Contents Of Non-enzymatic Antioxidants Research Articles

Exogenous Application of Melatonin on the Preservation of Physicochemical and Enzymatic Qualities of Pepper Fruit from Chilling Injury

This study investigates the impact of melatonin (MT) treatment at varying concentrations (0, 25, 50, 75, 100 µmol L−1) on the post-harvest quality and shelf life of long green pepper fruits stored under low temperature for 28 days. Every 4 days, pepper fruits were examined for the chilling injury (CI) index, weight loss (WL), respiration rates, firmness, electrolyte leakage (EL), reactive oxygen species (ROS), malondialdehyde (MDA) levels, non-enzymatic antioxidant (NEA) content, antioxidant (AO) enzyme activity (superoxide dismutase (SOD), catalase (CAT), and peroxidases (PODs)), and cellular degrading enzymes (polygalacturonase (PG), pectin methylesterase (PME), phospholipase D (PLD), and lipoxygenase (LOX)). MT-treated samples exhibited delayed and reduced CI stress compared to controls, with higher exogenous MT concentrations (>50 µmol L−1) offering significant (p < 0.05) CI reductions. During storage, WL was notably mitigated by MT treatment in the tested samples compared to control samples. This study also demonstrated that MT-treated pepper fruits effectively decelerated respiration rates and consequently preserved pepper firmness. A higher concentration of MT-treated pepper fruits demonstrated a significantly (p < 0.05) lowered level of ROS and MDA while maintaining membrane stability, as evidenced by reduced EL. MT treatment with increasing concentration increased the levels of glutathione (GSH), glutathione disulfide (GSSG), ascorbic acid (AsA), dehydroascorbate (DHA), and total phenolic content (TPC) in the pepper fruits compared to control and thus significantly (p < 0.05) suppressed the ROS production (superoxide anion (O2•−) and hydrogen peroxide (H2O2) radicals) in the pepper fruits. Furthermore, AO enzymes such as SOD, CAT, and POD were also high in the pepper fruits that were treated with higher concentrations of MT (>50 µmol L−1). Additionally, the activities of cellular degrading enzymes (PG, PME, PLD, and LOX), which are linked to senescence and stress-induced physiological disorders, were also effectively regulated by MT-treated (>75 µmol L−1) pepper fruits. Overall, the application of MT at higher concentrations (>75 µmol L−1) demonstrated substantial benefits in preserving the quality and extending the shelf life of pepper fruits during cold storage.

Silicon and nitric oxide modulate growth attributes, antioxidant defense system and osmolytes accumulation in radish (Raphanus sativus L.) under arsenic toxicity

Plants adjust their developmental processes for their survival against changing environments. Plant development is adversely affected by arsenic (As) contamination. In order to mitigate As toxicity, the effect of silicon (Si) (as silicic acid) and nitric oxide (NO) (as sodium nitroprusside; SNP) was observed on 7 days old radish (Raphanus sativus L.) seedlings under 0.3, 0.5 and 0.7 mM As concentrations. Plant growth traits, oxidative stress, carbohydrates, protein, antioxidants and osmolytes were measured. Arsenic stress inhibited the growth parameters and caused oxidative damage by elevating the level of oxidative stress markers and by causing membrane and nuclear damage, as shown by histochemical studies. Activities of antioxidative enzymes, content of non-enzymatic antioxidants, and levels of osmolytes were also decreased by As stress. However, Si and NO supplementation enhanced the As tolerance by improving the plant growth parameters. Moreover, Si and NO application improved carbohydrates and protein contents and stimulated plant antioxidant defense systems by decreasing the level of malondialdehyde and hydrogen peroxide and by diminishing the membrane and nuclear damage caused by As. An increase in the osmolytes levels were observed by the application of Si and NO. Fourier transform infrared analysis showed that Si and NO exerted various peaks in different lipids, proteins, carbohydrates and cell wall component regions. This study suggests that Si and NO can help mitigating As-induced toxicity in R. sativus seedlings and augment growth.

