Salt-tolerance

The most commonly used polymers are partially hydrolyzed polyacrylamides (32). The optimum degree of hydrolysis depends on the apphcation, injection water composition, and reservoir conditions (33,34). More salt-tolerant acrylamide copolymers may permit this technology in higher salinity injection water (35). Eield apphcations of cross-linked xanthan gum have also been reported (36). 

The alpha-olefin sulfonates (AOS) have been found to possess good salt tolerance and chemical stabiUty at elevated temperatures. AOS surfactants exhibit good oil solubilization and low iaterfacial tension over a wide range of temperatures (219,231), whereas less salt tolerant alkylaromatic sulfonates exhibit excellent chemical stabiUty. The nature of the alkyl group, the aryl group, and the aromatic ring isomer distribution can be adjusted to improve surfactant performance under a given set of reservoir conditions (232,233). 

Commercially, HEC is available in a wide range of viscosity grades, ranging from greater than 500 mPa-s(=cP) at 1% soHds to less than 100 mPa-s(=cP) at 5% total soHds. Because HEC is nonionic, it can be dissolved in many salt solutions that do not dissolve other water-soluble polymers. It is soluble in most 10% salt solutions and in many 50% (or saturated) salt solutions such as sodium chloride and aluminum nitrate. As a rule, the lower substitution grades are more salt-tolerant. 

Undoubtedly, the increasing salt tolerance of agricultural hydrogels is a very important task. As far as we know, this problem is far from having inexpensive solutions which could meet agricultural economy requirements. 

Caramel color can be made with either positively or negatively charged particles. This allows manufacturers to use negative colloidal caramel in acidic soft drinks, and positive colloidal caramel in beers and soy sauces. Beer has positively charged proteins suspended in it, and soy sauce has a high salt content that requires the more salt-tolerant positive caramel color. 

Special amphoterics are made by condensation of ether carboxylic acids with 2-aminoethylethanolamine followed by carboxymethylation with sodium mono-chloroacetate [45]. An advantage is that these compounds have a higher salt tolerance. 

Aughel and coworkers [63] studied the phase behavior of hydrocarbon-water mixtures in the presence of alkyl(aryl)polyoxyethylene carboxylates for enhanced oil recovery and found good salt tolerance with an alkyl ether carboxy-late (C13-C15) with 7 mol EO and a good microemulsion forming effect with the 3 EO type. 

The composition of a typical IOS system prepared by Stapersma et al. [4] is shown in Table 2, along with the analytical data of an AOS with the same chain length. Compositions containing IOS, a nonionic surfactant, glycols, and another salt-tolerant anionic surfactant which are pourable and pumpable at 20°C and can be used in the manufacturing of detergent compositions, have also been described by Stapersma et al. [36]. 

Comparison of results for the first and last entries in Table 7 (AOS 2024 and IOS 2024) was for samples for which the hydrophobe linearity, hydrophobe carbon number, and relative disulfonate content were held nearly constant. The major differences in these surfactants were possible differences in the relative locations of the double bond and the sulfonate group in the alkenesulfonate and in the relative locations of the hydroxy group and the sulfonate group in the hydroxyalkanesulfonate. Analyses to determine these are quite difficult. At calcium ion concentrations below 100-250 ppm, AOS 2024 appeared to be more salt-tolerant than linear IOS 2024. At higher calcium concentrations, the calcium ion tolerance of the two surfactants was similar. 

The effect of water salinity on crop growth is largely of osmotic nature. Osmotic pressure is related to the total salt concentration rather than the concentration of individual ionic elements. Salinity is commonly expressed as the electric conductivity of the irrigation water. Salt concentration can be determined by Total Dissolved Solids (TDS) or by Electrical Conductivity (EC). Under a water scarcity condition, salt tolerance of agricultural crops will be the primordial parameter when the quality of irrigation water is implicated for the integrated water resources management [10]. 

Table 1 shows the relative salt tolerances of agricultural crops. These data serve as a guide to the relative tolerance among crops to adapt the quahty of water to crops patterns under water scarcity. It is important to highlight that absolute tolerances vary with climate, soil conditions, and cultural practices. 

Table 1 Relative salt tolerance of agricultural crops [12]...

When data on the amphidiploid and the hexaploid wheats are considered (Table 5), the former being substantially more salt tolerant in hydroponic culture, then again several points are noted. First, the sap osmotic pressure in the young leaves is least in the tolerant amphidiploid. Secondly, Na" and Cl levels are also lower in the juvenile amphidiploid leaves. These data imply that minimal osmotic adjustment is more beneficial than apparently complete osmotic adjustment. 

Gorham, J., Forster, B.P., Budrewich, E., Wyn Jones, R.G., Miller, T.E. Law, C.N. (1986). Salt tolerance in the triticaceae - solute accumulation and distribution in an amphidiploid derived from Triticum aestivum c.v. Chinese Spring and Thinopyrum bessarabicum. Journal of Experimental Botany, 37, 1435-49. 

