Exogenous curcumin mitigates As stress in spinach plants: A biochemical and metabolomics investigation

The spinach (S. oleracea L.) was used as a model plant to investigate As toxicity on physio-biochemical processes, exploring the potential mitigation effect of curcumin (Cur) applied exogenously at three concentrations (1, 10, and 20 μM Cur). The employment of Cur significantly mitigated As-induced stress in spinach photosynthetic performance (Fv/Fm, Fo/Fm, and Fv/Fo). Moreover, the co-incubation of Cur with As improved physiological processes mainly associated with plant water systems affected by As stress by recovering the leaf's relative water content (RWC) and osmotic potential (ψπ) nearly to the control level and increasing the transpiration rate (E; 39-59%), stomatal conductivity (gs; 86-116%), and carbon assimilation rate (A; 84-121%) compared to As stressed plants. The beneficial effect of Cur in coping with As-induced stress was also assessed at the plant's oxidative level by reducing oxidative stress biomarkers (H2O2 and MDA) and increasing non-enzymatic antioxidant capacity. Untargeted metabolomics analysis was adopted to investigate the main processes affected by As and Cur application. A multifactorial ANOVA discrimination model (AMOPLS-DA) and canonical correlation analysis (rCCA) were employed to identify relevant metabolic changes and biomarkers associated with Cur and As treatments. The results highlighted that Cur significantly determined the accumulation of glucosinolates, phenolic compounds, and an increase in glutathione redox cycle activities, suggesting an overall elicitation of plant secondary metabolisms. Specifically, the correlation analysis reported a strong and positive correlation between (+)-dihydrokaempferol, L-phenylalanine (precursor of phenolic compounds), and serotonin-related metabolites with antioxidant activities (ABTS and DPPH), suggesting the involvement of Cur application in promoting a cross-talk between ROS signaling and phytohormones, especially melatonin and serotonin, working coordinately to alleviate As-induced oxidative stress. The modulation of plant metabolism was also observed at the level of amino acids, fatty acids, and secondary metabolites synthesis, including N-containing compounds, terpenes, and phenylpropanoids to cooperate with As-induced stress response.

UHPLC-ESI-QTOF-MS metabolite profiles of different extracts from Pelargonium endlicherianum parts and their biological properties based on network pharmacological approaches

In the present study, we aimed to investigate the chemical profiles and biological activities of different extracts (ethyl acetate, dichloromethane, ethanol, and water) of Pelargonium endlicherianum parts (aerial parts and roots). Free radical scavenging, reducing power, phosphomolybdenum, and metal chelating were assayed for antioxidant properties. To detect enzyme inhibitory properties, cholinesterase, amylase, glucosidase, and tyrosinase were chosen as target enzymes. The ethanol extract of the aerial parts contained higher amounts of total bioactive compounds (120.53 mg GAE/g-24.46 mg RE/g). The ethanol and water extracts of these parts were tentatively characterized by UHPLC-ESI-QTOF-MS and 95 compounds were annotated. In addition, the highest acetylcholiesterase (3.74 mg GALAE/g) and butyrylcholinesterase (3.92 mg GALAE/g) abilities were observed by the ethanol extract of roots. The water extract from aerial parts exhibited the most pronounced inhibitory effects on multiple cancer cell lines, especially A549 (IC50: 23.2 µg/mL) and HT-29 (IC50: 27.43 µg/mL) cells. Using network pharmacology, P. endlicherianum compounds were studied against cancer, revealing well-connected targets such as epidermal growth factor receptor (EGFR), phosphoinositide-3-kinase (PI3K), AKT, receptor tyrosine-protein kinase erbB-2, and growth factor receptor bound protein 2 (GRB2) with significant impact on cancer-related pathways. The results could open a new path from natural treasure to functional applications with P. endlicherianum and highlight a new study on other uninvestigated Pelargonium species.

The characterization of plant derived-carbon dots and its responses on chlorophyll a fluorescence kinetics, radical accumulation in guard cells, cellular redox state and antioxidant system in chromium stressed-Lactuca sativa

Based on their chemical structure and catalytic features, carbon dots (CDs) demonstrate great advantages for agricultural systems. The improvements in growth, photosynthesis, nutrient assimilation and resistance are provided by CDs treatments under control or adverse conditions. However, there is no data on how CDs can enhance the tolerance against chromium toxicity on gas exchange, photosynthetic machinery and ROS-based membrane functionality. The present study was conducted to evaluate the impacts of the different concentrations of orange peel derived-carbon dots (50-100-200-500 mg L-1 CD) on growth, chlorophyll fluorescence, phenomenological fluxes between photosystems, photosynthetic performance, ROS accumulation and antioxidant system under chromium stress (Cr, 100 μM chromium (VI) oxide) in Lactuca sativa. CDs removed the Cr-reduced changes in growth (RGR), water content (RWC) and proline (Pro) content. Compared to stress, CD exposures caused an alleviation in carbon assimilation rate, stomatal conductance, transpiration rate, carboxylation efficiency, chlorophyll fluorescence (Fv/Fm) and potential photochemical efficiency (Fv/Fo). Cr toxicity disrupted the energy fluxes (ABS/RC, TRo/RC, ETo/RC and DIo/RC), quantum yields and, efficiency (ΨEo and φRo), dissipation of energy (DIo/RC) and performance index (PIABS and PItotal). An amelioration in these parameters was provided by CD addition to Cr-applied plants. Stressed plants had high activities of superoxide dismutase (SOD), peroxidase (POX) and ascorbate peroxidase (APX), which could not prevent the increase of H2O2 and lipid peroxidation (TBARS content). While all CDs induced SOD and catalase (CAT) in response to stress, POX and enzyme/non-enzymes related to ascorbate-glutathione (AsA-GSH) cycle (APX, monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), the contents of AsA and, GSH) were activated by 50-100-200 mg L-1 CD. CDs were able to protect the AsA regeneration, GSH/GSSG and GSH redox status. The decreases in H2O2 content might be attributed to the increased activity of glutathione peroxidase (GPX). Therefore, all CD applications minimized the Cr stress-based disturbances (TBARS content) by controlling ROS accumulation, antioxidant system and photosynthetic machinery. In conclusion, CDs have the potential to be used as a biocompatible inducer in removing the adverse effects of Cr stress in lettuce plants.

The exogenous application of naringenin and rosmarinic acid modulates functional traits in Lepidium sativum

BACKGROUND

Phenolic modulators have attracted attention for their potential in shaping functional traits in plants. This work investigated the impact of naringenin (Nar) and rosmarinic acid (RA) on the functional properties of Lepidium sativum leaves and roots.

RESULTS

Untargeted metabolomics identified a diverse phenolic profile, including flavonoids, phenolic acids, low molecular weight phenolics, lignans, and stilbenes. Cluster, analysis of variance multiblock orthogonal partial least squares (AMOPLS), and orthogonal projection to latent structures discriminant analysis (OPLS-DA) multivariate analyses confirmed tissue-specific modulation of bioactive compounds. The tissue was the hierarchically most influential factor, explaining 27% of observed variability, while the treatment and their interaction were statistically insignificant. Thereafter, various in vitro assays were employed to assess antioxidant capacity, including 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging activity, cupric ion reducing antioxidant capacity (CUPRAC), and ferric ion reducing antioxidant power (FRAP), metal chelating ability, and phosphomolybdenum (PMD) assays. Extracts were also tested for inhibitory effects on cholinesterase, amylase, glucosidase, and tyrosinase enzymes. RA application positively impacted antioxidant and enzyme inhibitory activities, holding valuable implications in shaping the health-promoting properties of L. sativum.

CONCLUSION

The untargeted metabolomics analysis showed a significant tissue-dependent modulation of bioactive compounds, determining no synergistic effect between applying phenolic compounds in combination. Specifically, the sole application of RA increased anthocyanins and hydroxyphenyl propanoic acid content on leaves, which was strictly related to enhancing the biological activities. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Hesperidin and chlorogenic acid mitigate arsenic-induced oxidative stress via redox regulation, photosystems-related gene expression, and antioxidant efficiency in the chloroplasts of Zea mays

The ubiquitous metalloid arsenic (As), which is not essential, can be found extensively in the soil and subterranean water of numerous nations, raising substantial apprehensions due to its impact on both agricultural productivity and sustainability. Plants exposed to As often display morphological, physiological, and growth-related abnormalities, collectively leading to reduced productivity. Polyphenols, operating as secondary messengers within the intricate signaling networks of plants, assume integral functions in the acquisition of resistance to diverse environmental stressors, including but not limited to drought, salinity, and exposure to heavy metals. The pivotal roles played by polyphenols in these adaptive processes underscore their profound significance in plant biology. This study aims to elucidate the impact of hesperidin (HP) and chlorogenic acid (CA), recognized as potent bioactive compounds, on maize plants exposed to As. To achieve this objective, the study examined the physiological and biochemical impacts, including growth parameters, photosynthesis, and chloroplastic antioxidants, of HP (100 μM) and CA (50 μM) on Zea mays plants exposed to arsenate stress (AsV, 100 μM - Na2HAsO4⋅7H2O). As toxicity led to reductions in fresh weight (FW) and dry weight (DW) by 33% and 26%, respectively. However, the application of As+HP and As + CA increased FW by 22% and 40% and DW by 14% and 17%, respectively, alleviating the effects of As stress. As toxicity resulted in the up-regulation of PSII genes (psbA and psbD) and PSI genes (psaA and psaB), indicating a potential response to the re-formation of degraded regions, likely driven by the heightened demand for photosynthesis. Exogenous HP or/and CA treatments effectively counteracted the adverse effects of As toxicity on the photochemical quantum efficiency of PSII (Fv/Fm). H2O2 content showed a 23% increase under As stress, and this increase was evident in guard cells when examining confocal microscopy images. In the presence of As toxicity, the chloroplastic antioxidant capacity can exhibit varying trends, with either a decrease or increase observed. After the application of CA and/or HP, a significant increase was observed in the activity of GR, APX, GST, and GPX enzymes, resulting in decreased levels of H2O2 and MDA. Additionally, the enhanced functions of MDHAR and DHAR have modulated the redox status of ascorbic acid (AsA) and glutathione (GSH). The HP or CA-mediated elevated levels of AsA and GSH content further contributed to the preservation of redox homeostasis in chloroplasts facing stress induced by As. In summary, the inclusion of HP and CA in the growth medium sustained plant performance in the presence of As toxicity by regulating physiological and biochemical characteristics, chloroplastic antioxidant enzymes, the AsA-GSH cycle and photosynthesis processes, thereby demonstrating their significant potential to confer resistance to maize through the mitigation of As-induced oxidative damage and the safeguarding of photosynthetic mechanisms.

