Lateral Stresses in Membranes at Low Water Potential

1987 ◽  
Vol 14 (3) ◽  
pp. 311 ◽  
Author(s):  
J Wolfe
Keyword(s):  
Osmotic Stress ◽  
Water Potential ◽  
Cell Membranes ◽  
Cellular Damage ◽  
Biological Cells ◽  
Severe Dehydration ◽  
Stress Strain ◽  
Stress Measurements ◽  
Different Levels ◽  
Water Contents

Severe dehydration of biological cells can produce large stresses and substantial strains in the membranes of some organelles. Water contents and water potentials which are critical for cellular damage in rather dry tissues may reflect a limiting stress characteristic of cell membranes. Different levels of tolerance of extreme dehydration may therefore be a result of different cellular osmotic pressures or of different stress-strain characteristics of the cellular membranes. In this paper, data from phospholipid osmotic stress measurements are used to model the stresses generated in membranes in dehydrated phases.

scholarly journals The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

2021 ◽  
Vol 13 (4) ◽  
pp. 1759
Author(s):  
Said A. Hamido ◽  
Kelly T. Morgan
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Salinity ◽  
Planting Density ◽  
Stem Water Potential ◽  
Irrigation Rate ◽  
Biological Stress ◽  
Stem Water ◽  
Water Contents ◽  
Soil Water Contents

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

scholarly journals Selection of drought tolerant wheat genotypes by osmotic stress imposed at germination and early seedling stage

2018 ◽  
Vol 15 (2) ◽  
pp. 177-192
Author(s):  
RR Saha ◽  
A Hannan ◽  
A Nessa ◽  
MA Malek ◽  
MR Islam
Keyword(s):  
Osmotic Stress ◽  
Dry Weight ◽  
Seedling Stage ◽  
Metabolic Efficiency ◽  
Wheat Genotypes ◽  
Shoot Dry Weight ◽  
Vigour Index ◽  
Peg Treatment ◽  
Early Seedling ◽  
Different Levels

An experiment on hundred wheat genotypes under different levels of osmotic stress was carried out during 2014 to select the genotype(s) tolerant to drought at germination and early seedling stage. Different levels of osmotic stress were imposed by using polyethylene glycol (PEG). Three osmotic stress levels viz. control (distilled water), 15% PEG solution and 25% PEG solution were used. Among the 100 genotypes the rate of germination percentage, final germination (%), root and shoot dry weight, amount of respiration and vigour index under PEG treatment was found significantly lower than that of control condition. Compared to control condition relative decrease in rate of germination, final germination, amount of respiration and vigour index among the wheat genotypes were found more at 25% PEG than that of 15% PEG treatment. However, the seed metabolic efficiency was significantly higher in wheat genotypes under both 15% PEG and 25% PEG treatment compared to the control condition. A significant positive correlation exists between the important growth parameters like rate of germination (%), final germination (%), shoot dry weight, root dry weight and vigour index. On the basis of these physiological traits against osmotic stress, nine genotypes of wheat such as BD-480, BD-498, BD- 501, BD-513, BD-514, BD-519, BD-592, BD-618 and BD- 633 were selected as drought tolerant.SAARC J. Agri., 15(2): 177-192 (2017)

Osmotic stress measurements of dihexadecyldimethylammonium acetate bilayers as a function of temperature and added salt

Langmuir ◽  
1993 ◽  
Vol 9 (1) ◽  
pp. 233-241 ◽  
Author(s):  
Yi Hua Tsao ◽  
D. Fennell Evans ◽  
R. P. Rand ◽  
V. A. Parsegian
Keyword(s):  
Osmotic Stress ◽  
Stress Measurements ◽  
Added Salt

Effects of Slowly and Rapidly Permeating Osmotica on Permeability of Excised Roots of Zea mays

1974 ◽  
Vol 1 (2) ◽  
pp. 247 ◽  
Author(s):  
H Greenway
Keyword(s):  
Zea Mays ◽  
Ethylene Glycol ◽  
Water Potential ◽  
Free Space ◽  
Cell Membranes ◽  
Cellular Activity ◽  
Root Tissues ◽  
Three Phases

Excised roots of Z. mays were treated at a water potential of – 20.8 atm, using slowly and rapidly permeating solutes both as osmotica (800 mM ) and as permeants (10 mM ) . The temperature during all experiments was 2�C. The solutes were mannitol, glycerol, and ethylene glycol. In highly vacuolated root tissues there were at least three phases for the influx and efflux of the permeants. These phases presumably represented the free space, the 'cytoplasm', and the 'vacuoIe'. Treatment with slowly permeating osmotica increased the free space of both highly and slightly vacuolated tissues. In highly vacuolated tissues all osmotica doubled the rate of exchange for the 'cytoplasm', but had very little effect on the rate of exchange for the 'vacuole'. The latter observation suggests that the permeability of the tonoplast changed little during plasmolysis. In contrast to highly vacuolated tissues, exposure of slightly vacuolated tissue to osmotica decreased the rates of exchange of the permeant mannitol. Removal of slowly permeating osmotica dramatically increased the permeability of highly vacuolated tissues. Moreover, permeability to rapidly permeating ethylene glycol increased much less than permeability to slowly permeating mannitol and glycerol. These observations suggest that deplasmolysis changed the structure of cell membranes. Permeability of slightly vacuolated tissues was not greatly increased by removal of osmotica. These different effects on the permeability of highly and slightly vacuolated tissues are consistent with earlier results, which showed that removal of slowly permeating osmotica restored metabolism of slightly vacuolated tissues, while it strongly depressed cellular activity of highly vacuolated tissues.

