Osmotic Tension Research Articles

Steps toward an integrated soil water tension and osmotic tension sensor

Steps toward an integrated soil water tension and osmotic tension sensor

Drought and Maize Breeding

Tension caused by a lack of water (water stress or drought stress) represents the continuous and continuous threat to the survival of the plant, as many of the plants in which phenotypic or physiological modification takes place may not be able to continue and remain in the environment in which they live due to the water stress on it or the low soil moisture content. This of course is related to the prevailing weather conditions (lack of rain, high temperature, increased wind speed, low relative humidity in the atmosphere … etc.), so dry soil is defined as the shortage of soil water needed to the extent that its readiness for the plant decreases (that is, the threshold at which the plant cannot absorb Or drain the water at a speed that meets its requirements for vital activities, and photosynthesis that meets the requirements of evapotranspiration does not occur. Conversely, water tightening may be the result of increased water. An example of stretching as a result of increased water is flooding, which results in suffocation resulting from Reduced concentration of oxygen-prepared oxygen to the roots, which in turn will impair breathing. In general, tension due to a lack of water is the most common, which led specialists to call it “water deficit stress.” Because water tension occurs in natural environments as a result of rain entrapping, Such conditions are known as drought conditions and therefore drought stress is terme In laboratory conditions, water stress conditions can be achieved through the loss of water by transpiration from the leaves, a circumstance that is due to what is termed as a desiccation stress. That is, in the sense that water stress is one of the components of salt tension and osmotic tension, and in order to unify these differences according to the concept of water tension, it termed the concept of low water potential.

Osmotic-Tension-Induced Membrane Lateral Organization.

Alteration of lipid raft organization manifesting as phase separation is important for cellular processes, such as signaling and trafficking. Such behaviors and dynamics of lipid membranes can be affected by external stimuli including both physical and chemical stimuli. In this study, we focused on osmotic-tension-induced phase separation. The effects of osmotic tension on the phase behaviors of vesicles consisting of dioleoylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol) were quantitatively studied at different temperatures by fluorescence microscopy. We determined the ternary phase diagrams and found that tension leads to a shift in the miscibility temperature. Cholesterol plays a key role in determining the extent of this shift. In addition, we found that osmotic tension can enhance the line tension. The physicochemical mechanism of osmotic-pressure-induced phase separation is discussed.

Osmotic Tension, Plasticization and Viscoelastic response of amorphous Poly-Ether-Ether-Ketone (PEEK) equilibrated in humid environments

Dynamic-Mechanical Analysis (DMA), Differential scanning Calorimetry (DSC) and water moisture sorption-desorption kinetics and equilibria have been parallely investigated to monitoring the environmental and thermal sensitivity of amorphous thermoplastic Poly-Ether-Ether-Ketone (PEEK). Morphological modification occurring in PEEK during the calorimetric and thermo-mechanical characterizations and the hygrothermal stability are presented. An interpretation based on the free energy of mixing of a polymer chains with penetrant molecules and pseudo-equilibrium Flory-Huggins interaction parameter χ and related osmotic tension is proposed. The correlation between dynamic mechanical measurements and water saturation is discussed in terms of different levels of osmotic tension generated in the amorphous PEEK. From the analysis of the water diffusion coefficients in amorphous PEEK equilibrated at low and high activity environments, it has been found that even samples with very low water contents may undergo bulk matrix relaxation above 40°C.

Deformation analysis of vesicles in an alternating-current electric field.

In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields.

Comparative study between probe focussed sonication and conventional stirring in the evaluation of cadmium and copper in plants

Ultrasound (US)-assisted extraction has been widely used for metal ion extraction in plants due to its unique properties of decreased extraction time, minimal contamination, low reagent consumption and low cost. However, very few papers present a sound comparison between probe-focussed sonication and conventional stirring in the evaluation of metal ion extraction in plants. In this study, ultrasonic-assisted digestion has been evaluated and compared to magnetic stirring for total copper and cadmium determination by atomic absorption spectrometry in biological samples (plants, plankton and mussels). The same experimental conditions of sample amount and particle size, extractant solution and extraction time were applied for both ultrasound and magnetic stirring-assisted extraction methods in order to truly compare their effect on metal ion solubilisation. To gain further insight in this issue, dried and fresh plants were tested. The results obtained indicated that osmotic tension in cell walls, produced when dried and powdered samples were immersed in the extractant solution, had an important contribution to metal ion solubilisation, the enhancement due to US for the same purpose being negligible.

