<p> Bur oak (Quercus macrocarpa Michx.) savannas of the Great Plains have long been reported to be disappearing and/or progressing to other vegetative schemes. These losses are directly relatable to the arrival of European settlers and their subsequent suppression in natural prairie fires, along with the introduction of domestic livestock. A preliminary investigation of the floristic composition within remaining oak savannas of Custer County, Nebraska was conducted as a base means of documenting plant diversity within the remaining savannas of central Nebraska. The point-centered quarter method was used to determine species, density, relative density, frequency, relative frequency, dominance, relative dominance, and importance values (IV). The Swedish-increment boring method was applied to woody vegetation to document tree ages and compositional change in the savanna over time. Exclusion cages on oak seedlings, vegetative and soil sampling were also utilized. Results indicated a bleak future for the remaining savannas of Nebraska. Bur oak averaged an importance value of 159.10 out of 300.00, leaving a substantial portion of the importance values divided among several fire-sensitive species. The majority of bur oaks sampled were distributed among the higher size classes, indicating a low rate of recruitment. Age class distributions further support this conclusion with a minuscule number of oaks younger than 25 years of age and the majority of the species recorded over 100 years of age. Seedling survivability tests during summer months produced low survivorship (3.13%) due to drought and large/small mammal herbivory. Winter testing displayed similar results. Vegetation sampling indicated high percentages of exposed till and weedy plant species, indicating a long history of abuse. Soil tests resulted in significant differences in phosphorus and zinc concentrations. As oak recruitment failings continue on a near global scale, more research should be conducted to assist in the conservation and management of these vital ecosystems.</p>

<p> This research aimed to determine whether wood microsites ("nurse logs"), which are regeneration sites in Pacific Northwest (PNW) subalpine forests, supported regeneration at timberline-alpine meadow borders. Upward advance of forests and conifer invasion into alpine meadows, which may be occurring in conjunction with climate warming, have gained worldwide attention. Successful alpine meadow seedling regeneration depends on suitable substrate availability, or microsites, for seedling establishment. To better understand factors associated with wood microsite occurrence, mechanisms of wood input were determined and four specific hypotheses were posed to assess: (1) seedling density and seedling survival; (2) growing season length, summer mean growing temperature, and growing degree hours (GDH); (3) active measures of seedling growth; and (4) global wood microsite climate associations. Of four studies, three were conducted in the Cascade Mountains of Washington state along a west - east precipitation gradient and one study, assessed various microsites globally. For Cascades-related research, wood and adjacent soil substrate temperature, moisture, and associated seedling density, survival, stomatal conductance, water potential, and leaf nitrogen were compared by percent transmitted radiation at 4 to 14 study sites. Analysis of variance (ANOVA), t-tests, regressions, and classification and regression trees (CARTs) were used to assess significance of comparisons. Wood microsites, common at 13 of 14 random Cascade sites, had greater seedling densities, greater seedling survival, greater volumetric moisture content (VWC), greater temperature, and greater number of GDH, as compared to adjacent soils. Greater seedling densities were positively associated with VWC (> 12%), conditions most commonly associated with wood substrate presence. For sites having > 25% percent transmitted radiation, positive relationships existed between stomatal conductance and VWC. Globally, high-elevation forests with wood microsites had mean annual precipitation from 86 cm to 320 cm and mean annual temperatures from 1.5&deg;C to 4.7&deg;C. In general, wood microsites facilitated alpine meadow regeneration better than adjacent soils. Management implications included enhanced understanding of factors associated with upward forest advance and wood use for restoration. Globally, wood microsites importance is likely underrepresented. Wood microsites role with warming climate will depend on precipitation pattern, timing, magnitude, and frequency.</p>

