Effect of NaCl and isoosmotic polyethylene glycol stress on gas exchange in shoots of the C4 xerohalophyte Haloxylon aphyllum (Chenopodiaceae)

The effects of NaCl (200 mM) and osmotic stress generated by polyethylene glycol (PEG) on PSII maximal quantum efficiency, photosynthetic CO₂/H₂O gas exchange at two CO₂ concentrations, content of chlorophyll, proline, and malondialdehyde were investigated in shoots of C₄ xerohalophyte Haloxylon aphyllum (Chenopodiaceae). The PEG treatment induced a low water osmotic potential (?0.4 MPa) and inhibited photosynthesis (by a factor of 2) and transpiration (by a factor of 4). The NaCl treatment, at equal osmoticity conditions, reduced transpiration (by a factor of 2) and stimulated photosynthesis (by a factor of 2.5). Only the PEG-treated plants showed osmotic stress effects, which were demonstrated by an increase in proline and malondialdehyde contents in the shoot tissue. The data indicated that the halophilic character of this species was essential for maintaining the plant water status and photosynthesis under osmoticity induced by NaCl treatment. Herewith, the presence of C₄-type photosynthesis appeared to be just an auxiliary mechanism, because this xerohalophyte did not reveal the efficiency in water use typical for C₄ plants under osmotic stress, in the absence of a saline substrate.     

Increased cucumber salt tolerance by grafting on pumpkin rootstock and after application of calcium

Self-grafted and pumpkin rootstock-grafted cucumber plants were subjected to the following four treatments: 1) aerated nutrient solution alone (control), 2) nutrient solution with 10 mM Ca(NO₃)₂ (Ca), 3) nutrient solution with 90 mM NaCl (NaCl), and 4) nutrient solution with 90 mM NaCl + 10 mM Ca(NO₃)₂ (NaCl+Ca). The NaCl treatment decreased the plant dry mass and content of Ca²⁺ and K⁺ but increased the Na⁺ content in roots and shoots. Smaller changes were observed in pumpkin rootstock-grafted plants. Supplementary Ca(NO₃)₂ ameliorated the negative effects of NaCl on plant dry mass, relative growth rate (RGR), as well as Ca²⁺, K⁺, and Na⁺ content especially for pumpkin rootstock-grafted plants. Supplementary Ca(NO₃)₂ distinctly stimulated the plasma membrane (PM) H⁺-ATPase activity which supplies the energy to remove excess Na⁺ from the cells. The expressions of gene encoding PM H⁺-ATPases (PMA) and gene encoding a PM Na⁺/H⁺ antiporter (SOS1) were up-regulated when Ca(NO₃)₂ was applied. The pumpkin rootstock-grafted plants had higher PM H⁺-ATPase activity as well as higher PMA and SOS1 expressions than the self-grafted plants under NaCl + Ca treatment. Therefore, the addition of Ca²⁺ in combination with pumpkin rootstock grafting is a powerful way to increase cucumber salt tolerance.     

Salinity and Copper-Induced Oxidative Damage and Changes in the Antioxidative Defence Systems of Anabaena doliolum

Summary This study provides first-hand information on the salinity and copper-induced oxidative damage and its protection in Anabaena doliolum by the antioxidant defence system. Oxidative damage measured in terms of lipid peroxidation, electrolyte leakage and H₂O₂ production was induced by different concentrations of NaCl and Cu²⁺. A greater electrolyte leakage by NaCl than Cu²⁺ supported the hypothesis of salinity being more injurious than copper. To explore the survival strategies of A. doliolum under NaCl and Cu stress, enzymatic antioxidant activities e.g. superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) and nonenzymatic antioxidant contents such as glutathione reduced (GSH), ascorbate, α-tocopherol, and carotenoid were measured. A general induction in SOD and APX activities as well as ascorbate and α-tocopherol contents was found under NaCl and Cu²⁺ stress. In contrast to this, an appreciable decline in GR activity, GSH pool and carotenoid content under Cu²⁺ and an increase under NaCl stress were observed. CAT activity was completely inhibited at high doses of NaCl but stimulated following Cu²⁺ treatment. The above results suggest the involvement of APX and CAT in the scavenging of H₂O₂ under Cu²⁺ stress. In contrast to this, only APX was involved in H₂O₂ scavenging under salt stress. Our postulate of Cu²⁺-mediated antagonism of salt stress can be explained by a conceivable reversion of Na⁺-induced disturbance of cellular homeostasis by redox active Cu²⁺.     