Graphene oxide-based aerogel stimulates growth, mercury accumulation, photosynthesis-related gene expression, antioxidant efficiency and redox status in wheat under mercury exposure

Mercury (Hg) pollution is a global concern in cropland systems. Hg contamination causes a disruption in the growth, energy metabolism, redox balance, and photosynthetic activity of plants. In the removal of Hg toxicity, a recent critical strategy is the use of aerogels with biodegradability and biocompatibility. However, it is unknown how graphene oxide-based aerogels stimulate the defense systems in wheat plants exposed to Hg toxicity. Therefore, in this study, the photosynthetic, genetic, and biochemical effects of reduced graphene oxide aerogel treatments (gA; 50-100-250 mg L-1) were examined in wheat (Triticum aestivum) under Hg stress (50 μM HgCl2). The relative growth rate (RGR) significantly decreased (84%) in response to Hg stress. However, the reduced RGR and water relations (RWC) of wheat were improved by gA treatments. The impaired gas exchange levels (stomatal conductance, carbon assimilation rate, intercellular CO2 concentrations, and transpiration rate) caused by stress were reversed under Hg plus gAs. Additionally, stress hampered chlorophyll fluorescence (Fv/Fo, Fv/Fm), and under Hg toxicity the expression of psaA genes was reduced (>0.4-fold), but psaB gene was significantly up-regulated (>3-fold) which are the genes involved in PSI. By increasing expression patterns of both genes relating to PSI, gAs reversed the adverse consequences on Fv/Fo and Fv/Fm in the presence of excessive Hg concentration. The activities of glutathione S-transferase (GST), glutathione reductase (GR), catalase (CAT), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) decreased under Hg toxicity. On the other hand, the activities of superoxide dismutase (SOD), APX, GST, and glutathione peroxidase (GPX) increased following gA treatments against stress, leading to the successful elimination of toxic levels of H2O2 and lipid peroxidation (TBARS content) by decreasing the levels by about 30%, and 40%, respectively. By modulating enzyme/non-enzyme activity/contents including the AsA-GSH cycle, gAs contributed to the protection of the cellular redox state. Most important of all, gA applications were able to reduce Hg intake by approximately 66%. Therefore, these results showed that gAs were effective in highly inhibiting Hg uptake and could significantly increase wheat tolerance to toxicity by eliminating Hg-induced oxidative damage and inhibiting metabolic processes involved in photosynthesis. The findings obtained from the study provide a new perspective on the alleviation roles of reduced graphene oxide aerogels as an effective adsorbent for decreasing damages of mercury toxicity in wheat plants.

Polyvinylpyrrolidone-coated copper nanoparticles dose-dependently conferred tolerance to wheat under salinity and/or drought stress by improving photochemical activity and antioxidant system

Copper (Cu) is one of the essential micronutrients for plants and has been used extensively in agricultural applications from the past to the present. However, excess copper causes toxic effects such as inhibiting photosynthesis, and disrupting biochemical processes in plants. Nanotechnology applications have offered a critical method for minimizing adverse effects and improving the effectiveness of copper nanoparticles. For this purpose, this study investigated the physiological and biochemical effects of polyvinylpyrrolidone (PVP)-coated Cu nanoparticles (PVP-Cu NP, N1, 100 mg L-1; N2, 400 mg L-1) in Triticum aestivum under alone or combined with salt (S, 150 mM NaCl) and/or drought (D, %10 PEG-6000) stress. Salinity and water deprivation caused 51% and 22% growth retardation in wheat seedlings. The combined stress condition (S + D) resulted in an approximately 3-fold reduction in the osmotic potential of the leaves. PVP-Cu NP treatments to plants under stress, especially N1 dose, were effective in restoring growth rate and regulating water relations. All stress treatments limited gas exchange in stomata and suppressed the maximal quantum yield of PSII (Fv/Fm). More than 50% improvement was observed in stomatal permeability and carbon assimilation rate under S + N1 and S + N2 applications. Examination of OJIP transient parameters revealed that N1 treatments protected photochemical reactions by reducing the dissipated energy flux (DIo/RC) in drought and S + D conditions. Exposure to S and/or D stress caused high hydrogen peroxide (H2O2) accumulation and lipid peroxidation in wheat leaves. The results indicated that S + N1 and S + N2 treatments reduced oxidative damage by stimulating the activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX). Although similar effects were observed at D and S + D conditions with 100 mg L-1 PVP-Cu NP treatments (N1), the curative effect of the N2 dose was not observed. In D + N1 and S + D + N1 groups, AsA regeneration and GSH redox status were maintained by triggering APX, GR, and other enzyme activities belonging to the AsA-GSH cycle. In these groups, N2 treatment did not contribute to the availability of enzymatic and non-enzymatic antioxidants. As a result, this study revealed that N1 dose PVP-Cu NP application was successful in providing stress tolerance and limiting copper-induced adverse effects under all stress conditions.

Exploring for HPLC-MS/MS Profiles and Biological Activities of Different Extracts from Allium lycaonicum Siehe ex Hayek from Turkey Flora

The present study was designed to determine the phenolic constituents, antioxidant, and enzyme inhibition activities of aerial parts and bulbs of Allium lycaonicum (family Amaryllidaceae). Extracts were prepared by maceration and Soxhlet/infusion using hexane, methanol, and water as extraction solvents. Generally, extracts from the aerial parts showed higher total phenolic and individual components and antioxidant activity than their respective bulb extracts. Maceration with water was the best to extract total phenolic content from the aerial parts (29.00 mg gallic acid equivalents (GAE)/g), while the Soxhlet extraction with hexane (22.29 mg GAE/g) was the best for the bulb. Maceration with methanol recovered the highest total flavonoid content from both the aerial parts (41.95 mg (rutin equivalents (RE)/g) and bulb (1.83 mg RE/g). Polar extracts of aerial parts were characterized by higher abundance of kaempferol-3-glucoside (≤20,624.27 µg/mg), hyperoside (≤19,722.76 µg/g), isoquercitrin (≤17,270.70 µg/g), delphindin-3,5-diglucoside (≤14,625.21 µg/g), and rutin (≤10,901.61 µg/g) than the bulb. Aerial parts' aqueous extract, prepared by maceration, exerted the highest anti-ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical activity (64.09 mg trolox equivalents (TE)/g), Cu++ (83.03 mg TE/g) and Fe+++ (63.03 mg TE/g) reducing capacity while that prepared by infusion recorded the highest anti-DPPH (2,2-diphenyl-1-picrylhydrazyl) radical (31.70 mg TE/g) and metal chelating (27.66 mg EDTAE/g) activities. The highest total antioxidant activity (1.46 mmol TE/g) was obtained by maceration of the bulb with water. Extracts obtained by organic solvents showed remarkable enzyme inhibition properties against the tested enzymes. Soxhlet extraction of the bulb with hexane and methanol recorded the highest acetylcholinesterase inhibition (4.75 mg galanthamine equivalents (GALAE)/g) and tyrosinase inhibition (139.95 mg kojic acid equivalents/g) activities, respectively. Extracts obtained by maceration of the bulb with methanol and the aerial parts with hexane exerted the highest glucosidase inhibition (3.25 mmol acarbose equivalents/g) and butyrylcholinesterase inhibition (20.99 mg GALAE/g) activities, respectively. These data indicated that A. lycaonicum is a source of bioactive molecules with potential antioxidant and enzyme inhibition properties. Nonetheless, the extracts obtained through various solvents and extraction techniques showed variations in their phytoconstituent composition and biological properties.

A Comparative Study on UHPLC-HRMS Profiles and Biological Activities of Inula sarana Different Extracts and Its Beta-Cyclodextrin Complex: Effective Insights for Novel Applications

Within this particular framework, the extracts obtained from Inula sarana using a variety of solvents, included n-hexane, ethyl acetate, dichloromethane (DCM), 70% ethanol, ethanol, and water. The extracts obtained from n-hexane, ethyl acetate, and DCM were then subjected to a specific method for their incorporation into β-cyclodextrin (β-CD). The establishment of complex formation was validated through the utilization of scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The identification of phytochemical components was executed using UHPLC-HRMS. Furthermore, the total phenolic and flavonoid content was evaluated using the Folin-Ciocalteu assay and the AlCl3 method. Subsequently, the determination of antioxidant capacity was conducted utilizing DPPH, ABTS, CUPRAC, Frap, PBD, and MCA assays. The enzyme inhibitory activities of the samples (extracts and β-CD complexes) were also examined by AChE, BChE, tyrosinase, α-glucosidase, and α-amylase. The findings indicated that water and 70% ethanol extracts contained the highest phenolic content. One hundred and fourteen bioactive compounds were identified by UHPLC-HRMS analysis. This study unveiled a substantial array of flavonoids, phenolic acid-hexosides and caffeoylhexaric acids within I. sarana, marking their initial identification in this context. Among the various extracts tested, the 70% ethanol extract stood out due to its high flavonoid content (jaceosidin, cirsiliol, and eupatilin) and hydroxybenzoic and hydroxycinnamic acid hexosides. This extract also displayed notably enhanced antioxidant activity, with ABTS, CUPRAC, and FRAP test values of 106.50 mg TE/g dry extract, 224.31 mg TE/g dry extract, and 110.40 mg TE/g, respectively. However, the antioxidant values of the complex extracts with β-CD were generally lower than those of the pure extracts, an observation warranting significant consideration. In terms of enzyme inhibition activity, the ethanol and 70% ethanol extracts exhibited higher inhibitory effects on AChE, tyrosinase, and α-glucosidase. Conversely, n-hexane displayed stronger inhibitory activity against BChE. The ethyl acetate extract demonstrated elevated amylase inhibitory activity. However, the antioxidant values of the complex extracts with β-CD were generally lower than those of the pure extracts, a noteworthy observation, while water and extracts from the I. sarana complex with β-CD exhibited minimal or negatable inhibitory activity against specific enzymes.

Responses of salicylic acid encapsulation on growth, photosynthetic attributes and ROS scavenging system in Lactuca sativa exposed to polycyclic aromatic hydrocarbon pollution

Salicylic acid (SA) is a phytohormone that plays a key role in the regulation of the defense response against environmental variables in plants, and it provides increased yield and stress tolerance when exogenously applied to plants as a growth regulator. The role of SA-mediated signals in abiotic stress tolerance varies according to the species, stressor, application method, and dose. This study investigated the effects of salicylic acid (SA, 0.1 mg ml-1) or β-cyclodextrin encapsulated salicylic acid (e-SA, 0.1 mg ml-1) treatments on growth parameters, gas exchange, photosynthesis efficiency, and antioxidant capacity in lettuce seedlings exposed to polycyclic aromatic hydrocarbon pollution. Fluorene (FLN, 100 mg L-1) contamination resulted in a 27% growth rate and a 14% water content reduction in lettuce leaves. Significant suppressions of stomatal conductance, carbon assimilation, and PSII photochemistry were detected in plants under stress. FLN + SA and FLN + e-SA treatments regulated plant-water relations by stimulating proline accumulation and relieving stomatal limitations. As indicated by the high Fv/Fm ratio, photosynthesis efficiency was recovered in FLN + SA and FLN + e-SA group plants. FLN stress caused high oxidative stress in lettuce leaves and increased lipid peroxidation level by 40%. However, especially e-SA application to plants under stress, increased SOD activity by 3-fold and CAT activity by 80% and was successful in preventing H2O2 accumulation and lipid peroxidation. Both SA and e-SA treatments partially activated the AsA-GSH cycle. As a result, direct SA application was effective in mitigating stress-induced physiological limitations with high SA accumulation in the tissues, while encapsulated SA treatment was more effective in regulating photosynthetic and biochemical reactions, alleviating oxidative damage by activating the antioxidant defense, and promoting growth under stress with moderate SA accumulation.