Effect of polyethoxylated flavonoids (PMFs)-loaded citral and chitosan composite coatings on citrus preservation: From the perspective of fruit resistance

Previous studies have shown that polymethoxylated flavonoids-loaded citral emulsion (PCT) can inhibit the growth and reproduction of Penicillium in citrus; however, PCT is difficult to apply to fruit preservation due to its high fluidity and volatility. Therefore, in this study, we combined PCT with chitosan (CS) to investigate the effect of a composite coating on citrus preservation. The results showed that compared to the control group, the CS-PCT group could effectively reduce the decay rate and maintain moisture availability, color difference, and hardness. Moreover, the contents of nonenzymatic antioxidants and volatile substances with antimicrobial activity were better preserved. In addition, the activities of related antioxidant enzymes were greater in the treatment group, and the expression of the corresponding enzyme-encoding genes was upregulated. Consequently, CS-PCT treatment could effectively maintain fruit quality and improve the resistance of citrus fruits during storage; moreover, it can be considered a nontoxic and efficient citrus preservative.

Enhanced Heat Resistance in Morchella eximia by Atmospheric and Room Temperature Plasma.

This study focuses on optimizing the mutagenesis process for Morchella eximia (Mel-7) mycelia through atmospheric and room temperature plasma (ARTP) mutation and explores the resultant thermal adaptability and physiological responses of mutant strains. This research demonstrated a clear relationship between ARTP mutagenesis exposure duration and lethality rate, indicating that an exposure time of 40 s resulted in the optimal balance of inducing mutations without causing excessive mortality. Additionally, this study established 43 °C as the ideal screening temperature for identifying mutant strains with enhanced heat resistance, as this temperature significantly challenges the mycelia while allowing thermotolerant strains to be distinguishable. Among the screened mutants, strains L21, L23, L44, and L47 exhibited superior growth and high-temperature tolerance, with notable resilience at 30 °C, highlighting their enhanced adaptability to above-optimal temperatures. Furthermore, this research delved into biochemical responses, including lipid peroxidation and non-enzymatic antioxidant content, highlighting the diverse mechanisms, such as enhanced lipid peroxidation resistance and increased antioxidant content, employed by mutant strains to adapt to temperature fluctuations. The activities of antioxidant enzymes, including peroxidase (POD) and superoxide dismutase (SOD), were shown to be significantly influenced by temperature elevations, illustrating their critical roles in the thermal adaptation of mutant strains. These findings shed light on the importance of considering mutation duration and temperature screening in the development of thermotolerant fungal strains with potential applications in various industries. This study's breakthrough lies in its comprehensive understanding of the thermal adaptability of Mel-7 mycelia and the identification of promising mutant strains, offering valuable insights for both academic and industrial purposes.

Nonenzymatic Browning and Antioxidant Properties of Thermally Treated Cereal Grains and End Products

Thermal treatment can be applied to cereal grains as a pretreatment or processing step in the form of either hydrothermal or dry thermal treatment. These heat treatments result in the occurrence of nonenzymatic browning reactions by means of the Maillard reaction and caramelisation. Nonenzymatic browning is influenced by the type and concentration of sugars and proteins, and the presence of bran. Aside from increasing nonenzymatic browning, thermal treatment increases the antioxidant capacity of cereals and baked goods through the release of bound phenolics. The degree of nonenzymatic browning and antioxidant content in cereal-based products depend on the thermal treatment intensity. Some studies found a decrease in total phenolic content after thermal treatment, due to loss of thermally labile compounds. High-intensity treatment has been shown to produce 5-hydroxymethylfurfural (HMF), furfural, and potentially carcinogenic acrylamide. Acrylamide formation can be mitigated by altering the ingredient composition and the degree of thermal treatment. This review discusses the chemistry of nonenzymatic browning reactions, factors influencing the degree of these reactions, and mitigation strategies for acrylamide. An overview of the effect of dry thermal treatment on nonenzymatic browning and antioxidants in wheat and wheat-based products as well as other cereals is provided. Before concluding with perspectives, a discussion of the relationship between nonenzymatic browning and antioxidant properties is presented. This review of the published literature was conducted using two electronic databases and varying combinations of search terms related to the scope of the review.

