Zinc ameliorates copper-induced oxidative stress in developing rice (Oryza sativa L.) seedlings

Rice (Oryza sativa L.) seedlings were treated with different concentrations of copper (Cu) either in presence or absence of zinc (Zn), and different events were investigated to evaluate the ameliorative effect of Zn on Cu stress. In presence of high Cu concentration, growth of both root and shoots were considerably reduced. Decline in elongation and fresh mass was observed in root and shoot. Zn alone did not show any considerable difference as compared to control, but when supplemented along with high concentration Cu, it prompted the growth of both root and shoot. After 7 days, root growth was 9.36 and 9.59 cm, respectively, at 200 and 500 μM of Cu alone as compared to 10.59 and 12.26 cm at similar Cu concentrations, respectively, in presence of Zn. Cu accumulation was considerably high after 7 days of treatment. In absence of Zn, significant accumulation of Cu was observed. Zn supplementation ameliorated the toxic impact of Cu and minimized its accumulation. Cu treatment for 1 and 7 days resulted in a dose-dependent increase in hydrogen peroxide (H₂O₂). When Cu was added in presence of Zn, the H₂O₂ production in root and shoot was reduced significantly. The increase in H₂O₂ production under Cu stress was accompanied by augmentation of lipid peroxidation. In absence of Zn, Cu alone enhanced the malondialdehyde (MDA) production in both root and shoot after 1 and 7 days of treatment. The MDA content drastically reduced in root and shoot as when Zn was added during Cu treatment. The activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GPX) were elevated under Cu stress both in root and shoot. Addition of Zn further stimulated the activities of these enzymes. Both ascorbate (AsA) and glutathione (GSH) contents were high under Cu stress either in presence or absence of Zn. The results suggests that Zn supplementation improves plant survival capacity under high Cu stress by modulating oxidative stress through stimulation of antioxidant mechanisms and restricts the accumulation of toxic concentrations of Cu.     

Silicon increases boron tolerance and reduces oxidative damage of wheat grown in soil with excess boron

The effect of silicon on the growth, boron concentrations, malondialdehyde (MDA) content, lipoxygenase (LOX) activity, proline (PRO) and H₂O₂ accumulation, and the activities of major antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)] and non-enzymatic antioxidants (AA) of wheat grown in soil originally with toxic B concentrations were investigated. Applied of 5.0 and 10.0 mM Si to the B toxic soil significantly increased Si concentration of the wheat and counteracted the deleterious effects of B on shoot growth. The contents of PRO, H₂O₂, MDA, and LOX activity of wheat grown in B toxic soil were significantly reduced by Si treatments. Compared with control plants, the activities of SOD, CAT, APX and content of AA were decreased by applied Si. Based on the present work, it can be concluded that Si alleviates B toxicity of wheat by preventing oxidative membrane damage and also translocation of B from root to shoot and/or soil to plant.     

Effect of lycopene on As2O3 induced oxidative stress in SH-SY5Y cells

It is known that oxidative stress may cause neuronal injury and several experimental models showed that As₂O₃ exposure causes oxidative stress. Lycopene, a carotenoid, has been shown to have protective effect in neurological disease models due to antioxidant activity, but its effect on As₂O₃-induced neurotoxicity is not identified yet. The aim of this study is to investigate the effects of lycopene on As₂O₃-induced neuronal damage and the related mechanisms. Cell viability was determined by the MTT assay. Lycopene was administrated with different concentrations (2, 4, 6 and 8 µM) one hour before 2 µM As₂O₃ exposure in SH-SY5Y human neuroblastoma cells. The anti-oxidant effect of lycopene was determined by measuring superoxide dismutase (SOD), catalase (CAT) hydrogen peroxide (H₂O₂), malondialdehyde (MDA), total antioxidant status (TAS) and total oxidant status (TOS). MTT results and LDH cytotoxicity analyses showed that pretreatment with 8 µM lycopene significantly improved the toxicity due to As₂O₃ exposure in SH?SY5Y neuroblastoma cells. Pretreatment with lycopene significantly increased the activities of anti?oxidative enzymes as well as total antioxidant status and decreased total oxidative status in As₂O₃ exposed cells. The results of this study indicate that lycopene may be a potent neuroprotective against oxidative stress and could be used to prevent neuronal injury or death in several neurological diseases.

