Increased Electrolyte Leakage Research Articles

Redox priming could be an appropriate technique to minimize drought-induced adversities in quinoa.

The exogenous use of the redox compound (H2O2) plays a significant role in abiotic stress tolerance. The present study investigated various H2O2 application methods (seed priming, foliar spray, and surface irrigation) with varying concentration levels (0 mM, 5 mM, 10 mM, 15 mM, 40 mM, 80 mM, and 160 mM) to evaluate the efficiency of supplying exogenous H2O2 to quinoa under water-deficit conditions. Drought stress reduced quinoa growth and yield by perturbing morphological traits, leading to the overproduction of reactive oxygen species and increased electrolyte leakage. Although all studied modes of H2O2 application improved quinoa performance, surface irrigation was found to be sensitive, causing oxidative damage in the present study. Seed priming showed a prominent increase in plant height due to profound emergence indexes compared to other modes under drought conditions. Strikingly, seed priming followed by foliar spray improved drought tolerance in quinoa and showed higher grain yield compared to surface irrigations. This increase in the yield performance of quinoa was attributed to improvements in total chlorophyll (37%), leaf relative water content (RWC; 20%), superoxide dismutase (SOD; 35%), peroxidase (97%), polyphenol oxidase (60%), and phenylalanine ammonia-lyase (58%) activities, and the accumulation of glycine betaine (96%), total soluble protein (TSP; 17%), proline contents (35%), and the highest reduction in leaf malondialdehyde contents (MDA; 36%) under drought stress. PCA analysis indicated that physio-biochemical traits (proline, SOD, TSP, total chlorophyll, MSI, and RWC) were strongly positively correlated with grain yield, and their contribution was much higher in redox priming than other application methods. In conclusion, exogenous H2O2 application, preferably redox priming, could be chosen to decrease drought-induced performance and yield losses in quinoa.

Impact of cis-zeatin and lovastatin on antioxidant systems and growth parameters in Zea mays seedlings under phytohormonal crosstalks

ABSTRACT Phytohormones are essential regulators that control both plant growth and defense mechanisms, with cytokinins (CKs) playing a crucial role in regulating antioxidants. However, conflicting research results regarding their effect on antioxidants require further investigation. This study addresses the effects of cis-zeatin (cZ), a type of CK, and its inhibitor lovastatin (LT) on the antioxidant system of 29-day-old Zea mays plants. Seedlings were treated by aerial spraying with 5 M cZ, LT, or their combination (cZ-LT) five days after planting. The results showed that cZ significantly increased growth performance, antioxidant activity and photosynthesis efficiency. cZ treatment increased the accumulation of osmolytes (including total phenolics, total flavonoids, proline, and total soluble proteins), resulting in larger leaves, longer shoots, and increased biomass while reducing root length and biomass, respectively. In contrast, LT treatments resulted in reductions in leaf size, shoot length, and biomass, as well as impairment in photosynthesis rates. LT-treated seedlings showed reduced osmolyte accumulation but increased antioxidant enzymatic activity, which contributed to an increase in electrolyte leakage. Examination of phytohormonal crosstalk showed that cZ treatment increased endogenous GA4 and cZ levels while decreasing IAA levels, while LT had opposite effects. These results provide insights into the complex interplay of phytohormones in modulating both plant growth and antioxidant defense mechanisms.

Comparative morpho-physiological and biochemical responses of Capsicum annuum L. plants to multi-walled carbon nanotubes, fullerene C60 and graphene nanoplatelets exposure under water deficit stress

