APX Activity Research Articles

Combined transcriptomic and metabolomic analysis of alginate oligosaccharides alleviating salt stress in rice seedlings

BackgroundSalt stress is one of the key factors limiting rice production. Alginate oligosaccharides (AOS) enhance plant stress resistance. However, the molecular mechanism underlying salt tolerance in rice induced by AOS remains unclear. FL478, which is a salt-tolerant indica recombinant inbred line and IR29, a salt-sensitive rice cultivar, were used to comprehensively analyze the effects of AOS sprayed on leaves in terms of transcriptomic and metabolite profiles of rice seedlings under salt stress.ResultsIn this experiment, exogenous application of AOS increased SOD, CAT and APX activities, as well as GSH and ASA levels to reduce the damage to leaf membrane, increased rice stem diameter, the number of root tips, aboveground and subterranean biomass, and improved rice salt tolerance. Comparative transcriptomic analyses showed that the regulation of AOS combined with salt treatment induced the differential expression of 305 and 1030 genes in FL478 and IR29. The expressed genes enriched in KEGG pathway analysis were associated with antioxidant levels, photosynthesis, cell wall synthesis, and signal transduction. The genes associated with light-trapping proteins and RLCK receptor cytoplasmic kinases, including CBA, LHCB, and Lhcp genes, were fregulated in response to salt stress. Treatment with AOS combined with salt induced the differential expression of 22 and 50 metabolites in FL478 and IR29. These metabolites were mainly related to the metabolism of amino and nucleotide sugars, tryptophan, histidine, and β -alanine. The abundance of metabolites associated with antioxidant activity, such as 6-hydroxymelatonin, wedelolactone and L-histidine increased significantly. Combined transcriptomic and metabolomic analyses revealed that dehydroascorbic acid in the glutathione and ascorbic acid cycles plays a vital role in salt tolerance mediated by AOS.ConclusionAOS activate signal transduction, regulate photosynthesis, cell wall formation, and multiple antioxidant pathways in response to salt stress. This study provides a molecular basis for the alleviation of salt stress-induced damage by AOS in rice.

Combined efficiency of iron nanoparticles (IONPs) and salicylic acid (SA) on in vitro propagation of date palm (Phoenix dactylifera L.) under combined drought and salinity

Drought and salinity are the most important environmental factors that hamper agricultural productivity worldwide. Several adaptations and mitigation strategies are needed to deal with both stresses. The objective of the study was to determine the effect of the iron nanoparticles (IONPs) and salicylic acid (SA) under combined drought and salt stresses (DS) (PEG6000 + NaCl) on growth and some biochemical constituents of date palm cv Barhee cultured in vitro. The optimal combination was 1 mg L−1 IONPs and 50 mg L−1 SA. Such a combination under DS improved the callus growth and increased its weight to 219 mg. This combination also showed the highest response rate and the number of shoots per jar (55.65% and 6.80, respectively). The addition of IONPs and SA to the medium was most effective on the contents of organic solutes (soluble sugar, soluble protein, and proline), where the best results (4.213, 2.37, and 1.42) mgg−1 respectively, were obtained using 1 mg L−1 IONPs and 50 mg L−1 SA application under DS. This combination was also more effective under DS in increasing the chlorophylls, as well as K and Fe. Additionally, the 1 mg L−1 IONPs and 50 mg L−1 SA application under DS resulted in increasing the activities of antioxidant enzymes SOD and APX, to 31.9 and 3.28 unit−1min−1 respectively, compared to the other treatments. On the contrary, a combined application of 1 mg L−1 IONPs and 50 mg L−1 SA countered DS-induced damage by reducing levels of Malondialdehyde (MDA), Hydrogen Peroxide (H2O2), and Na in stressed plants to (0.88,1.71) µMgFw−1, and (1.688) mgg−1DW, respectively. The SDS-PAGE protein detection indicated changes in the amount and number of protein bands. New protein bands appeared in both stressed with IONPs and SA-treated plants. Based on the current study, the combined application of IONPs and SA is an effective strategy that can be used to enhance the combined drought and salt stress tolerance of date palm plants.