Polyamine, 1,3-diaminopropane, regulates defence responses on growth, gas exchange, PSII photochemistry and antioxidant system in wheat under arsenic toxicity

The metalloid arsenic (As) is extremely hazardous to all living organisms, including plants. Pollution with As is very detrimental to the photosynthetic machinery, cell division, energy generation, and redox status. In order to cope with stress, the use of growth regulators such as polyamines (PA), which strengthen the antioxidant system of plants, has become widespread in recent years. PAs can modulate the plant growth through basic mechanisms common to all living organisms, such as membrane stabilization, free radical scavenging, deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein synthesis, enzyme activities and second messengers. However, the effect of 1,3- diaminopropane (Dap), which is a product of PA catabolism, is not clear enough in plants exposed to As toxicity. In the current study, the different concentrations of 1,3-diaminopropane (0.1, 0.5 and 1 mM Dap) were hydroponically treated to wheat (Triticum aestivum) under arsenic stress (100 μM As) and then relative growth rate (RGR), relative water content (RWC), proline content (Pro), gas exchange parameters, PSII photochemistry, chlorophyll fluorescence kinetics, antioxidant activity and lipid peroxidation were assessed. RGR, RWC, osmotic potential and Pro content decreased in As-applied plants. The inhibition of these parameters could be reversed by Dap treatments. Besides, Dap applications mitigated the As toxicity-induced suppression on chlorophyll fluorescence (Fv/Fm, Fv/Fo and Fo/Fm) and the performance of PSII photochemistry. As impaired the balance on antioxidant capacity by decreased activities of catalase (CAT), peroxidase (POX), glutathione peroxidase (GPX), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and the contents of ascorbate (AsA) and glutathione (GSH) and then lipid peroxidation (TBARS content) increased. In the presence of Dap under As stress, the plants exhibited an increase in superoxide dismutase (SOD), POX, and GPX. Dap treatments contributed to the maintenance of cellular redox state (AsA/DHA and GSH/GSSG) by regulating the activities/contents of enzyme/non-enzyme involved in the AsA-GSH cycle. After Dap applications against stress, ROS accumulation (H2O2 content) and lipid peroxidation (TBARS) were effectively reduced. The findings showed that by eliminating As-induced oxidative damage and protecting the biochemical processes of photosynthesis, Dap treatments have a substantial potential to give resistance to wheat.

Protective role of quercetin and kaempferol against oxidative damage and photosynthesis inhibition in wheat chloroplasts under arsenic stress

Arsenic (As) toxicity negatively impacts plant development, limits agricultural production, and, by entering the food chain, endangers human health. Studies on the use of natural and bioactive molecules in increasing plants' resistance to abiotic stressors, such as As, have gained increasing attention in the last few years. Flavonols are plant secondary metabolites with high potential in stress tolerance due to their roles in signal transmission. Therefore, the focus of this study was to examine the effects of two flavonols, quercetin (Q, 25 μM) and kaempferol (K, 25 μM), on growth parameters, photosynthesis, and chloroplastic antioxidant activity in wheat leaves under As stress (100 μM). As stress reduced the relative growth rate by 50% and relative water content by 25% in leaves. However, applying Q and/or K alleviated the As-induced suppression of growth and water relations. Exogenous phenolic treatments reversed the effects of As toxicity in photochemistry and maintained the photochemical quantum efficiency of the Photosystem II (Fv /Fm ). As exposure increased, the H2 O2 content in wheat chloroplasts by 42% and high levels of H2 O2 accumulation were also observed in guard cells in confocal microscopy images. Analysis of the chloroplastic antioxidant system has shown that Q and K applications increase the activity of antioxidant enzymes, including superoxide dismutase, peroxidase, and ascorbate peroxidase. Phenolic applications have induced the ascorbate-glutathione (AsA-GSH) cycle in charge of the protection of the cellular redox balance in different ways. It has been determined that Q triggers the AsA renewal, and K maintains the GSH pool. As a result, Q and K applications provide tolerance to wheat plants under As stress by increasing the chloroplastic antioxidant system activity and protecting photosynthetic reactions from oxidative damage. This study reveals the potential use of plant phenolic compounds in agricultural systems as a biosafe strategy to enhance plant stress tolerance, hence increasing yield.

Halotolerant plant growth-promoting bacteria, Bacillus pumilus, modulates water status, chlorophyll fluorescence kinetics and antioxidant balance in salt and/or arsenic-exposed wheat

Seed priming is an effective and novel technique and the use of eco-friendly biological agents improves the physiological functioning in the vegetative stage of plants. This procedure ensures productivity and acquired stress resilience in plants against adverse conditions without contaminating the environment. Though the mechanisms of bio-priming-triggered alterations have been widely explained under induvial stress conditions, the interaction of combined stress conditions on the defense system and the functionality of photosynthetic apparatus in the vegetative stage after the inoculation to seeds has not been fully elucidated. After Bacillus pumilus inoculation to wheat seeds (Triticum aestivum), three-week-old plants were hydroponically exposed to the alone and combination of salt (100 mM NaCl) and 200 μM sodium arsenate (Na₂HAsO₄·7H₂O, As) for 72 h. Salinity and As pollutant resulted in a decline in growth, water content, gas exchange parameters, fluorescence kinetics and performance of photosystem II (PSII). On the other hand, the seed inoculation against stress provided the alleviation of relative growth rate (RGR), relative water content (RWC) and chlorophyll fluorescence. These negative impacts were reversed by B. pumilus inoculation. Since there was no effective antioxidant capacity, As and/or salinity caused induction of H₂O₂ accumulation and thiobarbituric acid reactive substances content (TBARS) in wheat leaves. The inoculated leaves had high activity of superoxide dismutase (SOD) under stress. B. pumilis decreased the NaCl-induced toxic H₂O₂ levels by increasing peroxidase (POX) and enzymes/non-enzymes related to ascorbate-glutathione (AsA-GSH) cycle. In the presence of As exposure, the inoculated plants exhibited an induction in CAT activity. On the other hand, for H₂O₂ scavenging, the improvement in the AsA-GSH cycle was observed in bacterium priming plants plus the combined stress treatment. Since B. pumilus inoculation reduced H₂O₂ levels against all stress treatments, lipid peroxidation subsequently decreased in wheat leaves. The findings obtained from our study explained that the seed inoculation with B. pumilus provided an activation in the defense system and protection in growth, water status, and gas exchange regulation in wheat leaves against the combination of salt and As.

Glutamate, Humic Acids and Their Combination Modulate the Phenolic Profile, Antioxidant Traits, and Enzyme-Inhibition Properties in Lettuce

Lettuce (Lactuca sativa L., Asteraceae) is a popular vegetable leafy crop playing a relevant role in human nutrition. Nowadays, novel strategies are required to sustainably support plant growth and elicit the biosynthesis of bioactive molecules with functional roles in crops including lettuce. In this work, the polyphenolic profile of lettuce treated with glutamic acid (GA), humic acid (HA), and their combination (GA + HA) was investigated using an untargeted metabolomics phenolic profiling approach based on high-resolution mass spectrometry. Both aerial and root organ parts were considered, and a broad and diverse phenolic profile could be highlighted. The phenolic profile included flavonoids (anthocyanins, flavones, flavanols, and flavonols), phenolic acids (both hydroxycinnamics and hydroxybenzoics), low molecular weight phenolics (tyrosol equivalents), lignans and stilbenes. Overall, GA and HA treatments significantly modulated the biosynthesis of flavanols, lignans, low molecular weight phenolics, phenolic acids, and stilbene. Thereafter, antioxidant capacity was evaluated in vitro with 2,2-diphenyln-1-picrylhydrazyl (DPPH), 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and cupric ion reducing antioxidant capacity (CUPRAC) assays. In addition, this study examined the inhibitory properties of enzymes, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), tyrosinase, alpha-amylase, and alpha-glucosidase. Compared to individual treatments, the combination of GA + HA showed stronger antioxidant abilities in free radical scavenging and reducing power assays in root samples. Moreover, this combination positively influenced the inhibitory effects of root samples on AChE and BChE and the tyrosinase inhibitory effect of leaf samples. Concerning Pearson's correlations, antioxidant and enzyme inhibition activities were related to phenolic compounds, and lignans in particular correlated with radical scavenging activities. Overall, the tested elicitors could offer promising insights for enhancing the functional properties of lettuce in agricultural treatments.

Responses of individual and combined polystyrene and polymethyl methacrylate nanoplastics on hormonal content, fluorescence/photochemistry of chlorophylls and ROS scavenging capacity in Lemna minor under arsenic-induced oxidative stress

Nanoplastics alter the adverse impacts of hazardous contaminants such as heavy metals by changing their adsorption and accumulation. Few findings are available on the interaction between nanoplastic and heavy metals in plants. However, there is no report on the mechanisms for removing metal stress-mediated oxidative damage by the combination treatments of nanoplastics. To address this lack of information, polystyrene nanoplastic (PS, 100 mg L^-1) and polymethyl methacrylate (PMMA, 100 mg L^-1) were hydroponically applied to Lemna minor exposed to arsenate (As, 100 μM) for 7 days. PS or PMMA caused a reduction in the contents of N, P, K, Ca, Mg and Mn, but the improved contents were detected in the presence of PS or PMMA plus As stress. The hormone contents (auxin, gibberellic acid, cytokinin, salicylic acid and jasmonic acid) reduced by stress were re-arranged through PS or PMMA applications. Based on chlorophyll efficiency, fluorescence kinetics and performance of PSII, the impaired photosynthesis by As stress was improved via PS or PMMA applications. This alleviation did not continue under the combined form of PS and PMMA in As-applied plants. All analyzed antioxidant activity (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR)) decreased or unchanged under As, PS or PMMA. Due to the inactivation of the defense system, L. minor had high levels of hydrogen peroxide (H₂O₂) and thiobarbituric acid reactive substances (TBARS), showing lipid peroxidation. After As toxicity, induvial applications of PS or PMMA indicated the activated enzyme capacity (SOD, POX, GST and GPX) and upregulated AsA/DHA, GSH/GSSG and redox state of GSH, which facilitated the removal of radical accumulation. The efficiency of the antioxidant system in As + PS + PMMA-applied L. minor was not enough to remove damage induced by As stress; hereby, TBARS and H₂O₂ contents were similar to the As-treated group. Our findings from alone or combined application of PS and PMMA provide new information to advance the tolerance mechanism against As exposure in L. minor.

Phytochemical Profile and Biological Activities of Different Extracts of Three Parts of Paliurus spina-christi: A Linkage between Structure and Ability

Paliurus spina-christi Mill., a member of the Rhamnaceae family, is a traditionally used medicinal plant in the management of a panoply of human ailments. The current research focused on its phytochemical profile and biological properties evaluated by its antioxidant and enzyme inhibitory properties. The methanol extract was found to be the most effective antioxidant as evidenced by its DPPH and ABTS scavenging activities, cupric and ferric reducing power (CUPRAC and FRAP), and high activity in phosphomolybdenum (PBD) assay, and also displayed the highest anti-tyrosinase activity. The n-hexane extract was the most effective AChE inhibitor (8.89 ± 0.08 mg GALAE/g) followed by the methanol (8.64 ± 0.01 mg GALAE/g) while the latter showed the highest BChE inhibition (2.50 ± 0.05 mg GALAE/g). Among the different solvent extracts of the stem, the methanolic extract showed highest antioxidant activity in the following assays: DPPH (909.88 ± 4.25 mg TE/g), ABTS (3358.33 ± 51.14 mg TE/g), CUPRAC (781.88 ± 16.37 mg TE/g), FRAP (996.70 ± 47.28 mg TE/g), and PBD (4.96 ± 0.26 mmol TE/g), while the dichloromethane extract showed the highest MCA (28.80 ± 0.32 mg EDTAE/g). The methanol extracts revealed the highest TPC and TFC among the different solvents used, and as for plant part, the stem extracts had the highest TPC ranging from 22.36 ± 0.26 to 121.78 ± 1.41 (mg GAE/g), while the leaf extracts showed the highest TFC ranging from 8.43 ± 0.03 to 75.36 ± 0.92 (mg RE/g). Our findings tend to provide additional scientific evidence on the biological and chemical activities of P. spina-christi, which may serve as a source of naturally occurring bioactive chemicals with potential biomedical applications.