Water deficit stress is one of the most significant environmental abiotic factors influencing plant growth and metabolism globally. Recently, encouraging outcomes for the use of nanomaterials in agriculture have been shown to reduce the adverse effects of drought stress on plants. The present study aimed to investigate the impact of various carbon nanomaterials (CNMs) on the physiological, morphological, and biochemical characteristics of bell pepper plants subjected to water deficit stress conditions. The study was carried out as a factorial experiment using a completely randomized design (CRD) in three replications with a combination of three factors. The first factor considered was irrigation intensity with three levels [(50%, 75%, and 100% (control) of the field capacity (FC)] moisture. The second factor was the use of carbon nanomaterials [(fullerene C60, multi-walled carbon nanotubes (MWNTs) and graphene nanoplatelets (GNPs)] at various concentrations [(control (0), 100, 200, and 1000 mg/L)]. The study confirmed the foliar uptake of CNMs using the Scanning Electron Microscopy (SEM) technique. The effects of the CNMs were observed in a dose-dependent manner, with both stimulatory and toxicity effects being observed. The results revealed that exposure to MWNTs (1000 mg/L) under well-watered irrigation, and GNPs treatment (1000 mg/L) under severe drought stress (50% FC) significantly (P < 0.01) improved fruit production and fruit dry weight by 76.2 and 73.2% as compared to the control, respectively. Also, a significant decrease (65.9%) in leaf relative water content was obtained in plants subjected to soil moisture of 50% FC over the control. Treatment with GNPs at 1000 mg/L under 50% FC increased electrolyte leakage index (83.6%) compared to control. Foliar applied MWNTs enhanced the leaf gas exchange, photosynthesis rate, and chlorophyll a and b concentrations, though decreased the oxidative shock in leaves which was demonstrated by the diminished electrolyte leakage index and upgrade in relative water content and antioxidant capacity compared to the control. Plants exposed to fullerene C60 at 100 and 1000 mg/L under soil moisture of 100 and 75% FC significantly increased total flavonoids and phenols content by 63.1 and 90.9%, respectively, as compared to the control. A significant increase (184.3%) in antioxidant activity (FRAP) was observed in plants exposed to 200 mg/L MWCNTs under irrigation of 75% FC relative to the control. The outcomes proposed that CNMs could differentially improve the plant and fruit characteristics of bell pepper under dry conditions, however, the levels of changes varied among CNMs concentrations. Therefore, both stimulatory and toxicity effects of employed CNMs were observed in a dose-dependent manner. The study concludes that the use of appropriate (type/dose) CNMs through foliar application is a practical tool for controlling the water shortage stress in bell pepper. These findings will provide the basis for more research on CNMs-plant interactions, and with help to ensure their safe and sustainable use within the agricultural chains.

Physiological and molecular changes of onion (Allium cepa L.) seeds under different aging conditions

BackgroundOnion seeds have limited storage capacity compared to other vegetable seeds. It is crucial to identify the mechanisms that induce tolerance to storage conditions and reduce seed deterioration. To address this goal, an experiment was conducted to evaluate changes in germination, biochemical, physiological, and molecular characteristics of onion seed landraces (Horand, Kazerun landraces and Zargan cultivar) at different aging levels (control, three-days and six-days accelerated aging, and natural aging for one year).ResultsThe findings suggest that there was an increase in glucose, fructose, total sugar, and electrolyte leakage in the Horand (HOR), Kazerun (KAZ) landraces, and Zarghan (ZAR) cultivar, with Kazerun exhibiting the greatest increase. The percentage and rate of germination of Kazerun decreased by 54% and 33%, respectively, in six-day accelerated aging compared to the control, while it decreased by 12% and 14%, respectively, in Horand. Protein content decreased with increasing levels of aging, with a decrease of 26% in Kazerun landrace at six days of aging, while it was 16% in Horand landrace. The antioxidant activities of catalase, superoxide dismutase, and glutathione peroxidase decreased more intensively in Kazerun. The expression of AMY1, BMY1, CTR1, and NPR1 genes were lower in Kazerun landraces than in Horand and Zargan at different aging levels.ConclusionsThe AMY1, BMY1, CTR1, and NPR1 genes play a pivotal role in onion seed germination, and their downregulation under stressful conditions has been shown to decrease germination rates. In addition, the activity of CAT, SOD, and GPx enzymes decreased by seed aging, and the amount of glucose, fructose, total sugar and electrolyte leakage increased, which ultimately led to seed deterioration. Based on the results of this experiment, it is recommended to conduct further studies into the molecular aspects involved in onion seed deterioration. More research on the genes related to this process is suggested, as well as investigating the impact of different priming treatments on the genes expression involved in the onion seed aging process.