Nitric oxide alleviates mercury toxicity by changing physiological and biochemical pathways in maize (Zea mays L.) seedlings

Like all life forms, plants suffer from high levels of mercury (Hg), known as one of the most harmful heavy metals in soil. The present study was performed to explore the effects of exogenous nitric oxide (NO) on Hg toxicity in maize (Zea mays L., cv. Arifiye-2) seedlings. Plants were grown in a hydroponic system containing 1/2 diluted Hoagland at 16 h day length, 25/20 °C (day/night) and 60% relative humidity. Eight day-old maize seedlings were first treated with NO (as 0.1 µM sodium nitroprusside) and then they were exposed to Hg toxicity (as 100 µM HgCl2) after 24 h. The toxic Hg decreased seedling growth, chlorophyll content, proline content, calcium and manganese contents, non-enzymatic antioxidant contents, cell membrane viscosity, and antioxidant enzyme activities (superoxide dismutase, catalase, peroxidases, and glutathione reductase) while it increased the generation of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and super oxide anion (O2.-), and lipid peroxidation (as malondialdehyde, MDA) content and the amount of sodium ion (Na+) in the seedlings. However, NO treatment markedly enhanced the growth parameters (dry and fresh weight, and plant height) and manganese and potassium contents as well as contents of antioxidants and chlorophyll thus alleviating the negative effects caused by the Hg stress. Also, it decreased the generation of ROS and lipid peroxidation level by activating the antioxidant enzymes. These results show that NO in maize seedlings under Hg toxicity may improve stress response and mitigate oxidative stress by stimulating the antioxidant system and modulating ion homeostasis.

Ipomoea cairica (L.) from Mangrove Wetlands Acquired Salt Tolerance through Phenotypic Plasticity

Palmate-leaved morning glory (Ipomoea cairica (L.) Sweet) is a fast-growing perennial herbaceous twining vine that was recently discovered to invade mangrove wetlands in China. To understand the mechanism of its successful invasion, the salt tolerance of a coastal ecotype from Zhuhai and a terrestrial ecotype from Guangzhou were compared under salt stress. The morphological, physiological, and biochemical parameters related to growth, ion homeostasis, photosynthetic pigments, chlorophyll fluorescence parameters, oxidative stress, and apoptosis were measured in both ecotypes. Monitoring apoptosis showed that the protoplasts of the coastal ecotype underwent apoptosis and were later compared with those of the terrestrial ecotype. The coastal ecotype was also found to have higher regenerated stems; less water loss, sodium (Na+) uptake, and membrane damage; higher salt gland density and area; and better photosynthetic performance than the terrestrial ecotype. The coastal ecotype probably prevented salt-related damage by reducing its water loss and secreting excess Na+ through its lower stomatal density and higher density and area of salt glands. The coastal ecotype also maintained a better balance of Na+, potassium ions, nitrogen, and phosphorus under salt stress. Moreover, the coastal ecotype had higher activities of antioxidant enzymes, including superoxide dismutase, peroxidase, and catalase, and a higher content of non-enzymatic antioxidants, including proline and anthocyanins, which indicate a stronger antioxidant ability. Our results suggest that the coastal ecotype adapts to a higher salt tolerance than the terrestrial ecotype by enhancing its exclusion of salt, adjusting its osmolytes, and through photosynthetic efficiency, which could explain its successful invasion in the mangrove wetland ecosystem.

ZnO quantum dots alleviate salt stress in Salvia miltiorrhiza by enhancing growth, scavenging reactive oxygen species, and modulating stress-responsive genes

Experiments were conducted to investigate the alleviating effects of ZnO quantum dots (ZnO QDs) on salt stress in Salvia miltiorrhiza by comparing them with conventional ZnO nanoparticles (ZnO NPs). The results demonstrated that compared with salt stress alone, foliar application of ZnO QDs significantly improved the biomass as well as the total chlorophyll and carotenoids contents under salt stress. ZnO QDs reduced H2O2 and MDA levels, decreased non-enzymatic antioxidant (ASA and GSH) content, and improved antioxidant enzyme (POD, SOD, CAT, PAL, and PPO) activity under salt stress. Metal elemental analysis further demonstrated that the ZnO QDs markedly increased Zn and K contents while decreasing Na content, resulting in a lower Na/K ratio compared to salt stress alone. Finally, RNA sequencing results indicated that ZnO QDs primarily regulated genes associated with stress-responsive pathways, including plant hormone signal transduction, the MAPK signaling pathway, and metabolic-related pathways, thereby alleviating the adverse effects of salt stress. In comparison, ZnO NPs did not exhibit similar effects in terms of improving plant growth, enhancing the antioxidant system, or regulating stress-responsive genes under salt stress. These findings highlight the distinct advantages of ZnO QDs and suggest their potential as a valuable tool for mitigating salt stress in plants.

