No description available.

NaCl-induced and -repressed cDNA clones had previously been isolated by differential screening of a cDNA library, prepared from poly(A(^+)) RNA isolated from Distichlis spicata (salt grass) cell cultures grown in the presence of 260 mM NaCl (Zhao, et al., 1989). Eight of these cDNA clones have now been subcloned and/or sequenced and the predicted polypeptides compared with owl sequence data base. Three clones pDZ6.2, pDZVIII 1.2.1 and pDZIX 3.1 encode proline rich proteins, containing an amino acid repeat [PPKKDH(H)Y(Y)]. They have similar amino acid usage to proline-rich cell wall proteins, being rich in P, K, H and Y. The first 20 amino acid residues encode a putative leader sequence, supporting the proposed extracellular role as a cell wall protein. This N-terminal sequence (MPLLVALLLVLAVVAAAGAD) shares some similarity with die leader sequence of a soyabean proline-rich cell wall protein precursor and other extracellular proteins (the conserved residues are underlined). There is an increase in abundance of transcripts hybridising to the inserts from pDZ6.2 and pDZVUI 1.2.1 in response to either 520 mM NaCl or 100 µM ABA, but a decrease in response to 5 mM exogenous proline. It is suggested that the corresponding gene(s) are regulated at the level of either transcription or transcript stability, in response to elevated NaCl, with ABA as a mediator of (or part of) tills response. pDZ6.2 and pDZXI 3.1 have identical nucleotide sequences, whilst pDZVni 1.2.1 differs in three base paks within the putative open reading frame, suggesting that there may be at least two members of a multi gene family. A 68 bp OA repeat has been found in the 5' untranslated region of pDZ6.2 and a corresponding transcript identified by northern analysis using this OA sequence as a probe. Such nucleotide repeats can form triplexes (DNA) or hakpin loops (RNA), which is dependent on pH and ionic conditions. Therefore this OA repeat may play a role in the regulation of the gene corresponding to pDZ6.2 at the level of transcription or translation, possibly by attenuation of these processes, either by the formation of triplexes or hah-pins, or the binding of a protein to this GA region, at low ionic strength. However initial in vitro ttanscription experiments, to compare the transcriptional activity of pDZ6.2 and pDZVin 5.1.1 at different ionic strengths, proved inconclusive. An attempt was also made to identify the corresponding genomic region from D. spicata by anchored PGR.A fourth clone pDZ2.8L encodes a histone 2B protein, having 97.9% similarity to a wheat histone 2B. Its transcript abundance decreased in response to either 520 mM NaCl, 5 mM proline or 100 µM ABA. The sequences of the remaining clones either revealed no significant similarity to any known sequences or were assigned as being cloning artefacts .D. spicata cells accumulate proline within eight hours of exposure to 260 mM NaCl (Heyser, et al., 1989b). An unsuccessful attempt was also made to isolate a pyrroline-5- carboxylate reductase gene homologue from D. spicata, by heterologous probing of Southern blots with a soyabean cDNA pProCl and PCR.

No description available.

Thesis (Ph.D.) - University of Glasgow, 2007. / Ph.D. thesis submitted to the Division of Biochemistry and Molecular Biology, Biomedical and Life Sciences (IBLS), University of Glasgow, 2007. Includes bibliographical references. Print version also available.

The response of in vitro-grown Solanum tuberosum L., cvs. Russet Burbank (RB) (salt-sensitive) and Sierra (S) (salt-tolerant) potatoes was investigated when [NaCl] was increased from 0 to 80 mM in the presence of 6, 20, and 30 mM [K] in a Murashige and Skoog (MS) basal medium. The tested growth parameters, Mg and Ca content, and K+/Na + ratios in the laminae and the roots were negatively affected as [NaCl] increased. The salt stress was relatively severe on growth of RB plants whereas the salt-tolerant (S) variety was affected to a lesser extent. There were indications that Na in the plant may promote Na translocation. In both cultivars, 22Na was not distributed equally in all plant parts; the lower lamina accumulated the highest amount (216 and 183 DPM mg -1 FW) followed by stem (197 and 182), petioles (187 and 168), and the upper lamina (149 and 121) for RB and S, respectively. / The salt resistance of S is associated not only with a superior capacity to accumulate high Na+ in the roots for osmotic adjustment, but also with resistance to Na movement to the shoot. / The effect of [K] on plant growth showed two main characteristics. In non-saline media, increasing [K] enhanced growth of S, while RB showed optimum growth when the normal (20 mM) level was present in the MS medium. In saline media, elevating [K] alleviated the growth reduction of RB at low salinity, and S at both low and high salinity. This ameliorative effect of K may be attributed to the suppression of both Na+ uptake, and Na + translocation in the plant.

Thesis (Ph. D. - Molecular and Cellular Biology)--University of Arizona, 1986. / Includes bibliographical references (leaves 97-104).

No description available.