Hormetic activation of nano-sized rare earth element terbium on growth, PSII photochemistry, antioxidant status and phytohormone regulation in Lemnaminor

Soils contaminated with rare earth elements (REEs) can damage agriculture by causing physiological disorders in plants which are evaluated as the main connection of the human food chain. A biphasic dose response with excitatory responses to low concentrations and inhibitory/harmful responses to high concentrations has been defined as hormesis. However, not much is clear about the ecological effects and potential risks of REEs to plants. For this purpose, here we showed the impacts of different concentrations of nano terbium (Tb) applications (5-10-25-50-100-250-500 mg L^-1) on the accumulation of endogeneous certain ions and hormones, chlorophyll fluoresence, photochemical reaction capacity and antioxidant activity in duckweed (Lemna minor). Tb concentrations less than 100 mg L^-1 increased the contents of nitrogen (N), phosphate (P), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), manganese (Mn²⁺) and iron (Fe²⁺). Chlorophyll fluorescence (F_v/F_m and F_v/F_o) was suppressed under 250-500 mg L^-1 Tb. In addition, Tb toxicity affected the trapped energy adversely by the active reaction center of photosystem II (PSII) and led to accumulation of inactive reaction centers, thus lowering the detected level of electron transport from photosystem II (PSII) to photosystem I (PSI). On the other hand, 5-100 mg L^-1 Tb enhanced the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), NADPH oxidase (NOX), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione S-transferase (GST). Tb (5-50 mg L^-1) supported the maintenance of cellular redox status by promoting antioxidant pathways involved in the ascorbate-glutathione (AsA-GSH) cycle. In addition to the antioxidant system, the contents of some hormones such as indole-3-acetic acid (IAA), gibberellic acid (GA), cytokinin (CK) and salicylic acid (SA) were also induced in the presence of 5-100 mg L^-1 Tb. In addition, the levels of hydrogen peroxide (H₂O₂) and lipid peroxidation (TBARS) were controlled through ascorbate (AsA) regeneration and effective hormonal modulation in L. minor. However, this induction in the antioxidant system and phytohormone contents could not be resumed after applications higher than 250 mg L^-1 Tb. TBARS and H₂O₂, which indicate the level of lipid peroxidation, increased. The results in this study showed that Tb at appropriate concentrations has great potential to confer tolerance of duckweed by supporting the antioxidant system, protecting the biochemical reactions of photosystems and improving hormonal regulation.

Rare earth element scandium mitigates the chromium toxicity in Lemna minor by regulating photosynthetic performance, hormonal balance and antioxidant machinery

Chromium (Cr) toxicity is a serious problem that threatens the health of living organisms and especially agricultural production. The presence of excess Cr leads to biomass loss by causing the imbalance of biochemical metabolism and inhibiting photosynthetic activity. A new critical approach to cope with Cr toxicity is the use of the rare earth elements (REEs) as an antioxidant defence system enhancer in plants. However, the effect of scandium (Sc), which is one of the REEs, is not clear enough in Lemna minor exposed to Cr toxicity. For this purpose, the photosynthetic and biochemical effects of scandium (50 μM and 200 μM Sc) treatments were investigated in Lemna minor under Cr stress (100 μM, 200 μM and 500 μM Cr). Parameters related to photosynthesis (F_v/F_m, F_v/F_o) were suppressed under Cr stress. Stress altered antioxidant enzymes activities and hormone contents. Sc applications against stress increased the activities of superoxide dismutase (SOD), NADPH oxidase (NOX), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and glutathione S-transferase (GST). In addition to the antioxidant system, the contents of indole-3-acetic acid (IAA), abscisic acid (ABA) and jasmonic acid (JA) were also rearranged. However, in all treatment groups, with the provision of ascorbate (AsA) regeneration and effective hormone signaling, reactive oxygen species (ROS) retention which result in high hydrogen peroxide (H₂O₂) content and lipid peroxidation (TBARS) were effectively removed. Sc promoted the maintenance of cellular redox state by regulating antioxidant pathways included in the AsA-GSH cycle. Our results showed that Sc has great potential to confer tolerance to duckweed by reducing Cr induced oxidative damage, protecting the biochemical reactions of photosynthesis, and improving hormone signaling.

Fe2O3-modified graphene oxide mitigates nanoplastic toxicity via regulating gas exchange, photosynthesis, and antioxidant system in Triticum aestivum

The ever-increasing plastic pollution in soil and water resources raises concerns about its effects on terrestrial plants and agroecosystems. Although there are many reports about the contamination with nanoplastics on plants, the presence of magneto-assisted nanomaterials enabling the removal of their adverse impacts still remains unclear. Therefore, the purpose of the current study is to evaluate the potential of nanomaterial Fe₂O₃-modified graphene oxide (FGO, 50-250 mg L^-1) to eliminate the adverse effects of nanoplastics in plants. Wheat plants exposed to polystyrene nanoplastics concentrations (PS, 10, 50 and 100 mg L^-1) showed decreased growth, water content and loss of photosynthetic efficiency. PS toxicity negatively altered gas exchange, antenna structure and electron transport in photosystems. Although the antioxidant system was partially activated (only superoxide dismutase (SOD), NADPH oxidase (NOX) and glutathione reductase (GR)) in plants treated with PS, it failed to prevent PS-triggered oxidative damage, as showing lipid peroxidation and hydrogen peroxide (H₂O₂) levels. FGOs eliminated the adverse impacts of PS pollution on growth, water status, gas exchange and oxidative stress markers. In addition, FGOs preserve the biochemical reactions of photosynthesis by actively increasing chlorophyll fluorescence parameters in the stressed-wheat leaves. The activities of all enzymatic antioxidants increased, and the H₂O₂ and TBARS contents decreased. GSH-mediated detoxifying antioxidants such as glutathione S-transferase (GST) and glutathione peroxidase (GPX) were stimulated by FGOs against PS pollution. FGOs also triggered the enzymes and non-enzymes related to the Asada-Halliwell cycle and protected the regeneration of ascorbate (AsA) and glutathione (GSH). Our findings indicated that FGO had the potential to mitigate nanoplastic-induced damage in wheat by regulating water relations, protecting photosynthesis reactions and providing efficient ROS scavenging with high antioxidant capacity. This is the first report on removing PS-induced damage by FGO applications in wheat leaves.

The impacts of nanoplastic toxicity on the accumulation, hormonal regulation and tolerance mechanisms in a potential hyperaccumulator - Lemna minor L

Plastic pollution, which is currently one of the most striking problems of our time, raises concerns about the dispersal of micro and nano-sized plastic particles in ecosystems and their toxic effects on living organisms. This study was designed to reveal the toxic effects of polystyrene nanoplastic (PS NP) exposure on the freshwater macrophyte Lemna minor. In addition, elucidating the interaction of this aquatic plant, which is used extensively in the phytoremediation of water contaminants and wastewater treatment facilities, with nanoplastics will guide the development of remediation techniques. For this purpose, we examined nanoplastic accumulation, oxidative stress markers, photosynthetic efficiency, antioxidant system activity and phytohormonal changes in L. minor leaves subjected to PS NP stress (P-1, 100 mg L^-1; P-2, 200 mg L^-1 PS NP). Our results showed no evidence of PS NP-induced oxidative damage in P-1 group plants, although PS NP accumulation reached 56 µg g^-1 in the leaves. Also, no significant changes in chlorophyll a fluorescence parameters were observed in this group, indicating unaffected photosynthetic efficiency. PS NP exposure triggered the antioxidant system in L. minor plants and resulted in a 3- and 4.6-fold increase in superoxide dismutase (SOD) activity in the P-1 and P-2 groups. On the other hand, high-dose PS NP treatment resulted in insufficient antioxidant activity in the P-2 group and increased hydrogen peroxide (H₂O₂) and lipid peroxidation (TBARS contents) by 25 % and 17 % compared to the control plants. Furthermore, PS NP exposure triggered abscisic acid biosynthesis (two-fold in the P-1 and three-fold in the P-2 group), which is also involved in regulating the stress response. In conclusion, L. minor plants tolerated NP accumulation without growth suppression, oxidative stress damage and limitations in photosynthetic capacity and have the potential to be used in remediation studies of NP-contaminated waters.

Polystyrene nanoplastic contamination mixed with polycyclic aromatic hydrocarbons: Alleviation on gas exchange, water management, chlorophyll fluorescence and antioxidant capacity in wheat

Polycyclic aromatic hydrocarbons (PAHs) constitute a significant environmental pollution group that reaches toxic levels with anthropogenic activities. The adverse effects of nanoplastics accumulating in ecosystems with the degradation of plastic wastes are also a growing concern. Previous studies have generally focused on the impact of single PAH or plastic fragments exposure on plants. However, it is well recognized that these contaminants co-exist at varying rates in agricultural soil and water resources. Therefore, it is critical to elucidate the phytotoxicity and interaction mechanisms of mixed pollutants. The current study was designed to comparatively investigate the single and combined effects of anthracene (ANT, 100 mg L^-1), fluorene (FLU, 100 mg L^-1) and polystyrene nanoplastics (PS, 100 mg L^-1) contaminations in wheat. Plants exposed to single ANT, FLU and PS treatments demonstrated decline in growth, water content, high stomatal limitations and oxidative damage. The effect of ANT + FLU on these parameters was more detrimental. In addition, ANT and/or FLU treatments significantly suppressed photosynthetic capacity as determined by carbon assimilation rate (A) and chlorophyll a fluorescence transient. The antioxidant system was not fully activated (decreased superoxide dismutase, peroxidase and glutathione reductase) under ANT + FLU, then hydrogen peroxide (H₂O₂) content (by 2.7-fold) and thiobarbituric acid reactive substances (TBARS) (by 2.8-fold) increased. Interestingly, ANT + PS and FLU + PS improved the growth, water relations and gas exchange parameters. The presence of nanoplastics recovered the adverse effects of ANT and FLU on growth by protecting the photosynthetic photochemistry and reducing oxidative stress. PAH plus PS reduced the ANT and FLU accumulation in wheat leaves. In parallel, the increased antioxidant system, regeneration of ascorbate, glutathione and glutathione redox status observed under ANT + PS and FLU + PS. These findings will provide an information about the phytotoxicity mechanisms of mixed pollutants in the environment.

Multiwalled Carbon Nanotubes Alter the PSII Photochemistry, Photosystem-Related Gene Expressions, and Chloroplastic Antioxidant System in Zea mays under Copper Toxicity

A critical approach against copper (Cu) toxicity is the use of carbon nanomaterials (CNMs). However, the effect of CNMs on Cu toxicity-exposed chloroplasts is not clear. The photosynthetic, genetic, and biochemical effects of multiwalled carbon nanotubes (50-100-250 mg L^-1 CNT) were investigated under Cu stress (50-100 μM CuSO₄) in Zea mays chloroplasts. F_v/F_m and F_v/F_o were suppressed under stress. Stress altered the antioxidant system and the expression of psaA, psaB, psbA, and psbD. The chloroplastic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under CNT + stress, and those of hydrogen peroxide (H₂O₂) and lipid peroxidation decreased. CNTs were promoted to the maintenance of the redox state by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. Furthermore, CNTs inverted the negative effects of Cu by upregulating the transcriptions of photosystem-related genes. However, the high CNT concentration had adverse effects on the antioxidant capacity. CNT has great potential to confer tolerance by reducing Cu-induced damage and protecting the biochemical reactions of photosynthesis.