Glucose-6-phosphate dehydrogenase-dependent hydrogen peroxide production is involved in the regulation of plasma membrane H+-ATPase and Na+/H+ antiporter protein in salt-stressed callus from Carex moorcroftii

Glucose‐6‐phosphate dehydrogenase (G6PDH) is important for the activation of plant resistance to environmental stresses, and ion homeostasis is the physiological foundation for living cells. In this study, we investigated G6PDH roles in modulating ion homeostasis under salt stress in Carex moorcroftii callus. G6PDH activity increased to its maximum in 100 mM NaCl treatment and decreased with further increased NaCl concentrations. K⁺/Na⁺ ratio in 100 mM NaCl treatment did not exhibit significant difference compared with the control; however, in 300 mM NaCl treatment, it decreased. Low‐concentration NaCl (100 mM) stimulated plasma membrane (PM) H⁺‐ATPase and NADPH oxidase activities as well as Na⁺/H⁺ antiporter protein expression, whereas high‐concentration NaCl (300 mM) decreased their activity and expression. When G6PDH activity and expression were reduced by glycerol treatments, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein level and K⁺/Na⁺ ratio dramatically decreased. Simultaneously, NaCl‐induced hydrogen peroxide (H₂O₂) accumulation was abolished. Exogenous application of H₂O₂ increased G6PDH, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein expression and K⁺/Na⁺ ratio in the control and glycerol treatments. Diphenylene iodonium (DPI), the NADPH oxidase inhibitor, which counteracted NaCl‐induced H₂O₂ accumulation, decreased G6PDH, PM H⁺‐ATPase and NADPH oxidase activities, Na⁺/H⁺ antiporter protein level and K⁺/Na⁺ ratio. Western blot result showed that G6PDH expression was stimulated by NaCl and H₂O₂, and blocked by DPI. Taken together, G6PDH is involved in H₂O₂ accumulation under salt stress. H₂O₂, as a signal, upregulated PM H⁺‐ATPase activity and Na⁺/H⁺ antiporter protein level, which subsequently resulted in the enhanced K⁺/Na⁺ ratio. G6PDH played a central role in the process.     

High-sensitivity sequence determination of proteins quantitatively recovered from sodium dodecyl sulfate gels using an improved electrodialysis procedure

An improved electrodialysis procedure has been developed to recover quantitatively proteins from sodium dodecyl sulfate (SDS)-polyacrylamide gels. The efficiency of the method has been demonstrated successfully on H-2K^k, β₂-microglobulin, complement factor D, and viral structural protein p27. The results indicate that yields exceeding 93% are obtainable, and that extended amino acid sequences of the eluted proteins in microgram quantities can be obtained in the presence of SDS without intrinsic and/or extrinsic labeling with radioisotopes.     

Effect of exogenous application of sugars on the salt tolerance of perennial ryegrass protoplasts

Various sugars were introduced by electroporation into perennial ryegrass protoplasts, and the involvement of intracellular functional groups of the sugars in salt tolerance was investigated. The protoplasts were prepared from the young leaves of perennial ryegrass, and those into which sugars were introduced were treated with NaCl solution (250 mM, pH 7.0) for 6 h at 10°C. The survival rate of the protoplasts increased when xylitol, cellobiose, 1-kestose, maltose, maltotriose, raffinose and trehalose were introduced, while no changes occurred when fructose, fucose, galactose, glucose, inositol, mannitol, mannose, rhamnose, sorbitol, sorbose, fructobiose, lactose and sucrose were introduced. Cellobiose, 1-kestose, maltose, maltotriose, raffinose and trehalose possess a number of equatorial OH (e-OH) groups that promote the structuration of H₂O. Xylitol, however, structures H₂O even though it does not possess the e-OH groups. Hence, it is suggested that under conditions of NaCl stress, structured H₂O protects the structure of cell membranes and the activity of enzymes, and that e-OH groups are involved in enhancing salt tolerance.     