In Libya salinization of land and ground water is a key problem. A. saligna is one species that offers potential for growth under these conditions. Experiments were undertaken to accelerate the germination of Acacia seeds, and various pre-treatment methods were assayed. Boiling water treatment, mechanical scarification and acid improved germination and germination rate. Sowing A. saligna seeds at 30 mm depth gave greatest seedling growth from large and medium seeds whereas 20 mm was more suitable for small seeds. This study aimed to improve the establishment of Acacia saligna irrigated with saline water, plants were grown for seven weeks under greenhouse or field conditions in (Libya) either sand or soil salinized with varying applications of NaCl. Irrigation with NaCl significantly decreased plant survival and growth and concentration of Ca, Na, K, Fe and P ions in plants with 0.5 M or 1.0 M NaCl. The experiments were repeated using a naturally occurring soil amendment called ‘Zander’. Seeds of A. saligna were grown for seven weeks in both greenhouse and field trials as before but with the addition of Zander and NaCl. Zander improved plant survival and growth with salinity and increased the elements in plants (Ca, Na, K, Fe and P). Field experiments were conducted to assess the effects of saline irrigation with 1.0 M NaCl and extra water added to 0% or 10% Zander on survival and growth, consequently, seedling growth significantly decreased with increase in soil salinity. Survival and growth increased with increase in extra water. The additional irrigation water caused an increase in the uptake of Ca++ and increased the Ca++/Na+ and K+/Na+ ratio. Zander did not appear to reduce net uptake of Na+ and its transport to shoot tissues. Mg++, P, K+ and Ca++ content significantly decreased in plants in response to salinity. Possible mechanisms to avoid Na+ toxicity in A. saligna in response to salinity included increasing the supply of Ca++. Extra Ca++ applied into the medium with and without salt increased survival and growth even in the absence of Zander. Calcium increased uptake of Ca++ and increased Ca++/Na+ and K+/Na+ ratio.

Three cotton (Gossypium hirsutum L.) germplasms (DP62, 84027, and 84033) were used to investigate the physiology of salt tolerance. Lines 84027 and 84033 were developed from the parental line DP62 and showed superior vigor under varying NaCl conditions (0.5 to 2.0 M) during germination and emergence. Proline levels increased in the leaves of all germplasms in response to increasing salinity. Varietal differences in proline levels did not reflect their variation in salt tolerance. Several physiological characteristics were also evaluated under non-saline condition in the greenhouse. There were no significant differences among germplasm sources for all parameters measured. However, salinity reduced transpiration rate, increased leaf diffusive resistance and leaf temperature for all lines. Ribosomal-RNA levels in all germplasms were evaluated after seeds were stressed for 24 hrs in various concentrations of NaCl and then germinated under normal conditions for 72 hrs. Ribosomal-RNA levels were inversely related to salt concentrations. Line 84033 followed by line 84027 had highest ribosomal-RNA content than the parental line DP62 when averaged over the four salt concentrations. Sodium content (ppm/g FW) and Cl⁻ content (ppm/g FW) were evaluated in microsomal and cell walls fractions as well as a cytoplasmic fraction which consisted of vacuoles, mitochondria, and plastids. The Cl⁻ ion exhibited a greater consistency in a concentration shift from one fraction to another as a function of time than did the Na⁺ ion. As a result, there may be a correlation between the drop in ribosomal-RNA and the amount of Cl⁻ in the microsomal fraction. Other parameters measured in the germinating seed were soluble protein (globulin), insoluble proteins (prolamin and glutelin) and fiber percentage. Variations within the germplasms were shown to exist. This study shows that even among lines that have been selected for salt tolerance from a single variety, the possibility exists that each of these lines may have a different mechanism to cope with salt stress.

The succulent, annual euhalophyte, Salicornia bigelovii was grown in 1, 10, 35, 45 and 60 ppt Instant Ocean. This range represents approximately 1/35 to nearly twice the salinity of seawater. The plants in the 4 highest salinities had common final dry weights and seed yields of about 60 and 11 g, respectively, while the 1 ppt plants had 28 and nearly 5 g, respectively. The water relations data reflected the growth and seed production of the plants. The plants in the 4 higher salinities had water potentials sufficient to generate large import gradients and osmotic potentials which contributed to substantial turgors. The 1 ppt plants had a gradient like the rest, but a very low turgor of 0.11 MPa which was barely 23% of that of the lowest of the other treatments. Higher salinities resulted in slightly greater organic and inorganic osmotica contents. Overall, these results suggest a relatively fixed genetic response to a wide range of salinities, as well as an inability to function well at very low salinities. No plant grown at 0 ppt was ever able to reproduce. Therefore, this plant is an obligate halophyte. Experiments in the plant's native coastal estuary indicated meristem water potentials fluctuate with the tides, although they remain about 1.5 MPa below the corresponding soil water potentials. The plants occupy a discrete elevational range throughout the estuary, spending about 1/3 of their daylight hours submerged, and apparently never see dryness. Phenotype differences in the estuary suggest that, within the habitat, pacing and consequent resource domination may be important parameters affecting plant size and possibly fitness. Nitrogen, which is characteristically rare in this and other estuaries, may be critical in this regard. The plants produce large quantities of glycine-betaine, which may be for simultaneous osmoticum use and nitrogen storage. Most roots occur in the first 3 inches of soil. A mechanism is proposed, based on highly efficient compartmentation at the cellular level and the shuttling of organic osmoticum across the tonoplast, by which the tidally based cyclical water potentials could be explained.