Simulating in ovulo osmotic potentials and O2 tensions normalize growth and pigmentation of immature cotton embryos

Oxygen tensions and osmotic potentials are important physiological factors of plant growth and development. To optimize these variables for cotton (Gossypium hirsutum L.) embryo culture, we quantified dissolved O2 (dO2) tensions, osmotic potentials, and pH at several locations in cotton ovules during embryony. Clark O2 microelectrodes were micromanipulated into intact ovules at an angle lateral to the developing embryo, and dO2 tensions were determined in integuments, nucelli and embryos. Ovular osmotic potentials and pH were determined from extracted ovule sap using vapor pressure osmometers and pH microelectrodes. Dissolved O2 tensions near or in embryos decreased from 104 mmol m−3 at 5 days post-anthesis (DPA) to 83 mmol m−3 at 18 DPA. Osmotic potentials of ovule sap decreased from −0.70 megapascals (MPa) at 2 DPA to −1.12 MPa at 8 DPA but then increased to −0.84 MPa by 17 DPA. Ovule sap pH at 5–17 DPA varied inconsistently and ranged from 5.4 to 6.5. Based on these results, a factorial experiment with two osmotic and three O2 treatments was designed. Immature embryos of cotton cultivar HS-26 were randomly assigned to the treatment combinations and cultured for 33 days. Oxygen treatments did not affect embryo growth, and there were no differences among treatments with regard to percentage of embryos that progressed to a more advanced stage of embryo development. However, cotyledons of embryos grown without osmotic adjustment were abnormally large, and embryos exposed to these treatments were abnormally brown. Browning was less severe for embryos exposed to low O2 tensions. Growth and pigmentation were most normal for embryos simultaneously exposed to O2 tensions and osmotic potentials that best simulated the observed in ovulo conditions.

Combined device for measuring of osmotic pressure, conductance, surface tension, and viscosity

Micro and multipurpose analytical tools are in high demand for procuring physicochemical data. Thereby conductance and specific conductance (κ), surface tension (γ) and viscosity (η) of 0.066 to 0.333 mol/kg urea and methylurea, the osmotic pressure (π) for 0.1 to 1.0 mol/kg sucrose with 0.01 mmol/kg aqueous KCl solutions simultaneously were studied with oscosurvismeter. The solutions of different compositions were taken in cells, partitioned by nitrocellulose semipermeable membrane (SPM) for osmotic pressure. Survismeter, osmometer, electrodes, metallic clamp, SPM and high potential metallic springs are key parts of the oscosurvismeter. The conductance data were in close agreement with those of Horiba Conductivity Meter DS-8 M, surface tension data with that of face automatic surface tensiometer, CBVP-Z, Kyowa Interface Science Co. Ltd., viscosity data with survismeter, Spectro Analytical Pvt Ltd. The conductance and viscosities for methylurea are higher than those of the urea with comparatively stronger hydrophobic interaction of the -CH3 group of the methylurea. Statistical analysis of cost involved with oscosurvismeter was 99% less as compared with individual methods.

A facile pathway to fabricate microcapsules by in situ polyelectrolyte coacervation on poly(styrene sulfonate)-doped CaCO3particles

Complex hollow microcapsules were fabricated by adsorbing polyelectrolytes (PEs) onto CaCO3 particles doped with oppositely charged PEs, followed by dissolution of the CaCO3 particles with disodium ethylene diamine tetraacetate dihydrate (EDTA). The shells were formed in situ by complexation of the oppositely charged PEs they encountered during core removal. For this context, sodium poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) are exemplified as the doping and adsorbing PEs, respectively. Characterization by modern techniques confirms the hollow nature and integrity of the resulting microcapsules. The capsules expanded their size to 150% of their templates due to the osmotic tension and plastic deformation of the primary shells. A microcapsule with a diameter of 7.5 µm weighed 3.8 pg, in which 74 wt% was contributed by PSS and 26 wt% by PAH. This created a negatively charged surface of the microcapsule (−33 ± 8.3 mV). Calculation revealed further that 75% of the initially doped PSS was released. An osmotic induced invagination method detected an elasticity modulus of 140 MPa for the complex PAH–PSS shell, which is only half of the value (290 MPa) of the orderly assembled PAH–PSS multilayers. This new technique has the advantages of time-saving and materials-saving, and can be easily scaled-up.