Elevated tropospheric ozone and crop production: potential negative effects and plant defense mechanisms.

Ozone (O3) levels on Earth are increasing because of anthropogenic activities and natural processes. Ozone enters plants through the leaves, leading to the overgeneration of reactive oxygen species (ROS) in the mesophyll and guard cell walls. ROS can damage chloroplast ultrastructure and block photosynthetic electron transport. Ozone can lead to stomatal closure and alter stomatal conductance, thereby hindering carbon dioxide (CO2) fixation. Ozone-induced leaf chlorosis is common. All of these factors lead to a reduction in photosynthesis under O3 stress. Long-term exposure to high concentrations of O3 disrupts plant physiological processes, including water and nutrient uptake, respiration, and translocation of assimilates and metabolites. As a result, plant growth and reproductive performance are negatively affected. Thus, reduction in crop yield and deterioration of crop quality are the greatest effects of O3 stress on plants. Increased rates of hydrogen peroxide accumulation, lipid peroxidation, and ion leakage are the common indicators of oxidative damage in plants exposed to O3 stress. Ozone disrupts the antioxidant defense system of plants by disturbing enzymatic activity and non-enzymatic antioxidant content. Improving photosynthetic pathways, various physiological processes, antioxidant defense, and phytohormone regulation, which can be achieved through various approaches, have been reported as vital strategies for improving O3 stress tolerance in plants. In plants, O3 stress can be mitigated in several ways. However, improvements in crop management practices, CO2 fertilization, using chemical elicitors, nutrient management, and the selection of tolerant crop varieties have been documented to mitigate O3 stress in different plant species. In this review, the responses of O3-exposed plants are summarized, and different mitigation strategies to decrease O3 stress-induced damage and crop losses are discussed. Further research should be conducted to determine methods to mitigate crop loss, enhance plant antioxidant defenses, modify physiological characteristics, and apply protectants.

Plant growth regulators as an inhibitory factor of fusarium on oat culture in vitro and in vivo

The antioxidant defense system can be stimulated by growth regulators in plants when they are under stress, such as exposure to pathogens. There are a lot of natural growth regulators on the market, but no research has been carried out yet to determine how effective they are. This field and laboratory study examines the impact of two commonly used Russian growth regulators, Crezacin and Zircon, along with artificial infection with Fusarium culmorum on the antioxidant system of naked oat. The results show that, compared to the control, Crezacin-treated plants had higher contents of low molecular weight fructose and nonenzymatic antioxidants like proline, phenolic compounds, and flavonoids. Zircon-treated plants had a lower content of proline, carbohydrates, and lower total antioxidant activity than the control plants. The obtained data show that Crezacin treatment mainly affected nonenzymatic systems of the antioxidant defense. This treatment was more successful than the Zircon application, which did not show any appreciable effectiveness and was typically associated with an improvement in oat productivity. The treatment with growth regulators and a fungal suspension performed at the flowering phase provided the best effect on the biochemical parameters and productivity of naked oats. Moreover, oat treatment with the pathogen promoted the reproductive capabilities of the plants, while growth regulators helped in avoiding infectious stress.

The Effects of Sudden Freezing on the Biochemical Status of Bamboo Leaves: A Case Study on Nine Species on a Subtropical Plateau

The differences in the response of the leaves of different bamboo types to sudden snowfalls in winter were analyzed in order to provide scientific references for the introduction and cultivation of cold-resistant bamboo species and to provide new theoretical information on bamboo afforestation and disaster reduction. A total of nine bamboo species were selected to analyze the physiological and chemical changes in the leaves caused by a sudden snowfall. The results showed that sudden snowfall in winter led to a decrease in the moisture, soluble sugar, and starch contents in the leaves of all of the bamboo species analyzed, but there were increases in the contents of proline, MDA, and H2O2 and in the ratios of AsA/DHA and GSH/GSSG. Both the enzymatic activities (SOD, POD, CAT, APX, DHAR, GPX, and GR) and non-enzymatic antioxidant contents (AsA and GSH) were increased after the snowfall, which indicated that the sudden snowfall caused an increase in the antioxidant abilities in the leaves of all bamboo species analyzed. Different bamboo species adopted different strategies for resisting the freezing damage caused by the sudden snowfall. The prevention and mitigation of snow disasters in winter can be scientifically carried out in bamboo forests according to their tolerance abilities.

