No description available.

<p>Roots are developmentally plastic and highly dependent on the immediate environment. By studying root responses to abiotic stress, we have identified novel regulators of developmental modulation. When roots are deprived of phosphate (Pi), developmental programs are modulated to slow primary root growth and expand surface area through emergence of root hairs. By focusing on exposure time-periods of less than two days, we have described very early changes to root development in response to this condition that may reveal new mechanisms of root hair specification and emergence. Also, using transcriptomic analyses with high spatial resolution, we identified a kinase that is specifically induced in root vascular tissue within three hours of exposure and acts to modulate aspects of root development in response to deprivation of Pi. These data suggest that individual tissues play unique roles in whole organ development, and that interpretation of Pi -deprivation responses may change as we develop methods with resolution necessary to understand these roles. Beyond Pi, we compared transcriptomic data for four additional stresses and identified a novel stress-responsive transcription factor that modulates expression of a cell expansion protein. This putative network connection demonstrates the value of using high-dimensional data for inference of regulatory relationships. Overall, we have combined "-omics" approaches with reverse genetics to identify novel developmental regulators and described a phenotypic frame-work with resolution at which cellular mechanisms can be studied.</p> / Dissertation

Low phosphate fertilizer efficiency in high pH soils is primarily due to the retardation of P movement in the soil-P fertilizer reaction zone. The objective of this study was to obtain fundamental information on the influence of multi-ionic interactions on the solubility and diffusion of P in columns containing a model soil system and two soil types. The study also aimed to identify the salt combinations and factors that have the potential to enhance the solubility and movement of P in calcareous soil condition. The results showed that the interaction of NH4+ and SO42- was consistent at enhancing the water solubility and movement of P under a high soil pH condition. This effect was attributed to the combination of various mechanistic factors associated with (NH4)2SO4 compound including significant pH reduction, cation exchange reaction of NH4+ with the exchangeable Ca2+, and anionic competition of SO42- with P for precipitation with Ca2+.

Cadmium (Cd) is a potentially toxic trace element. Two growth chamber studies were conducted to understand how: i) mono-ammonium phosphate affects durum wheat, flax or canola Cd uptake due to fertilizer induced changes in soil solution and plant; ii) preceding canola and barley affect the Cd uptake of subsequent durum wheat or flax. Durum wheat and flax shoot Cd concentrations were greater when grown on previous crop canola soil than when grown on previous crop barley soil regardless of what type of crop residue, if any, was added. The increase in Cd uptake for durum wheat and flax when on canola soil was probably due to increased availability of Cd in soil. Conversely, the application of mono-ammonium phosphate – reagent grade and the incorporation of preceding crop residue did not increase the crop Cd uptake of canola, durum wheat or flax and durum wheat or flax, respectively.

Inorganic phosphate is an essential nutrient for all organisms. It is required for many cellular components as nucleic acids and phospholipids, and as energy-carrying compounds such as ATP. Thus, a regulated uptake of this pivotal nutrient is of outermost importance. Depending of the availability of phosphate in the surroundings the yeast Saccharomyces cerevisiae make use of two different systems for transporting phosphate into the interior of the cell: a low-affinity system that is active during surplus phosphate conditions and a high-affinity system that is active when the availability becomes limited. This thesis focuses on the high-affinity system, which is comprised of the Pho84 and Pho89 transporters. Of the two transporters, Pho84 is the predominant one, responsible for almost all phosphate uptake during low phosphate conditions, and the contribution of Pho89 is of minor importance. Hence Pho84 is by far the most well characterized phosphate transporter. Even though much is known about phosphate transporters in yeast little in known about how phosphate is transported. The work in this thesis aims to broaden the knowledge about the transport mechanism by the means of site-directed mutagenesis and functional characterization. Also the similarity of Pho84 to glucose sensors and the potential role of conserved residues in phosphate signaling are investigated. By the use of a high-affinity system deletion strain (∆Pho84 ∆Pho89), we also managed to investigate the functional importance of well conserved residues in Pho89. In summary: the work presented in this thesis has contributed to increase the knowledge about transport mechanisms in phosphate transporters.

As consumer demand for all-natural marinades increases, the need to replace phosphate with a natural product that can produce equivalent or improved yield in products such as but not limited to rotisserie chickens (RWOG) and boneless/skinless breast (BSB) is a challenge for processors. The objective of this study was to determine if using an all-natural non-phosphate blend (savorphos-200, SP) in water-based (WB) and oil-based (OB) marinades would perform better in quality and yield parameters than a commercial phosphate blend (PB). The treatments included WB+PB (water, 0.4% phosphate, 0.7% salt), WB+SP (water, 0.5% savorphos-200, 0.7% salt), OB+PB (water, 3% canola oil, 0.4% phosphate, 0.7% salt), and OB+SP (water, 3% oil, 0.5% savorphos-200, 0.7% salt). RWOG and BSB were injected with a multi-needle injector to 20% (wt/wt) pick-up at a constant pressure (15-20 psi). The parameters measured were marinade pick-up %, 20 min and 24 hr marinade retention %, and cook loss %. Color, tenderness, total moisture, and sensory test were conducted on BSB. Data were analyzed within marination type (WB and OB). Results for the RWOG indicated SP obtained higher pick-up yield (p<0.05) and lower cook loss in the OB marinade compared to the PB. For the BSB, pick-up yield on OB marinades are higher for SavoPhos (p<0.05) when compared to the PB. On WB marinades cook loss was lower on SavorPhos compared to the PB. On RWOG and BSB variability is lower for SP on pick-up and 20 min retention yield values. Texture shear values were lower (p<0.05) on SP samples when compared to the PB. A consumer triangle sensory test was not able to distinguish between treatments (p>0.05). Therefore, savorphos-200 can be used as a natural non-phosphate blend in water based marinades with no detriment to yield. In addition, savorphos-200 can be used as a natural non-phosphate blend in oil-based marinades with yield improvements.

Low phosphate fertilizer efficiency in high pH soils is primarily due to the retardation of P movement in the soil-P fertilizer reaction zone. The objective of this study was to obtain fundamental information on the influence of multi-ionic interactions on the solubility and diffusion of P in columns containing a model soil system and two soil types. The study also aimed to identify the salt combinations and factors that have the potential to enhance the solubility and movement of P in calcareous soil condition. The results showed that the interaction of NH4+ and SO42- was consistent at enhancing the water solubility and movement of P under a high soil pH condition. This effect was attributed to the combination of various mechanistic factors associated with (NH4)2SO4 compound including significant pH reduction, cation exchange reaction of NH4+ with the exchangeable Ca2+, and anionic competition of SO42- with P for precipitation with Ca2+.

Zugl.: Weimar, Bauhausuniv., Diss., 2007

Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.

BauhausUniversiẗat, Diss., 2007--Weimar.