Thesis (Ph. D.)--Landbouwhoogeschool te Wageningen, 1937. / Summary, table of contents and list of ill. in English.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Plant invertases (EC 3.2.1.26) represent a multi-gene family of β-fructofuranosidases that perform integral roles in several biochemical processes. The central importance of this family of enzymes to plant growth and development has made them a primary target of investigation in plant biology. Research has principally focused on sink-source interactions, and the potential to increase sink capacity in several economically important crop species, including potato and tomato. However, studies exploring the impacts of invertase mis-regulation on cellulose and lignin, the two most abundant biopolymers on earth, had not been conducted. Consequently, we investigated the effects of overexpressing yeast-derived invertases in tobacco and hybrid poplar. Transgenic tobacco expressing the yeast-derived invertases showed reduced height and interference in sink-source metabolism. In addition, some transgenic lines showed significant changes in cellulose and lignin content, providing evidence that sink capacity can be altered via the overexpression of this class of enzyme. In contrast, hybrid poplar expressing foreign invertase genes showed no visible phenotype, with only minor changes to the structural polymers cellulose and lignin, suggesting the mechanism of carbohydrate transport differs between tobacco and hybrid poplar. However, there was evidence for post-translational modification of the foreign invertases in hybrid poplar, which may also explain the difference in phenotypes observed. We suggest that the yeast-derived invertases may not be the most effective target to alter sink biopolymers, and that mis-regulating endogenous invertases may be a more suitable alternative. Consequently, we identified three cell-wall invertase genes in hybrid poplar and investigated their spatial and temporal expression profiles during the complete first year of growth. In addition, we heterologously expressed and characterized two hybrid poplar cell-wall invertase genes involved in vegetative growth. Collectively, the expression and functional characterization data suggest that one floral-specific and two vegetative cell-wall invertases exist in hybrid poplar. Of the two vegetative cell-wall invertases, one (PaxgINV1) appears to be involved in processes relating to dormancy, while the other (PaxgINV2) appears to be involved in phloem unloading and the seasonal reallocation of carbohydrate. We therefore hypothesize that PaxgINV2 may be a suitable target for future mis-regulation studies aimed at altering sink capacity. / Forestry, Faculty of / Graduate

Thesis (M.S.)--Oregon State University, 2008. / Printout. Accompanied by zipped folders that include Excel and pdf files. Includes bibliographical references. Also available on the World Wide Web.

The purpose of this study was to investigate variation in selected anatomical, physical and mechanical properties of three Populus x euramericana (Dode) Guinier hybrid clones grown on two dissimilar sites in Hungary. Six 15 years old trees from three clones on one site and six 10 years old trees from two clones on the other site were sampled at breast height. Anatomical properties, including vessel lumen diameter, area and shape factor, number of vessels per unit area, fiber lumen diameter and area, fiber length, ray area, and cell wall area percent were measured by an image analyzer. Site, clone and/or their interaction significantly affected one or more of these properties except fiber length. Variations were significant among trees within clone and site for all variables except vessel lumen diameter. However, most of the variations was within tree as a result of the effect of age. Statistically significant correlations were found between anatomical properties. For specific gravity, there was no significant differences between sites but there was a significant clone effect with a repeatability of 0.51 indicating genetic control on this property. There were no significant differences among clones for modulus of rupture, crushing strength, maximum tensile strength, and tension modulus of elasticity. Strength properties were significantly higher near the bark than close to the pith except for maximum tensile strength. Specific gravity was not the single most important factor affecting strength properties of the clones. The effect of age and growth rate on specific gravity and anatomical properties were also investigated. Differences among clones for growth ring widths were significant in the "good" years only. Specific gravity was high near the pith, then each of the clones exhibited a different radial pattern. Based on segmented regression, a quadratic model with a plateau proved to be useful for estimating the demarcation between juvenile and mature anatomical characteristics. The ages of maturation were not the same for all properties; however, the order of maturation was the same on both sites. No consistent relationships between growth rate and specific gravity and anatomical properties were found when growth rings of the same age were compared. / Ph. D.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 105-116). Also available on the World Wide Web.

Poplar Bark Storage Proteins (BSP) are important in storing nitrogen (N) recovered from autumn-senescent leaves, and supply N for spring growth. Plants of Populus tremula x P. alba were transformed with a poplar BSP antisense cDNA fused to a double 35S promoter. Regenerated lines were screened for reduced BSP accumulation in short day photoperiod, and two lines were selected for further studies. Under long-day conditions, both BSP-antisense lines were characterized by larger leaves, longer internodes and slower growth rates, for a net shift in dry-matter partitioning from stem to leaf. Antisense lines also show reduced N concentration in leaf and stem tissue, and altered nitrate uptake. Grafting studies show that these effects on leaf and stem partitioning and N content are determined by the shoot genotype. These results indicate an important role of BSP in long day growth and partitioning. BSP-antisense plants did not show altered Nitrate Reductase activity, as determined by in vivo assay. Wild-type poplar plants were grown hydroponically on solutions of 0 to 30 mM nitrate, and NR activity determined on leaf, stem and root tissue. Leaf activity was >20x higher than root or stem, with the highest activity found in young expanding leaves. NR activity of both leaves and roots increased with N supply. During autumn, BSP-antisense leaves abscised earlier than the untransformed wt. Abscised wt leaves contained a higher proportion of pre-senescent N levels. Comparisons among ecotypes of P. deltoides and among clones of P. trichocarpa x P. deltoides demonstrated genetic variation in both time of BSP induction, and amount of BSP accumulation. In six P. deltoides ecotypes grown at a common site, time of maximum BSP mRNA was inversely correlated with latitude of origin. Eight to ten clones from each of six full-sib families of P. trichocarpa x P. deltoides were screened for SD BSP accumulation. Clonal differences in BSP accumulation were significant in 5 of 6 families, and clones with high BSP levels also had higher total stem N content. These results further confirm the importance of BSP in autumn N resorption. / Graduation date: 2000

Thesis (Ph. D.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 233-268). Also available on the World Wide Web.

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen (viewed 1/24/2008). "MES thesis." Includes bibliographical references (leaves 150-156).

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 71-84). Also available on the World Wide Web.