Salinity stress limits the growth and productivity of agricultural crops in many regions of the world. Whole plant tolerance to soil salinity involves numerous processes in many different tissues and cell types. For many cereals, sensitivity to salinity is due to the accumulation of sodium (Na⁺) to toxic concentrations in the leaves. This thesis investigates a mechanism of control of Na⁺ accumulation in leaves of wheat. Bread wheat excludes sodium from the leaves better than durum wheat. Bread wheat is hexaploid (AABBDD) whereas durum wheat is tetraploid (AABB). The D-genome in bread wheat carries a major locus for sodium exclusion, Kna1, which may contribute to the differences in sodium exclusion between bread wheat and durum wheat. An unusual durum wheat, Line 149, excludes sodium to a similar degree as bread wheat. Line 149 was derived from a cross between a Triticum monococcum (accession C68-101; AA) and a durum wheat (T. turgidum ssp. durum cv. Marrocos; AABB). Line 149 had been found to contain two major genes for sodium exclusion, named Nax1 and Nax2, which appeared to retrieve sodium from the xylem sap in the roots and so prevent it reaching the leaves. Line 149 had been crossed with the durum wheat cv. Tamaroi, which accumulates high concentrations of Na⁺ in the leaves, and near-isogenic single-gene mapping populations had been developed for Nax1 and Nax2. Nax1 had been located on chromosome 2A. The objective of this thesis was to map Nax2 and identify a candidate gene. Nax2 mapped to chromosome 5AL based on linkage to microsatellite markers. A high-affinity potassium (K⁺) transporter (HKT)-like gene, HKT1;5 was considered as a candidate gene for Nax2, based on similarity of the phenotype to a rice orthologue. Sequence information from a wheat HKT1;5-like expressed sequence tag in the public database was used to develop a probe for use in Southern hybridsation. A HKT1;5-like fragment was identified in Line 149 and T. monococcum C68-101, but was absent in Tamaroi. The HKT1;5-like gene, named TmHKT1;5-A, co-segregated with Nax2 in the Nax2 single-gene mapping population. The HKT1;5 probe identified three putative HKT1;5-like genes on the long arm of chromosome 4B, and one HKT1;5-like gene on the long arm of chromosome 4D, in Langdon (T. turgidum ssp. durum) substitution lines, and in Chinese Spring (T. aestivum) ditelomeric lines. No A-genome HKT1;5 like gene was identified in Langdon or Chinese Spring. The D-genome HKT1;5 gene, named TaHKT1;5-D, was found to co-locate with Kna1, the gene for sodium exclusion in bread wheat, in Chinese Spring chromosome 4D deletion lines. Nax2 (TmHKT1;5-A) was found to be homoeologous with the gene for sodium exclusion in bread wheat, Kna1 (TaHKT1;5-D). TmHKT1;5-A and TaHKT1;5-D, and their promoters, were 94% identical, and both were expressed in the roots of wheat plants. This is consistent with the genes being located in the stele of the roots and retrieving Na⁺ from the xylem sap as it flows towards the shoot, and so excluding Na⁺ from the leaves. A marker for TmHKT1;5-A was developed to track this gene in durum wheat breeding programs. A study of the HKT1;5 gene in diploid ancestors of wheat indicated that this gene is present in most Triticum monococcum accessions, some T. boeoticum accessions, but not present in any T. urartu accessions. T. urartu is the likely A genome ancestor of modern wheat. This may explain the absence of HKT1;5 in the A genome of modern wheat. The protein encoded by TaHKT1;5-D transported sodium when expressed in Xenopus laevis oocytes. The inward currents were specific to Na⁺, but at particular mole fractions of Na⁺ and K⁺ outward currents were observed that were consistent with outward K⁺ transport. These data were consistent with the putative physiological function, of retrieving Na⁺ from the xylem sap as it flows to the leaves, and resulting in a net exchange with K⁺. A construct designed to silence the expression of TaHKT1;5-D was introduced to bread wheat cv. Bob White. Nineteen putative transgenic plants were developed. The leaf Na⁺ concentrations and genotype of the T1 individuals were assayed. The data from two of the transgenic plants indicated that TaHKT1;5-D may have been silenced and that this may have lead to the increase in Na⁺ accumulation in the leaves. However, this data is not conclusive at this time. The information gained from this study will assist the introduction of the Na⁺ exclusion trait into current durum cultivars, which are poor at excluding Na⁺ and are salt sensitive. This information will also contribute to the body of knowledge of ion transport in plants and salinity tolerance in wheat. / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