     

Ascorbic acid improves the tolerance of wheat plants to lead toxicity

Among the heavy metals (HMs), lead (Pb) is considered as a toxic HM which adversely affects growth and development of crop plants. The present experiment was aimed to investigate the potential role of ascorbic acid (ASC) in the reversal of Pb-inhibited nitrogen and sulfur assimilation enzymes activity and activity of photosynthesis enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and growth response in wheat plants. Wheat seedlings were subjected to 0 mM (control) and 0.2 mM and 0.6 mM of ASC with and without 2 mM of Pb. Plants treated with Pb exhibited the following reduced growth characteristics (root length, shoot length, root fresh weight (FW), shoot FW, root dry weight (DW) and shoot DW). A decrease was also observed in the activity of Rubisco and ATP sulfurylase (ATP-S), relative water content (RWC), accumulation of total chlorophyll (Total Chl) and content of nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg)] in Pb-treated plants. However, an increase in Chl degradation and in the activity of O-acetylserine(thiol)lyase (OAS-TL) and accumulation of cysteine (Cys), malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) was observed in plants under Pb stress. On the contrary, exogenous application of ASC mitigated the Pb-toxicity-induced oxidative damage by enhancing the activities of antioxidant enzymes, such as superoxide dismutase, catalase and glutathione reductase. Improved activity of antioxidant enzymes suppressed the formation of MDA and H₂O₂, which was reflected in the form of improved growth characteristics. Moreover, ASC induced improvement in plants defense systems by reduced Chl degradation and improved the content of essential nutrients (N, P, K, Ca and Mg) and Cys, RWC and the activity of Rubisco, ATP-S, NR and OAS-TL.     

The ecotoxicological and interactive effects of chromium and aluminum on growth,oxidative damage and antioxidant enzymes on two barley genotypes differing in Al tolerance

The effects of single or combined stress of aluminum (Al) and chromium (Cr) on plant growth, root dehydrogenase, oxidative stress and antioxidative enzymes were studied using two barley genotypes differing in Al tolerance in a hydroponic experiment. Al or Cr stress decreased plant growth, lowered root dehydrogenase activity and caused oxidative damage, as characterized by increased MDA and H₂O₂ contents. Under Al or Cr stress, the activities of antioxidative enzymes, including superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and catalase (CAT), were dramatically increased in plant tissues. Gebeina, an Al-tolerant genotype, had less oxidative damage than Shang 70-119, an Al-sensitive genotype. The extent of oxidative damage induced by Cr varied with the pH of the culture solution, with lower pH values (4.0) being more severe than higher pH values (6.5). The combination of Cr and Al caused a further decrease in plant growth, a decrease in root dehydrogenase activity and an increase in MDA and H₂O₂ contents as well as the activities of antioxidative enzymes. There was also a marked difference between the two barley genotypes in the extent of increased antioxidative enzyme activity under the Cr and Al stresses.     