Singh, N.K., La Rosa, P.C., Handa, A.K., Hasegawa, P.M. Bressan, R.A. (1987f>). Hormonal regulation of protein synthesis associated with salt tolerance in plant cells. Proceedings of the National Academy of Sciences, USA, 84,739-43. 

One of the metabolic responses of plants exposed to environmental stress is the production of proteins which may be qualitatively and/or quantitatively different from those produced in the absence of the stress (see Chapter 9 for general discussion). In some cases these responses have been found to depend on genotype for example, when a salt-tolerant cultivar and a salt-sensitive cultivar of barley were exposed to salt stress the shoot tissue responded by synthesising proteins which were cultivar specific. Five new proteins not found in the salt-sensitive barley were identified in the salt-tolerant cultivar (Ramagopal, 1987). No differences in proteins were found in the roots of either cultivar. 

The literature is less extensive on the use of protoplasts in stress-tolerance investigations however, some applications have been attempted. For example, in one study protoplasts were isolated from the leaves of a wild relative of tomato shown to be salt tolerant and from a salt-sensitive, cultivated species (Rosen Tal, 1981). In the presence of NaCI the plating efficiency (number of surviving cells/number of cells applied to the plate) of the wild relative was greater than the cultivated, sensitive cultivar. Proline, when added to the culture media, was found to enhance the plating efficiency of the salt-sensitive cultivar but not the wild, salt-tolerant relative. These results suggest that traits related to salt tolerance are expressed by the isolated protoplasts and that the response of protoplasts to environmental stress can be manipulated, i.e. the proline response. 

A more significant body of literature focuses on the use of protoplasts in understanding processes related to stress tolerance. The role of Ca in salt toleranee has been evaluated using maize root protoplasts. Exposure of the plasmalemma directly to external media revealed a non-specific replacement of Ca by salt. Sodium was found to replace Ca though this could be reversed by adding more Ca (Lynch, Cramer Lauchli, 1987). This approach assists in understanding the role of specific ion interaction in enhancing salt tolerance and is potentially applicable to studies on the molecular basis for ion specificity of plant membranes. 

Ben-Hayyim, G. (1987). Relationship between salt tolerance and resistance to polyethylene glycol-induced water stress in cultured citrus cells. Plant Physiology, 85, 430-4. 

Blumwald, E. Poole, R.J. (1987). Salt tolerance in suspension cultures of sugar beet. Induction of Na /H" antiport activity at the tonoplasts by growth and salt. Plant Physiology, 83, 884-7. 

Harms, C.T. Oertli, J.J. (1985). The use of osmotically adapted cell cultures to study salt tolerance in vitro. Journal of Plant Physiology, 120, 29-38. 

Lone, M.I., Kueh, J.S.H., Wyn Jones, R.G. Bright, S.W.J. (1987). Influence of proline and glycinebetaine on salt tolerance of cultured barley embryos. Journal of Experimental Botany, 38, 479-90. 

Rains, D.W., Croughton, S.S. Croughan, T.P. (1986). Isolation and characterization of mutant cell lines and plants Salt tolerance. In Cell Culture and Somatic Cell Genetics of Plants, Vol. 3, ed. I. Vasil, pp. 537-47. New York Academic Press. 

Rosen, A. Tal, M. (1981). Salt tolerance in the wild relatives of the cultivated tomato responses of naked protoplasts isolated from leaves of Lycopersicon esculentum and L. peruvianum to NaCl and proline. Zeitschrift fur Pflanzenphy-siologie, 102, 91-4. 

Stavarek, S.J. Rains, D.W. (19846) Cell culture techniques Selection and physiological studies of salt tolerance. In Salinity Tolerance in Plants Strategies for Crop Improvement, ed. R.C. Staples and G.H. Toeniessen, pp. 321-34. New York Wiley. 

Selection for physiological characters - examples from breeding for salt tolerance... 

Bhaskaran, S., Smith, R.H. Schertz, K.F. (1986). Progeny screening of sorghum plants regenerated from sodium chloride-selected callus for salt tolerance. Journal of Plant Physiology, 122, 205-10. 

Maas, E.V. Hoffman, G.J. (1976). Crop salt tolerance evaluation of existing data. In Managing Water for Saline Irrigation, ed. H.E. Dregre. Lubbock Texas Technical University. 

McHughen, A. Swartz, M. (1984). A tissue-culture derived salt-tolerant line of flax (Linum mitatissimum). Journal of Plant Physiology, 117, 109-17. 

Nyman, L.P., Gonzalez, C.J. Arditti, J. (1983). In v/tro selection for salt tolerance of taro Colochasia esculenta var antiquorum). Annals of Botany, 51, 229-36. 

Rush, D.W. Epstein, E. (1976). Genotypic responses to salinity. Differences between salt-sensitive and salt-tolerant genotypes of the tomato. Plant Physiology, 57, 162-6. 

Rush, D.W. Epstein, E. (1981). Breeding and selection for salt tolerance by the incorporation of wild germplasm into a domestic tomato. Journal of the American Society for Horticultural Science, 106, 699-704. 

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