Structural changes in acclimated and unacclimated leaves during freezing and thawing

2004 ◽  
Vol 31 (1) ◽  
pp. 29 ◽  
Author(s):  
Marilyn C. Ball ◽  
Martin J. Canny ◽  
Chen X. Huang ◽  
Roger D. Heady
Keyword(s):  
Low Temperatures ◽  
Structural Changes ◽  
Living Cells ◽  
Evolutionary Significance ◽  
Intercellular Spaces ◽  
Freezing And Thawing ◽  
Specific Expansion ◽  
Intracellular Ice ◽  
Leaf Tissues ◽  
Leaf Survival

Freeze-induced damage to leaf tissues was studied at different states of acclimation to low temperatures in snow gum, Eucalyptus pauciflora Sieber ex Sprengel. Intact, attached leaves of plants grown under glasshouse or field conditions were frozen at natural rates (frost-freezing) and thawed under laboratory conditions. Leaves were cryo-fixed unfrozen, during frost-freezing or after thawing for observation in a cryo-scanning electron microscope. Frost-freezing in unacclimated tissues caused irreversible tissue damage consistent with tissue death. Intracellular ice formed in the cambium and phloem, killing the cells and leaving persistent gaps between xylem and phloem. Many other cells were damaged by frost-freeze-induced dehydration and failed to resorb water from thawed extracellular ice, leaving substantial amounts of liquid water in intercellular spaces. In contrast, acclimated leaves showed reversible tissue displacements consistent with leaf survival. In these leaves during freezing, massive extracellular ice formed in specific expansion zones within the midvein. On thawing, water was resorbed by living cells, restoring the original tissue shapes. Possible evolutionary significance of these expansion zones is discussed. Acclimated leaves showed no evidence of intracellular freezing, nor tissue lesions caused by extracellular ice. While the observations accord with current views of freeze-sensitivity and tolerance, cryo-microscopy revealed diverse responses in different tissue types.

Histological aspects of the cryopreservation of potato

2008 ◽  
Vol 56 (3) ◽  
pp. 341-348
Author(s):  
P. Pepó ◽  
A. Kovács
Keyword(s):  
Cell Wall ◽  
Low Temperatures ◽  
Cell Walls ◽  
Cellular Level ◽  
Adaptive Mechanism ◽  
Epidermal Layer ◽  
Freezing And Thawing ◽  
Meristematic Cells ◽  
Suitable Solution ◽  
Vacuolated Cells

Cryopreservation appears to be a suitable solution for the maintenance of potato germplasms. The protocol described in this paper can be applied for the vitrification and preservation of meristems. During histo-cytological studies it is possible to observe modifications at the cellular level and to understand the adaptive mechanism to low temperatures. Control potato meristem tissue contained a number of meristematic cells with a gradient of differentiation. After freezing there were a large number of vacuolated cells, some of which exhibited broken cell walls and plasmolysis. The thickening of the cell wall, giving them a sinuous appearance, was observed after freezing and thawing the meristems, with ruptures of the cuticle and epidermal layer.

Model for the structural changes occurring at low temperatures inPdDx

1981 ◽  
Vol 24 (1) ◽  
pp. 277-282 ◽  
Author(s):  
O. Blaschko ◽  
P. Fratzl ◽  
R. Klemencic
Keyword(s):  
Low Temperatures ◽  
Structural Changes

Volumetric Changes in Cells During Freezing and Thawing

1980 ◽  
Vol 102 (2) ◽  
pp. 91-97 ◽  
Author(s):  
J. M. Knox ◽  
G. S. Schwartz ◽  
K. R. Diller
Keyword(s):  
Experimental Data ◽  
Image Analysis ◽  
Close Agreement ◽  
Living Cells ◽  
Freezing Process ◽  
Freezing And Thawing ◽  
Image Analysis Technique ◽  
Computerized Image Analysis ◽  
Analysis Technique ◽  
Thawing Process

A thermodynamic model is presented to describe the combined freezing and thawing process for living cells. Continuous changes in the cell volume are predicted according to the thermal protocol imposed on the system. Experimental verification of the model is sought by monitoring continuously the volume of cells as frozen on a cryomicroscope. The volumes of individual cells are measured from sequential photomicrographs by a computerized image analysis technique. The model and experimental data are in quite close agreement for the freezing process, but upon thawing the experimentally measured volumes consistently increased much more rapidly than predicted by the model. The model can be made to conform to the data by accounting for a substantial influx of electrolyte to the cell at subfreezing temperatures.

Nanoscale structure of amorphous solid water: What determines the porosity in ASW?