Formação de mudas de goiabeira sob estresse salino e aplicação foliar de peróxido de hidrogênio

ABSTRACT The occurrence of water with high concentrations of salts hinders the expansion of irrigated agriculture in the semi-arid region of the Brazilian Northeast, making it necessary to adopt strategies capable of minimizing the effects of salt stress on plants. In this context, the objective of present study was to evaluate the effects of hydrogen peroxide application on water relations, gas exchange, photosynthetic pigments, and growth of guava cv. Paluma under irrigation with saline waters in the seedling formation stage. A randomized block design was used, in a 5 × 4 factorial scheme, with three replicates, with five levels of electrical conductivity of water - ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1) and four concentrations of hydrogen peroxide - H2O2 (0, 25, 50, and 75 µM). Irrigation water salinity above 0.3 dS m-1 increased electrolyte leakage in the leaf blade and reduced the relative water content, synthesis of photosynthetic pigments, gas exchange, and growth of seedlings of guava cv. Paluma, at 80 days after sowing. Foliar application of hydrogen peroxide at concentrations of up to 75 µM reduces the relative water content in the leaf blade of guava seedlings and did not mitigate the effects of salt stress on guava plants in the seedling formation stage.

Effects of zinc-nano oxide, salicylic acid and sodium nitroprusside on physiological properties, antioxidant enzyme activities and secondary metabolites of Viola odorata under drought stress

One of the most important abiotic stresses and limiting factors (closing pores, lack of CO2 entry, reduced photosynthesis, and reduced yield) of plant products around the world is water-deficit stress. This study aimed to examine the water deficit stress and foliar application with anti-stress compounds (ASC) on characteristics of Viola odorata. The study was carried out as a factorial experiment based on a randomized complete design. The factors consisted of water deficit and the foliar application of ASC at six levels [zinc-nano oxide (ZnO, 1000 and 1500 mg l–1), salicylic acid (SA, 200 and 300 mg l–1), and sodium nitroprusside (SNP, 200 and 300 μM)], and the control. The water deficit reduced the leaf water potential, cell membrane stability, and the shoot and root fresh weight but increased electrolyte leakage and soluble sugar accumulation. However, foliar applications, particularly SA and SNP, positively affected the measured parameters. The activities of superoxide dismutase and guaiacol peroxidase at all three field capacity levels were higher in the plants treated with SA and SNP than in the control and plants treated with ZnO. In sum, using 200 mg l–1 of SA as a foliar application, in addition to improvement of the growth and developmental conditions of the aromatic violet plant, moderated the adverse effects of water deficit stress and increased the plant resistance to water deficit stress. Based on the results, the application of SA, SNP, and ZnO reduced electrolyte leakage and enhanced the plant’s resistance to water deficit by increasing the compatible osmolyte accumulation and antioxidant enzyme activity.

Antifungal effects of carvacrol, the main volatile compound in Origanum vulgare L. essential oil, against Aspergillus flavus in postharvest wheat

Plant volatile organic compounds (VOCs) with antimicrobial activity could potentially be extremely useful fumigants to prevent and control the fungal decay of agricultural products postharvest. In this study, antifungal effects of volatile compounds in essential oils extracted from Origanum vulgare L. against Aspergillus flavus growth were investigated using transcriptomic and biochemical analyses. Carvacrol was identified as the major volatile constituent of the Origanum vulgare L. essential oil, accounting for 66.01 % of the total content. The minimum inhibitory concentrations of carvacrol were 0.071 and 0.18 μL/mL in gas-phase fumigation and liquid contact, respectively. Fumigation with 0.60 μL/mL of carvacrol could completely inhibit A. flavus proliferation in wheat grains with 20 % moisture, showing its potential as a biofumigant. Scanning electron microscopy revealed that carvacrol treatment caused morphological deformation of A. flavus mycelia, and the resulting increased electrolyte leakage indicates damage to the plasma membrane. Confocal laser scanning microscopy confirmed that the carvacrol treatment caused a decrease in mitochondrial membrane potential, reactive oxygen species accumulation, and DNA damage. Transcriptome analysis revealed that differentially expressed genes were mainly associated with fatty acid degradation, autophagy, peroxisomes, the tricarboxylic acid cycle, oxidative phosphorylation, and DNA replication in A. flavus mycelia exposed to carvacrol. Biochemical analyses of hydrogen peroxide and superoxide anion content, and catalase, superoxide dismutase, and glutathione S-transferase activities showed that carvacrol induced oxidative stress in A. flavus, which agreed with the transcriptome results. In summary, this study provides an experimental basis for the use of carvacrol as a promising biofumigant for the prevention of A. flavus contamination during postharvest grain storage.