The hormetic dose-risks of polymethyl methacrylate nanoplastics on chlorophyll a fluorescence transient, lipid composition and antioxidant system in Lactuca sativa

Nanoplastic pollution has become an increasing problem due to over-consumption and degradation in ecosystems. A little is known about ecological toxicity and the potential risks of nanoplastics on plants. To better comprehend the hormetic effects of nanoplastics, the experimental design was conducted on the impacts of polymethyl methacrylate (PMMA) on water status, growth, gas exchange, chlorophyll a fluorescence transient, reactive oxygen species (ROS) content (both content and fluorescence visualization), lipid peroxidation and antioxidant capacity (comparatively between leaves and roots). For this purpose, PMMA (10, 20, 50 and 100 mg L-1) was hydroponically applied to Lactuca sativa for 15 days(d). PMMA exposure resulted a decline in the growth, water content and osmotic potential. As based on assimilation rate (A), stomatal conductance (gs), and intercellular CO2 concentrations (Ci), the decreased stomatal limitation (Ls) and, A/Ci and increased intrinsic mesophyll efficiency proved low carboxylation efficiency showing impaired photosynthesis as a non-stomatal limitation. PMMA toxicity increased the trapping fluxes and absorption with a decrease in electron transport fluxes caused the disruption in reaction centers of photosystems. The leaves and roots had a similar effect against PMMA toxicity, with increased superoxide dismutase (SOD) activity. Although, catalase (CAT) and peroxidase (POX) of leaves increased under 10 mg L-1 PMMA, these defense activities failed to prevent radicals from attacking. Compared to the leaves, the lettuce roots showed an intriguing result for AsA-GSH cycle against PMMA exposure. In the roots, the lowest PMMA application provided the high ascorbate/dehydroascorbate (AsA/DHA), GSH/GSSG and the pool of AsA/glutathione (GSH) and non-suppressed GSH redox state. Also, 10 mg L-1 PMMA helped remove high hydrogen peroxide (H2O2) by both glutathione peroxidase (GPX) and glutathione S-transferase (GST). Since this improvement in the antioxidant system could not be continued in roots after higher applications than 20 mg L-1 PMMA, TBARS (Thiobarbituric acid-reactive substances), indicating the level of lipid peroxidation, and H2O2 increased. Our findings obtained from PMMA-applied lettuce provide new information to advance the tolerance mechanism against nanoplastic pollution.

Phytochemical Screening, Antioxidant, and Enzyme Inhibitory Properties of Three Prangos Species (P. heyniae, P. meliocarpoides var. meliocarpoides, and P. uechtritzii) Depicted by Comprehensive LC-MS and Multivariate Data Analysis

The aim of the present study was to identify/quantify bioactive compounds and determine the antioxidant activity and enzyme inhibitory effects of various solvent extracts (n-hexane, ethyl acetate, methanol, and water) of Prangos heyniae H. Duman and M.F. Watson, Prangos meliocarpoides var. meliocarpoides, and Prangos uechtritzii Boiss. and Hausskn. This is the first time such a report has been designed to validate the phytochemical composition and bioactivity (especially enzyme inhibitory properties) of these plants. A combined approach of liquid chromatography (LC) with mass spectrometry (HR-MS and MSⁿ) allowed to identify that P. heyniae contains condensed tannins; P. meliocarpoides is rich in hydrolysable tannins; and P. uechtritzii possesses coumarins, flavonoids, and hydroxycinnamic acids. Different extracts were tested for antioxidant activities using a battery of assays, such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC), total antioxidant capacity (TAC) (phosphomolybdenum), and metal chelating. Enzyme inhibitory effects were investigated using acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, α-amylase, and α-glucosidase as target enzymes. The obtained results depended on the extraction solvents used for each Prangos species. The methanol extract of P. meliocarpoides var. meliocarpoides exhibited significant radical scavenging activity (DPPH: 52.27 mg Trolox equivalent (TE)/g; ABTS: 92.84 mg TE/g), the most potent-reducing potential (CUPRAC: 154.04 mg TE/g; FRAP: 104.34 mg TE/g), and high TAC (2.52 mmol TE/g). Moreover, the strongest BChE (7.97 mg galantamine equivalent/g), α-amylase (0.46 mmol acarbose equivalent/g), and tyrosinase (81.15 mg kojic acid equivalent/g) inhibitory effects were observed for the hexane extract of P. meliocarpoides var. meliocarpoides. Correlation analysis showed a significant positive correlation between hydrolysable tannins and antioxidant activities. The same trend was also observed between the same class of compounds and the inhibitory effects on enzymatic activities. These results suggest a principal role of hydrolysable tannins in the observed bioactivities of Prangos. Our results suggested that the tested Prangos species could be valuable as sources of natural agents in the development of health-promoting applications.

The biphasic responses of nanomaterial fullerene on stomatal movement, water status, chlorophyll a fluorescence transient, radical scavenging system and aquaporin-related gene expression in Zea mays under cobalt stress

Nanomaterial fullerene (FLN) has different responses called the hormesis effect against stress conditions. The favorable/adverse impacts of hormesis on crop quality and productivity are under development in agrotechnology. In this study, the effect of FLN administration (100-250-500mg L^-1 for FLN1-2-3, respectively) on growth, water management, gas exchange, chlorophyll fluorescence kinetics and cobalt (Co)-induced oxidative stress in Zea mays was investigated. The negative alterations in relative growth rate (RGR), water status (relative water content, osmotic potential and proline content) and gas exchange/stomatal regulation were removed by FLNs. FLNs were shown to protect photosynthetic apparatus and preserve the photochemistry of photosystems (PSI-PSII) in photosynthesis, chlorophyll fluorescence transients and energy flux damaged under Co stress. The maize leaves exposed to Co stress exhibited a high accumulation of hydrogen peroxide (H₂O₂) due to insufficient scavenging activity, which was confirmed by reactive oxygen species (ROS)-specific fluorescence visualization in guard cells. FLN regulated the gene expression of ribulose-1,5-bisphosphate carboxylase large subunit (rbcL), nodulin 26-like intrinsic protein1-1 (NIP1-1) and tonoplast intrinsic protein2-1 (TIP2-1) under stress. After stress exposure, FLNs successfully eliminated H₂O₂ content produced by superoxide dismutase (SOD) activity of catalase (CAT) and peroxidase (POX). The ascorbate (AsA) regeneration was achieved in all FLN applications together with Co stress through the elevated monodehydroascorbate reductase (MDHAR, under all FLNs) and dehydroascorbate reductase (DHAR, only FLN1). However, dose-dependent FLNs (FLN1-2) provided the induced pool of glutathione (GSH) and GSH redox state. Hydroponically applied FLNs removed the restrictions on metabolism and biological process induced by lipid peroxidation (TBARS content) and excessive ROS production. Considering all data, the modulation of treatment practices in terms of FLN concentrations and forms of its application will provide a unique platform for improving agricultural productivity and stress resistance in crops. The current study provided the first findings on the chlorophyll a fluorescence transient and localization of ROS in guard cells of Zea mays exposed to FLN and Co stress.

Rosmarinic acid and hesperidin regulate gas exchange, chlorophyll fluorescence, antioxidant system and the fatty acid biosynthesis-related gene expression in Arabidopsis thaliana under heat stress

The impacts of exogenous rosmarinic acid (RA, 100 μM) and/or hesperidin (HP, 100 μM) were evaluated in improving tolerance on the gas exchange, chlorophyll fluorescence and efficiencies, phenomenological fluxes of photosystems, antioxidant system and gene expression related to the lipid biosynthesis under heat stress. For this purpose, Arabidopsis thaliana was grown under RA and HP with heat stress (S, 38 °C) for 24 h(h). As shown in gas exchange parameters, heat stress caused mesophyll efficiency and non-stomatal restrictions. Both alone and combined forms of RA and HP to stress-treated A. thaliana alleviated the disturbance of carbon assimilation, transpiration rate and internal CO2 concentrations. Stress impaired the levels of energy flow reaching reaction centers of PSII and the photon capture ability of active reaction centers. RA and/or HP enhanced photosystems' structural/functional characteristics and photosynthetic performance. Histochemical staining and biochemical analyses revealed that heat stress caused the oxidation in A. thaliana. By activating several defensive mechanisms, RA and/or HP could reverse the harm caused by radical production. Both alone and combined forms of RA and HP removed superoxide anion radical (O2•-) accumulation, inducing superoxide dismutase (SOD). The common enzyme that scavenged hydrogen peroxide (H2O2) at all three applications (S + RA, S + HP and S + RA + HP) was POX. Also, only RA could utilize the ascorbate (AsA) regeneration in response to stress, suggesting increased ascorbate peroxidase (APX), monodehydroascorbate (MDHAR) and dehydroascorbate (DHAR) activities. However, the regeneration/redox state of AsA and glutathione (GSH) did not maintain under S + HP and S + RA + HP. While RA had no positive influence on the saturated fatty acids under stress, HP increased the total saturated fatty acids (primarily palmitic acid). Besides, the combined application of RA + HP effectively created the stress response by increasing the expression of genes involved in fatty acid synthesis. The synergetic interactions of RA and HP could explain the increased levels of saturated fatty acids in combining these compounds. The data obtained from the study will contribute to the responses of phenolic compounds in plants to heat stress.

COMBATING OF ESCHERICHIA COLI STRAINS AGAINST SALINITY BY THE ANTIOXIDANT DEFENSE SYSTEM AND OSMOREGULATION: BIOCHEMICAL AND PHYSIOLOGICAL APPROACHES

The study was designed to elucidate the impacts of salinity on biochemical and physiological properties of two Escherichia coli strains (6E and S39) isolated from different sites. The strains were exposed to 600 and 1200 mM NaCl and were harvested after 12th and 24th h of incubation. The lipid peroxidation levels, osmolyte accumulation, H2O2 content and antioxidant system [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase(GR)] of the bacteria were investigated. While thiobarbituric acid reactive substances (TBARS) and H2O2 content of S39 has increased steadily with salinity, however, it has not changed at 600 mM NaCl concentration in strain 6E. Accumulation of the osmolytes in 6E increased depending on salinity and application time. In S39 except for glycine-betaine, contents of other osmolytes were either unchanged or decreased. Activities of SOD, CAT, POX, APX, GR and NOX have increased as compared to the control group in 6E exposed to 600 and 1200 mM salt for 12h. In S39, CAT, POX, and GR activities decreased exposed to salinity. Consequently, it can be argued that (i) the different antioxidant responses of 6E in salinity plays a key role which tend to make 6E the more tolerant (ii) this tolerance is closely related to the increased antioxidant capacity against reactive oxygen species and is related to the increased accumulation of osmolytes.