This thesis presents the study of films derived from the reduction of aryldiazonium salts at gold surfaces. The properties of bare polycrystalline surfaces were investigated via the observation of the electrochemical oxidation and reduction of the gold. Films derived from diazonium salts were electrochemically grafted to the gold surface. The structure and stability of these interfaces was examined through the use of redox probes, gold oxide electrochemistry and water contact angle measurements. The spontaneous reduction of aryldiazonium salts at gold surfaces was investigated and the possible applications it presented towards printing and patterning of the gold surface with films were explained. Polycrystalline gold surfaces were prepared and subjected to various treatments, to observe the behaviour of gold oxide formation and reduction at the surface. Various effects on the surface structure were observed after treatment in solvents and electrolyte solutions. The surface structure of the gold atoms frequently changed due to the high mobilities of the gold atoms, and it is difficult to achieve a reproducibly stable surface. The electrochemical modification of gold surfaces via the reduction of aryldiazonium salts was investigated. Surfaces were modified with methylphenyl and carboxyphenyl films and exposed to various treatments. Monitoring the gold oxide reduction changes enabled the surface coverage of modifier directly attached to the surface to be calculated. The films appear to be stable, loosely packed and porous. The films are flexible in nature; redox probe responses showed reversible changes after repeated sonication in solvents of differing polarities and hydrophilicities. Contact angle measurements further support the notion of films that can reorganise in response to their environment. The spontaneous reduction of aryldiazonium salts at gold surfaces was observed. Film coverage was significantly lower at the spontaneously grafted surface than for films grafted electrochemically. Gold surfaces were successfully modified via microcontact printing, and surface coverages similar to the spontaneously grafted film were achieved. Microcontact printing was also used to pattern surfaces with films derived from diazonium salts. Feature sizes down to 100 µm were successfully achieved.