Improvement of biochemical and antioxidant responses of borage (Borago officinalis L.) under drought stress conditions with the use of vermicompost and zinc sulfate.

Drought poses a significant threat to crop production systems. Therefore, this study aimed to investigate the impact of vermicompost and foliar application of zinc sulfate under conditions of reduced irrigation on the physiological properties of Borage. A two-year experiment was conducted following a split factorial design within a randomized complete block design with three replications at Yasouj University Research Station in 2017 and 2018. The primary factor involved three levels of irrigation cut-off (I1: full irrigation, I2: irrigation cut-off at the flowering stage, and I3: irrigation cut-off during the seed-filling stage). The sub-factor included vermicompost fertilizer at three different levels (N0: control, N1: 5tonha-1, and N2: 10tonha-1), and foliar application of zinc sulfate at three levels (Z0: control, Z1: 2 and Z2: 4mgl-1). During the flowering stage stress, foliar application of 4mgl-1 of zinc sulfate resulted in an increased chlorophyll a + b content in plants (2.91mgg-1FW), while the control showed the lowest amount (2.56mgg-1FW). Vermicompost supplementation improved chlorophyll a + b content during the seed-filling stage under conditions of irrigation cut-off. The results indicated that an increase in vermicompost fertilizer application led to an elevation in relative water content (RWC), with the highest RWC (79.2%) achieved when 10tonha-1 of vermicompost was applied. Irrigation cut-off during the seed-filling stage resulted in increased electrolyte leakage and higher fertilizer usage, thus reducing cell damage. Furthermore, the findings revealed that applying 2 and 4mgl-1 zinc sulfate reduced malondialdehyde content by 5% and 9%, respectively. The catalase, peroxidase, and superoxide dismutase activities demonstrated an increased response to stress mitigation treatments. However, their activities decreased as vermicompost and zinc sulfate levels increased. The study demonstrated that the highest biomass was obtained when 10tonha-1 of vermicompost and 2mgl-1 of zinc sulfate were applied. The flowering stage of the plant exhibited the most significant negative impact under stress conditions. Nonetheless, using vermicompost and zinc sulfate, particularly during the seed-filling phase, alleviated the adverse effects of drought stress. In conclusion, our findings indicate that, although drought stress resulted in increased electrolyte leakage due to elevated free radical production, vermicompost, and zinc sulfate played a role in reducing stress.

Impact of pharmaceutical industry wastewater on stress physiological responses of Spirodela polyrhiza (L.) Schleiden.

Impact of pharmaceutical wastewater collected from aeration tank on aquatic macrophyte Spirodela polyrhiza (L.) Schleiden was studied in the present study. Various plant parameters such as chlorophyll, protein, and proline content of wastewater-exposed plants were examined to determine the toxic impacts of pharmaceutical wastewater. In addition to these parameters, electrolyte leakage (EL) and catalase (CAT) activities in S. polyrhiza were assessed for each day of exposure to the wastewater. S. polyrhiza was exposed to four different wastewater concentrations (25%, 50%, 75%, and 100%) under laboratory conditions for 7 days. The plants experienced severe toxicity as revealed by the reduction in photosynthetic pigments, increase in electrolyte leakage, and enhancement of antioxidant enzyme (CAT) activity in S. polyrhiza with an increase in concentration and time of exposure to pharmaceutical effluent.