"Hairy" roots hold the potential for economically feasible biotechnological routes to the controlled biosynthesis of complex, plant-derived, 'natural' molecules. A novel transgenic root system of the tropical plant Catharanthus roseus was established and analyzed for the synthesis of indole alkaloids, including the valuable anti-cancer drugs vinblastine and vincristine. A structured approach to developing the biosynthetic potential of hairy roots is presented: transformation, screening, selection, optimization of culture protocols, and product enhancement. Five hairy root clones with unoptimized doubling times of 3-4 days and vindoline output of 0.005-0.07% dry weight, were screened from 150 transformants. Hairy root morphology likely under the control of rol genes transferred from the Agrobacterium plasmid, was identified as a key determinant of fitness in liquid culture and a target for transgenic design for large-scale bioreactor environments. The hairy root inoculum was optimized and standardized to facilitate the assessment of culture performance under diverse environmental treatments and in process scale-up. The length of the root tip has a dominant effect on growth, uninfluenced by clonal variability. The optimum inoculum is comprised of 5 root tips, each 35-40 mm long, in 50 mL media. Long-term dose-response and transient studies examined heterotrophic and photoheterotrophic carbon regimes. These studies are unique in the metabolic adaptation of cultures, and examined the putatively antagonistic kinetics of nutrient utilisation and secondary metabolite accumulation. The activities of the cathenamine and bisindole alkaloid pathways responded, respectively to high and moderate sucrose concentrations. The cultures were nitrogen limited with 2-4% sucrose in B5/2 salt. Organic acids were excreted in the presence of excess sugars. The ordered assimilation of macronutrients--ammonium, phosphate and nitrate--corroborated by changes of extracellular pH, have important implications on fed-batch strategies. Tabersonine accumulation was growth-associated, while serpentine accumulated in a non-growth manner. Ajmalicine, catharanthine, vindoline, and compounds tentatively identified as vinblastine and vincristine, accumulated optimally in the late-exponential or early-stationary phase. Photoheterotrophic conditions incremented peak biomass by 60-300%, doubling times by 60%, and vindoline levels by an order of magnitude, likely due to the anapleurotic activity of PEPCase and the light induction of nitrate reductase and vindoline synthesis.

Plant metabolic engineering is a developing field still in need of improved tools and an increased understanding of relevant pathways. This thesis addresses both those needs by testing a new tool for improved metabolic engineering studies and utilizing that tool for the exploration of monoterpenoid indole alkaloid biosynthetic pathways. Using GFP as a model protein in Catharanthus roseus hairy roots, we report that the glucocorticoid inducible promoter system is active and has a tightly controlled, reversible, and dosage-dependent response to dexamethasone. Furthermore, it provides an improved negative control useful for the study of genes affecting alkaloid synthesis. The most exhaustive transgenic studies reported here focus on the indole pathway. Expressing a feedback-resistant Arabidopsis anthranilate synthase alpha subunit results in dramatic increases in tryptophan and tryptamine yields. On induction, tryptophan increases from undetectable levels to 2.5 mg/g DW, while tryptamine increases from 25 mug/g DW to 267 mug/g DW. Additionally, a transient improvement in lochnericine yield indicates a possible increase in alkaloid flux countered by tight regulation of alkaloid levels. In lines transgenic for inducible tryptophan decarboxylase, serpentine specific yields increased by as much as 129% on induction. The reported studies on the indole pathway demonstrate successful methods to improve indole flux and show that increased indole flux can lead to improvements in certain alkaloids. Precursors from the complementing terpenoid pathway are also required for alkaloid synthesis. A feeding study utilizing an intermediate and a specific inhibitor of the nonmevalonate pathway validates the importance of this pathway for improved alkaloid yields and points to the potential success of upstream metabolic engineering efforts. In preliminary results, improved yields of certain alkaloids are reported for hairy root lines transgenic for 1-deoxy-D-xylulose-5-phosphate synthase and geraniol 10-hydroxylase, while an ORCA3 study highlights some potential problems with the use of transcriptional activators. In the last study, we focus on the engineering of a valuable alkaloid pathway and report a transgenic hairy root line overexpressing the full coding sequence of tabersonine 16-hydroxylase. On induction, the line produces 16-methoxytabersonine. Overall, a valuable new tool is introduced and subsequently used to manipulate the indole, terpenoid, and alkaloid pathways.