Investigation on the inhibition mechanism and binding behavior of paeonol to tyrosinase and its anti-browning property by multi-spectroscopic and molecular docking methods

Paeonol, as one effective tyrosinase inhibitor, had been used as food preservative and clinical medication for skin disorders. In this study, the inhibition mechanism and binding behavior of paeonol to tyrosinase and its anti-browning property were investigated using multi-spectroscopic and molecular docking methods. Activity assay and kinetic results confirmed paeonol as a reversible mixed-type tyrosinase inhibitor. Results of the mechanistic studies were clarified using fluorescence quenching, synchronous fluorescence, CD spectra and 3D fluorescence, and showed that the binding of paeonol to tyrosinase might change the chromophore microenvironment and conformation of tyrosinase to inhibit enzyme catalytic activity. Molecular docking results revealed the detailed binding between paeonol and tyrosinase. Moreover, paeonol could prevent the browning of fresh-cut apples, as well as inhibiting PPO and POD activities and increasing APX activity. All above findings established a reliable basis for the inhibitory mechanism of paeonol against tyrosinase and therefore contributed to its application in anti-browning.

Inhibition of wound healing in fresh-cut potatoes by ascorbic acid is associated with control of the levels of reactive oxygen species and the AsA-GSH cycle

This study aimed to investigate the regulatory mechanisms of ascorbic acid (AsA) treatment on reactive oxygen species (ROS) and the ascorbate-glutathione (AsA-GSH) cycle during wound healing of fresh-cut potatoes (FCPes). AsA treatment at two concentrations (5 and 10 g L−1) was used to measure changes in H2O2 and O2.− contents, antioxidant enzymes of SOD, POD, and CAT activities, StPOD-related genes expression levels, and the AsA-GSH cycle metabolism activity. The results showed that AsA treatment could reduce the contents of H2O2 and O2.−, downregulate the expressions of suberization-associated StPOD genes, decrease the activities of SOD, POD, MDHAR, and DHAR, induce the activities of CAT, APX, GR, and GPX, as well as maintain high levels of AsA and GSH and AsA/(AsA + DHA) and GSH/(GSH + GSSG) ratios. In summary, exogenous AsA treatment delayed the wound-healing process and maintained the quality of FCPes by reducing ROS production, inducing antioxidant enzyme activities, and enhancing the AsA-GSH cycle metabolism activity, thus improving the overall antioxidant capacity and balancing the generation of ROS and the antioxidant defense system.

Effect of foliar application of nanoparticles on growth, physiology, and antioxidant enzyme activities of lettuce (Lactuca sativa L.) plants under cadmium toxicity.

Nanotechnology has attracted the interest of scientists due to its wide range of application specifically in agriculture. Nanoparticles (NPs) may act as a promising materials to alleviate cadmium (Cd) stress in plants. This study aims to assess the impact of multiple nanoparticles including nSiO2 (50mg L-1:100mg L-1), nTiO2 (20mg L-1:60mg L-1), nZnO (50mg L-1:100mg L-1), nFe3O4 (100mg L-1:200mg L-1), nCuO (50mg L-1:100mg L-1), and nCeO2 (50mg L-1:100mg L-1) in combination with CdCl2 (5µM) to mitigate Cd toxicity in lettuce through foliar application in hydroponic solution. Current findings indicate that foliar application of nSiL + Cd (50mg L-1), nZnL + Cd (50mg L-1), and nTiL + Cd (20mg L-1) is more effective in improving growth, biomass, root architecture, and elevated photosynthetic efficiency, which might be attributed to the increasing uptake of essential micronutrient (K, Mg, Ca, Fe, Zn) under Cd stress. Similarly, treatment with nanoparticles leads to reduced accumulation of ROS and MDA in lettuce, while enhancing the SOD, POD, CAT, and APX activities. The results showed that nanoparticles have high tolerance against Cd as depicted by the inhibition in Cd accumulation by 3.2-58% and 10-72% in roots as well as edible parts of lettuce, respectively. In addition, Cd alone reduces the morphological traits, antioxidant enzyme activity, and photosynthetic activity, while increasing the ROS, MDA, and Cd accumulation in lettuce. This comprehensive study suggests the role of nanoparticles in reducing Cd toxicity in lettuce, signifying their importance as stress mitigation agents. However, long-term pot, priming, and field trials are needed to identify the optimal nanoparticle for the lettuce under variable environmental conditions.

