No abstract available. / Dissertation (MSc)--University of Pretoria, 2011. / Geology / unrestricted

Ecophysiology studies are needed to predict plant responses in relation to climate change. Variations in salinity and inundation are expected to influence the survival and distribution of salt marsh. The following species were chosen to study as they occur in most South African salt marshes and are representative of different tidal ranges; namely Triglochin buchenaui (lower intertidal), Bassia diffusa (upper intertidal succulent) and Limonium linifolium (upper intertidal non-succulent). To simulate climate change conditions as predicted for South Africa, a 3 x 5 controlled experiment of three inundation levels (tidal, submerged and drought) and five salinity levels (0, 8, 18, 35, 45 ppt) was conducted for each species. This resulted in 15 treatments per species. Plant responses were measured over a three month period. Triglochin buchenaui showed significant variation in height (7.57 ± 0.5 to 29 ± 1.55 cm, p < 0.005, DF = 55) with optimum growth at 0 ppt under tidal conditions; leaf area increments and relative growth rates which decreased with increasing salinity under all inundation states. There was almost a cessation of growth under submergence which reduces the plant’s regeneration potential under these conditions. Proline accumulation (1.84 ± 0.23 to 3.36 ± 0.38 mg l-1), response of photosynthetic pigments and electrolyte leakage (8.17 ± 0.80 to 38.36 ± 7.42 percent) were fundamental to osmotic and membrane response regulation. Plants survived in all inundation states at salinity up to 45 ppt, but the optimum range was 0 to 18 ppt, and best water state was the tidal condition. Viable rhizomes were produced under drought conditions. Bassia diffusa (Thunb.) Kuntze plants under submergence died within one month, irrespective of the salinity. Optimum growth occurred in plants of the tidal treatment at 18 ppt, and reduced with increased salinity and drought conditions. Plants in the tidal treatments were more succulent than the drought-treated plants. There was reduced leaf mass and high anthocyanin concentrations in drought-treated plants and these effects increased with salinity. Soil and leaf water potential were positively correlated with anthocyanin concentration in leaves and stems, suggesting anthocyanin accumulated in response to drought and could be an adaptation to lower the plant’s water potential under drought conditions. A shift of anthocyanin from leaves to stems was found in drought-treated plants, and this possibly enables the maximization of photosynthesis in leaves, to complement its role in osmotic balance and photo-protection. Growth of Limonium linifolium showed that the plant was tolerant to a wide range of salinity under both tidal and drought conditions, but was susceptible to complete submergence, with high membrane damage even in tidal-treated plants. Plants died within 2 weeks of complete submergence. Results further indicated that L. linifolium tolerates extreme drought by accumulating large quantities of proline and oxalic acid, which consequently lowers its water potential for uptake of soil water of high salinity. Excess salts were excreted through salt glands. This is an important adaptation for a plant that thrives in a highly variable saline habitat Further investigation of submergence effects on upper intertidal species using B. diffusa showed three key stages in the response. A drop in chlorophyll a+b within 6 hours (4.2 ± 0.2 to 2.4 ± 0.3 mg l-1) with a corresponding increase in carotenoid concentration (0.6 ± 0.1 mg l-1) indicated an immediate response to submergence. Oxalic acid concentration was highest on Day 4 (13.6 mM) as opposed to control levels, indicative of its role in submergence tolerance, thus Day 4 may be the peak of positive acclimation. The third phase was marked by a sharp increase in electrolyte leakage to 47.5 ± 2.6 percent on Day 10, from 9.4 ± 1.4 percent on Day 7, with a corresponding decrease in total dissolved solutes between Days 7 and 10. Results suggest that oxalic acid accumulates under submergence possibly as a stabilizing osmolyte. The threshold for tolerance of the species under submergence is 7 days with membrane damage thereafter. Bassia diffusa would not survive prolonged submergence (> 7 days) but could survive submergence of short duration (< 7 days) through continuous underwater photosynthesis, accumulation of osmolytes such as oxalic acid and carotenoid, and maintenance of relative water content and succulence within control levels. When considered together, results showed that the two upper intertidal species were sensitive to waterlogging and would not survive complete submergence, whereas the lower intertidal species could in addition to its natural range, thrive in conditions typical of the upper intertidal range, namely prolonged dry conditions and high sediment salinity. These results have important implications for the future management of salt marshes under predicted climate change conditions. In permanently open South African estuaries, a landward migration of salt marsh will be possible if coastal squeeze is limited and the rate of landward recruitment is on par with sea level rise. In this case salt marsh species would retain their current zonation while shifting inland. Increased sea storms and saltwater intrusion could lead to high salinity concentration in the sediment and significantly reduce growth of salt-sensitive plants. In estuaries that are temporarily open to the sea, reduced freshwater inflow will result in an increase in mouth closure, high water levels, prolonged submergence, and consequently die back of salt marsh vegetation. On the other hand increased abstraction and drought would result in low water levels and high sediment salinity which would decrease growth and survival of salt marsh. This research has provided new knowledge on the ecophysiology of salt marsh plants which can be used to predict the responses of plants to climate change.