Caffeine Produced in Rice Plants Provides Tolerance to Water-Deficit Stress.

Exogenous or endogenous caffeine application confers resistance to diverse biotic stresses in plants. In this study, we demonstrate that endogenous caffeine in caffeine-producing rice (CPR) increases tolerance even to abiotic stresses such as water deficit. Caffeine produced by CPR plants influences the cytosolic Ca2+ ion concentration gradient. We focused on examining the expression of Ca2+-dependent protein kinase genes, a subset of the numerous proteins engaged in abiotic stress signaling. Under normal conditions, CPR plants exhibited increased expressions of seven OsCPKs (OsCPK10, OsCPK12, OsCPK21, OsCPK25, OsCPK26, OsCPK30, and OsCPK31) and biochemical modifications, including antioxidant enzyme (superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase) activity and non-enzymatic antioxidant (ascorbic acid) content. CPR plants exhibited more pronounced gene expression changes and biochemical alterations in response to water-deficit stress. CPR plants revealed increased expressions of 16 OsCPKs (OsCPK1, OsCPK2, OsCPK3, OsCPK4, OsCPK5, OsCPK6, OsCPK9, OsCPK10, OsCPK11, OsCPK12, OsCPK14, OsCPK16, OsCPK18, OsCPK22, OsCPK24, and OsCPK25) and 8 genes (OsbZIP72, OsLEA25, OsNHX1, OsRab16d, OsDREB2B, OsNAC45, OsP5CS, and OsRSUS1) encoding factors related to abiotic stress tolerance. The activity of antioxidant enzymes increased, and non-enzymatic antioxidants accumulated. In addition, a decrease in reactive oxygen species, an accumulation of malondialdehyde, and physiological alterations such as the inhibition of chlorophyll degradation and the protection of photosynthetic machinery were observed. Our results suggest that caffeine is a natural chemical that increases the potential ability of rice to cope with water-deficit stress and provides robust resistance by activating a rapid and comprehensive resistance mechanism in the case of water-deficit stress. The discovery, furthermore, presents a new approach for enhancing crop tolerance to abiotic stress, including water deficit, via the utilization of a specific natural agent.

Silicon reduces cadmium accumulation and toxicity by regulating transcriptional and physiological pathways, and promotes the early growth of tomato seedlings

Cadmium (Cd) pollution is a serious threat to plant growth and human health. Ample evidence suggests that silicon (Si) enhances plant Cd resistance; however, the precise underlying mechanism remains unclear. In this study, tomato (Solanum lycopersicum) was used as the test material for exploring the alleviating effect of 1 mM Na2SiO3 on Cd stress induced by 10 µM CdCl2. The transcriptional and physiological experiments revealed that (Ⅰ) Si downregulated the iron-regulated transporter (SlIRT1), zinc and iron regulated transporter-like proteins (SlZIP4), and reduced Cd absorption by tomato seedlings. (Ⅱ) Si upregulated the genes related to plant Cd resistance (SlPCR), pleiotropic drug resistance (SlPDR), and ATP-binding cassette G transporters (SlABCG), which promoted Cd efflux and suppressed Cd accumulation in tomato seedlings. (Ⅲ) Si increased the activities of antioxidant enzymes and contents of non-enzymatic antioxidants, reduced the contents of reactive oxygen species and malondialdehyde, and suppressed Cd-induced oxidative damages. (Ⅳ) Si inhibited Cd-induced chlorophyll degradation, alleviated damages to chloroplast ultrastructure. (Ⅴ) Si enhanced the activity of enzymes related to carbon-nitrogen metabolism, and promoted the growth of tomato seedlings. (Ⅵ) Si increased the contents of auxin and gibberellin, reduced the salicylic acid content, and maintained growth and resistance. (Ⅶ) Si regulated the expression of WRKY, NAC, ERF, MYB, HSF, and bHLH transcription factors, reduced Cd accumulation and improved Cd tolerance in tomato seedlings. These results indicated that Si effectively reduced Cd accumulation in tomato seedlings and improved Cd tolerance, and may therefore be applied for alleviating the inhibitory effect of Cd on crop growth and ensuring food security.