Metabolomic and physiological changes of acid-tolerant Graesiella sp. MA1 during long-term acid stress.

Algae plays a significant role for the primary production in the oligotrophic ecosystems such as the acid mine pit lakes. Graesiella sp. MA1 was a new acid-tolerant photosynthetic protist isolated from an acid mine pit lake. To understand the acid responses of Graesiella sp. MA1, its physiological changes and metabolomics were studied during long-term acid stress. Photosynthetic pigments, soluble proteins, and antioxidant systems of Graesiella sp. MA1 cells displayed two phases, the adaptation phase and the growth phase. During the adaptation phase, both photosynthetic pigments and soluble proteins were inhibited, while antioxidant activity of SOD, APX, and GSH were promoted to response to the organism's damage. Metabolomics results revealed lipids and organic acids were abundant components in Graesiella sp. MA1 cells. In response to acid stress, the levels of acid-dependent resistant amino acids, including glutamate, aspartate, arginine, proline, lysine, and histidine, accumulated continuously to maintain orderly intracellular metabolic processes. In addition, fatty acids were mainly unsaturated, which could improve the fluidity of the cell membranes under acid stress. Metabolomic and physiological changes showed that Graesiella sp. MA1 had tolerance during long-term acid stress and the potential to be used as a bioremediation strain for the acidic wastewater.

Mitigation of Salt Stress in Reaumuria soongarica Seedlings by Exogenous Ca2+ and NO Compound Treatment

Soil salinization is a common abiotic stress that severely limits the growth of Reaumuria soongarica and reduces its application value. To better understand the response of R. soongarica to salt stress and the physiological mechanisms of exogenous Ca2+ and NO compound treatment in alleviating salt stress, the growth parameters, antioxidant system, carbohydrate metabolism and nitrogen compound metabolism were compared on Days 0, 1, 3, 6, 9, 15 and 30. The results showed that salt stress could significantly reduce the plant height, root length, fresh and dry weights of aboveground and underground parts, as well as the relative water content, severely inhibiting the growth of R. soongarica seedlings. After Ca2+ and NO compound treatment, these growth parameters were significantly improved, and the harm caused by stress in R. soongarica was alleviated. Regarding the antioxidant system, the Ca2+ and NO compound treatment could significantly increase the activities of SOD, CAT, APX and GR, as well as the contents of ASA and GSH, which indicated that exogenous Ca2+ and NO could eliminate the accumulated active oxygen by increasing the activities of oxidoreductases and the content of nonenzymatic antioxidant substances, thereby improving the salt tolerance of R. soongarica. Regarding carbon metabolism, after Ca2+ and NO compound treatment, the soluble sugar and sucrose contents, as well as the activities of sucrose phosphate synthase and sucrose synthase, were significantly increased, which indicated that Ca2+ and NO compound treatment could maintain higher soluble sugar and sucrose contents in R. soongarica and reduce osmotic stress caused by salt treatment. Regarding nitrogen metabolism, the Ca2+ and NO compound treatment reduced the harm of salt stress by regulating the nitrogen compound contents and nitrogen compound-related enzyme activities, including increases in the NO3− content and NR, NiR, GS, GOGAT and GDH activities and a reduction in the NO2− content. The results of this study indicate that the inhibition of the growth and development of R. soongarica by salt stress can be alleviated by regulating the antioxidant system, carbohydrate metabolism and nitrogen compound metabolism, which provides a theoretical basis for Ca2+ and NO compound treatment to improve plant salt tolerance.

Exogenous dopamine ameliorates chilling injury in banana fruits by enhancing endogenous dopamine and glycine betaine accumulation and promoting ROS scavenging system activity