Salinity stress limits the growth and productivity of agricultural crops in many regions of the world. Whole plant tolerance to soil salinity involves numerous processes in many different tissues and cell types. For many cereals, sensitivity to salinity is due to the accumulation of sodium (Na⁺) to toxic concentrations in the leaves. This thesis investigates a mechanism of control of Na⁺ accumulation in leaves of wheat. Bread wheat excludes sodium from the leaves better than durum wheat. Bread wheat is hexaploid (AABBDD) whereas durum wheat is tetraploid (AABB). The D-genome in bread wheat carries a major locus for sodium exclusion, Kna1, which may contribute to the differences in sodium exclusion between bread wheat and durum wheat. An unusual durum wheat, Line 149, excludes sodium to a similar degree as bread wheat. Line 149 was derived from a cross between a Triticum monococcum (accession C68-101; AA) and a durum wheat (T. turgidum ssp. durum cv. Marrocos; AABB). Line 149 had been found to contain two major genes for sodium exclusion, named Nax1 and Nax2, which appeared to retrieve sodium from the xylem sap in the roots and so prevent it reaching the leaves. Line 149 had been crossed with the durum wheat cv. Tamaroi, which accumulates high concentrations of Na⁺ in the leaves, and near-isogenic single-gene mapping populations had been developed for Nax1 and Nax2. Nax1 had been located on chromosome 2A. The objective of this thesis was to map Nax2 and identify a candidate gene. Nax2 mapped to chromosome 5AL based on linkage to microsatellite markers. A high-affinity potassium (K⁺) transporter (HKT)-like gene, HKT1;5 was considered as a candidate gene for Nax2, based on similarity of the phenotype to a rice orthologue. Sequence information from a wheat HKT1;5-like expressed sequence tag in the public database was used to develop a probe for use in Southern hybridsation. A HKT1;5-like fragment was identified in Line 149 and T. monococcum C68-101, but was absent in Tamaroi. The HKT1;5-like gene, named TmHKT1;5-A, co-segregated with Nax2 in the Nax2 single-gene mapping population. The HKT1;5 probe identified three putative HKT1;5-like genes on the long arm of chromosome 4B, and one HKT1;5-like gene on the long arm of chromosome 4D, in Langdon (T. turgidum ssp. durum) substitution lines, and in Chinese Spring (T. aestivum) ditelomeric lines. No A-genome HKT1;5 like gene was identified in Langdon or Chinese Spring. The D-genome HKT1;5 gene, named TaHKT1;5-D, was found to co-locate with Kna1, the gene for sodium exclusion in bread wheat, in Chinese Spring chromosome 4D deletion lines. Nax2 (TmHKT1;5-A) was found to be homoeologous with the gene for sodium exclusion in bread wheat, Kna1 (TaHKT1;5-D). TmHKT1;5-A and TaHKT1;5-D, and their promoters, were 94% identical, and both were expressed in the roots of wheat plants. This is consistent with the genes being located in the stele of the roots and retrieving Na⁺ from the xylem sap as it flows towards the shoot, and so excluding Na⁺ from the leaves. A marker for TmHKT1;5-A was developed to track this gene in durum wheat breeding programs. A study of the HKT1;5 gene in diploid ancestors of wheat indicated that this gene is present in most Triticum monococcum accessions, some T. boeoticum accessions, but not present in any T. urartu accessions. T. urartu is the likely A genome ancestor of modern wheat. This may explain the absence of HKT1;5 in the A genome of modern wheat. The protein encoded by TaHKT1;5-D transported sodium when expressed in Xenopus laevis oocytes. The inward currents were specific to Na⁺, but at particular mole fractions of Na⁺ and K⁺ outward currents were observed that were consistent with outward K⁺ transport. These data were consistent with the putative physiological function, of retrieving Na⁺ from the xylem sap as it flows to the leaves, and resulting in a net exchange with K⁺. A construct designed to silence the expression of TaHKT1;5-D was introduced to bread wheat cv. Bob White. Nineteen putative transgenic plants were developed. The leaf Na⁺ concentrations and genotype of the T1 individuals were assayed. The data from two of the transgenic plants indicated that TaHKT1;5-D may have been silenced and that this may have lead to the increase in Na⁺ accumulation in the leaves. However, this data is not conclusive at this time. The information gained from this study will assist the introduction of the Na⁺ exclusion trait into current durum cultivars, which are poor at excluding Na⁺ and are salt sensitive. This information will also contribute to the body of knowledge of ion transport in plants and salinity tolerance in wheat. / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Most research to date has focused on non-pregnant sheep grazing saltbush to fill the summer/autumn feed gap in temperate regions of southern Australia. However, the summer/autumn period coincides with late pregnancy for autumn- or winter-lambing ewes, and feeding saltbush may reduce the amount and cost of supplementary feed that is required to meet the energy demands of late pregnancy. The challenge of dealing with a high-salt diet may be exacerbated during pregnancy since pregnancy is a salt-retaining physiological state, yet a high-salt intake requires an increase in mechanisms to excrete salt. The effect of high dietary salt on the developing foetus(es) has been studied in rodent models, but less so in sheep. Hence the aims of this thesis were to determine whether pregnant ewes can manage a high dietary salt content resembling that found in saltbush, and whether there are consequences to the offspring’s physiological responses to ingested salt. Merino ewes were synchronized for ovulation and artificially inseminated. To mimic the concentration of salt in animals grazing saltbush-based pastures in summer and autumn, a diet of 13% NaCl was fed from insemination through to parturition. It was found that pregnant ewes can be fed a 13% NaCl diet and manage the physiological conflict of high salt and pregnancy by decreasing their aldosterone concentrations and increasing their water consumption. There was no effect of high dietary salt on pregnancy rates, lamb birth weights, lamb survival or milk composition (fat and protein percentages). A series of experiments were conducted to test if the high-salt intake of ewes during pregnancy was associated with a change in the dietary preference for salt and/or changes in physiological responses to ingested salt in the offspring (‘S lambs’ vs. control, ‘C lambs’). C lambs and S lambs were exposed to short- and long-term preference testing to determine if there were differences in their voluntary selection for salt in their diet. There were no significant differences in dietary salt preference between C and S lambs. The lambs were subjected to salt 'challenges' (oral dose of 40 g NaCl in 25% w/v solution) from 3-10 months of age and their water intake, urinary output, sodium excretion and hormone concentrations were measured over the ensuing 23 hours, and compared against counterparts dosed with an equal volume of water without salt. Following the initial salt challenge further experiments were conducted with slight alterations; water intake was manipulated immediately following the salt challenge; two consecutive salt challenges, 8 hours apart, were administered; and C and S lambs were offered salty water (1.5% NaCl) over a period of two days. The results of these salt challenge experiments showed that C and S lambs excreted a salt load at a similar rate, but they differed in the magnitude of changes in water intake and hormone concentrations required to achieve sodium homeostasis. S lambs were able excrete sodium at the same rate as C lambs but without decreasing aldosterone concentrations to the same extent and whilst consuming 400 mL less water in the first two hours post challenge. The aldosterone results suggested a lowered responsiveness to aldosterone and the lower water consumption suggested an altered thirst threshold. The experiment in which water consumption was manipulated suggested that when the supply or access to fresh water is limited, the capacity to remove a salt load is likely to be less impaired in S lambs than C lambs; S lambs were able to excrete the salt load faster than the C lambs when the availability of drinking water was limited. From the experiment in which lambs were treated with two consecutive salt challenges, the rate of sodium excretion increased after the second dose, but there remained no difference in the rate of excretion between C and S lambs; all animals were able to excrete 95% of the administered dose of sodium within 23 hours. The final experiment in which animals were given salty water (1.5% NaCl) for a period of two days showed consistent results with the previous experiments for water consumption and aldosterone concentrations between C and S lambs. There was no difference in sodium excretion between C and S lambs. A novel finding was a markedly lower voluntary feed intake in S lambs than C lambs. Although mechanisms for this are unknown, it may have profound effects on the productivity of the animals. The experiments reported in this thesis provide new information of relevance to pregnant ewes grazing halophytic forages. It is apparent that they can withstand a high NaCl content typical, of a saltbush-based pasture. Further work is warranted to conclude whether high salt during pregnancy is (i) beneficial to the offspring in regards to a higher capacity to deal with excess salt under farming conditions and (ii) consistently associated with a lower voluntary feed intake of the offspring. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1290752 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007.

Thesis (Ph. D.)--Miami University, Dept. of Geology, 2007. / Title from second page of PDF document. Includes bibliographical references (p. 192-199).

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 107-114). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph.D.)--University of Western Australia, 2006.

Univ., Diss.-1999--Göttingen, 1998.

Thesis (Ph. D.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.