Oscosurvismeter, A New Instrument for Osmotic Pressure, Conductance, Viscosity, and Surface Tension Measurements of Liquid Solutions of Chemical Substances

The Oscosurvismeter is made of borosil glass material for measuring osmotic pressure (π), specific conductance (κ), viscosity (η), and surface tension (γ) of solutions. Solutions of different strengths are taken in two cells/compartments, partitioned by a semi‐permeable membrane (SPM). A concentration gradient makes the solvent move towards the concentrated solution to establish an equilibrium; this measures osmotic pressure (π). The Oscosurvismeter saves time and materials, and enhances accuracy and precision in measurements; the instrument consists of six parts: (1) survismeter; (2) osmometer; (3) electrode; (4) metallic clamp; (5) semipermeable membrane (SPM); and (6) high potential metallic springs. High accuracy data are noted with the instrument.

Isolation and metabolite production by Penicillium roqueforti, P. paneum and P. crustosum isolated in Canada

Penicillium roqueforti, P. crustosum and P. paneum grow on ensiled grain and recycled feed unless properly treated. The former two species occur also on cut lumber in Canada. These are known to produce a number of secondary metabolites including roquefortine. In cooler dairy production areas, including Scandinavia and North America, cattle toxicosis has been associated with silage contaminated by these fungi. We collected strains associated with cow or cattle toxicoses. The principal metabolites were determined making use of a new extraction method and analysis combining HPLC, LC/MS/MS, and LC/NMR. Penicillium roqueforti and P. crustosum required amino acid nitrogen for metabolite formation and their toxins were formed under conditions of low oxygen (20-30% saturation). Production of roquefortine C occurred on depletion of the available nitrogen and penitrem A on depletion of carbon source. Yield was reduced by excess carbon. Medium osmotic tension (aw) affected metabolite production by the two species differently. Penicillium paneum was associated with ill-thrift of dairy cows and P. roqueforti was associated with more serious symptoms. Our data suggest a physiological basis for the common occurrence of roquefortine C in silage without serious consequences and the alternative, the presence of roquefortine C and toxicoses. The strain isolated from lumber was the best producer of the toxins studied. This is the first report of the toxigenic potential of P. roqueforti and P. paneum from Canada.

Reply to Comment on the “Osmotic Coefficients and Surface Tensions of Aqueous Electrolyte Solutions: Role of Dispersion Forces”

Reply to Comment on the “Osmotic Coefficients and Surface Tensions of Aqueous Electrolyte Solutions: Role of Dispersion Forces”

GABA Provides a Swell Route to Calcium

In addition to its role as neurotransmitter, γ-aminobutyric acid (GABA) mediates trophic effects during neuronal development. These long-term actions have been hypothesized to depend on Ca 2+ influx through voltage-dependent Ca 2+ channels, a consequence of activation of GABA A receptors (ligand-gated ion channels that are permeable to Cl − and HCO 3 − ), which can lead to depolarization in developing neurons. Chavas et al. loaded interneurons in cerebellar slices from juvenile rats with a calcium indicator and observed that application of the GABA agonist muscimol elicited a rise in [Ca 2+ ] i , which was greater in dendrites than in the cell body. The authors used cell-attached recordings in which they measured currents through single BK channels to simultaneously evaluate membrane potential and [Ca 2+ ] i , and they observed that a late phase of increased [Ca 2+ ] i did not correlate with membrane depolarization. Moreover, the [Ca 2+ ] i increase was not blocked by cadmium, and the threshold for calcium channel activation was higher than the peak depolarization in response to muscimol. Both changes in membrane potential and changes in [Ca 2+ ] i required HCO 3 − ; the late phase of increased [Ca 2+ ] i was inhibited by ryanodine. Dendrites expanded in size during muscimol application, and hypoosmotic solutions mimicked, whereas hyperosmotic solutions inhibited, the [Ca 2+ ] i response to muscimol. Thus, the authors proposed that the rise in [Ca 2+ ] i that occurs following GABA A receptor activation depends on increased osmotic tension following bicarbonate-dependent influx of Cl − . The sensitivity to ryanodine suggested that this might involve release of Ca 2+ from intracellular stores, linking ion flux through a ligand-gated channel to a metabotropic receptor-like response. J. Chavas, M. E. Forero, T. Collin, I. Llano, A. Marty, Osmotic tension as a possible link between GABA A receptor activation and intracellular calcium elevation. Neuron 44 , 701-713 (2004). [Online Journal]

Osmotic Tension as a Possible Link between GABAA Receptor Activation and Intracellular Calcium Elevation

Intracellular calcium concentration rises have been reported following activation of GABA(A) receptors in neonatal preparations and attributed to activation of voltage-dependent Ca(2+) channels. However, we show that, in cerebellar interneurons, GABA(A) agonists induce a somatodendritic Ca(2+) rise that persists at least until postnatal day 20 and is not mediated by depolarization-induced Ca(2+) entry. A local Ca(2+) elevation can likewise be elicited by repetitive stimulation of presynaptic GABAergic afferent fibers. We find that, following GABA(A) receptor activation, bicarbonate-induced Cl(-) entry leads to cell depolarization, Cl(-) accumulation, and osmotic tension. We propose that this tension induces the intracellular Ca(2+) rise as part of a regulatory volume decrease reaction. This mechanism introduces an unexpected link between activation of GABA(A) receptors and intracellular Ca(2+) elevation, which could contribute to activity-driven synaptic plasticity.