This study explored the efficiency of exogenous dopamine in ameliorating chilling injury in banana fruits during storage at 7 ºC for 21 days. By 150 µM dopamine treatment, alleviating chilling injury in banana fruits was associated with lower electrolyte leakage and MDA accumulation, revealing membrane integrity maintenance. Banana fruits treated with 150 µM dopamine exhibited higher endogenous dopamine accumulation, which could be ascribed to triggering the expression of TyrDC gene. By 150 µM dopamine treatment, higher endogenous dopamine accumulation in banana fruits was concomitant with higher endogenous glycine betaine accumulation arising from provoking the expression of CMO and BADH genes and enhancing the activity of BADH enzyme. Banana fruits treated with 150 µM dopamine exhibited higher chlorophyll accumulation due to lower expression of MDC, PPH, PaO, and RCCR genes, while by enhancing the activity of SOD, CAT, APX, and GR enzymes, banana fruits treated with 150 µM dopamine exhibited lower H2O2 accumulation. In addition, lower electrolyte leakage and MDA accumulation in banana fruits treated with 150 µM dopamine demonstrated membrane integrity maintenance. Therefore, dopamine could be exogenously applied to alleviate chilling injury in banana fruits by enhancing the endogenous dopamine and glycine betaine accumulation and promoting the activity of ROS system activity.

Waterlogging Tolerance of Actinidia valvata Dunn Is Associated with High Activities of Pyruvate Decarboxylase, Alcohol Dehydrogenase and Antioxidant Enzymes.

Kiwifruit (Actinidia spp.) is susceptible to waterlogging stress. Although abundant wild germplasm resources exist among Actinidia plants for improving the waterlogging tolerance of kiwifruit cultivars, the underlying mechanisms remain largely unknown. Here, a comparative study was undertaken using one wild germplasm, Maorenshen (A. valvata Dunn, MRS), and one cultivar, Miliang-1 (A. chinensis var. deliciosa (A.Chev.) A.Chev. cv. Miliang-1, ML). Under stress, the ML plantlets were seriously damaged with wilted chlorotic leaves and blackened rotten roots, whereas the symptoms of injury in the MRS plantlets were much fewer, along with higher photosynthetic rates, chlorophyll fluorescence characteristics and root activity under stress conditions. However, neither aerenchyma in the root nor adventitious roots appeared in both germplasms upon stress exposure. The activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), as well as their transcript levels, were constitutively higher in MRS than those in ML under both normal and stress conditions. Waterlogging stress significantly enhanced the PDC and ADH enzyme activities in both germplasms, which were 60.8% and 22.4% higher in the MRS roots than those in the ML roots under waterlogging stress, respectively. Moreover, MRS displayed higher activities of antioxidant enzymes, including SOD, CAT, and APX, as well as DPPH-radical scavenging ability, and decreased H2O2 and MDA accumulation under both normal and stress conditions. Our findings suggest that the waterlogging tolerance of the wild A. valvata germplasm was associated with high PDC and ADH, as well as antioxidant ability.

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.

Priming seeds with salicylic acid modulates membrane integrity, antioxidant defense, and gene expression in Medicago sativa grown under iron deficiency and salinity.

Exposure of plants to adverse environmental conditions reduces their growth and productivity. Currently, seed priming with phytohormones is considered one of the most reliable and cost-effective approaches that can help alleviate the toxic effects of environmental stress. In this context, the present study aims to investigate the effect of priming alfalfa seeds with salicylic acid (SA) on oxidative stress markers, including malonyldialdehyde, protein content, activities of antioxidant enzymes, and expression of genes encoding these enzymes in leaves and roots of alfalfa (Gabes ecotype) grown under saline stress, iron deficiency, or both. Our results showed that the application of salt stress and iron deficiency separately or simultaneously induces changes in the activities of antioxidant enzymes, but these are organ- and stress-dependent. The Gabes ecotype was able to increase the activities of these enzymes under salt stress to alleviate oxidative damage. Indeed, priming seeds with 100 μM SA significantly increases the enzymatic activities of APX, GPX, CAT, and SOD. Therefore, this concentration can be considered optimal for the induction of iron deficiency tolerance. Our results showed not only that Gabes ecotype was able to tolerate salt stress by maintaining high expression of the Fe-SOD isoform, but also that the pretreatment of seeds with 100 μM SA improved the tolerance of this ecotype to iron deficiency by stimulating Fe-SOD expression and inhibiting CAT and APXc.

