. Results revealed that the rhizospheric application of melatonin (10 μmol L-1 ) remarkably enhanced the drought tolerance of alfalfa plants, as evidenced by the observed plant tolerant phenotype, as well as by the higher levels of chlorophyll fluorescence and stomatal conductance, compared with nontreated drought-stressed plants. In addition, lower levels of lipid peroxidation (MDA content) as well as of both H2 O2 and NO contents in primed compared with nonprimed stressed plants suggest that melatonin pretreatment resulted in the systemic mitigation of drought-induced nitro-oxidative stress. Nitro-oxidative homeostasis was achieved by melatonin through the regulation of reactive oxygen (SOD, GR, CAT, APX) and nitrogen species (NR, NADHde) metabolic enzymes at the enzymatic and/or transcript level. Moreover, melatonin pretreatment resulted in the limitation of cellular redox disruption through the regulation of the mRNA levels of antioxidant and redox-related components (ADH, AOX, GST7, GST17), as well via osmoprotection through the regulation of proline homeostasis, at both the enzymatic (P5CS) and gene expression level (P5CS, P5CR). Overall, novel results highlight the importance of melatonin as a promising priming agent for the enhancement of plant tolerance to drought conditions through the regulation of nitro-oxidative and osmoprotective homeostasis.

[Background] Carotenoids are the main colouring substances found in orange-fleshed loquat fruits. The aim of this study was to unravel the carotenoid biosynthetic pathway of loquat fruit (cv. ‘Obusa’) in peel and flesh tissue during distinct on-tree developmental stages through a targeted analytical and molecular approach., [Results] Substantial changes regarding colour parameters, both between peel and flesh and among the different developmental stages, were monitored, concomitant with a significant increment in carotenoid content. Key genes and individual compounds that are implicated in the carotenoid biosynthetic pathway were further dissected with the employment of molecular (RT-qPCR) and advanced analytical techniques (LC-MS). Results revealed significant differences in carotenoid composition between peel and flesh. Thirty-two carotenoids were found in the peel, while only eighteen carotenoids were identified in the flesh. Trans-lutein and trans-β-carotene were the major carotenoids in the peel; the content of the former decreased with the progress of ripening, while the latter registered a 7.2-fold increase. However, carotenoid profiling of loquat flesh indicated trans-β-cryptoxanthin, followed by trans-β-carotene and 5,8-epoxy-β-carotene to be the most predominant carotenoids. High amounts of trans-β-carotene in both tissues were supported by significant induction in a chromoplast-specific lycopene β-cyclase (CYCB) transcript levels. PSY1, ZDS, CYCB and BCH were up-regulated and CRTISO, LCYE, ECH and VDE were down-regulated in most of the developmental stages compared with the immature stage in both peel and flesh tissue. Overall, differential regulation of expression levels with the progress of on-tree fruit development was more evident in the middle and downstream genes of carotenoid biosynthetic pathway., [Conclusions] Carotenoid composition is greatly affected during on-tree loquat development with striking differences between peel and flesh tissue. A link between gene up- or down-regulation during the developmental stages of the loquat fruit, and how their expression affects carotenoid content per tissue (peel or flesh) was established., The authors would like to acknowledge support by Remedica through the “Cyprus University of Technology Open Access Author Fund” for covering the cost of publication fees.

The term vitamin E refers to a group of eight lipophilic compounds known as tocochromanols. The tocochromanols are divided into two groups, that is, tocopherols and tocotrienols, with four forms each, namely α-, β-, γ-, and δ-. In order to explore the temporal biosynthesis of tocochromanols in olive (Olea europaea cv. ‘Koroneiki’) fruit during on-tree development and ripening over successive growing years, a combined array of analytical, molecular, bioinformatic, immunoblotting and antioxidant techniques were employed. Fruits were harvested at eight successive developmental stages (10-30 weeks after flowering (WAF)), over three consecutive years. Intriguingly, climatic conditions affected relative transcription levels of vitamin E biosynthetic enzymes; a general suppression to induction pattern (excluding VTE5) was monitored moving from the 1st to the 3rd growing year, probably correlated to decreasing rainfall levels and higher temperature, particularly at the fruit ripening stage. A gradual diminution of VTE5 protein content was detected during the fruit development of each year, with a marked decrease occurring after 16 WAF. Alpha-tocopherol was the most abundant metabolite with an average percentage of 96.82 ± 0.23%, 91.13 ± 0.95% and 88.53 ± 0.96% (during the 1st, 2nd and 3rd year, respectively) of total vitamin E content in 10–30 WAF. The concentrations of α-tocopherol revealed a generally declining pattern, both during the on-tree ripening of the olive fruit and across the three years, accompanied by a parallel decline of the total antioxidant activity of the drupe. Contrarily, all other tocochromanols demonstrated an inverse pattern with lowest levels being recorded during the 1st year. It is likely that, in a defense attempt against water deficit conditions and increased air temperature, transcription of genes involved in vitamin E biosynthesis (excluding VTE5) is up-regulated in olive fruit, probably leading to the blocking/deactivating of the pathway through a negative feedback regulatory mechanism.

Nitric oxide (NO) is a bioactive, diffusible molecule involved in a multitude of physiological and developmental processes in plants, which has been reported to display both antioxidant and pro-oxidant properties in plants. Several reports exist highlighting the protective action of sodium nitroprusside (SNP), an NO donor, which demonstrate its important role as a signal molecule in plants responsible for the expression regulation of antioxidant and other defense enzymes. However, the mode of application of this compound varies greatly between studies. The present study provides a comprehensive efficiency comparison of the most commonly used application methods using 2.5 mM SNP on mature (40 day) Medicago truncatula plants. Measurement of NO content in both leaves and roots suggests that vacuum infiltration is the most efficient method for NO donation in leaf tissue, whereas hydroponic application resulted in highest NO content in roots. NO content correlated with activity levels of nitrate reductase (NR; EC 1.7.99.4), a key enzyme involved in the generation of NO in plants and which is known to be regulated by NO itself.

Abiotic stresses severely limit crop yield and their detrimental effects are aggravated by climate change. Chemical priming is an emerging field in crop stress management. The exogenous application of specific chemical agents before stress events results in tolerance enhancement and reduction of stress impacts on plant physiology and growth. However, the molecular mechanisms underlying the remarkable effects of chemical priming on plant physiology remain to be elucidated. Reactive oxygen, nitrogen and sulfur species (RONSS) are molecules playing a vital role in the stress acclimation of plants. When applied as priming agents, RONSS improve stress tolerance. This review summarizes the recent knowledge on the role of RONSS in cell signalling and gene regulation contributing to abiotic stress tolerance enhancement.