2019 ◽  
Vol 15 (S350) ◽  
pp. 368-369
Author(s):  
Sabrina Gärtner ◽  
Thomas F. Headen ◽  
Tristan G. A. Youngs ◽  
Catherine R. Hill ◽  
Natalia Pascual ◽  
...  
Keyword(s):  
Activation Energy ◽  
Pore Structure ◽  
Low Temperatures ◽  
Structural Changes ◽  
Amorphous Solid ◽  
Type Model ◽  
Star Forming ◽  
Star Forming Regions ◽  
Enhanced Mobility ◽  
Nanoscale Structure

AbstractThe pore structure of vapour deposited ASW is poorly understood, despite its importance to fundamental processes such as grain chemistry, cooling of star forming regions, and planet formation. We studied structural changes of vapour deposited D2O on intra-molecular to 30 nm length scales at temperatures ranging from 18 to 180 K and observed enhanced mobility from 100 to 150 K. An Arrhenius type model describes the loss of surface area and porosity with a common set of kinetic parameters. The low activation energy (428 K) is commensurate with van der Waals forces between nm-scale substructures in the ice. Our findings imply that water porosity will always change with time, even at low temperatures.

scholarly journals Changes in predatory behavior & efficiency: gastropod drilling patterns in Miocene-Pliocene Turritella (Gastropoda)

1992 ◽  
Vol 6 ◽  
pp. 117-117
Author(s):  
James W. Hagadorn ◽  
George E. Boyajian
Keyword(s):  
Time Scales ◽  
Shell Thickness ◽  
Structural Changes ◽  
Predatory Behavior ◽  
Metabolic Energy ◽  
Evolutionary Significance ◽  
Shell Shape ◽  
Visceral Mass ◽  
Predator Prey ◽  
Predatory Efficiency

The escalation of predator-prey interactions over the Phanerozoic is described as an “arms race” among the Gastropoda. Examples of escalation have been extensively documented on the scale of hundreds of millions of years, however, these patterns are not well documented on shorter time scales. Effective escalation of prey defenses should cause a drop in predatory efficiency. We study the efficiency of Naticid and Muricid predation upon Turritelline gastropods from the Miocene to the Pliocene. These predators leave a well preserved trace of predation in the form of a borehole in the shell of the prey. This study focuses on 18 species of Miocene and Pliocene Turritella from the southeastern United States. Over five thousand individual shells were examined and measured, collected from 13 localities from Maryland to southern Florida.Predatory efficiency is determined by a number of factors: shell thickness at drillhole site, vertical location of drillhole, percent of shells that have multiple drillholes, and percent of shells that contain incomplete drillholes. Shell thickness at drillhole and location of drillhole are measured because predators would benefit by expending less energy drilling into the thinnest part of the shell that is nearest the visceral mass of the prey. Multiple complete boreholes represent at least one failure to obtain food. Incomplete boreholes represent a drilling attempt which has failed to produce food at the cost of metabolic energy.While the intensity of Naticid and Muricid predation of Turritella increases (χ2, α<.01), predators become less efficient from the Miocene to the Pliocene. Decreased predatory efficiency is indicated by an increase in the number of shells with multiple and incomplete drilling sites (χ2, α<.01). Although predators appear to have little radial preference, they indicate strong vertical preference for centrally located drilling sites (t-test, α<.01). Predators appear to be drilling into thicker parts of Turritelline shells and thus expending more energy in drilling -however, this pattern is not statistically significant (χ2, α>.20).We show that the efficiency of Naticid and Muricid predators decreased from the Miocene to Pliocene. Decreased efficiency of predators might result from newly evolved structural changes in prey shells, new prey escape responses or problems in predator recognition of live versus dead prey shells resulting from high densities of both living and dead individuals.It remains to be seen whether predatory efficiency declines over longer time scales. In light of previous studies which have concentrated on evolution in the shell shape and ornamentation of prey in response to predators, a more promising and direct measure of the efficiency of predation may lie in the study of the frequency of multiple and incompletely drilled shells. By this method we might better judge the effectiveness of defense mechanisms and the evolutionary significance of predator-prey escalation.

scholarly journals Effects of Zn and Cd accumulation on structural and physiological characteristics of barley plants

2007 ◽  
Vol 19 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Balaji B. Maruthi Sridhar ◽  
Fengxiang X. Han ◽  
Susan V. Diehl ◽  
David L. Monts ◽  
Yi Su
Keyword(s):  
Structural Changes ◽  
Metal Accumulation ◽  
Morphological Changes ◽  
Dry Weight ◽  
Vascular Bundles ◽  
Fresh Weight ◽  
Intercellular Spaces ◽  
Cd Accumulation ◽  
Potted Plants ◽  
High Concentrations

The objectives of this study were to identify the structural changes caused by Zn and Cd accumulation in shoots and roots of barley (Hordeum vulgare) plants; and to correlate metal accumulation with anatomical, physiological and morphological changes. Potted plants were exposed to metal treatments of Zn and Cd for 19 and 16 d respectively. Leaves, stems and roots were harvested to identify structural changes and analyze metal accumulation. Barley effectively accumulated Zn (up to 11283 mg kg-1) and Cd (up to 584 mg kg-1) in the shoots. Microscopic structural changes, such as a decrease in intercellular spaces, breakdown of vascular bundles, and shrinkage of palisade and epidermal cells, occurred in leaves, stems and roots of plants treated with high concentrations of Zn. Zinc accumulation also resulted in a significant decrease in water content, fresh weight, dry weight and plant height. Cadmium only caused structural changes in roots at the higher concentrations. Barley plants were able to accumulate significant amounts of Zn and Cd without exhibiting symptoms of phytotoxicity when the metal concentrations were relatively low.