The Malus domestica metal tolerance protein MdMTP11.1 was involved in the detoxification of excess manganese in Arabidopsis thaliana

Ion homeostasis is maintained in plant cells by specialized transporters. However, functional studies on Mn transporters in apple trees have not been reported. MdMTP11.1, which encodes a putative Mn-MTP transporter in Malus domestica, was expressed highly in leaves and induced by Mn stress. Subcellular localization analysis of the MdMTP11.1-GFP fusion protein indicated that MdMTP11.1 was targeted to the Golgi. Meanwhile, overexpression of MdMTP11.1 in Arabidopsis thaliana conferred increased resistance to plants under toxic Mn levels, as evidenced by increased biomass of whole plant and length of primary root. Analysis of Mn bioaccumulation indicated that overexpression of MdMTP11.1 effectively reduced the content of Mn in every subcellular component and chemical forms when the plants were subjected with Mn stress. The majority of Mn of action were bound to cell wall and combined with un-dissolved phosphate. Besides, contents of malondialdehyde (MDA), proline and hydrogen peroxide (H2O2) were significantly lower, while content of chlorophyll and activities of CAT, SOD, POD and APX were significantly higher in MdMTP11.1-over-expressing plants compared with that in wild type plants under Mn stress. Taken together, these results suggest that MdMTP11.1 is a Mn specific transporter localized to the Golgi can maintain the phenotype, reduce the Mn accumulation and alleviate damage of oxidative stress, conferring the positive role of Mn tolerance.

Arabidopsis Protein Phosphatase PIA1 Impairs Plant Drought Tolerance by Serving as a Common Negative Regulator in ABA Signaling Pathway.

Reversible phosphorylation of proteins is a ubiquitous regulatory mechanism in vivo that can respond to external changes, and plays an extremely important role in cell signal transduction. Protein phosphatase 2C is the largest protein phosphatase family in higher plants. Recently, it has been found that some clade A members can negatively regulate ABA signaling pathways. However, the functions of several subgroups of Arabidopsis PP2C other than clade A have not been reported, and whether other members of the PP2C family also participate in the regulation of ABA signaling pathways remains to be studied. In this study, based on the previous screening and identification work of PP2C involved in the ABA pathway, the clade F member PIA1 encoding a gene of the PP2C family, which was down-regulated after ABA treatment during the screening, was selected as the target. Overexpression of PIA1 significantly down-regulated the expression of ABA marker gene RD29A in Arabidopsis protoplasts, and ABA-responsive elements have been found in the cis-regulatory elements of PIA1 by promoter analysis. When compared to Col-0, transgenic plants overexpressing PIA1 were less sensitive to ABA, whereas pia1 showed the opposite trait in seed germination, root growth, and stomatal opening experiments. Under drought stress, SOD, POD, CAT, and APX activities of PIA1 overexpression lines were lower than Col-0 and pia1, while the content of H2O2 was higher, leading to its lowest survival rate in test plants, which were consistent with the significant inhibition of the expression of ABA-dependent stress-responsive genes RD29B, ABI5, ABF3, and ABF4 in the PIA1 transgenic background after ABA treatment. Using yeast two-hybrid and luciferase complementation assays, PIA1 was found to interact with multiple ABA key signaling elements, including 2 RCARs and 6 SnRK2s. Our results indicate that PIA1 may reduce plant drought tolerance by functioning as a common negative regulator involved in ABA signaling pathway.

Antioxidant effects of phenolic extract from sugarcane straw and mannan extract from brewer's spent yeast on fresh-cut apples.

Fresh-cut fruit are convenient ready-to-eat products increasingly demanded by consumers, but highly susceptible to oxidation. To increase the shelf life of these products, this industry is currently facing the challenge of finding sustainable natural preservatives capable of maintaining fresh-cut fruit quality while meeting consumers expectations regarding health and environmental concerns. In this work, fresh-cut apple slices were treated with two antioxidant extracts derived from industrial by-products, a phenolic rich extract produced from sugarcane straw (PE-SCS) and applied at 15 g L-1 , and a mannan rich extract obtained from brewers' spent yeast (MN-BSY) applied at two concentrations, 1 and 5 g L-1 . The PE-SCS, having a brown color, imparted a brownish hue to the fruit and increased the browning rate during storage, and neither the initial robust antioxidant response (high SOD, CAT, APX and POX activities), prevented oxidation. The fruit treated with MN-BSY extract at 5 g L-1 showed lower color loss rate and higher PPO inhibition while at 1 g L-1 , it showed lower firmness loss rate and lower lipid peroxidation after 6 days of storage. The results showed that the PE-SCS triggers a potent antioxidant response in fresh-cut fruit and despite at 15 g L-1 it imparted a brown color to the fruit, it may have potential for application at lower concentrations. Regarding MN-BSY, it generally decreased oxidative stress, but its effect on quality maintenance was dependent on the concentration and, thus, to conclude about its potential as a fruit preservative more concentrations must be tested. This article is protected by copyright. All rights reserved.