Impact of exogenously applied tocopherol on some key physio-biochemical and yield attributes in mungbean [<Emphasis Type="Italic">Vigna radiata</Emphasis> (L.) Wilczek] under limited irrigation regimes

The lipophilic vitamin E, α-Tocopherol (α-Toc), has been considered as a potent cellular antioxidant naturally occurring in biological membranes. It plays a number of key metabolic roles in plants exposed to various stressful cues. A field experimental was conducted on mungbean [Vigna radiata (L.) Wilczek] under varying water-limited regimes and the plants were sprayed with four levels of α-Toc (0, 100, 200, and 300 mg L^?1) at the vegetative stage of plant growth. The results showed that limited field irrigation regimes (desiccated conditions) caused a marked reduction in growth parameters (shoot and root fresh and dry weights; shoot and root lengths), photosynthetic pigments (chlorophyll a and b), total soluble proteins (TSP) and yield attributes (number of pods, seeds per plant, weight of ripened pods and 100-seeds weight), while, in contrast, water deficiency induced an increase in phenolics, proline, glycine betaine (GB), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), reducing and non-reducing sugars, total free amino acids, endogenous tocopherol levels, and activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, the foliar spray of α-Toc significantly improved shoot and root fresh and dry weights, shoot and root lengths, chlorophyll a and b contents, phenolics, proline, GB, reducing and non-reducing sugars, TSP, total free amino acids, endogenous tocopherol level, and activities of antioxidant enzymes (SOD, POD, and CAT), as well as yield parameters. On the other hand, it significantly decreased the MDA and H₂O₂ levels. Of all varying levels of α-Toc used, 100 mg L^?1 was most effective in causing enhanced accumulation of ascorbic acid (AsA), MDA, and cellular tocopherols particularly in cv. Cyclone 7008, while proline and catalase in cv. Cyclone 8009. Of both cultivars, Cyclone 7008 was superior to the other cultivar in proline, TSP, SOD, and POD enzymes, but cv. Cyclone 8009 being superior in shoot fresh weights, root fresh weight, shoot and root lengths, chlorophyll a and b, phenolics, H₂O₂, AsA, MDA, CAT, number of pods, seeds, weight of ripened pods, and weight of 100 seeds under dry land conditions. Overall, exogenously applied tocopherol improved yield and myriad of key physio-biochemical attribute in mungbean.     

The effect of zinc stress combined with high irradiance stress on membrane damage and antioxidative response in bean seedlings

Zinc (Zn) is a necessary element for plants, but excess Zn can be detrimental. The effect of Zn and high irradiance (HI) stress on the growth, lipid peroxidation (MDA), membrane permeability (EC), hydrogen peroxide (H₂O₂) accumulation, non-enzymatic antioxidants like proline accumulation and ascorbic acid (AsA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POX; polyphenol oxidase, PPO) of bean leaves were investigated under controlled growth conditions. The root length was not reduced at excess Zn level. Application of Zn significantly increased Zn concentration in the leaves of bean plants. Under Zn and HI stress, the Zn-deficient and Zn-excess conditions significantly increased the EC, MDA and H₂O₂ content of excised leaves of bean. The SOD activity was found to be increased significantly in both Zn-deficiency and Zn-excess leaves under Zn and HI stress. Under both Zn and HI stress conditions, the antioxidant enzyme activities; POX, PPO and the non-enzymatic antioxidants, AsA and proline accumulation were found to be significantly increased in the Zn-excess leaves which showed that the bean plant had the ability to tolerate the excess level of Zn and HI stress. A significant increase in MDA, H₂O₂, and EC with a simultaneous decrease in the antioxidant enzyme activities under Zn-deficiency compared to Zn-sufficient condition shows the inefficiency of the bean plant in response to Zn deficiency. To the best of our knowledge, this is the first report on the effect of Zn stress combined with HI stress in bean plant.     