Modulation of AsA-GSH cycle by exogenous nitric oxide and hydrogen peroxide to minimize the Cd-induced damages in photosynthetic cyanobacteria

Cyanobacteria, the prominent nitrogen fixers, are facing many stressful situations throughout their life span, hence in recent years the yield and productivity of paddy crops are highly compromised. To address this problem, this study is structured to investigate how signaling molecules can positively influence the ability of tested cyanobacteria to counteract the adverse effects of metal stress. Thus, the main objective of this study is to elucidate the importance and crosstalk of intracellular signaling molecules, nitric oxide (NO), and hydrogen peroxide (H2O2) during Cd stress tolerance in cyanobacteria. The effect of exogenous gasotransmitter, NO and redox molecule, H2O2, in mitigation of cadmium (Cd, 6 µM) toxicity on different physiological and biochemical activities were well recorded in economically important cyanobacteria Nostoc muscorum ATCC 27893 and Anabaena sp. PCC 7120. Under Cd stress increased Cd accumulation and oxidative stress in test cyanobacteria, impaired the functioning of the ascorbate-glutathione (AsA-GSH) cycle. Exogenous application of NO (10 µM) and H2O2 (1 µM) ameliorated the negative effects of Cd through boosting-up the activities of enzymatic (ascorbate peroxidase, glutathione reductase and dehydroascorbate reductase) and the contents of non-enzymatic (cysteine, proline, ascorbate, glutathione and non-protein-thiols) antioxidants. The application of NO scavenger (PTIO) or NO synthase enzyme inhibitor (LNAME) to the Cd-stressed cells abolished the recovery of the above parameters, even in the presence of exogenous H2O2. Notwithstanding to this, under similar stress exogenous addition of scavenger of H2O2 (NAC) or inhibitor of NADPH oxidase enzyme (DPI) to the growth medium could not restrict the recovery of the above parameters in the presence of NO, hence pointing towards the major role of NO in tolerance of the test organisms to Cd stress. In conclusion, the finding revealed that NO plays a vital role in H2O2 signaling to attain Cd stress tolerance in cyanobacteria. Moreover, the study has created a scope to search for deeper insight into signaling interactions between other gasotransmitters and redox molecules in cyanobacteria. Further, the current finding recommends using a lower dose of SNP (NO donor, a cost-effective chemical) in paddy fields may ensure better growth of cyanobacteria (biofertilizer) even under prevailing stress conditions for sustainable agriculture to maintain productivity of rice crops.

Starch/carboxymethyl cellulose-based photodynamic packaging material delays the quality deterioration of snap beans via ROS metabolism regulation

Snap beans (Phaseolus vulgaris L.) are prone to rapid senescence and quality deterioration during postharvest storage. In this study, the effect of a novel carbon dot/g-C3N4-mediated starch/carboxymethyl cellulose-based photodynamic film (CCPF) on the postharvest quality deterioration and reactive oxygen species (ROS) metabolism of snap bean pods was investigated. CCPF packaging influenced gas composition regulation, ethylene degradation and microbial infection, which resulted in snap bean pods with lower respiratory metabolism and less quality loss. In addition, the snap bean pods in the CCPF group maintained the content of nonenzymatic antioxidants, low activities of pro-oxidative enzymes and high activities of antioxidant enzymes compared to other groups, thus decreasing electrolyte leakage, malondialdehyde accumulation, H2O2 accumulation and the O2·- generation rate. Overall, CCPF packaging effectively delayed postharvest senescence and extended the shelf life of snap beans by reducing respiration and regulating ROS metabolism. Pearson’s correlation analysis confirmed that postharvest senescence correlated with ROS metabolism in snap bean pods. This study offers theoretical evidence for a method to preserve snap bean pods and can be used as a valuable reference for the practical application of novel CCPF packaging.

Naked Oat and Fusarium culmorum (W.G.Sm.) Sacc. Responses to Growth Regulator Effects.