Cis-Trans Isomerization in Natural Polyisoprenes

1960 ◽  
Vol 33 (2) ◽  
pp. 445-456 ◽  
Author(s):  
J. I. Cunneen
Keyword(s):  
Sulfur Dioxide ◽  
Natural Rubber ◽  
Ultraviolet Light ◽  
Low Temperatures ◽  
Structural Changes ◽  
Trans Isomers ◽  
Gutta Percha ◽  
Trans Isomerization ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Abstract The cis and trans isomers of many simple olefins and conjugated polyolefins can be interconverted by the action of heat, light, and various catalysts, and in many such systems the changes in geometric configuration can be readily followed and the isomers separated and identified. Previous attempts to isomerize natural rubber and gutta-percha by treatment with ultraviolet light and various chemicals gave no detectable cis-trans isomerization, and in general configurational changes in unconjugated polyolefins have been unknown until recently when Golub converted the cis-1,4 units in polybutadiene into the corresponding trans units. This isomerization was achieved by irradiation of the cis-polymer with ultraviolet light in the presence of various organic bromides and sulfur compounds, but apparently this method did not isomerize natural rubber. In attempts to retard the rate of crystallization of natural rubber at moderately low temperatures—i.e., −10° to −40° C—by the attachment of side groups which would interfere with the molecular packing, it was observed that very small amounts of thiol acids were remarkably effective. This suggested that structural changes other than simply the attachment of side groups were occurring in the polyisoprene molecule. Recently it was found that thiol acids could interconvert the cis and trans forms of a simple trialkyl ethylene—e.g., 3-methylpent-2-ene—and subsequently, the isomerization of natural rubber and gutta-percha by these reagents was also observed. Following this, natural rubber, gutta-percha, squalene and cis and trans forms of 3-methylpent-2-ene have also been isomerized by treatment with sulfur dioxide and allied compounds; this work, including an investigation of the physical properties of the vulcanizates obtained from some of the isomerized polyisoprenes, is described in the present paper.

scholarly journals An Antiviral Compound That Blocks Structural Transitions of Poliovirus Prevents Receptor Binding at Low Temperatures

2000 ◽  
Vol 74 (8) ◽  
pp. 3929-3931 ◽  
Author(s):  
Alan W. Dove ◽  
Vincent R. Racaniello
Keyword(s):  
Receptor Binding ◽  
Low Temperatures ◽  
Structural Changes ◽  
Cellular Receptor ◽  
Structural Transitions ◽  
Wild Type ◽  
Antiviral Compound

ABSTRACT Drugs such as WIN51711 that inhibit picornavirus replication are thought to block poliovirus infectivity by binding to the capsid and preventing structural transitions required for uncoating. We examined the activity of WIN51711 at temperatures where capsid flexibility is thought to be decreased. Below 37°C, WIN51711 inhibits the binding of wild-type poliovirus to cells but does not affect the binding of a poliovirus mutant which is believed to undergo structural transitions more readily. These results suggest that the poliovirus capsid must undergo structural changes to bind to its cellular receptor.

Direct visualization of the isolated and perfused macula densa

1985 ◽  
Vol 248 (6) ◽  
pp. F890-F894 ◽  
Author(s):  
K. L. Kirk ◽  
P. D. Bell ◽  
D. W. Barfuss ◽  
M. Ribadeneira
Keyword(s):  
Structural Changes ◽  
Macula Densa ◽  
Thick Ascending Limb ◽  
Direct Visualization ◽  
Differential Interference Contrast Microscopy ◽  
Intercellular Spaces ◽  
Small Water ◽  
Nacl Concentration ◽  
Interference Contrast Microscopy ◽  
And Function

Direct examination of the structure and function of the macula densa is compromised by the relative inaccessibility and small size of this cell plaque. We report the isolation and perfusion of rabbit nephron segments with attached glomeruli and the direct visualization of the macula densa with differential interference-contrast microscopy. We used this technique to examine the structural sensitivity of the macula densa to perturbations in luminal osmolality and NaCl concentration. Reducing luminal osmolality from 290 to 70 mosmol/kg by removing NaCl resulted in a dilation of the lateral intercellular spaces that was both reversible and specific to the region of the macula densa. Associated with the dilation of the intercellular spaces was a small (congruent to 10%), but statistically significant, increase in the height of the macula densa cells. These structural events were related to the reduction in luminal osmolality, since isosmotic replacement of NaCl with mannitol resulted in no detectable structural changes. Thus, the macula densa may represent a small water-permeable plaque of cells within the remaining water-impermeable thick ascending limb of Henle's loop.

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