Isotope and dye estimates were made of body fluid compartment sizes in White Leghorn roosters, Glaucous-winged gulls, and in groups of Pekin ducks which were raised on either fresh water or regimes of hypertonic NaCl solution. The gulls and both groups of ducks were observed to have plasma (T-1824 dye) and total body water (H₂³O) volumes larger than thoseof the roosters, whereas the reverse was true for Br⁸² space (extracellular fluid; ECF) measurements. Salt fed ducks showed smaller, but insignificantly different compartment sizes (% body weights) when compared to fresh water raised ducks. The effects of an intravenous injection of hypertonic NaCl on the distribution of body water were compared among birds which differed in their capacity for renal and extra-renal salt elimination. In those birds (gulls, salt water ducks, and fresh water ducks with functional salt glands) which exhibited extra-renal salt secretion, the increase in ECF was significantly greater in response to the intravenous injection of hypertonic NaCl than in those birds (roosters and non-secreting fresh water ducks) which did not utilize the salt glands. The relative amounts and concentrations of the salt load removed by renal and extra-renal routes of elimination were compared. Birds with actively secreting nasal glands voided a major equivalent of the injected NaCl as solutions hypertonic to plasma NaCl levels. Renally eliminated NaCl represented a much smaller portion of the load and was in all cases hypo- or isotonic with plasma ion levels. Isotopically labelled Na²² CI administered concomitantly with the salt load in several of the test birds revealed that a large portion of the labelled sodium chloride was removed by the nasal glands and kidneys before there was equilibration of the injected load with extravascular compartments. A preliminary report is made on the composition and possible source of an excess eye secretion observed in the rearing of saline fed Pekin ducks. The enlarged Harderian glands of these birds were implicated as the source of a fluid several fold hyperkalemic to plasma ion concentrations. The secreted fluid was observed to accumulate and encrust the feathers below the inner canthus of the eye. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

With a global growing demand in food production, agricultural output must increase accordingly. An increased use of saline soils and brackish water would contribute to the required increase in world food production. Abiotic stresses, such as salinity and drought, are also major limiters of crop growth globally - most crops are relatively salt sensitive and are significantly affected when exposed to salt in the range of 50 to 200 mM NaCl. Genomic resources from plants that naturally thrive in highly saline environments have the potential to be valuable in the generation of salt tolerant crops; however, these resources have been largely unexplored. Salicornia bigelovii is a plant native to Mexico and the United States that grows in salt marshes and coastal regions. It can thrive in environments with salt concentrations higher than seawater. In contrast to most crops, S. bigelovii is able to accumulate very high concentrations (in the order of 1.5 M) of Na+ and Cl- in its photosynthetically active succulent shoots. Part of this tolerance is likely to include the storage of Na+ in the vacuoles of the shoots, making S. bigelovii a good model for understanding mechanisms of Na+ compartmentalization in the vacuoles and a good resource for gene discovery. In this research project, phenotypic, genomic, transcriptomic, and proteomic approaches have been used for the identification of candidate genes involved in salinity tolerance in S. bigelovii. The genomes and transcriptomes of three Salicornia species have been sequenced. This information has been used to support the characterization of the salt-induced transcriptome of S. bigelovii shoots and the salt-induced proteome of various organellar membrane enriched fractions from S. bigelovii shoots, which led to the creation of organellar membrane proteomes. Yeast spot assays at different salt concentrations revealed several proteins increasing or decreasing yeast salt tolerance. This work aims to create the basis for Salicornia research by providing a genome, transcriptomes, and organellar proteomes, contributing to salinity tolerance research overall. We identified a set of candidate genes for salinity tolerance with the aim of shedding some light on the mechanisms by which this plant thrives in highly saline environments.

The Onion Creek Diapir is one of many salt domes proximal to the Uncompahgre thrust front of the ancestral rockies in the Paradox Basin. It is comprised of Paradox Formation evaporites and large blocks of Honaker Trail Formation carbonates that were deformed by loading of Permian Cutler Formation progradational alluvial to fluvial fans. The history of salt movement in the Onion Creek Diapir is recorded in the near-salt strata. Large salt bodies and their adjacent mini-basins evolve conforming to a complex relationship between salt withdrawal, creating localized accommodation, and sediment deposition. Migrating mini-basin depo-centers, thinned and folded strata, and spatial facies trends reveal the relative rates of diapirism and sedimentation. The study area outcrop, north of the diapir, is divided by significant stratigraphic horizons that help define depositional periods. Six measured sections in the study area reveal higher preservation rates of fine grained floodplain deposits, typically destroyed in alluvial environments, than at locations correlating to stratigraphic levels high in the outcrop suggesting a low accommodation environment evolving into higher accommodation where stacked channel complexes are preserved. Preserved slump folding at the base of the outcrop reveals that although some salt emergence occurred in the earliest depositional period it was not significant enough to preclude sediment deposition or to divert the Cutler fluvial network and destroy floodplain facies. A 3-D digital outcrop, modeled from photogrammetric data, illustrates the development of localized accommodation, attracting fluvial channel in a near-salt, tight axial syncline during the later depositional period. These evidences suggest a greater emergence of the diapir and likely diversion of the Cutler channel complexes.

