Further Increase In Salinity Research Articles

Salt Tolerance in the Succulent, Coastal Halophyte,Sarcocornia natalensis

The effects of 0, 50, 100, 200, 300, 400 and 500 mol m'3 NaCl on growth and ion accumulation in the succulent, coastal halophyte Sarcocornia natalensis (Bunge ex Ung.-Sternb.) A. J. Scott were investigated. Increase in salinity from 0 to 300 mol m-3 NaCl stimulated production of fresh, dry, and organic dry mass, increased succulence and shifted resource allocation from roots to shoots. Growth was optimal at 300 mol m-3 and decreased with further increase in salinity. Water contributed to a large proportion of the increase in fresh mass. Inorganic ions, especially Na+ and CI, contributed substantially to the dry mass. At 300 mol m3 NaCl inorganic ions contributed to 37% of total dry mass and NaCl concentration in the shoots was 482 mol m-3. Expressed sap osmotic potentials decreased from — 2-10 to — 3-95 MPa as salinity increased from 0 to 300 mol m-3 NaCl. Massive accumulation of inorganic ions, especially Na+ and CP, accounted for 86% of the osmotic adjustment at 300 mol m 3 NaCl. Salinity treatments decreased the concentrations of K+ in shoots. Plant Na + :K+ ratios increased steadily with salinity and reached a maximum of 16-6 at 400 mol m ~3 NaCl. It is suggested that the exceptional salt tolerance of S. natalensis is achieved by massive inorganic ion accumulation which provides sufficient solutes for osmoregulation, increased water flux and turgor-induced growth.

Salt tolerance studies on atriplex rhagodioides F. Muell.

The effects of different levels of salinity on seed germination, plant growth and chemical composition of Atriplex rhagodioides F. Muell were studied in gravel culture experiments. Increased biomass yields were obtained in saline treatments up to electrical conductivity (EC) 15 mScm −1. With further increase in salinity, growth was adversely affected. However, the plants could survive at a salinity level as high as 50 mScm −1. Na and Cl contents in plant parts increased, and K and Ca contents decreased with increasing culture solution salinity. All plant parts (root, stem and leaf) contained higher K/Na ratios than the culture solution, indicating selectivity for K (or against Na) uptake. K/Na ratios decreased from roots to stems to leaves, indicating selectivity in the uptake and transport of these ions between different plant parts. Accumulation of ions against a concentration gradient, selective K uptake, and partitioning of excess salts in the leaf seem attributable to the high salt tolerance of the species.

The influence of salinity on the cercariae of three species of Schistosoma

Donnelly F. A., Appleton C. C. and Schutte C. H. J. 1984. The influence of salinity on the cercariae of three species of Schistosoma. International Journal for Parasitology 14: 13–21. The effect of salinity on the longevity and infectivity of cercariae of Schistosoma mattheei, Schistosoma haematobium and Schistosoma mansoni was determined. No significant differences in cercarial longevity occurred ( p > 0.05) in low salinities (0–5.25%), whereas further increases in salinity resulted in progressive decreases in survival. In salinities ≳ 17.5%, cercariae were incapable of surviving for longer than 11 min. A maximum life-span of up to 122 h was recorded for some S. mattheei cercariae. Cercarial infectivity, as indicated by worm returns, was reduced progressively with increasing salinity up to a lethal limit of 10.5%. Differences in the salinity tolerance of the cercariae of the three species were discussed.

The influence of salinity on certain aspects of the biology of Bulinus (Physopsis) africanus

The hatchability of eggs and the fecundity and survival of adult Bulinus (Physopsis) africanus was investigated in different salinities. Experimental results revealed egg masses and hatchlings to be considerably more sensitive to salinity than the adult snails. Egg-laying was recorded in salinities ⩽ 4·5 ‰ and further increases in salinity resulted in a progressive reduction in the hatching success up to a lethal concentration of 5·25 ‰ Survival of these hatchings was adversely affected by salinities as low as 1·0 ‰ and a salinity of 4·5 ‰ was lethal within 6 days. In contrast, adult survival was unaffected in salinities < 3·5 ‰ while further increases in salinity resulted in significant reductions in survival up to a lethal salinity of 8·7 ‰, which caused 100% mortality within 24 h. The survival of B. africanus infected with Schistosoma haematobium and Schistosoma mattheei was lower in the different salinities and control than that of their uninfected counterparts.

The role of critical phenomena in oil recovery systems employing surfactants

Abstract The physical properties of the phases generated by tertiary oil recovery systems containing surfactants are interpreted in terms of critical phenomena. It was shown previously that the phase volumes of surfactant systems as a function of a composition variable, e.g., salinity, can be quantitatively interpreted in terms of critical phenomena. For a surfactant system forming three liquid phases (an aqueous phase, a microemulsion phase, and an oil phase) the appearance of the aqueous phase as salinity is increased was associated with an aqueous phase-microemulsion critical endpoint while the disappearance of the oil phase upon further increase in salinity was associated with an oil phase- microemulsion critical endpoint. Here, we show that the behavior of other physical properties of these systems can also be quantitatively described in terms of the same critical phenomena. In particular, the electrical conductivities, densities, viscosities, and compositions of the phases are described in terms of these critical end points. Most importantly, the low interfacial tensions between the phases in these systems can be associated with these critical end points where the interfacial tensions between the two near-critical phases vanish. These results verify that there are two important functions to surfactant action, one associated directly with the surface-active nature of the surfactant molecule and the other associated with the solvent character of the material which makes critical points accessible at moderate temperatures and pressures.