Caffeic acid inhibits in vitro rooting in mung bean [Vigna radiata (L.) Wilczek] hypocotyls by inducing oxidative stress

Caffeic acid (CA), which is ubiquitously present in plants, is a potent phytotoxin affecting plant growth and physiology. The aim of our study was to investigate whether CA-induced inhibition of adventitious root formation (ARF) in mung bean {Vigna radiata (L.) Wilczek [Phaseolus aureus Roxb.]} involves the induction of conventional stress responses. The effect of CA (0–1000 μM) on ARF in mung bean was determined by measuring the generation of reactive oxygen species (ROS) in terms of malondialdehyde and hydrogen peroxide (H₂O₂) content, root oxidizability and changes in levels of antioxidant enzymes. Our results show that CA significantly enhanced MDA content, indicating severe lipid peroxidation, and increased H₂O₂ accumulation and root oxidizability in the lower rooted hypocotylar region (LRHR) of mung bean, thereby inducing oxidative stress and cellular damage. In response to CA, there was a significant upregulation in the activities of scavenging enzymes, such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, catalase and glutathione reductase, in LRHRs of mung bean. Based on these results, we conclude that CA inhibits ARF in mung bean hypocotyls by inducing ROS-generated oxidative stress and upregulating the activities of antioxidant enzymes.     

Silicon-mediated changes of some physiological and enzymatic parameters symptomatic for oxidative stress in spinach and tomato grown in sodic-B toxic soil

We investigated effect of silicon (Si) on the growth, uptake of sodium (Na), chloride (Cl), boron (B), stomatal resistance (SR), lipid peroxidation (MDA), membrane permeability (MP), lipoxygenase (LOX) activity, proline (PRO) accumulation, H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of spinach and tomato grown in sodic-B toxic soil. Si applied to the sodic-B toxic soil at 2.5 and 5.0 mM concentrations significantly increased the Si concentration in the plant species and counteracted the deleterious effects of high concentrations of Na, Cl and B on root and shoot growth by lowering the accumulation of these elements in the plants. Stomatal resistance, MP, MDA and the concentrations of H₂O₂ and PRO were higher in the plants grown in sodic-B toxic soil without Si: LOX activity of excised leaves of both species was increased by Si. Antioxidant activities of both species were significantly affected by Si, with the activities of SOD, CAT and APX decreased and AA increased by applied Si. For most of the parameters measured, it was found that 5 mM Si was more effective than the 2.5 mM Si. Based on the present work, it can be concluded that Si alleviates sodicity and B toxicity of the plants grown in sodic-B toxic soil by preventing both oxidative membrane damage and also translocation of Na, Cl and B from root to shoots and/or soil to plant, and lowering the phytotoxic effects of Na, Cl and B within plant tissues. It was concluded that tomato was more responsive to Si than spinach since it was more salt sensitive than spinach. To our knowledge, this is the first report that Si improves the combined salt and B tolerance of spinach and tomato grown in naturally sodic-B toxic soil, and which describes membrane-related parameters and antioxidant responses.     

Implications of paraquat and hydrogen peroxide-induced oxidative stress treatments on the GABA shunt pathway in Arabidopsis thaliana calmodulin mutants

Arabidopsis mutants with T-DNA insertion in seven calmodulin genes (CAM) were used to determine the specific role of CAM in the tolerance of plants to oxidative stress induced by paraquat and hydrogen peroxide (H₂O₂) treatments. Arabidopsis calmodulin mutants (cam) were screened for seedling growth, seed germination, induced oxidative damage, and levels of γ-aminobutyric acid (GABA) shunt metabolites. Only the cam5-4 and cam6-1 mutants exhibited an increased sensitivity to paraquat and H₂O₂ during seed germination and seedling growth. In response to treatments with 3 μM paraquat and 1 mM H₂O₂, only the cam5-4, cam6-1 mutants showed significant changes in malonaldehyde (MDA) levels in root and shoot tissues, with highly increased levels of MDA. In terms of the GABA shunt metabolites, GABA was significantly elevated in root and shoot tissues in response to the paraquat treatments in comparison to alanine and glutamate, while the levels of all shunt metabolites increased in root tissue but not in the shoot tissue following the H₂O₂ treatments. GABA, alanine and glutamate levels were significantly increased in root and shoot of the cam1, cam4, cam5-4, and cam6-1 mutants in response to paraquat (0.5, 1 and 3 μM), while they were increased only in the root tissue of the cam1, cam4, cam5-4, and cam6-1 mutants in response to H₂O₂ (200 and 500 μM, 1 mM). These data show that the cam5-4 and cam6-1 mutants were sensitive to the induced oxidative stress treatments in terms of seed germination, seedling growth, and oxidative damage. The accumulation of GABA shunt metabolites as a consequence of the induced oxidative stress treatments (paraquat and H₂O₂ treatments) suggests that the GABA shunt pathway and the accumulation of GABA metabolites may contribute in antioxidant machinery associated with reactive oxygen species and in the acquisition of tolerance in response to induced oxidative stress in Arabidopsis seedlings.     