Solution Characteristics Affect Pollen Germination and Growth, and Pistil Viability: Implications for Developing Chemical Blossom Thinners for Apple

A strategy of chemical crop load control has been to use chemical desiccants to prevent fertilization and cause fruitlet drop. However, little is known of the solution characteristics that reduce pollen viability, inhibit pollen germination and growth, and cause pistil damage. This project was established to determine the solution characteristics effecting those results. Apple pollen was dispersed on germination media mixed with PEG (MW 10,000) to attain osmotic tensions from 0 to -5.0 MPa to evaluate effect on pollen germination and growth. Similarly, apple pollen was dispersed on germination adjusted to a range of pH from 2.3 to 12.0 with acids and NaOH. Excised apple pistils were place on filter paper supports saturated with solutions with osmotic tension adjusted by PEG in the range of 0 to -5.0 M Pa, and pH from 3.0 to 12.0. Solutions of osmotic tension in the range of 0 to -5.0 M Pa were applied by brush to intact pistils on apple flowers in a greenhouse and under field conditions. Pollen germination decreased with increasing osmotic tension and no pollen germinated at tensions greater than 4.0. Pistils, either excised or intact, had significant desiccation and death when treated with solution osmotic tensions greater than 4.0. Fruit set of individual spurs of the cvs Jonagold, Gala, and Arkansas Black were highly related to pistil survival 48 h after treatment with PEG. When solution osmotic potential exceeded 4.0, fruit set was reduced by more than 80%. Pollen germination was reduced by more than 50% at solution pH below or equal to 4.0 and greater than 10.0 and completely inhibited at solution pH below or equal to 3.0 and greater than 11.0. Similar results were observed for excised pistil and intact viability.

Osmotically Induced Membrane Tension Modulates Membrane Permeabilization by Class L Amphipathic Helical Peptides: Nucleation Model of Defect Formation

The mechanism of action of lytic peptides on membranes is widely studied and is important in view of potential medical applications. Previously (I. V. Polozov, A. I. Polozova, E. M. Tytler, G. M. Anantharamaiah, J. P. Segrest, G. A. Woolley, and R. M. Epand, 1997, Biochemistry, 36:9237–9245) we analyzed the mechanism of membrane permeabilization by 18L, the archetype lytic peptide featuring the class L amphipathic α-helix, according to the classification of Segrest et al. (J. P. Segrest, G. de Loof, J. G. Dohlman, C. G. Brouillette, and G. M. Anantharamaiah, 1990, Proteins, 8:103–117). We concluded that the 18L peptide destabilizes membranes, leading to a transient formation of large defects that result in contents leakage and, in the presence of bilayer-bilayer contact, could lead to vesicle fusion. Here we report that this defect formation is strongly enhanced by the membrane tension induced by osmotic swelling of vesicles. Even below standard leakage-inducing peptide/lipid ratios, membrane resistance to osmotic tension drops from hundreds to tens of milliosmoles. The actual decrease is dependent on the peptide/lipid ratio and on the type of lipid. We propose that under membrane tension a peptidic pore serves as a nucleation site for the transient formation of a lipidic pore. The tension is released upon pore expansion with inclusion of more peptides and lipids into the pore lining. This tension modulation of leakage was observed for other class L peptides (mastoparan, K18L) and thus may be of general applicability for the action of membrane active lytic peptides.