Remediation potential of biochar and selenium for mitigating chromium-induced stress in spinach to minimize human health risk

The contamination of agricultural soils with metals and metalloids significantly affects crop productivity. The objective of the present study was to investigate how the combined application of biochar and selenium (Se) could mitigate the adverse effects of chromium (Cr) stress on spinach. The effects of selenium (Na2SeO4) (1 mg L − 1) and biochar (5 %, w/w) application both individually and in combination were evaluated on the basis of growth, physio-biochemical and antioxidant potential of spinach grown under Cr stress (100 µM [29.40 mg] using K2Cr2O7 of soil) and without Cr stress as control (0 µM). The results indicated that Cr stress decreased the root length (34.62 %), shoot length (35.32 %), number of leaves (23.18 %), root dry weight (12.00 %), and leaf dry weight (24.36 %) under Cr stress by lowering relative water content (RWC) and chlorophyll concentrations due to increased electrolyte leakage (64.03 %) and the Cr accumulation in leaves. However, the combined application of biochar and Se significantly enhanced the fresh and dry biomass under Cr stress and control conditions. The synergistic effect of Se and biochar partly alleviates the effects of Cr stress in spinach by up-regulating the antioxidant system, reducing lipid peroxidation (60.00 %), increasing leaf soluble sugars (25.22 %), and simultaneously decreasing electrolyte leakage. The combined effect of Se and biochar proved better results as compared to the sole application in minimizing Cr uptake in leaves (52.08 %) and limiting the health risk assessment values. Overall, this study highlights that the combined application of biochar and Se is an innovative and eco-friendly approach to improving the physio-biochemical defense responses against Cr stress in spinach plants.

Effects of artificial sweeteners on antioxidant enzymes and physiological parameters in Triticum aestivum (Poaceae)

Due to increased consumption, artificial sweeteners are often present in the environment but their effects on plants are largly unknown. In this research, the effects of four artificial sweeteners on plant stress markers in Triticum aestivum L. were investigated. Wheat seedlings were grown from seeds in soil containing artificial sweeteners (saccharin, sodium cyclamate, sucralose, aspartame) in different concentrations (0, 25, 50, 100 mg kg-1). Plants were irrigated at regular intervals to maintain field capacity moisture and harvested after 15 days of growth. Electrolyte leakage, chlorophyll and carotenoid content, and antioxidant enzyme (superoxide dismutase, peroxidase, catalase) activities were determined in harvested leaves. Comparisons between control samples and test samples were statistically evaluated at a 95% confidence interval to determine significant differences. Overall, significant increases in chlorophyll and carotenoid content, and some antioxidant enzyme activities were observed in wheat plants exposed to artificial sweeteners in the soil. A significant increase in electrolyte leakage was observed with saccharin and aspartame treatment, indicating that these sweeteners can cause membrane damage in wheat. Chlorophyll a nd POX activity were the most sensitive stress parameters in wheat. This study showed the importance of evaluating the potential impact of anthropogenic pollutants that may be present in treated wastewater and consequently affect plants.

Humic Acid and Selenium Supplementation Modulate the Growth and Antioxidant Potential of Chili under Cadmium Stress

Maximizing food production under adverse conditions is a major challenge to food security and sustainability in the face of population growth and climatic change. The use of amendments applied as a supplement under adverse conditions may play a significant role in the mitigation of biotic and abiotic stress. This study aimed to explore the morpho-physio-biochemical changes in chili in response to cadmium (Cd) stress. The present study investigated the effects of foliar-applied selenium (Na2SeO4) (3 µM) and soil-applied humic acid (250 mg kg−1 w/w soil) in the sole and synergistic form under varying levels of cadmium stress (0, 2, and 4 mM using CdCl2) in chili. Results revealed that a linear decrease was noticed in the growth, biomass, and phenological attributes of chili plants by increasing the Cd stress. More reduction was noticed at the higher levels of Cd stress as compared to control due lowering plant dry weight (18.15 and 39.67%), relative water content (RWC) (10.73 and 24.17%), total chlorophyll concentrations (16.01 and 31.44%) and increased electrolyte leakage (49.44 and 129.35%) and malonaldehyde contents (MDA) (68.41 and 104.04%). Dry biomass significantly increased with humic acid and selenium treatments, regardless of cadmium level. The reduced enzymatic activities associated with reactive oxygen species (ROS) detoxification, underscores the pivotal role of Se and humic acid in maintaining redox homeostasis. The combined effect of selenium and humic acid proved better results as compared to the sole application in minimizing Cd uptake in roots and fruit. This study demonstrates that the application of humic acid and selenium activates physio-biochemical defense responses against cadmium stress in chili plants and provides significant pavement for the cultivation of chili in cadmium-containing soils with a target of high-yielding and quality.