Responses of antioxidant enzymes to cold and high light are not correlated to freezing tolerance in natural accessions of Arabidopsis thaliana

Low temperatures and high light cause imbalances in primary and secondary reactions of photosynthesis, and thus can result in oxidative stress. Plants employ a range of low‐molecular weight antioxidants and antioxidant enzymes to prevent oxidative damage, and antioxidant defence is considered an important component of stress tolerance. To figure out whether oxidative stress and antioxidant defence are key factors defining the different cold acclimation capacities of natural accessions of the model plant Arabidopsis thaliana, we investigated hydrogen peroxide (H₂O₂) production, antioxidant enzyme activity and lipid peroxidation during a time course of cold treatment and exposure to high light in four differentially cold‐tolerant natural accessions of Arabidopsis (C24, Nd, Rsch, Te) that span the European distribution range of the species. All accessions except Rsch (from Russia) had elevated H₂O₂ in the cold, indicating that production of reactive oxygen species is part of the cold response in Arabidopsis. Glutathione reductase activity increased in all but Rsch, while ascorbate peroxidase and superoxide dismutase were unchanged and catalase decreased in all but Rsch. Under high light, the Scandinavian accession Te had elevated levels of H₂O₂. Te appeared most sensitive to oxidative stress, having higher malondialdehyde (MDA) levels in the cold and under high light, while only high light caused elevated MDA in the other accessions. Although the most freezing‐tolerant, Te had the highest sensitivity to oxidative stress. No correlation was found between freezing tolerance and activity of antioxidant enzymes in the four accessions investigated, arguing against a key role for antioxidant defence in the differential cold acclimation capacities of Arabidopsis accessions.     

Effect of salinity and waterlogging on growth,anatomical and antioxidative responses in <Emphasis Type="Italic">Mentha aquatica</Emphasis> L.

Salinity and waterlogging are two stresses which in nature often occur simultaneously. In this work, effects of combined waterlogging and salinity stresses are studied on the anatomical alteration, changes of enzymatic antioxidant system and lipid peroxidation in Mentha aquatica L. plants. Seedlings were cultured in half-strength Hoagland medium 50 days after sowing, and were treated under combination of three waterlogging levels (well drained, moderately drained and waterlogging) and NaCl (0, 50, 100, 150 mM) for 30 days. Moderately drained and waterlogging conditions induced differently aerenchyma formation in roots of M. aquatica salt-treated and untreated plants. Moreover, stele diameter and endodermis layer were also affected by salt stress and waterlogging. Salt stress significantly decreased growth, relative water content (RWC), protein level, catalase (CAT) and polyphenol oxidase (PPO) activities, and increased proline content, MDA content, H₂O₂ level and activities of superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX). Waterlogging in salt-untreated plants increased significantly growth parameters, RWC, protein content, antioxidant enzyme activity, and decreased proline content, H₂O₂ and MDA levels. In salt-treated plant, waterlogging caused strong induction of antioxidant enzymes activities especially at severe stress condition. These results suggest M. aquatica is a waterlogging tolerant plant due to significant increase of antioxidant activity, membrane stability and growth under water stress. High antioxidant capacity under waterlogging can be a protective strategy against oxidative damage, and help to salt stress alleviation.     