Signal regulation of proline metabolism in callus of the halophyte Nitraria tangutorum Bobr. grown under salinity stress

Callus of the halophyte Nitraria tangutorum Bobr. was used to investigate proline metabolism and its signal regulation under salinity stress. Enhanced levels of proline and hydrogen peroxide (H₂O₂) were observed in calli exposed to salinity stress, and elevated levels of calcium (Ca) were detected in early responses to 75?mM NaCl treatment. Additionally, NaCl treatment induced significant elevation of ornithine-??-aminotransferase (OAT) activity, but notable decreases occurred in the activities of glutamyl kinase (GK) and proline dehydrogenase (PDH). H₂O₂ scavenger dimethylthiourea and pyruvate inhibited the accumulation of proline and the stimulation of OAT in salinity-stressed calli. Moreover, the utilization of Ca chelator EGTA and Ca channel blocker verapamil abolished the enhancement of proline level induced by 75?mM NaCl treatment for 3?days. These results suggest that the accumulation of proline is correlated to the increase of OAT activity and the decrease of PDH activity in response to salinity, and that elevated Ca signal during the early stage of NaCl treatment and the excitation of OAT activity resulting from the increase of H₂O₂ generation are essential for proline accumulation in salinity-stressed calli.     

Purification,characterization, and coal depolymerizing activity of lignin peroxidase from <Emphasis Type="Italic">Gloeophyllum sepiarium</Emphasis> MTCC-1170

Lignin peroxidase from the liquid culture filtrate of Gloeophyllum sepiarium MTCC-1170 has been purified to homogeneity. The molecular weight of the purified enzyme was 42 kDa as determined by SDS-PAGE. The K _m values were 54 and 76 μM for veratryl alcohol and H₂O₂, respectively. The pH and temperature optima were 2.5 and 25°C, respectively. Depolymerization of coal by the fungal strain has been demonstrated using humic acid as a model of coal. Depolymerization of humic acid by the purified lignin peroxidase has been shown by the decrease in absorbance at 450 nm and increase in absorbance at 360 nm in presence of H₂O₂. Depolymerization of humic acid by the purified enzyme has also been demonstrated by the decrease in the viscosity with time of the reaction solution containing humic acid, H₂O₂, and the purified lignin peroxidase. The influence of NaCl and NaN₃ and inhibitory effects of various metal chelating agents on the lignin peroxidase activity were studied.     

Salinity-induced subcellular accumulation of H2O2 in leaves of rice

The localization of salt-induced H₂O₂ accumulation in the leaves of rice was examined using 3,3-diaminobenzidine and CeCl₃ staining at ultrastructure level. When the 3-week-old rice plants were affected by 100 mM NaCl for 14 days, the swelling of thylakoids and the destruction of thylakoid membranes were observed. H₂O₂ accumulation was also observed in the chloroplast of the leaf treated with NaCl. The electron dense products of 3,3-diaminobenzidine and CeCl₃ were mainly observed especially around the swelling of thylakoids. H₂O₂ accumulation and any ultrastructural changes were not observed in the chloroplasts under dark condition. Furthermore, treatment with ascorbic acid suppressed both H₂O₂ accumulation and the changes in chloroplast ultrastructure. These results suggest that light-induced production of excess H₂O₂ under salinity is responsible for the changes in chloroplast ultrastructure. H₂O₂ accumulation was also observed in the mitochondria, peroxisomes, plasma membrane, and cell walls under light but not dark, suggesting that these organelles are also the source of H₂O₂ and the production is light dependent under salinity.     

Nitrogen deprivation induces cross-tolerance of Poa annua callus to salt stress

Alternative respiration pathway (AP) is an important pathway which can be induced by environment stresses in plants. In the present study, we show a new mechanism involving the AP in nitrogen deprivation-induced tolerance of Poa annua callus to salt stress. The AP capacity markedly increased under a 600 mM NaCl treatment or nitrogen deprivation pretreatment and reached a maximum under the nitrogen deprivation pretreatment combined with the NaCl treatment (–N+NaCl). Malondialdehyde (MDA) and H₂O₂ content and Na⁺/K⁺ ratio significantly increased under the 600 mM NaCl treatment but less under the–N+NaCl treatment. Moreover, both the nitrogen deprivation and the NaCl stress stimulated the plasma membrane (PM) H⁺-ATPase activity and increased pyruvate content. The maximal stimulating effect was found under the–N+NaCl treatment. When the AP capacity was reduced by salicylhydroxamic acid (SHAM, an inhibitor of AP), content of MDA and H₂O₂ and Na⁺/K⁺ ratio dramatically increased, whereas PM H⁺-ATPase activity decreased. Moreover, exogenous application of pyruvate produced a similar effect as the nitrogen deprivation pretreatment. The effects of SHAM on the Poa annua callus were counteracted by catalase (a H₂O₂ scavenger) and diphenylene iodonium (a plasma membrane NADPH oxidase inhibitor). Taken together, our results suggest that the nitrogen deprivation enhanced the capacity of AP by increasing pyruvate content, which in turn prevented the Poa annua callus from salt-induced oxidative damages and Na⁺ over-uptake.     