Tolerância de cultivares de maracujazeiro-azedo ao estresse salino numa área semiárida

ABSTRACT Given the quantitative scarcity of low-salinity water resources in the Brazilian semi-arid region, it is necessary to use water with a high concentration of salts. Thus, identifying salt-stress tolerant cultivars of crops is an alternative for expanding irrigated agriculture. The objective of this study was to evaluate the tolerance of passion fruit cultivars as a function of irrigation water electrical conductivity. The experimental design was randomized blocks, in a 5 × 3 factorial scheme, whose treatments consisted of the combination of five values of electrical conductivity of irrigation water - ECw (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) and three sour passion fruit cultivars (BRS GA1, BRS SC1, and SCS437, with three replicates. Electrical conductivity of water from 0.3 dS m-1 reduces the relative water content, gas exchange, and the number of fruits and increased electrolyte leakage in the leaf blade of passion fruit plants, at 153 days after transplantation. The passion fruit cultivars BRS GA1, BRS SC1, and SCS437 were classified as sensitive, with threshold electrical conductivity of water of 0.3, 1.0, and 0.3 dS m-1, respectively.

A mobile device to investigate the response of grapevine berries to heat stress

Reproducibly comparing the heat stress response of grapevine berries from different cultivars in the field is often limited by weather conditions during the growing season. This work presents a mobile heating device capable of controlled heat-stress induction on grapevine berries. The heater consisted of six 150 W infrared lamps mounted in a profile frame. The heating power of the lamps could be set individually by a control unit consisting of a single board computer and six temperature sensors positioned as desired. The heat energy applied to individual berries within a cluster decreases by the squared distance to the heat source, enabling the establishment of temperature profiles within individual clusters. Infrared thermography of the fruit surface and measurements conducted with a thermocouple inserted at the epidermis level showed comparable temperatures. Berries treated with high temperatures were sampled according to their visual appearance (i.e., sunburn symptoms). Only symptomatic berries showed a significant increase in electrolyte leakage, indicating cell damage. In a field experiment, the induction of sunburn necrosis symptoms with the presented device was used to predict a Lethal Dose (LD50) for sunburn necrosis symptoms of the Vitis vinifera L. cultivars Bacchus and Silvaner. The LD50 of Bacchus, known as a heat-sensitive cultivar, was about 3.2 °C lower than that of Silvaner. The presented device offers possibilities for a wide range of applications and the induction of precise temperature dynamics in the context of heat stress on fleshy fruit.

Heat shock pretreatment and low temperature fluctuation cold storage maintains flesh quality and retards watercore dissipation of watercored 'Fuji' apples

Watercored apples have a unique flavor and particular flesh morphology. However, watercored apples are subject to loss of water core, browning, and softening during postharvest storage. In this study, heat shock pretreatment, hot air (HA) or hot water (HW), was combined with low temperature fluctuation (LTF) cold storage to delay the disappearance of the water cores and the flesh browning and softening during a 120 d storage. The apples were evaluated for appearance characteristics, texture parameters, enzyme activities, reactive oxygen content, membrane lipid oxidation degree, tissue microstructure, and cell morphology during the storage period. The results showed that HW combined with LTF was most effective in maintaining the visual quality and texture quality of watercored apples compared with other treatments and the control. Moreover, HW-LTF could effectively inhibit the accumulation of malondialdehyde (MDA), retard the increase of electrolyte leakage (EL), reduce the membrane lipid peroxidation, and maintain the tissue microstructure and cell morphology. Meanwhile, HW-LTF inhibited the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) and reduced the degree of flesh browning. Therefore, the HW-LTF is of guiding significance for the cold storage of watercored apples.

