Bielefeld, Universiẗat, Diss., 2001.

No description available.

No description available.

The focus of this research was on the xylem sap of cucumber plants during arsenic stress. A better understanding of the uptake and translocation mechanisms within the plant is crucial for the assessment of arsenic impact on fruits and cereals of the human diet. The impact of four different arsenic species (As(III), As(V), DMA(V) and MMA(V)) on the xylem sap production and their respective concentration in the xylem was studied. Cucumbers behave similar under arsenic stress as other non-tolerant plant species regarding uptake and translocation; high inorganic uptake into the roots but higher translocation of methylated arsenic into shoots and leafs. In plant physiology spectroscopic techniques coupled to separation techniques are usually deployed for metal(loid) studies. These techniques are well known and used. However, their robustness might be a disadvantage when it comes to biological dynamic systems. To overcome this, voltammetry was used as a new technique for xylem sap and hydroponic nutrient solution analysis. Voltammetry was used to analyse the nutrient solution of hydroponically grown cucumbers and their xylem sap during arsenate treatment in order to detect weak arsenite complexes. Furthermore, assessment of complexation capacities and ligand concentrations were performed. In order to identify possible arsenite ligands, xylem sap was analyzed by metabolomics, a recently developed tool for analyzing biological samples. Here, xylem sap samples of arsenate stressed plants were compared with control plants to identify organic compounds which are up- or down-regulated due to arsenate stress. Nine m/z values were identified to be up- or down-regulated under arsenate stress of which five were used for identification. LC-MS spectra obtained by high-resolution LC-MS were used for identification of organic compounds regulated due to arsenate stress. Isoleucine was found to be down-regulated under arsenate stress.

Thesis (M.S.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 44-45). Also available on the World Wide Web.

No description available.

No description available.

Thesis (Ph. D.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 85-91). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 192-222). Also available via the World Wide Web.