Internal Water Balance of Brigalow (Acacia harpophylla F. Muell.) Under Natural Conditions

1975 ◽  
Vol 2 (4) ◽  
pp. 489 ◽  
Author(s):  
BR Tunstall ◽  
DJ Connor
Keyword(s):  
Water Potential ◽  
Water Status ◽  
Carbon Uptake ◽  
Diurnal Changes ◽  
Plant Water ◽  
Litter Fall ◽  
Tissue Water ◽  
Diffusive Resistance ◽  
Plant Water Potential ◽  
Water Contents

On one day each month over a period of 2½ years, diurnal measurements of plant water status, leaf diffusive resistance, carbon uptake, irradiance, ambient temperature and humidity were made in a brigalow community. Diurnal changes in leaf diffusive resistance, osmotic potential, plant water potential, and carbon uptake are shown to follow general patterns and the changes in plant water potential were related to the dawn value of plant water potential. The data suggest the development of negative turgor in brigalow and demonstrate the capacity of the plant to maintain high tissue water contents at low water potentials. Measurements of shoot extension and litter fall showed that litter fall occurred principally following shoot extension.

scholarly journals Volumetric Stress-Strain Analysis of Optohydrodynamically Suspended Biological Cells

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Sean S. Kohles ◽  
Yu Liang ◽  
Asit K. Saha
Keyword(s):  
Single Cells ◽  
Strain Analysis ◽  
Optical Tweezer ◽  
Three Dimensions ◽  
Shear Stresses ◽  
Strain Response ◽  
Biological Cells ◽  
Two Dimensional ◽  
Stress Strain ◽  
Volumetric Stress

Ongoing investigations are exploring the biomechanical properties of isolated and suspended biological cells in pursuit of understanding single-cell mechanobiology. An optical tweezer with minimal applied laser power has positioned biologic cells at the geometric center of a microfluidic cross-junction, creating a novel optohydrodynamic trap. The resulting fluid flow environment facilitates unique multiaxial loading of single cells with site-specific normal and shear stresses resulting in a physical albeit extensional state. A recent two-dimensional analysis has explored the cytoskeletal strain response due to these fluid-induced stresses [Wilson and Kohles, 2010, “Two-Dimensional Modeling of Nanomechanical Stresses-Strains in Healthy and Diseased Single-Cells During Microfluidic Manipulation,” J Nanotechnol Eng Med, 1(2), p. 021005]. Results described a microfluidic environment having controlled nanometer and piconewton resolution. In this present study, computational fluid dynamics combined with multiphysics modeling has further characterized the applied fluid stress environment and the solid cellular strain response in three dimensions to accompany experimental cell stimulation. A volumetric stress-strain analysis was applied to representative living cell biomechanical data. The presented normal and shear stress surface maps will guide future microfluidic experiments as well as provide a framework for characterizing cytoskeletal structure influencing the stress to strain response.

Application of SMA Wire for an Active Steerable Cannula

2013 ◽  
Author(s):  
Bardia Konh ◽  
Mohammad Honarvar ◽  
Parsaoran Hutapea
Keyword(s):  
Solution Procedure ◽  
Design Parameters ◽  
Fe Model ◽  
Stress Strain ◽  
Thermomechanical Characteristics ◽  
Nitinol Wire ◽  
Series Of Experiments ◽  
The One ◽  
Different Levels ◽  
Steerable Cannula

In this article we present the feasibility of using the shape memory alloy (SMA) wires, namely Nitinol, as an actuator for a steerable surgical cannula. A 3D finite element (FE) model of the actuated steerable cannula was then developed in ANSYS to show deflection of the surgical cannula under the actuation force. The behavior of SMAs was simulated by defining the isothermal stress-strain curves using the multi-elasticity capability of ANSYS. The transformation temperatures of the Nitinol wire at different levels of stress were gathered to form the transformation diagram. Using the one-dimensional Brinson model, the isothermal stress-strain response of the wire was obtained. The thermomechanical characteristics of SMAs were also studied completely by a series of experiments performed on the wires. Birth and death method was used in the solution procedure to have the prestrain condition on Nitinol wire prior to the actuation step. A prototype of the actuated steerable cannula was also developed to validate the numerical simulation. Finally a study was done on design parameters affecting the deflection such as Young’s modulus of cannula, SMA diameter and its offset from the neutral axis of the cannula which can be useful in design optimization.

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