The effect of selenium concentration on growth and stress markers in two Iranian strains of Dunaliella salina Teodoresco

Selenium toxicity and selenium stress were investigated by comparison of molecular, physiological and genetic response in plants and algae recently. In this study, the phycological responses of two strains of Dunaliella salina (Gavkhooni and Maharloo) to different Na2SeO3 concentrations (0, 0.25, 0.75, 1, 1.5, 2 mg/l) were evaluated. Our results showed that carotenoid, astaxanthin, total antioxidant, proline content, and activity of enzymatic antioxidant (especially CAT and APX) increased by adding low concentration of Na2SeO3 (up to 1 mg/l) in the medium, which also was accompanied by increase cell division, chlorophyll pigments content in both strains. Selenite concentration higher than 1 mg/l in the medium, resulted a decrease in the activity of SOD (about 19%, and 41% in Gavkhooni and Maharloo treated with 2 mg/l Na2SeO3 respectively), CAT, and APX as well as the total antioxidant capacity (about 39%, and 23% in Gavkhooni and Maharloo treated with 2 mg/l Na2SeO3 respectively) that led to increased electrolyte leakage (98%, and 62% increase in Gavkhooni and Maharloo treated with 2 mg/l Na2SeO3 respectively)and MDA content (45% and 31% in Gavkhooni and Maharloo at highest Na2SeO3 concentration respectively)in both strains. Consequently, the cell number and growth of both strains decreased in the high selenium concentration medium. The cell division of Gavkhooni strain was statistically higher than Maharloo strain under low level of selenium. Moreover, a delay in the growth of Maharloo strain was illustrated under selenium stress. Generally, it can be concluded that the better growth of Gavkhooni under low level of Se can probably be caused by the increase in the power of total antioxidant, enzymatic and non-enzymatic antioxidants.

Overexpression of OsPIN9 Impairs Chilling Tolerance via Disturbing ROS Homeostasis in Rice.

The auxin efflux transporter PIN-FORMED (PIN) family is one of the major protein families that facilitates polar auxin transport in plants. Here, we report that overexpression of OsPIN9 leads to altered plant architecture and chilling tolerance in rice. The expression profile analysis indicated that OsPIN9 was gradually suppressed by chilling stress. The shoot height and adventitious root number of OsPIN9-overexpressing (OE) plants were significantly reduced at the seedling stage. The roots of OE plants were more tolerant to N-1-naphthylphthalamic acid (NPA) treatment than WT plants, indicating the disturbance of auxin homeostasis in OE lines. The chilling tolerance assay showed that the survival rate of OE plants was markedly lower than that of wild-type (WT) plants. Consistently, more dead cells, increased electrolyte leakage, and increased malondialdehyde (MDA) content were observed in OE plants compared to those in WT plants under chilling conditions. Notably, OE plants accumulated more hydrogen peroxide (H2O2) and less superoxide anion radicals (O2-) than WT plants under chilling conditions. In contrast, catalase (CAT) and superoxide dismutase (SOD) activities in OE lines decreased significantly compared to those in WT plants at the early chilling stage, implying that the impaired chilling tolerance of transgenic plants is probably attributed to the sharp induction of H2O2 and the delayed induction of antioxidant enzyme activities at this stage. In addition, several OsRboh genes, which play a crucial role in ROS production under abiotic stress, showed an obvious increase after chilling stress in OE plants compared to that in WT plants, which probably at least in part contributes to the production of ROS under chilling stress in OE plants. Together, our results reveal that OsPIN9 plays a vital role in regulating plant architecture and, more importantly, is involved in regulating rice chilling tolerance by influencing auxin and ROS homeostasis.

Salicylic Acid as a Salt Stress Mitigator on Chlorophyll Fluorescence, Photosynthetic Pigments, and Growth of Precocious-Dwarf Cashew in the Post-Grafting Phase.

Salicylic acid is a phytohormone that has been used to mitigate the effects of saline stress on plants. In this context, the objective was to evaluate the effect of salicylic acid as a salt stress attenuator on the physiology and growth of precocious-dwarf cashew plants in the post-grafting phase. The study was carried out in a plant nursery using a randomized block design in a 5 × 4 factorial arrangement corresponding to five electrical conductivity levels of irrigation water (0.4, 1.2, 2.0, 2.8, and 3.6 dS m-1) and four salicylic acid concentrations (0, 1.0, 2.0, and 3.0 mM), with three replications. Irrigation water with electrical conductivity levels above 0.4 dS m-1 negatively affected the relative water content in the leaf blade, photosynthetic pigments, the fluorescence of chlorophyll a, and plant growth and increased electrolyte leakage in the leaf blade of precocious-dwarf cashew plants in the absence of salicylic acid. It was verified through the regression analysis that salicylic acid at a concentration of 1.1 mM attenuated the effects of salt stress on the relative water content and electrolyte leakage in the leaf blade, while the concentration of 1.7 mM increased the synthesis of photosynthetic pigments in precocious-dwarf cashew plants.