Impact of carbon starvation on stress resistance, survival in soil habitats and biocontrol ability of Pseudomonas putida strain 2C8

Exposure to carbon-limited growth conditions has been shown to induce resistance to a variety of environmental stresses in bacteria. Adaptation to nutrient-limited conditions by repeated culture on soil agar media was found to induce resistance to osmotic tension, oxidative stress and carbon limited culture conditions in Pseudomonas putida strain 2C8. Rifampicin resistant derivatives of strain 2C8 adapted to nutrient-limited conditions (strains 2C8-26A rif and 2C8-28C rif) did not exhibit enhanced survival in bulk soil relative to the parental strain. However, colonization of the apple rhizosphere by 2C8-26A rif and 2C8-28C rif was superior to that of the parental strain, 2C8 rif. Improved colonization of the apple rhizosphere was not the result of an elevated ability to utilize apple root exudates as a sole carbon source. Enhanced colonization of the rhizosphere by carbon starved derivatives of 2C8 rif was associated with improved biological control of Rhizoctonia root rot of apple caused by an introduced strain of Rhizoctonia solani AG 5. These findings demonstrate that inoculum production conditions can significantly alter the survival and efficacy of strain 2C8, and should be carefully considered in optimizing the use of this biocontrol rhizobacterium.

Infecção de sementes e anormalidade de plântulas de feijão, em função do condicionamento osmótico induzido por polietileno glicol-6000

Sementes de dez cultivares de feijão (Phaseolus vulgaris L.) foram submetidas a seis níveis de tensão osmótica (0, - 0,2, - 0,4, - 0,6, - 0,8 e - 1,0 MPa) induzidos por polietileno glicol-6000 (PEG-6000) com o objetivo de se estudar os seus efeitos sobre a percentagem de sementes infectadas e plântulas anormais, durante teste de germinação, identificando-se os genótipos mais tolerantes. O experimento foi conduzido em germinador com temperatura e umidade relativa controladas, utilizando-se como substrato o papel-toalha com pH neutro. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 10 x 6, com 4 repetições contendo, cada uma, cinqüenta sementes, para o teste de germinação. Segundo os resultados obtidos, a percentagem de sementes infectadas aumenta à medida que se elevam os níveis de concentração do PEG-6000. Na maior parte dos genótipos aumenta a anormalidade com a concentração de PEG-6000 até a faixa de pressão osmótica entre - 0,6MPa e - 0,8MPa, com exceção das cultivares 'Goytacazes' e 'Onix', em que foi sempre crescente com a concentração de PEG-6000. A cultivar 'Corrente' teve sempre os menores índices de anormalidade e de infecção, podendo ser classificada como a mais tolerante. As cultivares 'Novo Jalo', 'Jalo Precoce' e 'Goytacazes' foram as mais afetadas por infecção de sementes e anormalidade de plântulas.

The use of some ingredients for microemulsion preparation containing retinol and its esters

A study of microemulsions with retinol and its esters. Physical properties of w/o and o/w microemulsions containing Tween 60, Tween 80, Epicurone 135 (soy bean lecithin) as surfactants, n-butanol, triacetin, propylene glycol as cosurfactants were examined. The drug-containing systems were characterised in regard to their ophthalmic parameters. Physiologically well-tolerated and physically stable multiple-components were developed. The concentrations of surfactants and cosurfactants which are necessary to form stable systems were evaluated. The values of the following parameters — refractive index, viscosity, pH value, osmotic tension, obtained in the study, proved suitable for the purpose and the preparations were physiologically tolerated, the use of microemulsions as potential drug delivery systems for ocular administration has been discussed. The influence of retinol and its esters on the physical parameters the preparation was investigated. Microemulsion stored at 20°C up to 6 months showed no significant physical changes.

Differentiation between osmotic injury and chloride toxicity of rice seedlings grown under saline conditions1

Rice (Oryza sativa, L.) is most sensitive to salinity injury as a seedling. Information describing the effects of salinity on the seedling rice plant is limited. Therefore, the current study was conducted to determine if salinity injury to rice seedlings is the result of toxic levels of chloride, or if a change in osmotic potential interferes with the plant's ability to absorb water and nutrients. Rice was grown in controlled environmental conditions through the seedling growth stage. In hydroponic culture with a 50% Hoagland's solution, the rice was exposed to osmotic tensions of 0, 50, 100, 200, 400, 800, or 1,600 kPa imposed by either CaCl2 or polyethylene glycol (PEG). The rice was grown for 1 wk following imposition of the osmotic treatments. Visual ratings were then obtained and plants were harvested for dry matter determination and Cl‐ concentration. Shoot weights were lowered for PEG treatments compared to CaCl2. Root weights differed little between CaCl2 and PEG treatments. Root weights decreased with increasing osmotic tension whether decreased by CaCl2 or PEG. Salinity related damage to leaves and roots was worse for PEG than for CaCl2 treatments. Not surprisingly, uptake of Cl‐ tended to increase with increasing rates of CaCl2, but not with PEG. These data suggest that rice sensitivity to salinity is the result of changes in the osmotic potential gradient rather than to chloride toxicity.