The effects of fullerene on photosynthetic apparatus, chloroplast-encoded gene expression, and nitrogen assimilation in Zea mays under cobalt stress

Carbon nanostructures, such as the water-soluble fullerene (FLN) derivatives, are considered perspective agents for agriculture. FLN can be a novel nano-agent modulating plant response against stress conditions. However, the mechanism underlying the impacts of FLN on plants in agroecosystems remains unclear. Zea mays was exposed to exogenous C₆₀ -FLN applications (FLN1: 100; FLN2: 250; and FLN3: 500 mg L^-1 ) with/without cobalt stress (Co, 300 μM) for 3 days (d). In the maize chloroplasts, Co stress disrupted the photosynthetic efficiency and the expression of genes related to the photosystems (psaA and psbA). FLNs effectively improved the efficiency and photochemical reaction of photosystems. Co stress induced the accumulation of reactive oxygen species (ROS) as confirmed by ROS-specific fluorescence in guard cells. Co stress increased only chloroplastic superoxide dismutase (SOD) and peroxidase (POX). Stress triggered oxidative damages in maize chloroplasts, measured as an increase in TBARS content. In Co-stressed seedlings exposed to FLN1 and FLN2 exposures, the hydrogen peroxide (H₂ O₂ ) was scavenged through the nonenzymes/enzymes-related to the AsA-GSH cycle by preserving ascorbate (AsA) conversion, as well as GSH/GSSG and glutathione (GSH) redox state. Also, the alleviation effect of FLN3 against stress could be attributed to increased glutathione S-transferase (GST) activity and AsA regeneration. FLN applications reversed the inhibitory effects of Co stress on nitrogen assimilation. In maize chloroplasts, FLN increased the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), nitrite reductase (NiR), and glutamine synthetase (GS), which provided conversion of inorganic nitrogen (N) into organic N. The ammonium (NH₄ ⁺ ) toxicity was removed via GS and GDH but not glutamate synthase (GOGAT). The increased NAD-GDH (deaminating) and NADH-GDH (aminating) activities indicated that GDH was needed more for NH₄ ⁺ detoxification. Therefore, FLN exposure to Co-stressed maize plants might play a role in N metabolism regarding the partitioning of N assimilates. Exogenous FLN conceivably removed Co toxicity by improving the expressions of genes related to reaction center proteins of photosystems, increasing the level of enzymes related to the defense system, and improving the N assimilation in maize chloroplasts.

A Comparative Study of Chemical Profiling and Biological Effects of Doronicum orientale Extracts

In this study, phytochemical and pharmacological screening of the aerial part and roots extracts from Doronicum orientale Hoffm. (Asteraceae) was carried out. Plant extracts were obtained using solvents of different polarity (hexane, ethyl acetate, ethanol, ethanol/water, water) for selection the most optimal solvent for the extraction of active compounds. For instance, the extracts yielded total phenolic and flavonoid contents in the range of 12.13-45.67 mg GAE/g and 0.75-12.44 mg QE/g, respectively, while the total antioxidant capacity of the extracts determined by the phosphomolybdenum assay ranged from 0.88-2.53 mmol TE/g. HPLC/MS/MS analysis revealed 5-caffeoylquinic acid (2.52-337.05 μg/g) and 3,5-dicaffeoylquinic acid (3.12-299.36 μg/g) to be the major components present in the investigated extracts. Antioxidant activity in terms of radical scavenging ability of the extracts ranged from 0.82-45.56 mg TE/g in DPPH assay and from 5.07-104.58 mg TE/g in ABTS assay. The tested extracts were found to inhibit acetylcholinesterase (aerial part: 0.50-2.33 mg GALAE/g; roots: 0.40-2.43 mg GALAE/g), while with the exception of the water extracts, the other extracts showed butyrylcholinesterase inhibition (aerial part: 2.46-5.02 mg GALAE/g; root: 2.93-4.17 mg GALAE/g). Overall, this study presented an interesting scope of this species in phytomedicine with preliminary data demonstrating some of the tested extracts to possess high bioactive contents, antioxidant potential and enzyme inhibitory activity. Thus, additional investigations are necessary to confirm their safety in herbal drug applications.

Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum

The current study was designed to assess nanomaterial sulfonated graphene oxide (SGO) potential in improving tolerance of wheat chloroplasts against nitrate (NS) and ammonium (AS) toxicity. Triticum aestivum cv. Ekiz was grown under SGOs (50-250-500 mg L^-1) with/without 140 mM NS and 5 mM AS stress. SGOs were eliminated the adverse effects produced by stress on chlorophyll fluorescence, potential photochemical efficiency and physiological state of the photosynthetic apparatus. SGO reversed the negative effects on these parameters. Upon SGOs exposure, the induced expression levels of photosystems-related reaction center proteins were observed. SGOs reverted radical accumulation triggered by NS by enabling the increased superoxide dismutase (SOD) activity and ascorbate (AsA) regeneration. Under AS, the turnover of both AsA and glutathione (GSH) was maintained by 50-250 mg L^-1 SGO by increasing the enzymes and non-enzymes related to AsA-GSH cycle. 500 mg L^-1 SGO prevented the radical over-accumulation produced by AS via the regeneration of AsA and peroxidase (POX) activity rather than GSH regeneration. 50-250 mg L^-1 SGO protected from the NS+AS-induced disruptions through the defense pathways connected with AsA-GSH cycle represented the high rates of AsA/DHA and, GSH/GSSG and GSH redox state. Our findings specified that SGO to NS and AS-stressed wheat provides a new potential tool to advance the tolerance mechanism.

Exogenous hesperidin and chlorogenic acid alleviate oxidative damage induced by arsenic toxicity in Zea mays through regulating the water status, antioxidant capacity, redox balance and fatty acid composition

Arsenic (As) toxicity is a problem that needs to be solved in terms of both human health and agricultural production in the vast majority of the world. The presence of As causes biomass loss by disrupting the balance of biochemical processes in plants and preventing growth/water absorption in the roots and accumulating in the edible parts of the plant and entering the food chain. A critical method of combating As toxicity is the use of biosafe, natural, bioactive compounds such as hesperidin (HP) or chlorogenic acid (CA). To this end, in this study, the physiological and biochemical effects of HP (100 μM) and CA (50 μM) were investigated in Zea mays under arsenate stress (100 μM). Relative water content, osmotic potential, photosynthesis-related parameters were suppressed under stress. It was determined that stress decreased the activities of the antioxidant system and increased the level of saturated fatty acids and, gene expression of PHT transporters involved in the uptake and translocation of arsenate. After being exposed to stress, HP and CA improved the capacity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), glutathione S-transferase (GST) and glutathione peroxidase (GPX) and then ROS accumulation (H₂O₂) and lipid peroxidation (TBARS) were effectively removed. These phenolic compounds contributed to maintaining the cellular redox status by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. HP and CA reversed the adverse effects of excessive metal ion accumulation by re-regulated expression of the PHT1.1 and PHT1.3 genes in response to stress. Exogenously applied HP and CA effectively maintained membrane integrity by regulating saturated/unsaturated fatty acid content. However, the combined application of HP and CA did not show a synergistic protective activity against As stress and had a negative effect on the antioxidant capacity of maize leaves. As a result, HP and CA have great potentials to provide tolerance to maize under As stress by reducing oxidative injury and preserving the biochemical reactions of photosynthesis.

Metabolomics and Physiological Insights into the Ability of Exogenously Applied Chlorogenic Acid and Hesperidin to Modulate Salt Stress in Lettuce Distinctively

Recent studies in the agronomic field indicate that the exogenous application of polyphenols can provide tolerance against various stresses in plants. However, the molecular processes underlying stress mitigation remain unclear, and little is known about the impact of exogenously applied phenolics, especially in combination with salinity. In this work, the impacts of exogenously applied chlorogenic acid (CA), hesperidin (HES), and their combination (HES + CA) have been investigated in lettuce (Lactuca sativa L.) through untargeted metabolomics to evaluate mitigation effects against salinity. Growth parameters, physiological measurements, leaf relative water content, and osmotic potential as well as gas exchange parameters were also measured. As expected, salinity produced a significant decline in the physiological and biochemical parameters of lettuce. However, the treatments with exogenous phenolics, particularly HES and HES + CA, allowed lettuce to cope with salt stress condition. Interestingly, the treatments triggered a broad metabolic reprogramming that involved secondary metabolism and small molecules such as electron carriers, enzyme cofactors, and vitamins. Under salinity conditions, CA and HES + CA distinctively elicited secondary metabolism, nitrogen-containing compounds, osmoprotectants, and polyamines.

The Combination of Mild Salinity Conditions and Exogenously Applied Phenolics Modulates Functional Traits in Lettuce

The quest for sustainable strategies aimed at increasing the bioactive properties of plant-based foods has grown quickly. In this work, we investigated the impact of exogenously applied phenolics, i.e., chlorogenic acid (CGA), hesperidin (HES), and their combinations (HES + CGA), on Lactuca sativa L. grown under normal- and mild-salinity conditions. To this aim, the phenolic profile, antioxidant properties, and enzyme inhibitory activity were determined. The untargeted metabolomics profiling revealed that lettuce treated with CGA under non-stressed conditions exhibited the highest total phenolic content (35.98 mg Eq./g). Lettuce samples grown under salt stress showed lower phenolic contents, except for lettuce treated with HES or HES + CGA, when comparing the same treatment between the two conditions. Furthermore, the antioxidant capacity was investigated through DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,20-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), and FRAP (ferric reducing antioxidant power) assays, coupled with metal-chelating activity and phosphomolybdenum capacity. An exciting increase in radical scavenging capacity was observed in lettuce treated with exogenous phenolics, in both stress and non-stress conditions. The inhibitory activity of the samples was evaluated against target health-related enzymes, namely cholinesterases (acetylcholinesterase; AChE; butyryl cholinesterase; BChE), tyrosinase, α-amylase, and α-glucosidase. Lettuce treated with HES + CGA under non-stress conditions exhibited the strongest inhibition against AChE and BChE, while the same treatment under salinity conditions resulted in the highest inhibition capacity against α-amylase. Additionally, CGA under non-stress conditions exhibited the best inhibitory effect against tyrosinase. All the functional traits investigated were significantly modulated by exogenous phenolics, salinity, and their combination. In more detail, flavonoids, lignans, and stilbenes were the most affected phenolics, whereas glycosidase enzymes and tyrosinase activity were the most affected among enzyme assays. In conclusion, the exogenous application of phenolics to lettuce represents an effective and green strategy to effectively modulate the phenolic profile, antioxidant activity, and enzyme inhibitory effects in lettuce, deserving future application to produce functional plant-based foods in a sustainable way.

Naringenin induces tolerance to salt/osmotic stress through the regulation of nitrogen metabolism, cellular redox and ROS scavenging capacity in bean plants

The present study was conducted to uncover underlying possible effect mechanisms of flavonoid naringenin (Nar, 0.1-0.4 mM) in nitrogen assimilation, antioxidant response, redox status and the expression of NLP7 and DREB2A, on salt (100 mM NaCl) and osmotic-stressed (10% Polyethylene glycol, -0.54 MPa) Phaseolus vulgaris cv. Yunus 90). Nar ameliorated salt/osmotic stresses-induced growth inhibition and improved the accumulation of proline, glycine betaine and choline. In response to stress, Nar increased endogenous content of nitrate (NO₃^-) and nitrite (NO₂^-) by regulating of nitrate reductase and nitrite reductase. Stress-triggered NH₄⁺ was eliminated with Nar through increases in glutamine synthetase and glutamate synthase. After NaCl or NaCl + PEG exposure, Nar utilized the aminating activity of glutamate dehydrogenase in the conversion of NH₄⁺. The stress-inducible expression levels of DREB2A were increased further by Nar, which might have affected stress tolerance of bean. Nar induced effectively the relative expression of NLP7 in the presence of the combination or alone of stress. Also, the impaired redox state by stress was modulated by Nar and hydrogen peroxide (H₂O₂) and TBARS decreased. Nar regulated the different pathways for scavenging of H₂O₂ under NaCl and/or PEG treatments. When Nar + NaCl exposure, the damage was removed by superoxide dismutase (SOD), catalase (CAT), POX (only at 0.1 mM Nar + NaCl) and AsA-GSH cycle. Under osmotic stress plus Nar, the protection was manifested by activated CAT and, glutathione S-transferase and the regeneration of ascorbate. 0.1 mM Nar could protect bean plant against salt/osmotic stresses, likely by regulating nitrogen assimilation pathways, improving expression levels of genes associated with tolerance mechanisms and modulating the antioxidant capacity and AsA-GSH redox-based systems.

