Biomedical subjects
D Siminovitch
Publications and source records attributed to D Siminovitch.
Drought and freezing tolerance and adaptation in plants: some evidence of near equivalences.
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Twenty-four-hour induction of freezing and drought tolerance in plumules of winter rye seedlings by desiccation stress at room temperature in the dark.
Exposure of seedlings of winter rye (Secale cereale L., cv. Puma) for 2 weeks or 24 hours to desiccation stress (40% relative humidity) at room temperature (21 degrees C) in the dark induced degrees of freezing and drought tolerance in the plumules comparable to those produced by cold conditioning for 2 weeks at 3 degrees C. The induction was associated with repression of growth and could not be produced in plumules excised from the seedlings indicating a requirement for translocation of nutrients from the endosperm. Rapid increase in osmotic pressure, soluble proteins, and phospholipids in plumules in association with the development of freezing and drought tolerance and the requirement of endosperm suggested diversion of nutrient from use in extension growth, to use in augmentation of protoplasm in plumule cells. Since cold acclimation slowed or arrested growth and is associated with augmentation of protoplasm, it is suggested that the common element in the induction of freezing tolerance by cold and drought is the necessity for producing a condition of augmented protoplasm and membranes in cells thus reinforcing a similar conclusion reached from seasonal studies on woody plants.
Correlation between Cold- and Drought-Induced Frost Hardiness in Winter Wheat and Rye Varieties.
Exposure of six wheat (Triticum aestivum L.) and one rye (Secale cereale L.) cultivar to 40% relative humidity for 24 hours induced the same degree of freezing tolerance in seedling epicotyls as did cold conditioning for 4 weeks at 2 degrees C.Frost hardiness varietal relationships were the same in desiccation-stressed and cold-hardened seedlings. Drought stress could, therefore, be used as a rapid and simple method for inducing frost hardiness in seedling shoots in replacement of cold conditioning.
Common and disparate elements in the processes of adaption of herbaceous and woody plants to freezing--a perspective.
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Protoplasts surviving freezing to -196 C and osmotic dehydration in 5 molar salt solutions prepared from the bark of winter black locust trees.
Free protoplasts were prepared from the living bark tissue of the trunk of summer and winter black locust trees by enzymic digestion of thin slices of the tissue for 3 hours in a medium containing 2% Onozuka cellulase, 2% Rhozyme pectinase, and 2% Driselase in mannitol solutions using 0.4 molar mannitol for summer tissue and 1.0 molar mannitol for winter tissues. Cleaned suspensions of protoplasts and also thin slices of tissue with cells intact were frozen to temperatures of -10 C, -20 C, -30 C, -40 C and liquid nitrogen in sucrose and balanced salt solutions. Similar suspensions of protoplasts were also subjected to strong osmotic dehydration (plasmorrhysis) in a series of balanced salt solutions of increasing molarity. Tests for survival showed that protoplasts retain the same properties of either extreme susceptibility or extreme resistance to injury by freezing or osmotic dehydration as the cells from which they are prepared. Winter protoplasts showed capability for tolerating freezing to -196 C and plasmorrhysis in 5 molar salt solutions. These results indicate that protoplasts are a valid and useful system for investigating the properties of the protoplasm and surface membranes associated with the seasonal development of extreme hardiness in the cells of woody plants.
Freezing behavior of free protoplasts of winter rye.
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Differential scanning calorimeter analyses of membrane lipids isolated from hardened and unhardened black locust bark and from winter rye seedlings.
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Relative insensitivity of mitochondria in hardened and nonhardened rye coleoptile cells to freezing in situ.
Mitochondria were isolated from excised coleoptiles of hardened and nonhardened winter rye (Secale cereale L. cv. Puma) seedlings which had been frozen extracellularly to different temperatures. No significant differences in the respiratory functions (ADP/O and respiratory control) were observed between mitochondria isolated from nonlethally and lethally frozen cells of both the hardened and nonhardened rye. These results suggest that mitochondria in situ can retain their normal function even after the cell was killed by the dehydrative stresses of extracellular freezing. Presumably, a different level of sensitivity to freezing stresses exists between mitochondrial and other membranous elements in the cell.
A reliable method for the estimation of DNA in higher plant tissues.
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Studies on membranes in plant cells resistant to extreme freezing. I. Augmentation of phospholipids and membrane substance without changes in unsaturation of fatty acids during hardening of black locust bark.
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Liposome bilayer model systems of freezing living cells.
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Studies on the Chemistry of the Living Bark of the Black Locust in Relation to Its Frost Hardiness. VII. A Possible Direct Effect of Starch on the Susceptibility of Plants to Freezing Injury.
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Studies on the Chemistry of the Living Bark of the Black Locust in Relation to its Frost Hardiness. VIII. Possible Enzymatic Processes Involved in Starch-Sucrose Interconversions.
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Studies on the Chemistry of the Living Bark of the Black Locust in Relation to Its Frost Hardiness. III. The Validity of Plasmolysis and Desiccation Tests for Determining the Frost Hardiness of Bark Tissue.
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Studies on the Chemistry of the Living Bark of the Black Locust Tree in Relation to Frost Hardiness. IV. Effects of Ringing on Translocation, Protein Synthesis and the Development of Hardiness.
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Studies on the Chemistry of the Living Bark of the Black Locust in Relation to Its Frost Hardiness. V. Seasonal Transformations and Variations in the Carbohydrates: Starch-Sucrose Interconversions.
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Studies on the Chemistry of the Living Bark of the Black Locust Tree in Relation to Frost. VI. Amylase and Phosphorylase Systems of the Bark Tissues.
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