Plant growth and responses of antioxidants of <Emphasis Type="Italic">Chenopodium album</Emphasis> to long-term NaCl and KCl stress

The effects of long-term NaCl and KCl treatment on plant growth and antioxidative responses were investigated in Chenopodium album, a salt-resistant species widely distributed in semi-arid and light-saline areas of Xinjiang, China. Growth parameters [plant height, branch number, leaf morphology and chlorophyll (Chl) content], the level of oxidative stress [superoxide anion radical (O₂ ⁻), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) concentrations], activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX)], the contents of non-enzymatic antioxidants [carotenoids (Car) and ascorbic acid (AsA)] and expression of selected genes were investigated. Plants were grown in the presence of 0, 50, and 300 mM NaCl or KCl for 2 months. Growth was stimulated by 50 mM NaCl or KCl, maintained stable at 300 mM NaCl, but was inhibited by 300 mM KCl. Three hundred mM NaCl did not affect O₂ ⁻, H₂O₂, MDA, Car and AsA, but increased the activities of SOD, CAT and POX compared to the controls. RT-PCR analysis suggested that expression of some genes encoding antioxidant enzymes could be induced during long-term salt stress, which was consistent with the enzyme activities. Treatment with 300 mM KCl was associated with elevated oxidative stress, and significantly decreased Car and AsA contents. These results suggest that an efficient antioxidant machinery is important for overcoming oxidative stress induced by treatment with high NaCl concentrations in C. album. Other strategies of ion regulation may also contribute to the differential tolerance to Na and K at higher concentrations.     

Acclimation of hydrogen peroxide enhances salt tolerance by activating defense-related proteins in Panax ginseng C.A. Meyer

The effect of exogenously applied hydrogen peroxide on salt stress tolerance was investigated in Panax ginseng. Pretreatment of ginseng seedlings with 100 μM H₂O₂ increased the physiological salt tolerance of the ginseng plant and was used as the optimum concentration to induce salt tolerance capacity. Treatment with exogenous H₂O₂ for 2 days significantly enhanced salt stress tolerance in ginseng seedlings by increasing the activities of ascorbate peroxidase, catalase and guaiacol peroxidase and by decreasing the concentrations of malondialdehyde (MDA) and endogenous H₂O₂ as well as the production rate of superoxide radical (O₂ ^?). There was a positive physiological effect on the growth and development of salt-stressed seedlings by exogenous H₂O₂ as measured by ginseng dry weight and both chlorophyll and carotenoid contents. Exogenous H₂O₂ induced changes in MDA, O₂ ^?, antioxidant enzymes and antioxidant compounds, which are responsible for increases in salt stress tolerance. Salt treatment caused drastic declines in ginseng growth and antioxidants levels; whereas, acclimation treatment with H₂O₂ allowed the ginseng seedlings to recover from salt stress by up-regulation of defense-related proteins such as antioxidant enzymes and antioxidant compounds.     

Paraquat pre-treatment increases activities of antioxidant enzymes and reduces lipid peroxidation in salt-stressed cucumber leaves

To investigate whether paraquat (PQ) is involved in regulation of antioxidant enzymes and lipid peroxidation under short-term salt stress, and to elucidate the physiological mechanism of salt stress mitigated by PQ, a cucumber cultivar (cv. Chunguang no. 2) was exposed to 100 mM NaCl for 48 h after pre-treatment with 10 μM PQ for 1 h. When compared to the control, salt stress increased the levels of malonaldehyde (MDA), superoxide radical (O₂^·−) and hydrogen peroxide (H₂O₂) and the activities of antioxidant enzymes, such as superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) in the cucumber leaves. Under salt conditions, PQ pre-treatment prevented oxidative stress as observed by the decreases in MDA, H₂O₂ and O₂^·− that correlated with the increase in antioxidant defenses. We propose that, at low concentrations, the PQ pre-treatment can reduce the salt-induced oxidative damage by increasing the antioxidative mechanisms in cucumber plants.     