Rare-earth element scandium improves stomatal regulation and enhances salt and drought stress tolerance by up-regulating antioxidant responses of Oryza sativa

Oryza sativa L. cv. Gönen grown in hydroponic culture was treated with scandium (Sc; 25 and 50 μM) alone or in combination with salt (100 mM NaCl) and/or drought (5% PEG-6000). Stress caused a decrease in growth (RGR), water content (RWC), osmotic potential (ΨΠ), chlorophyll fluorescence (Fv/Fm) and potential photochemical efficiency (Fv/Fo). Sc application prevented the decreases of these parameters. Sc also alleviated the changes on gas exchange parameters (carbon assimilation rate (A), stomatal conductance (gs), intercellular CO2 concentrations (Ci), transpiration rate (E) and stomatal limitation (Ls)). Stress caused no increase in superoxide dismutase (SOD) activity. After induvial applied NaCl or PEG, catalase (CAT) and ascorbate peroxidase (APX) showed an enhancement in activation and tried to scavenge of hydrogen peroxide (H2O2). On the other hand, in plants with the combination form of NaCl and PEG, only CAT activity was induced. Sc applications to NaCl-treated rice led to an increase of SOD, APX, glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) as well as peroxidase (POX). Sc under NaCl could be maintained both ascorbate (AsA) and glutathione (GSH) regeneration. Despite of induction of MDHAR and DHAR under Sc plus PEG, Sc did not maintain AsA redox state because of no induction in APX activity. However, GSH pool could be regenerated by induction in DHAR and GR in this group. Sc application (especially for 25 μM) in rice exposed to NaCl + PEG resulted an enhancement in APX and MDHAR and so Sc could be partially provided AsA regeneration. Since no increases in DHAR and GR were observed, GSH pool was reduced. Due to this activation of antioxidant enzymes, stress-induced H2O2 and TBARS content (lipid peroxidation) significantly decreased in rice with Sc applications. Sc in plants with stress also increased the transcript levels of OsCDPK7 and OsBG1 related to stomatal movement and signaling pathway. Consequently, Sc protected the rice plants by minimizing disturbances caused by NaCl or PEG exposure via the AsA-GSH redox-based systems.

Hydrogen sulfide (H2S) and nitric oxide (NO) alleviate cobalt toxicity in wheat (Triticum aestivum L.) by modulating photosynthesis, chloroplastic redox and antioxidant capacity

The role of hydrogen sulfide (H₂S)/nitric oxide (NO) in mitigating stress-induced damages has gained interest in the past few years. However, the protective mechanism H₂S and/or NO has towards the chloroplast system through the regulation of redox status and activation of antioxidant capacity in cobalt-treated wheat remain largely unanswered. Triticum aestivum L. cv. Ekiz was treated with alone/in combination of a H₂S donor (sodium hydrosulfide (NaHS,600μM)), a NO donor (sodium nitroprusside (SNP,100μM)) and a NO scavenger (rutin hydrate (RTN,50μM)) to assess how the donors affect growth, water relations, redox and antioxidant capacity in chloroplasts, under cobalt (Co) concentrations of 150-300 μM. Stress decreased a number of parameters (growth, water content (RWC), osmotic potential (Ψ_Π), carbon assimilation rate, stomatal conductance, intercellular CO₂ concentrations, transpiration rate and the transcript levels of rubisco, which subsequently disrupt the photosynthetic capacity). However, SNP/NaHS counteracted the negative effects of stress on these aforementioned parameters and RTN application with stress/non-stress was reversed these effects. Hydrogen peroxide (H₂O₂) and TBARS were induced under stress in spite of activated ascorbate peroxidase (APX). SNP/NaHS under stress increased activation of superoxide dismutase (SOD), peroxidase (POX), APX, glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), ascorbate (tAsA) and glutathione (GSH). In conclusion, NaHS/SNP are involved in the regulation and modification of growth, water content, rubisco activity and up-regulation of ascorbate-glutathione cycle (AsA-GSH) in chloroplast under stress.

Chemical characterization, antioxidant, enzyme inhibitory and cytotoxic properties of two geophytes: Crocus pallasii and Cyclamen cilicium

The Crocus and Cyclamen genus have been reported to possess diverse biological properties. In the present investigation, two geophytes from these genus, namely Crocus pallasi and Cyclamen cilicium have been studied. The in vitro antioxidant, enzyme inhibitory, and cytotoxic effects of the methanol extracts of Crocus pallasii and Cyclamen cilicium aerial and underground parts were investigated. Antioxidant abilities of the extracts were investigated via different antioxidant assays (metal chelating, radical quenching (ABTS and DPPH), reducing power (CUPRAC and FRAP) and phosphomolybdenum). Cholinesterases, amylase, tyrosinase, and glucosidase were used as target enzymes for detecting enzyme inhibitory abilities of the samples. Regarding the cytotoxic abilities, breast cancer cell lines (MDA-MB 231 and MCF-7) and prostate cancer cell lines (DU-145) were used. The flowers extracts of Crocus pallasii and C. cilicium possessed the highest flavonoid content. The highest phenolic content was recorded from C. cilicium root extract (47.62 mg gallic acid equivalent/g extract). Cyclamen cilicium root extract showed significantly (p < 0.05) high radical scavenging (94.28 and 139.60 mg trolox equivalent [TE]/g extract, against DPPH and ABTS radicals, respectively) and reducing potential (173.30 and 109.53 mg TE/g extract, against CUPRAC and FRAP, respectively). The best acetylcholinesterase, glucosidase and tyrosinase inhibition was observed in C. cilicium root (4.46 mg GALAE/g; 15.75 mmol ACAE/g; 136.99 mg KAE/g, respectively). Methanolic extracts of C. pallasii and C. cilicium showed toxicity against breast cancer cell lines. In light of the above findings, C. cilicium might be considered as an interesting candidate in the development of anti-cancer agent coupled with antioxidant properties.

Flavonoid Naringenin Alleviates Short-Term Osmotic and Salinity Stresses Through Regulating Photosynthetic Machinery and Chloroplastic Antioxidant Metabolism in Phaseolus vulgaris

The current study was conducted to demonstrate the possible roles of exogenously applied flavonoid naringenin (Nar) on the efficiency of PSII photochemistry and the responses of chloroplastic antioxidant of salt and osmotic-stressed Phaseolus vulgaris (cv. Yunus90). For this aim, plants were grown in a hydroponic culture and were treated with Nar (0.1 mM and 0.4 mM) alone or in a combination with salt (100 mM NaCl) and/or osmotic (10% Polyethylene glycol, -0.54 MPa). Both caused a reduction in water content (RWC), osmotic potential (Ψ_Π), chlorophyll fluorescence (F_v/F_m), and potential photochemical efficiency (F_v/F_o). Nar reversed the changes on these parameters. The phenomenological fluxes (TR_o/CS and ET_o/CS) altered by stress were induced by Nar and Nar led to a notable increase in the performance index (PI_ABS) and the capacity of light reaction [ΦP_o/(1-ΦP_o)]. Besides, Nar-applied plants exhibited higher specific fluxes values [ABS/RC, ET_o/RC, and ΨE_o/(1-ΨE_o)] and decreasing controlled dissipation of energy (DI_o/CS_o and DI_o/RC). The transcripts levels of psbA and psbD were lowered in stress-treated bean but upregulated in Nar-treated plants after stress exposure. Nar also alleviated the changes on gas exchange parameters [carbon assimilation rate (A), stomatal conductance (g_s), intercellular CO₂ concentrations (C_i), transpiration rate (E), and stomatal limitation (L_s)]. By regulating the antioxidant metabolism of the isolated chloroplasts, Nar was able to control the toxic levels of hydrogen peroxide (H₂O₂) and TBARS (lipid peroxidation) produced by stresses. Chloroplastic superoxide dismutase (SOD) activity reduced by stresses was increased by Nar. In response to NaCl, Nar increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR), as well as peroxidase (POX). Nar protected the bean chloroplasts by minimizing disturbances caused by NaCl exposure via the ascorbate (AsA) and glutathione (GSH) redox-based systems. Under Nar plus PEG, Nar maintained the AsA regeneration by the induction of MDHAR and DHAR, but not GSH recycling by virtue of no induction in GR activity and the reduction in GSH/GSSG and GSH redox state. Based on these advances, Nar protected in bean chloroplasts by minimizing disturbances caused by NaCl or PEG exposure via the AsA or GSH redox-based systems and POX activity.

The humic acid-induced changes in the water status, chlorophyll fluorescence and antioxidant defense systems of wheat leaves with cadmium stress

The using of bio-stimulant in plants grown under stress conditions for enhancing nutrition efficiency and crop quality traits is an effective approach. One of the bio-stimulants, humus material, is defined as humic acid (HA). HA application as a promotion of plant growth to plants grown in the heavy metals-contaminated soils has promised hope in terms of effects on plants but the its limiting effect is the application dose. Therefore, the wheat seedlings were grown in hydroponic culture for 21 d and the various concentrations of humic acid (HA; 750 or 1500 mg L^-1) were treated alone or in combination with cadmium (Cd) stress (100 or 200 μM) for 7 d. The results showed that after Cd stress treatment, water content (RWC), osmotic potential (Ψ_Π) and chlorophyll fluorescence parameters decreased and proline content (Pro) increased for 7 d. In spite of activated peroxidase (POX) and ascorbate peroxidase (APX), stress induced the toxic levels of hydrogen peroxide (H₂O₂) accumulation. Cd stress triggered lipid peroxidation (TBARS content). HA application successfully eliminated the negative effects of stress on RWC, Ψ_Π and photosynthetic parameters. In the presence of HA under stress, the increased activation of superoxide dismutase (SOD), catalase (CAT) and NADPH-oxidase (NOX) enzymes and ascorbate, glutathione and GSH/GSSG ratio observed. Only 750 mg L^-1 HA under stress conditions induced the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), and dehydroascorbate (DHA) content. After the combined application of HA and Cd stress, the low contents of H₂O₂ and TBARS maintained in wheat leaves. Hence, HA successfully eliminated the toxicity of Cd stress by modulating the water status, photosynthetic apparatus and antioxidant activity in wheat leaves.