The antioxidant defense system can be stimulated by growth regulators in plants when they are under stress, such as exposure to pathogens. There are a lot of natural growth regulators on the market, but no research has been carried out yet to determine how effective they are. This field and laboratory study examines the impact of two commonly used Russian growth regulators, Crezacin and Zircon, along with artificial infection with Fusarium culmorum on the antioxidant system of naked oat. The results show that, compared to the control, Crezacin-treated plants had higher contents of low molecular weight fructose and nonenzymatic antioxidants like proline, phenolic compounds, and flavonoids. Zircon-treated plants had a lower content of proline, carbohydrates, and lower total antioxidant activity than the control plants. The obtained data show that Crezacin treatment mainly affected nonenzymatic systems of the antioxidant defense. This treatment was more successful than the Zircon application, which did not show any appreciable effectiveness and was typically associated with an improvement in oat productivity. The treatment with growth regulators and a fungal suspension performed at the flowering phase provided the best effect on the biochemical parameters and productivity of naked oats. Moreover, oat treatment with the pathogen promoted the reproductive capabilities of the plants, while growth regulators helped in avoiding infectious stress.

Effective citric acid and EDTA treatments in cadmium stress tolerance in pepper (Capsicum annuum L.) seedlings by regulating specific gene expression

Soil contamination with toxic environmental pollutants [such as cadmium (Cd)] is becoming a serious global problem due to rapid development of social economy. To improve the growth and yield of a plant, various chelating agents, such as ethylenediaminetetraacetic acid (EDTA) and citric acid (CA), can be applied to the soil; such application not only increases plant uptake of metals from the soil but also promotes plant absorption of micronutrient fertilizers from the medium. For this purpose, we have conducted a pot experiment using the exogenous application of CA (2.5 mM) and EDTA (2.5 mM) in pepper (Capsicum annuum L.) seedlings grown under the varying levels of Cd (0, 50 and 100 µM) in the soil. M]. Our results depicted that Cd addition to the soil significantly (P < 0.05) decreased plant growth and biomass, gas exchange attributes, and mineral uptake by C. annuum when compared to the plants grown without the addition of Cd. However, Cd toxicity boosted the production of reactive oxygen species (ROS) by increasing the content of malondialdehyde (MDA), which is the indication of oxidative stress in C. annuum, and was also manifested by hydrogen peroxide (H2O2) content and electrolyte leakage to the membrane-bound organelles. The results showed that the activities of various antioxidative enzymes, such as superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and their specific gene expression and also the content of non-enzymatic antioxidants, such as phenolic, flavonoid, ascorbic acid, and anthocyanin, initially increased with an increase in the Cd concentration in the soil. The results also revealed that the levels of soluble sugar, reducing sugar, and non-reducing sugar were decreased in plants grown under elevating Cd levels, but the accumulation of the metal in the roots and shoots of C. annuum, was found to be increased. The negative impacts of Cd injury were reduced by the application of EDTA and CA, which increased plant growth and biomass, improved photosynthetic apparatus, antioxidant enzymes and their gene expression, and mineral uptake, as well as diminished the exudation of organic acids and oxidative stress indicators in C. annuum by decreasing Cd toxicity. Here, we conclude that the application of EDTA and CA under the exposure to Cd stress significantly improved plant growth and biomass, photosynthetic pigments, and gas exchange characteristics; regulated antioxidant defense system and essential nutrient uptake; and balanced organic acid exudation pattern in C. annuum.

Antioxidative Defense, Suppressed Nitric Oxide Accumulation, and Synthesis of Protective Proteins in Roots and Leaves Contribute to the Desiccation Tolerance of the Resurrection Plant Haberlea rhodopensis.

The desiccation tolerance of plants relies on defense mechanisms that enable the protection of macromolecules, biological structures, and metabolism. Although the defense of leaf tissues exposed to solar irradiation is challenging, mechanisms that protect the viability of the roots, yet largely unexplored, are equally important for survival. Although the photosynthetic apparatus in leaves contributes to the generation of oxidative stress under drought stress, we hypothesized that oxidative stress and thus antioxidative defense is also predominant in the roots. Thus, we aimed for a comparative analysis of the protective mechanisms in leaves and roots during the desiccation of Haberlea rhodopensis. Consequently, a high content of non-enzymatic antioxidants and high activity of antioxidant enzymes together with the activation of specific isoenzymes were found in both leaves and roots during the final stages of desiccation of H. rhodopensis. Among others, catalase and glutathione reductase activity showed a similar tendency of changes in roots and leaves, whereas, unlike that in the leaves, superoxide dismutase activity was enhanced under severe but not under medium desiccation in roots. Nitric oxide accumulation in the root tips was found to be sensitive to water restriction but suppressed under severe desiccation. In addition to the antioxidative defense, desiccation induced an enhanced abundance of dehydrins, ELIPs, and sHSP 17.7 in leaves, but this was significantly better in roots. In contrast to leaf cells, starch remained in the cells of the central cylinder of desiccated roots. Taken together, protective compounds and antioxidative defense mechanisms are equally important in protecting the roots to survive desiccation. Since drought-induced damage to the root system fundamentally affects the survival of plants, a better understanding of root desiccation tolerance mechanisms is essential to compensate for the challenges of prolonged dry periods.