Phosphate Solubility and the Cyanate-Mediated Synthesis of Pyrophosphate

The justification for a less alkaline primordial ocean (than present) is briefly reviewed, along with constraints on aqueous phosphate under such conditions. Based on the assumption that CaHPO₄ dihydrate determined the availability of phosphorus species, we have carried out laboratory simulations to determine equilibrium concentrations as a function of pH (in PIPES buffer) with added NaCl and CaCl₂. Consistent with expectations, solubility declines with higher pH and [CaCl₂], but increases only slightly with [NaCl]. Significantly, PIPES shows no specific effect on the dissolution beyond its influence on pH and ionic strength. Data are also presented on the synthesis of pyrophosphate from the NaOCN/CaHPO₄·2H₂O system, which could have provided a source of this phosphate anhydride on the early Earth.     

Hybrid Composite Coatings for Durable and Efficient Solar Hydrogen Generation under Diverse Operating Conditions

Safe and practical solar‐driven hydrogen generators must be capable of efficient and stable operation under diurnal cycling with full separation of gaseous H₂ and O₂ products. In this study, a novel architecture that fulfills all of these requirements is presented. The approach is inherently scalable and provides versatility for operation under diverse electrolyte and lighting conditions. The concept is validated using a 1 cm² triple‐junction photovoltaic cell with its illuminated photocathode protected by a composite coating comprising an organic encapsulant with an embedded catalytic support. The device is compatible with operation under conditions ranging from 1 m H₂SO₄ to 1 m KOH, enabling flexibility in selection of semiconductor, electrolyte, membrane, and catalyst. Stable operation at a solar‐to‐hydrogen conversion efficiency of >10% is demonstrated under continuous operation, as well as under diurnal light cycling for at least 4 d, with simulated sunlight. Operational characteristics are validated by extended time outdoor testing. A membrane ensures products are separated, with nonexplosive gas streams generated for both alkaline and acidic systems. Analysis of operational characteristics under different lighting conditions is enabled by comparison of a device model to experimental data.     

Transition temperature and enthalpy change dependence on stabilizing and destabilizing ions in the helix–coil transition in native tendon collagen

The transition temperatures t_t and enthalpy changes ΔH in the helix–coil transition of solid tendon collagen soaked in a solution containing one of the following stabilizing or destabilizing agents, HCHO, NaF, NaCl, NaI, NaBr, NaOH, NH₂CONH₂, CaCl₂, MgCl₂, were measured as a function of molar concentration by a calorimetric method. The temperature and the enthalpy changes accompanying the transition behaved in a similar manner: when the t_t was depressed by the presence of ions, similar behaviour was observed in ΔH. Both parameters (t_t and ΔH) increased for HCHO, and decreased for NaF and NaCl at concentrations lower than 0.2 M. Above 0.2 M they increased for NaF and NaCl, and decreased in the presence of the other reagents listed above. The average t_t and the ΔH observed in collagen soaked in water were 63.5°C and 12.3 cal/g, respectively. In addition to the parameters mentioned above, the molar effectiveness of the various reagents was obtained for the cases where there was a linear relationship between the t_t and molar concentration of the reagent in the solution. Since both the t_t and the ΔH were observed to vary, the entropy change (ΔS) accompanying the transition was calculated using thermodynamic relations. In order to explain the ΔS observed as a function of ionic concentration, the thermodynamic relationships have been obtained from a partition function under suitable assumptions. Since the partition function is dependent on the number of hydrogen bonds responsible for collagen stability, the result obtained has been compared with the values predicted by the two most quoted models for collagen. The present study is in accordance with the Ramachandran model for collagen structure, which predicts more than one hydrogen bond per three residues.     

Biological removal of H2S from the livestock manure using a biofilter

In this paper, the biological removal of H₂S from air had been investigated using a self-made biofilter with efficient bioceramics and a polyhedral hollow ball. The biological removal efficiency of H₂S had been analyzed at different experimental conditions, such as inlet H₂S concentration, residence time, initial pH value, and reaction temperature etc. The results showed that the initial pH value had a slight effect on H₂S removal efficiency from pH 3 to 9. The optimal initial pH value was 5.5, while the H₂S removal efficiency was 100%. The H₂S removal efficiency increased with increases in the nutrient solution spraying rate. The appropriate temperature was 25°C in the temperature range from 15 to 30°C. The H₂S removal efficiency dropped with the increase of air input and inlet H₂S concentration. After being isolated and screened, six strains of heterotrophic sulfide oxidizing bacteria and one strain autotrophic sulfide oxidizing bacteria were determined to be involved in the removal of H₂S within the biofilter. The reaction kinetics of H₂S was in accordance with first order reaction kinetics.     

