Thesis (M.S. in chemical engineering)--Washington State University, August 2009. / Title from PDF title page (viewed on July 15, 2009). "School of Chemical Engineering and Bioengineering." Includes bibliographical references.

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

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Abstracted in Dissertation abstracts, v. 25 (1965) no. 7, p. 4310. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 170-190).

Thesis (Ph. D.)--Washington State University, December 2006. / Includes bibliographical references.

Thesis (M.S. in mechanical engineering)--Washington State University, August 2006. / Includes bibliographical references.

Thesis (M.S. in natural resource sciences)--Washington State University, August 2006. / Includes bibliographical references (p. 42-45).

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 144-161). Also available on the World Wide Web.

Secondary metabolites play important roles in tree defense. Proanthocyanidins (PAs), one of the most common secondary metabolites, are widely distributed in trees and woody plants, and are abundant in poplar. In my research, molecular biology and biochemistry techniques were used to investigate the function of two important transcription factors, MYB115 and MYB134, in regulating the PA pathway in hybrid poplars. The importance of these transcription factors in regulating PA synthesis in leaves has recently emerged, but their roles in roots are not known. MYB134- and MYB115-overexpressing transgenic poplars showed a strong high-PA phenotype in leaves, but how these two regulators interact in vivo is still a mystery. This research aims to test the function of both MYBs in the regulation of PAs in poplar roots, and to explore the antimicrobial functions of root PAs. Both alleles of the MYB genes were sequenced in wild type poplars to design gRNAs for creating transgenic poplars with knocked-out (KO) MYB115 and MYB134 using the CRISPR Cas9 system. Both hairy root and whole plant transgenics with respective single- and double knock-outs were generated. Chemical and genetic characterization of both mutant types showed reduced PA content and down-regulated flavonoid genes in leaves. In poplar roots, only double-KOs showed a significant change in PA and salicinoid metabolism. These results indicated that the regulatory pathways for PA biosynthesis may differ in poplar leaves and roots. Significant PA concentrations remained in double-KO plants, suggesting other transcription factors for PA regulation are active. Because poplars accumulate large amounts of PAs in roots, potential functions of root tannins were also investigated. Antimicrobial activity of PAs was tested by disc inhibition assay in vitro and mycorrhizal co-culture sandwich assay in vivo. Pure PAs showed no inhibition towards the pathogenic fungi Armillaria ostoyae and A. sinapina but displayed slight inhibition to the mycorrhiza fungus Laccaria bicolor. These results provide preliminary insight into the functions of PAs in roots. / Graduate / 2023-04-24

Plant mechanisms regulating environmental heavy metal interactions are vital for plant survival. Plants must maintain adequate metal levels while preventing excesses. Several mechanisms involved in heavy metal uptake and sequestration have been identified and studied in hyperaccumulating plants such as Thlaspi caerulescens. These plants accumulate large quantities of metals, but their use in remediation is limited by their small size. On the other hand, mechanisms in high-biomass, non-hyperaccumulating perennial species such as poplar (Populus spp.) are unknown. The central goal of this project is to delineate specific mechanisms in poplar regulating the heavy metal zinc (Zn) for potential use in bioremediation and real-time monitoring. Specifically, project aims are: 1) Determine the role of HMA4 and PCS1 genes in poplar; 2) Delineate the ZIP gene family including ZIP1 and ZNT1 activity; and 3) Harness fluorescent energy transfer to engineer a poplar tree that monitors Zn-soil contamination. These are addressed using current technologies including phylogenetic analysis, gene transformation, expression assays, promoter-GUS assays, fluorescent-gene imaging, and metal assays. Through these experiments, mechanisms controlling heavy metal interaction are identified and characterized in poplar. Poplar contains a large number of genes in both the ZIP and HMA4 families, but only two members in the PCS family. Poplar also contains several genes that share close sequence and structural homology to those in hyperaccumulators. However, there is an overall divergence from hyperaccumulators in regards to expression across an environmental Zn gradient. Poplar tightly regulates Zn intake by suppressing absorption avenues under Zn excess. Over-expression of HMA4 and PCS1 resulted in more tolerance and more accumulation, respectively, in poplar lines. These findings support a regulatory system used in poplar to limit Zn under excess and promote Zn under deficiency. Using ZNT1 and its natural expression gradient, a chimeric protein was created that served as a biosensor in both poplar and Arabidopsis thaliana host plants and was able to discriminate between 1μM and 10mM Zn concentrations. These findings add to current knowledge of heavy metal regulation and help fill the gap of knowledge currently existing on the regulatory mechanisms that perennial trees use to control heavy metals.

Estimations of plant water use can provide great assistance to growers, irrigators, engineers and water resource planners. This is especially true concerning the introduction of a new crop into irrigated agriculture. Growing hybrid poplar trees for wood chip stock and veneer production under agronomic practices is currently being explored as an alternative to traditional forestry practices. To this author's knowledge, no water use estimates or crop coefficients, the ratio of a specified crop evapotranspiration to a reference crop evapotranspiration, have been verified for hybrid poplars grown under drip irrigation. Four years of weekly, neutron probe measured, soil water data were analyzed to determine averaged daily, monthly and seasonal plant water use, or crop evapotranspiration. The plantation studied was located near Boardman, Oregon on the arid Columbia River Plateau of North-Central Oregon. Water was applied by periodic applications via drip irrigation. Irrigation application data, weekly recorded rainfall and changes in soil water content permitted the construction of a soil water balance model to calculate weekly hybrid poplar water use. Drainage was estimated by calculating a potential soil water flux from the lower soil profile. Sites with significant estimated potential drainage were removed from the analysis so that all sites used in the development coefficients were calculated using reference evapotranspiration estimates obtained from a nearby AGRIMET weather station. Mean crop coefficients were estimated using a 2nd order polynomial with 95% confidence intervals. Plant water use estimates and crop curves are presented for one, two and three year old hybrid poplars. Numerical simulation of irrigation practices was attempted using weekly soil water content and soil physical characterization data. Parameter optimization and numerical simulations were attempted using the HYDRUS-2D Soil Water and Solute Transport model. Parameter optimization and numerical simulations were largely unsuccessful due to lack of adequate soil physical and root zone system representation and dimensional differences between drip irrigation processes and the model design used in this study. / Graduation date: 1998