Exogenous acetone O-(2-naphthylsulfonyl)oxime improves the adverse effects of excess copper by copper detoxification systems in maize

The current study is to elucidate the responses of maize seedlings to excess copper and acetone O-(2-naphthylsulfonyl)oxime (NS) pretreatment. The study was divided into the following experimental groups: 18 h distilled water (DW) control (C), 6 h 0.3 mM NS + then 12 h DW (NS), 6 h DW + then 12 h 1 mM CuSO4.5H2O (CuS), 0.3 mM NS for 6 h + then 1 mM CuSO4.5H2O (NS + CuS) for 12 h. When the NS + CuS group is compared with the CuS group; It accumulated 10% more copper, while the ABA, H2O2, MDA, and carotenoid contents decreased significantly, the total chlorophyll, proline, gallic acid, ascorbic acid, catechol, trans-P-qumaric acid, and cinnamic acid contents increased. While SOD activity, which is one of the antioxidant system enzymes, decreased with NS application, GPX, CAT, and APX activities increased despite copper stress. When all the findings are evaluated as a whole, exogenous NS, despite excessive copper, ameliorated the adverse effects of copper stress by increasing the effectiveness of the enzymatic and non-enzymatic components of the antioxidant system and the contents of phenolic substances. In addition, increasing the copper content by 10% reveals its importance in terms of NS phytoremediation. Abbreviation: Style-sheet: When full form and abbreviated form both are used as keywords, retain both as provided by the author

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.

Physiological and Biochemical Traits of Needles Imply That Understory Light Conditions in the Growing Season May Be Favorable to Pinus koraiensis Trees

Light is often considered the primary factor leading to the regeneration failure of Korean pines (Pinus koraiensis) under the forest canopy. However, studies on the effect of light on Korean pines mainly focus on the use of an artificial sunshade net to control shade; field studies on the canopy are extremely scarce, and the current experimental results are contradictory. For a deeper understanding of the relationship between light conditions and understory Korean pine trees, the conditions of low, middle, high and full light (control) under the forest were tested at 18 years of age. The photosynthetic pigments, chlorophyll fluorescence, non-structural carbohydrate metabolism, antioxidant enzyme activity, and nutrient concentrations of current-year needles from Korean pine trees were measured. From June to September, light intensity and quality decreased under full light, but following leaf fall, understory light conditions improved slightly. As the light conditions improved, the photosynthetic pigments in the needles decreased, but Car/Chl were highest in the needles under full light. All light conditions had a positive correlation with glucose concentrations and Rubisco activity. Full-light needles had the highest APX activity, DPPH scavenging capacity, and proline concentration, as well as higher NPQ and lower Fv/Fm readings. This indicated that full-light Korean pine trees were stressed and inhibited photosynthesis to some extent, while the understory light environment may alleviate stress. The conservative strategy of storing more starch and using less glucose in understory Korean pine trees may be one of the reasons for the observed differences in growth rates among Korean pine trees under varying light conditions. Overall, this study implies that understory light during the growing season is not always unfavorable to 18-year-old Korean pine trees; this means that 18-year-old Korean pine trees still have shade tolerance to some extent and are capable of living under a canopy of deciduous trees.

Mechanisms associated with the synergistic induction of resistance to tobacco black shank in tobacco by arbuscular mycorrhizal fungi and β-aminobutyric acid.