Response of Barley Seedlings to UV-B Radiation as Affected by Proline and NaCl

Barley (Hordeum vulgare L. cv. Alfa) seedlings were treated for 4 d before UV-B irradiation with 0.05 mM proline or 150 mM NaCl. UV-B exposure induced synthesis of yellow coloured compounds with maximum absorbance at 438 nm. The content of these compounds was increased in proline-treated and decreased in NaCl-treated plants. UV-B radiation reduced chlorophyll/carotenoids ratio, oxygen evolution rate and photochemical efficiency of PS 2 as estimated by chlorophyll fluorescence and increased proline accumulation, H₂O₂ generation and lipid peroxidation. Exogenous proline had no effect on the parameters studied and did not change the response of plants to UV-B radiation. NaCl inhibited photochemical efficiency of PS 2, reduced oxygen evolution and increased H₂O₂ concentration and lipid peroxidation. The combination of NaCl and proline treatment led to lowering the inhibitory effect of NaCl in non UV-B irradiated seedlings. There was not relationship between the level of UV-B-induced compounds and UV-B tolerance of barley seedlings.     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

Valinomycin inhibited methane synthesis in Methanobacteriumthermoautotrophicum

$\text{Methanobacterium}\text{thermoautotrophicum}$ cells, incubated anaerobically under H₂ in 0.1 M KCl or 0.1 M NaCl, above pH 7.5, are interior acid with respect to the incubation medium. The pH gradient thus established can be discharged by either carbonyl cyanide m-chlorophenylhydrazone or valinomycin at high concentration (17μM). In these cells, which actively synthesize CH₄ from CO₂ and H₂, methanogenesis is strongly inhibited when the pH gradient is discharged.     

Changes in the antioxidative systems of Ocimum basilicum L. (cv. Fine) under different sodium salts

The effects of different sodium salts on some physiological parameters and antioxidant responses were investigated in a medicinal and aromatic plant, Ocimum basilicum L. (cultivar Fine). Plants were subjected to an equimolar concentration of Na₂SO₄ (25?mM) and NaCl (50?mM) for 15 and 30?days. Growth, oxidative stress parameters [electrolyte leakage, peroxidation, and hydrogen peroxide (H₂O₂) concentration], antioxidant enzyme activities [ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), and peroxidases (POD, EC 1.11.1.7)], as well as antioxidant molecules [ascorbate and glutathione] were determined. The two salts affected leaf growth rates to the same extent, after 15 or 30?days of treatment, indicating a similar effect of Na₂SO₄ and NaCl salinity on growth, even if different (enzymatic and non-enzymatic) antioxidant mechanisms were involved in H₂O₂ detoxification. However, under both salts, the efficiency of the antioxidant metabolism seemed to be sufficient to avoid the deleterious effects of reactive oxygen species (ROS). Indeed, both ion leakage and peroxidation did not change under either Na₂SO₄ or NaCl salinity. As a whole, these data suggest that a cooperative process between the antioxidant systems is important for the tolerance of Ocimum basilicum L., cv. Fine to Na₂SO₄ and NaCl salinity.     

DNA Quadruplexes Assembled by Simple Peptide: Effects of DNA Homology and Peptide Removal

Abstract

Formation of heterologous (calf thymus dsDNA) and homologous (linearized pBR322 plasmid dsDNA) quadruplexes upon binding with the simple aliphatic tripeptide derivative (L- Val)₃?N₂H₂?DNS CF₃COOH—;DHTV) was examined by fluorimetry, flow linear (LD), circular dichroism (CD), and electron microscopy (EM). The morphology of the rod-like compact particles formed due to the association of dsDNA segments proved to be the same for both DNAs, whereas the stability of the compact DNA structure upon tripeptide removal from the complex with DNA differed substantially for homologous versus non-homologous dsDNA used. The increase in NaCl concentration in the solution up to 30 mM removes the peptide from both types of the complexes completely. At the same time at 20 mM NaCl calf thymus DNA quadruplexes readily dissociate, whereas the structures formed by plasmid DNA retain their morphology in the solution containing NaCl with concentrations up to 40 mM and are only partially disrupted at even higher NaCl concentration. These results provide an analogy between trivaline-DNA model complexes and RecA-DNA binding.