Effects of putrescine on oxidative stress induced by hydrogen peroxide in Salvinia natans L.

Salvinia natans L. response to hydrogen peroxide (H₂O₂) induced oxidative stress through physiological activities was evaluated. The plants were incubated with varying concentrations (0, 50, 100 µM) of H₂O₂ and 100 µM of H₂O₂ supplemented with 1 mM putrescine (Put) in hydroponic culture. This is observed with the decline in proline content and its biosynthetic enzymes viz. γ-glutamyl kinase and γ-glutamyl phosphate reductase activity. Protein carbamylated derivative by protein oxidation was another trait for oxidative damages by H₂O₂. The antioxidative enzymes like guaiacol peroxidase (GPX), glutathione reductase (GR), and catalase (CAT) recorded to express through in-gel staining with the H₂O₂ exposure. On nuclear level, plants were sensitive to H₂O₂ where the DNA disintegration was studied with comet assay and maximum comet tail observed at 100 µM H₂O₂ treatment. Application of Put reduced the generation of protein oxidation and comet tail length as well as moderated the enzyme activity as revealed through in-gel staining.     

Epibrassinolide Application Regulates Some Key Physio-biochemical Attributes As Well As Oxidative Defense System in Maize Plants Grown Under Saline Stress

It was aimed to investigate the ameliorative effect of exogenously applied 24-epibrassinolide (EBR) on some key growth parameters and mineral elements in two salt-stressed maize (PR 32T83 and PR 34N24) cultivars. A factorial experiment was designed with two electrical permeability (EC) levels (1.1 and 8.0 dS/m) and two levels (1.5 and 2.0 µM) of EBR supplied as a seed treatment, foliar spray, or both in combination. The foliar application of EBR was done once a week during the experiment. After 42 days of these treatments, the plants were harvested to assess growth, water relations, and oxidative and antioxidative systems. Salt stress markedly reduced plant fresh and dry weights, maximum fluorescence yield of PS-II, chlorophyll contents, leaf water potential, and leaf K and Ca, but it increased membrane permeability, the activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), and catalase (CAT; EC. 1.11.1.6) enzymes, and the contents of proline and glycine betaine, leaf sap osmotic pressure, lipid peroxidation, hydrogen peroxide, and leaf Na and Cl. However, both seed treatment and foliar application of EBR to the maize plants exposed to saline conditions enhanced key growth attributes, water relations, and the activities of various antioxidant enzymes as well as the levels of proline, but they reduced electrolyte leakage, and H₂O₂ and MDA contents. Saline stress reduced leaf N, Ca²⁺, K⁺, and P contents as compared to those in the non-stressed plants. Both seed treatment and foliar application of EBR reduced Na⁺ and Cl^? concentrations, but increased those of N, Ca²⁺, K⁺, and P. Foliar application of EBR was more effective in increasing nutrient levels of plants grown at the high saline regime compared to the seed treatment of EBR. The study clearly indicates that both seed treatment and foliar application of EBR at the rate of 2.0 µM can overcome the detrimental effect of salinity stress on maize growth, which was found to be significantly linked to reduced concentrations of Na, Cl, MDA, and H₂O₂ as well as EL and increased activities of key antioxidant enzymes in the maize plants.     

Changes in photosynthesis and antioxidant defenses of Picea asperata seedlings to enhanced ultraviolet-B and to nitrogen supply