Halophytes as a source of salt tolerance genes and mechanisms: a case study for the Salt Lake area, Turkey

The worst case scenario of global climate change predicts both drought and salinity would be the first environmental factors restricting agriculture and natural ecosystems, causing decreased crop yields and plant growth that would directly affect human population in the next decades. Therefore, it is vital to understand the biology of plants that are already adapted to these extreme conditions. In this sense, extremophiles such as the halophytes offer valuable genetic information for understanding plant salinity tolerance and to improve the stress tolerance of crop plants. Turkey has ecological importance for its rich biodiversity with up to 3700 endemic plants. Salt Lake (Lake Tuz) in Central Anatolia, one of the largest hypersaline lakes in the world, is surrounded by salty marshes, with one of the most diverse floras in Turkey, where arid and semiarid areas have increased due to low rainfall and high evaporation during the summer season. Consequently, the Salt Lake region has a large number of halophytic, xerophytic and xero-halophytic plants. One good example is Eutrema parvulum (Schrenk) Al-Shehbaz & Warwick, which originates from the Salt Lake region, can tolerate up to 600mM NaCl. In recent years, the full genome of E. parvulum was published and it has been accepted as a model halophyte due to its close relationship (sequence identity in range of 90%) with Arabidopsis thaliana (L. Heynh.). In this context, this review will focus on tolerance mechanisms involving hormone signalling, accumulation of compatible solutes, ion transporters, antioxidant defence systems, reactive oxygen species (ROS) signalling mechanism of some lesser-known extremophiles growing in the Salt Lake region. In addition, current progress on studies conducted with E. parvulum will be evaluated to shed a light on future prospects for improved crop tolerance.

Profiling of rutin-mediated alleviation of cadmium-induced oxidative stress in Zygophyllum fabago

Zygophyllum fabago grows in arid, saline soil, or disturbed sites, such as former industrial or mining areas. This species is able to grow in coarse mineral substrates contaminated with heavy metals. To investigate the effects of the flavonoid rutin (Rtn) on certain heavy metal stress responses such as antioxidant defense systems and water status, seedlings were subjected to 100 and 200 μM CdCl2 treatment without or with 0.25 and 1 mM Rtn for 7 and 14 d (days). Cd stress decreased growth (RGR), water content (RWC), leaf osmotic potential (Ψ(Π)), and chlorophyll fluorescence, all of which could be partly alleviated by addition of Rtn. Activities of superoxide dismutase, peroxidase (POX), ascorbate peroxidase, and glutathione reductase increased within the first 7 d after exposure to Cd. However, failure of antioxidant defense in the scavenging of reactive oxygen species (ROS) was evidenced by an abnormal rise in superoxide anion radical ( O2(•-)) and hydrogen peroxide contents and a decline in hydroxyl radical (OH(•)) scavenging activity, resulting in enhancement of lipid peroxidation (TBARS) as a marker of Cd-induced oxidative stress. However, exogenously applied Rtn considerably improved the stress tolerance of plants via a reduction in Cd accumulation, modulation of POX activity, increase of proline (Pro) content, decrease in TBARS and ROS content and consequent lowering of oxidative damage of membrane. Overall, 0.25 and 1 mM Rtn could protect Z. fabago from the harmful effects of 100 μM Cd-induced oxidative stress throughout the experiment.

Changes in the alternative electron sinks and antioxidant defence in chloroplasts of the extreme halophyte Eutrema parvulum (Thellungiella parvula) under salinity

BACKGROUND AND AIMS

Eutrema parvulum (synonym, Thellungiella parvula) is an extreme halophyte that thrives in high salt concentrations (100-150 mm) and is closely related to Arabidopsis thaliana. The main aim of this study was to determine how E. parvulum uses reactive oxygen species (ROS) production, antioxidant systems and redox regulation of the electron transport system in chloroplasts to tolerate salinity.

METHODS

Plants of E. parvulum were grown for 30 d and then treated with either 50, 200 or 300 mm NaCl. Physiological parameters including growth and water relationships were measured. Activities of antioxidant enzymes were determined in whole leaves and chloroplasts. In addition, expressions of chloroplastic redox components such as ferrodoxin thioredoxin reductases (FTR), NADPH thioredoxin reductases (NTRC), thioredoxins (TRXs) and peroxiredoxins (PRXs), as well as genes encoding enzymes of the water-water cycle and proline biosynthesis were measured.

KEY RESULTS

Salt treatment affected water relationships negatively and the accumulation of proline was increased by salinity. E. parvulum was able to tolerate 300 mm NaCl over long periods, as evidenced by H2O2 content and lipid peroxidation. While Ca(2+) and K(+) concentrations were decreased by salinity, Na(+) and Cl(-) concentrations increased. Efficient induction of activities and expressions of water-water cycle enzymes might prevent accumulation of excess ROS in chloroplasts and therefore protect the photosynthetic machinery in E. parvulum. The redox homeostasis in chloroplasts might be achieved by efficient induction of expressions of redox regulatory enzymes such as FTR, NTRC, TRXs and PRXs under salinity.

CONCLUSIONS

E. parvulum was able to adapt to osmotic stress by an efficient osmotic adjustment mechanism involving proline and was able to regulate its ion homeostasis. In addition, efficient induction of water-water cycle enzymes and other redox regulatory components such as TRXs and PRXs in chloroplasts were able to protect the chloroplasts from salinity-induced oxidative stress.

Upregulation of antioxidant enzymes by exogenous gallic acid contributes to the amelioration in Oryza sativa roots exposed to salt and osmotic stress

The aim of this study is to elucidate the influence of the exogenous application of gallic acid (GLA) in alleviating the detrimental effects of salinity (NaCl), osmotic stress (polyethylene glycol; PEG), and their combination in Oryza sativa L. roots. To produce same osmotic potential (-0.5 MPa), 3-week-old rice seedlings were treated with 120 mM NaCl and/or 20 % PEG6000 with/without GLA (0.75 and 1.5 mM) treatments for 72 h. Both alone and combination of stresses decreased growth (RGR) and osmotic potential (Ψ Π). Moreover, stress caused a significant increase in proline (Pro) and hydrogen peroxide (H2O2) contents. Also, Pokkali and IR-28 had higher H2O2-scavenging enzyme activities including catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities in NaCl-treated roots. Only CAT activity was induced in both cultivars with PEG. Therefore, the enhanced levels of lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) were more pronounced under PEG than NaCl. However, GLA significantly mitigated NaCl and/or PEG-induced stress injury. Under salinity, TBARS was lesser in GLA-applied rice that was associated with greater activities of superoxide dismutase (SOD), peroxidase (POX), and APX. GLA in the presence of PEG improved the activities of CAT and POX. According to these findings, GLA alleviated the damaging effects of NaCl and/or PEG (especially under NaCl) by improving the antioxidative system in rice. This is the first study elucidating the effects of GLA on tolerance to salinity, osmotic stress, and their combination in plants.

The role of antioxidant responses on the tolerance range of extreme halophyte Salsola crassa grown under toxic salt concentrations

Salsola crassa (Amaranthaceae) is an annual halophytic species and naturally grows in arid soils that are toxic to most plants. In order to study the effects of salinity on their antioxidant system and to determine the tolerance range against salt stress, S. crassa seeds were grown with different concentrations of NaCl (0, 250, 500, 750, 1000, 1250 and 1500mM) for short (15d) and long-term (30d). Results showed that growth (RGR), water content (RWC) and osmotic potential (ΨΠ) decreased and, proline content (Pro) increased at prolonged salt treatment. Unlike K(+) and Ca(2+) contents, S. crassa highly accumulated Na(+) and Cl(-) contents. Chlorophyll fluorescence (Fv/Fm) only decreased in response to 1500mM NaCl at 30d. No salt stimulation of superoxide anion radical (O2(•-)) content was observed in plants treated with the range of 0-500mM NaCl during the experimental period. NaCl increased superoxide dismutase (SOD) activity depending on intensities of Mn-SOD and Fe-SOD isozymes except in 1500mM NaCl-treated plants at 30d. In contrast to catalase (CAT), peroxidase (POX) activity increased throughout the experiment. Also, salinity caused an increase in glutathione reductase (GR) and glutathione peroxidase (GPX) and decreased in ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) at 15d. Both total ascorbate (tAsA) and glutathione (tGlut) contents significantly increased in treated plants with 1000-1500mM NaCl at 15d. After 0-1000mM NaCl stress, H2O2 and TBARS contents were similar to control groups at 15d, which were consistent with the increased antioxidant activity (POX, GR and GPX). However, H2O2 content was more pronounced at 30d. Therefore, S. crassa exhibited inductions in lipid peroxidation (TBARS content) in response to extreme salt concentrations. These results suggest that S. crassa is tolerant to salt-induced damage at short-term treatments as well as extreme salt concentrations.

Variations in osmotic adjustment and water relations of Sphaerophysa kotschyana: Glycine betaine, proline and choline accumulation in response to salinity

BACKGROUND

Sphaerophysa kotschyana Boiss. is naturally distributed in overly salty regions. The key to the completion of the life cycles of S. kotschyana in harsh saline soils may be hidden in changes of its osmo-protectants, but there is currently no information about the interaction between osmotic adjustment and water relations in adaptation to saline conditions. The aim of this article was to determine growth, relative growth rate (RGR), relative water content (RWC), osmotic potential (Ψ_Π), photosynthetic efficiency (F_v/F_m), thiobarbituric acid-reactive substances (TBARS) and osmo-protectant contents [proline (Pro), choline (Cho) and glycine betaine (GB)] in S. kotschyana leaves and roots exposed to 0, 150 or 300 mM NaCl for 7 and 14 d (days).

RESULTS

The results clearly showed that the reductions in growth, RWC, F_v/F_m, RGR and Ψ_Π were more pronounced at 300 mM, especially after 14 d. In the same group, the highest increase in TBARS was recorded in roots (126%) and leaves (31%). The induction at 150 mM was not as high. Therefore, roots appear to be the most vulnerable part of this plant. Moreover, S. kotschyana was able to withstand short-term low salinity.

CONCLUSIONS

The osmo-protectant accumulation in S. kotschyana as a salinity acclimation or adaptation was sufficient for toleration of low salt concentration (150 mM). In contrast, the plants exposed to the highest NaCl concentration (300 mM) were not able to maintain the ability to prevent water loss because of further decrease in root/shoot ratio of fresh weight (FW) and dry weight (DW), RWC and RGR.

Sphaerophysa kotschyana, an endemic species from Central Anatolia: antioxidant system responses under salt stress

Sphaerophysa kotschyana is a Turkish endemic and endangered plant that grows near Salt Lake, in Konya, Turkey. However, little is known about the ability of this plant to generate/remove reactive oxygen species (ROS) or its adaptive biochemical responses to saline environments. After exposure of S. kotschyana to 0, 150, and 300 mM NaCl for 7 and 14 days, we investigated (1) the activities and isozyme compositions of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), and glutathione reductase (GR); (2) the oxidative stress parameters NADPH oxidase (NOX) activity, lipid peroxidation (MDA), total ascorbate (tAsA) content, and total glutathione content (tGlut); and (3) ROS levels for superoxide anion radical (O 2 (·-) ), hydrogen peroxide (H2O2), hydroxyl radicals (OH·), and histochemical staining of O 2 (·-) and H2O2. H2O2 content increased after 14 days of salt stress, which was consistent with the results from histochemical staining and NOX activity measurements. In contrast, oxidative stress induced by 150 mM NaCl was more efficiently prevented, as indicated by low malondialdehyde (MDA) levels and especially at 7 days, by increased levels of SOD, POX, APX, and GR. However, at 300 mM NaCl, decreased levels of protective enzymes such as SOD, CAT, POX, and GR, particularly with long-term stress (14 days), resulted in limited ROS scavenging activity and increased MDA levels. Moreover, at 300 mM NaCl, the high H2O2 content caused oxidative damage rather than inducing protective responses against H2O2. These results suggest that S. kotschyana is potentially tolerant to salt-induced damage only at low salt concentrations.