The Qadimah Fault has been mapped as a normal fault running through the middle of a planned $$$50 billion city. For this reason, there is an urgent need to evaluate the seismic hazard that the fault poses to the new development. Although several geophysical studies have supported the existence of a fault, the driving mechanism remains unclear. While a fault controlled by gravity gliding of the overburden on a mobile salt layer is unlikely to be of concern to the city, one caused by the continued extension of a normal rotational fault due to Red Sea rifting could result in a major earthquake. A number of geomorphology and geodetic techniques were used to better understand the fault. An analysis of topographic data revealed a sharp discontinuity in slope aspect and hanging wall tilting which strongly supports the existence of a normal fault. A GPS survey of an emergent reef platform which revealed a tilted coral surface also indicates that deformation has occurred in the region. An interferometric synthetic aperture radar investigation has also been performed to establish whether active deformation is occurring on the fault. Ground movements that could be consistent with inter-seismic strain accumulation have been observed, although the analysis is restricted by the limited data available. However, a simple fault model suggests that the deformation is unlikely due to continued crustal stretching. This, in addition to the lack of footwall uplift in the topography data, suggests that the fault is more likely controlled by a shallow salt layer. However, more work will need to be done in the future to confirm these findings.

Utilization of salt-tolerant species or cultivars is one the most effective methods to address salinity problems in turfgrass management. The relative salt tolerance in 26 commercial creeping bentgrass (Agrostis stolonifera) cultivars during germination was studied. Final germination rate (FGR) and daily germination rate (DGR) decreased as salinity levels increased; however, DGR was more sensitive to salinity stress. Substantial differences in salt tolerance were observed in bentgrass cultivars, with 'Declaration', 'Seaside II', 'T-1 ', and 'Bengal' being the most salt-tolerant (averaged predicted salinity level causing 50% reduction of DGR [PSLD] = 8.2 g L -1 NaCl) and 'Tyee', 'Kingpin'. and 'SRI 150' being the most salt-sensitive (averaged PLSD = 6.5 g L -1 NaCl). Relative salinity tolerance in four populations of prairie junegrass (Koeleriu macrantha) collected from Colorado, Minnesota, Nebraska, and North Dakota and two improved turf-type cultivars from Europe ('Barleria' and 'Barkoel') was determined and compared to Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), sheep fescue (Festuca ovina), hard fescue (F. brevipila), and tall fescue (F. arundinacea). All populations of prairie junegrass showed similar salt tolerance with an average of PSLF and PSLD being 7.1 and 5.3 g L -1 NaCl, respectively, comparable to Kentucky bluegrass and hard and sheep fescue but lower than tall fescue and perennial rye grass. In junegrasses, larger variations were observed in visual quality (VQ) than in electrolyte leakage (EL) and dry weight (OW) at vegetative growth stage. 'Barleria' junegrass showed the highest VQ, following two salt-tolerant grasses, tall fescue and sheep fescue. Junegrass - Nebraska population was the least salt-tolerant within the species, but still exhibited similar or higher tolerance than Kentucky bluegrass and perennial ryegrass cv. Arctic Green. Overall, junegrass was more salt sensitive during germination but more tolerant to salinity when mature.

No description available.

Aim: Limited information exists regarding the implementation of salt reduction strategies on collective food services, such as restaurants and food concessionaires. The present study aimed to assess the effect of a salt reduction strategy on blood pressure levels and food acceptability among customers of a food concessionaire. Methods: A quasi-experimental study with two phases was conducted. In the pre-intervention phase, the amount of salt used in food preparation was determined. In the intervention phase, a reduction of 20% in salt added to food preparations was implemented. Four hedonic tests and two blood pressure measurements were performed before and after the intervention implementation using standardised techniques. In addition, an evaluation of uneaten food was conducted daily on all customers' plates. Mixed linear regression models were generated to assess the effect of the intervention on blood pressure and acceptability. Results: A total of 71 workers were evaluated, mean age of 37.5 years, 57.8% females, who consumed the food of the concessionaire, on average, 4.4 (SD: 0.7) days per week. Systolic and diastolic blood pressure were reduced by 3.1 (P<0.001) and 2.9 (P<0.001) mmHg at the end of the study, respectively. The results of the hedonic tests and the uneaten food before and after the intervention did not vary significantly. Conclusions: The reduction of 20% of salt added to food from a concessionaire had a positive impact on the reduction of customers' blood pressure without reducing food acceptability. This strategy could be implemented in other contexts. / Revisión por pares