Exploring the Role of Novel Biostimulators in Suppressing Oxidative Stress and Reinforcing the Antioxidant Defense Systems in Cucurbita pepo Plants Exposed to Cadmium and Lead Toxicity

The use of bio-stimulants (BSs) has become an important policy in managing many stressed crop plants through the regulation of the balance of phytohormones, osmo-protectors (OPs), antioxidant systems, and gene expression, all of which reflect plant growth and productivity. Garlic + onion extract (GOE) at a concentration of 2.0–3.0% and diluted bee honey solution (BHs) at a concentration of 1.0–1.5% were applied exogenously to squash (Cucurbita pepo) plants subjected to cadmium (Cd) + lead (Pb) stress (0.3 mM CdCl2 + 0.3 mM PbCl2). The objective was to determine the effects of these treatments on growth characteristics, organic metabolites/biomolecules, and mineral nutrients. Cd + Pb stress significantly increased electrolyte leakage (EL, 103%) and malondialdehyde (MDA, 90%) because of an increase in hydrogen peroxide (H2O2, 145%) and superoxide (O2•−, 152%) levels, and contents of abscisic acid (ABA, 164%), Cd (674–711%), and Pb (754–805%). Consequently, marked increases in the contents of OPs and non-enzymatic antioxidants (28–133%), activities of antioxidant enzymes (48–80%), and expressions of enzyme genes (60–84%) were observed. The administration of Cd + Pb treatment reduced plant growth and development parameters (25–59%), yield components (61–86%), photosynthetic components (27–67%), leaf proportional water content (26%), indole-3-acetic acid (IAA, 44%), gibberellic acid (GA3, 56%), and cyto-kinin (CKs, 49%) contents. Nonetheless, the administration of GOE, BHs, and GOE + BHs attenuated the adverse impacts of Cd + Pb stress. The best treatment was GOE + BHs which significantly decreased EL (52%) and MDA (49%) because of a reduction of O2•– (61%), H2O2 (60%), ABA (63%), Cd (89–91%), and Pb (89–91%) levels. This positive outcome was linked to an increase in the OPs’ (22–46%) and non-enzymatic antioxidant (27–46%) levels, activities of enzymes (26–44%), and enzyme gene expressions (35–40%), all of which contributed to the promoted relative water content (RWC, 37%), pigment contents (47–194%), hormonal levels (82–132%), growth traits (31–149%), yield components (154–626%), and fruit quality traits (31–92%). From these results, it can be concluded that treatment of GOE + BHs is recommended as a foliar application to reduce the adverse effects of Cd + Pb stress treatment in squash.

Fe–Mn nanocomposites doped graphene quantum dots alleviate salt stress of Triticum aestivum through osmolyte accumulation and antioxidant defense

An investigation was carried out to evaluate the effect of graphene quantum dots (GQD) and its nanocomposites on germination, growth, biochemical, histological, and major ROS detoxifying antioxidant enzyme activities involved in salinity stress tolerance of wheat. Seedlings were grown on nutrient-free sand and treatment solutions were applied through solid matrix priming and by foliar spray. Control seedlings under salinity stress exhibited a reduction in photosynthetic pigment, sugar content, growth, increased electrolyte leakage, and lipid peroxidation, whereas iron-manganese nanocomposites doped GQD (FM_GQD) treated seedlings were well adapted and performed better compared to control. Enzymatic antioxidants like catalase, peroxidase, glutathione reductase and NADPH oxidase were noted to increase by 40.5, 103.2, 130.19, and 141.23% respectively by application of FM_GQD. Histological evidence confirmed a lower extent of lipid peroxidation and safeguarding the plasma membrane integrity through osmolyte accumulation and redox homeostasis. All of these interactive phenomena lead to an increment in wheat seedling growth by 28.06% through FM_GQD application. These findings highlight that micronutrient like iron, manganese doped GQD can be a promising nano-fertilizer for plant growth and this article will serve as a reference as it is the very first report regarding the ameliorative role of GQD in salt stress mitigation.