Biochemical Alterations in Triticale Seedlings Pretreated with Selective Herbicide and Subjected to Drought or Waterlogging Stress.

Waterlogging and drought disrupt crop development and productivity. Triticale is known to be relatively tolerant to different stress factors. In natural conditions, plants are rather subjected to multiple environmental factors. Serrate® (Syngenta) is a systemic selective herbicide suitable for cereal crops such as triticale and wheat to restrain annual grass and broadleaf weeds. Triticale (×Triticosecale Wittm., cv. Rozhen) was grown as soil culture under controlled conditions. Seventeen-day-old plantlets were leaf sprayed with Serrate®. The water stress (drought or waterlogging) was applied after 72 h for 7 days, and then the seedlings were left for recovery. The herbicide does not provoke sharp alterations in the antioxidant state (stress markers level, and antioxidant and xenobiotic-detoxifying enzymes activity). The water stresses and combined treatments enhanced significantly the content of stress markers (malondialdehyde, proline, hydrogen peroxide), non-enzymatic (total phenolics and thiol groups-containing compounds), and enzymatic (activities of superoxide dismutase, catalase, guaiacol peroxidase, glutathione reductase) antioxidants, and xenobiotic-detoxifying enzymes (activities of glutathione S-transferase, NADPH:cytochrome P450 reductase, NADH:cytochrome b5 reductase). These effects were more severely expressed after the drought stress, suggesting that this cultivar is more tolerant to waterlogging than to drought stress.

Effects of hydrogen sulfide on the growth and physiological characteristics of Miscanthus sacchariflorus seedlings under cadmium stress

As a gas signal molecule, hydrogen sulfide (H2S) can participate in many physiological and biochemical processes such as seed germination and photosynthesis regulation. In order to explore the regulatory effect of H2S on the growth of Miscanthus sacchariflorus under Cd stress and to provide sufficient theoretical basis for the complex action of H2S and energy plants to remediate soil pollution. In this experiment, the effects of different concentrations of H2S (10, 25, 50, 100, 300, 400, 500 μmol·L−1 (μM)) pretreatment on the growth index, lipid peroxidation degree, chlorophyll (Chl) content, osmoregulation substance content, antioxidant enzyme activity and non-enzymatic antioxidant content of M. sacchariflorus under Cd stress (50 μM) were studied. The results showed that under Cd stress, the reactive oxygen species (ROS) content in the body of M. sacchariflorus was unbalanced, and the growth were severely inhibited, the activities of antioxidant enzymes, such as catalase (CAT) and superoxide dismutase (SOD) significantly decreased, and the content of osmoregulation substance, ascorbic acid (AsA) and glutathione (GSH) significantly increased. With the increase of H2S concentration, its effect on resisting Cd stress can be shown as "low concentration promotes, high concentration inhibits". When the concentration of H2S ≤ 300 μM, although there was no significant difference in Cd content compared with Cd treatment alone, it can regulate the activities of peroxidase (POD), SOD, glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR), increase the content of osmoregulation substances, oxidized glutathione (GSSG), and the transformation rate of AsA and dehydroascorbic acid (DHA) to reduce the oxidative damage and improve the growth and photosynthetic indicators of plants; when the concentration of H2S ≥ 400 μM, Cd content in the ground and root decreased significantly, but the transport factor increased significantly, the growth status of M. sacchariflorus were more severely inhibited by the combined stress of H2S and Cd. In this experiment, it was found that the concentration of H2S pretreatment ≤ 300 μM could regulate the growth of M. sacchariflorus under Cd stress to normal level, and when the treatment concentration was 50 μM, the effect was the best. It will provide a new idea for the treatment of contaminated soil by energy plants.