The paper mainly studied the effects of ultraviolet‐B (UV‐B) radiation, nitrogen, and their combination on photosynthesis and antioxidant defenses of Picea asperata seedlings. The experimental design included two levels of UV‐B treatments (ambient UV‐B, 11.02 KJ m⁻² day⁻¹; enhanced UV‐B, 14.33 KJ m⁻² day⁻¹) and two nitrogen levels (0; 20 g m⁻² a⁻¹ N) – to determine whether the adverse effects of UV‐B are eased by supplemental nitrogen. Enhanced UV‐B significantly inhibited plant growth, net photosynthetic rate (A), stomatal conductance to water vapor (Gs), transpiration rate and photosynthetic pigment, and increased intercellular CO₂ concentration, UV‐B absorbing compounds, proline content, malondialdehyde (MDA) content, and activity of antioxidant enzymes (peroxidase (POD), superoxide dimutase, and glutathione reductase). Enhanced UV‐B also reduced needle DW and increased hydrogen peroxide (H₂O₂) content and the rate of superoxide radical (O₂⁻) production only under supplemental nitrogen. On the other hand, supplemental nitrogen increased plant growth, A, Gs, chlorophyll content and activity of antioxidant enzymes (POD, ascorbate peroxidase, and catalase), and reduced MDA content, H₂O₂ content, and the rate of O₂⁻ production only under ambient UV‐B, whereas supplemental nitrogen reduced activity of antioxidant enzymes under enhanced UV‐B. Carotenoids content, proline content, and UV‐B absorbing compounds increased under supplemental nitrogen. Moreover, significant UV‐B × nitrogen interaction was found on plant height, basal diameter, A, chlorophyll a, activity of antioxidant enzymes, H₂O₂, MDA, and proline content. These results implied that supplemental nitrogen was favorable for photosynthesis and antioxidant defenses of P.asperata seedlings under ambient UV‐B. However, supplemental nitrogen made the plants more sensitive to enhanced UV‐B, although some antioxidant indexes increased.     

Salicylic acid,hydrogen peroxide and calcium-induced saline tolerance associated with endogenous hydrogen peroxide homeostasis in naked oat seedlings

This study investigates the role of salicylic acid (SA), hydrogen peroxide (H₂O₂) and calcium chloride (CaCl₂) singly or in combination, in inducing naked oat plant tolerance to sodium chloride (NaCl). Two-week-old naked oat plants were pretreated with both single and double of 0.5 mM SA, 0.5 mM H₂O₂ and 5 mM CaCl₂ by adding them to the culture solution for 24 h. At the end of the pretreatment, the plants were subjected to 200 mM NaCl exposure for 7 days. Data were collected on plant biomass, H₂O₂ level, antioxidant enzyme activity, non-enzymatic antioxidant content and malondialdehyde (MDA) content. Results showed that exposure to salt significantly inhibited plant growth, and the shoot and root dry weights were reduced 47.5% and 63.4%, and the H₂O₂ levels elevated 5.8 and 2.4 times in comparison with those in the control, respectively. Under the saline stress, the activities of superoxide dismutase (SOD) and catalase (CAT) were induced, but the contents of ascorbic acid (AA) and glutathione (GSH) decreased, and MDA largely accumulated. The various pretreatments efficiently counteracted the salt-caused growth inhibition, especially with H₂O₂ + CaCl₂ the shoot and root dry weights reduced only 9.4% and 24.4% of the non salt-stressed plants. The determination of endogenous H₂O₂ level demonstrated that the pretreatments induced H₂O₂ accumulation, with H₂O₂ + CaCl₂ being most efficient, but the effect was transient. After 7 days of saline stress, the H₂O₂ contents in the pretreated shoots and roots accounted for 23.7–41.8% and 31.7–57.3% of the non-pretreated plants, varying according to the different pretreatments. Under saline stress, SOD and CAT further increased, AA and GSH maintained higher levels and MDA decreased in the pretreated plants compared to the untreated plants. With application of diphenylene iodonium (DPI) during the pretreatment, which inhibited the accumulation of H₂O₂, the ameliorative effect of the pretreatment on salt-caused plant growth inhibition was reduced. However, applied DPI at the immediate end of the pretreatment did not alter its favorable role, indicating a H₂O₂ peak formed at the early time of saline stress might play an important role in regulating plant tolerance to saline stress.