Tobacco black shank (TBS), caused by Phytophthora nicotianae, is one of the most harmful diseases of tobacco. There are many studies have examined the mechanism underlying the induction of disease resistance by arbuscular mycorrhizal fungi (AMF) and β-aminobutyric acid (BABA) alone, but the synergistic effects of AMF and BABA on disease resistance have not yet been studied. This study examined the synergistic effects of BABA application and AMF inoculation on the immune response to TBS in tobacco. The results showed that spraying BABA on leaves could increase the colonization rate of AMF, the disease index of tobacco infected by P.nicotianae treated with AMF and BABA was lower than that of P.nicotianae alone. The control effect of AMF and BABA on tobacco infected by P.nicotianae was higher than that of AMF or BABA and P.nicotianae alone. Joint application of AMF and BABA significantly increased the content of N, P, and K in the leaves and roots, in the joint AMF and BABA treatment than in the sole P. nicotianae treatment. The dry weight of plants treated with AMF and BABA was 22.3% higher than that treated with P.nicotianae alone. In comparison to P. nicotianae alone, the combination treatment with AMF and BABA had increased Pn, Gs, Tr, and root activity, while P. nicotianae alone had reduced Ci, H2O2 content, and MDA levels. SOD, POD, CAT, APX, and Ph activity and expression levels were increased under the combined treatment of AMF and BABA than in P.nicotianae alone. In comparison to the treatment of P.nicotianae alone, the combined use of AMF and BABA increased the accumulation of GSH, proline, total phenols, and flavonoids. Therefore, the joint application of AMF and BABA can enhance the TBS resistance of tobacco plants to a greater degree than the application of either AMF or BABA alone. In summary, the application of defense-related amino acids, combined with inoculation with AMF, significantly promoted immune responses in tobacco. Our findings provide new insights that will aid the development and use of green disease control agents.

Understanding physiological and molecular adaptations of three diverse halophytic grasses under saline and sodic stresses

Physiological and biochemical analyses of three halophytes were conducted to explore their tolerance and phytoremediation potential. The halophytes Urochondra setulosa, Sporobolus marginatus and Leptochloa fusca were categorised based on gas exchange attributes, antioxidant system, biomass production under soil salinity (ECe 30-50 dS/m) and sodicity (pH 9.5-10). L. fusca and S. marginatus produced slightly higher biomass under the sodic condition of pH 9.5, while in U. setulosa, it increased under salinity stress. Under sodic conditions, L. fusca showed less reduction in potassium content and maintained a higher K+/Na+ ratio in their leaf tissues. A maximum decrease in net photosynthesis was observed in L. fusca (28.55%) at ECe ~ 50 dS m-1 while minimum in S. marginatus (13.73%) at pH ~ 10.0. Comparatively, U. setulosa showed higher stomatal conductance and transpiration rate than L. fusca and S. marginatus. At the highest pH and salinity, the antioxidant activities of enzymes APX, SOD, GR and POX increased in all three halophytes. Quantitative expression of MnSOD, NHX1 and FuSOS1 genes in all three halophytes increased with salt stresses. Based on these indicators, these halophytes were categorised as salt-tolerant or alkaline-stress-tolerant.

Silicon alleviates drought damage by increasing antioxidant and photosynthetic performance in cowpea

AbstractWater deficits have been considered the most restrictive environmental constraint on agricultural production worldwide. The current study aimed to investigate the role of silicon nutrition (Si) in activating defence mechanisms against drought damage in cowpea cultivars. The experiments were carried out in a randomized block design in a 2 × 2 × 4 factorial scheme, corresponding to two cowpea cultivars (BRS Novaera and BRS Tumucumaque), two water regimes (control well‐irrigated and water deficit) and four Si levels (0, 1.0, 2.0 and 4.0 mM). Plant growth and physiological and biochemical indicators were evaluated 28 days after drought imposition. Drought significantly reduced the photosynthetic pigments (Chl b and Chl total), gas exchanges (net photosynthesis, transpiration and stomatal conductance) and, consequently, all growth parameters of cowpea plants compared with well‐irrigated plants. However, Si at 2.0 mM activated critical responses in the BRS Novaera cultivar under drought, almost recovering plant performance and increasing drought tolerance. The beneficial Si‐induced effects were closely related to increased accumulation of Si, carbohydrates and free amino acids that likely promoted osmoregulation and were associated with an improved antioxidant system composed of proline and the activity of SOD, CAT and APX. These metabolic alterations were sufficient to enable enhanced net photosynthesis and plant growth. In conclusion, Si counteracts the deleterious effects of water deficit by efficiently inducing antioxidant defence and photosynthetic performance in Novaera plants. Si nutrition may constitute a potential strategy to cultivate cowpea plants in water‐scarce areas from arid and semiarid regions.