No description available.

<p> As interest in new sweetpotato (<i>Ipomoea batatas</i> (L.) Lam.) markets such as starch feedstocks, anthocyanin production, chips and French fries, and other processed food products have increased, breeders have begun developing sweetpotatoes with unique compositions. This dissertation describes a three-pronged strategy to understand the genetic control of sweetpotato composition and modify it using near infrared spectroscopy (NIRS), quantitative inheritance studies, molecular markers, and exotic germplasm.</p><p> In our first experiment, a 5 &times; 5 NCII crossing block with 25 full-sib families was designed to study the inheritance of sweetpotato starch and anthocyanin content. Linear regression modeling was used to determine the effect of general combining ability (GCA) and specific combining ability (SCA) on dry matter, total monomeric anthocyanin (TMA) concentration, fresh yield, and total dry matter and anthocyanin yield. All five traits were moderately to highly heritable with significant general combining abilities. Yield and dry matter yield had significant specific combining abilities and significant differences among parents were discovered for all traits. Yield, dry matter, dry matter yield, and TMA yield were significantly impacted by spatial gradients within the field, but TMA concentration was not. Phenotypic and genotypic correlations among traits indicated that many traits of interest shared either genotypic and/or phenotypic correlations.</p><p> In our second experiment, a nested crossing block was used to estimate the heritability of sweetpotato yield and storage root composition traits in a population incorporating exotic germplasm obtained from the US sweetpotato germplasm repository and a core set of elite US sweetpotato lines crossed in a modification of the NCI design. Yield traits were recorded in the field and biochemical composition was phenotyped using NIRS. Heritability was measured on a half-sib family basis and a full-sib family basis to allow comparison between the commonly used polycross nurseries and paired crossing blocks. Parent offspring regression, which has been commonly used by sweetpotato breeders, was also used to provide another heritability estimate. Starch and sugar contents had relatively high heritabilities on both a GCA (h² > 0.32) and SCA basis (h² > 0.77). Yield traits had low heritability on a GCA basis (h² &lt; 0.16), but moderate heritability on an SCA basis (h² = 0.21 &ndash; 0.51). Heritability trends suggested that polycross nurseries could be effective for modifying sweetpotato composition, while paired crosses would be more effective for the modification of sweetpotato yield. Based on the performance of a wide range of crosses between exotic and heirloom varieties, we hypothesize that the global sweetpotato germplasm base contains many useful alleles for continued sweetpotato improvement. </p><p> Our final study involved a previously described sweetpotato quantitative trait loci (QTL) mapping population developed from a Tanzania x Beauregard cross (Cervantes-Flores 2006). This population was phenotyped using NIRS to identify QTL for sugar and starch content. In Beauregard, six QTL were associated with decreased starch and dry matter content and eight QTL were associated with increased sugar content. One QTL in Beauregard was associated with decreased yield. In Tanzania, two QTL were associated with increased starch and two QTL were associated with decreased starch; there were also two QTL associated with decreased sugars and one associated with increased sugar content; one QTL was associated with decreased culls. In most cases, newly identified QTL co-locate with those previously described.</p><p> Collectively, this research represents a significant effort in sweetpotato to merge molecular markers with NIRS phenotyping, and it has opened the doorway to further developments that merge these two new technologies for sweetpotato improvement.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7030. Adviser: Randall L. Nelson. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2007. / Title from PDF t.p. (viewed Nov. 18, 2008). Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6842. Adviser: James D. Bever.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3290. Adviser: Lila O. Vodkin. Includes bibliographical references (leaves 159-165) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6315. Adviser: John W. Erdman, Jr. Includes bibliographical references (leaves 126-152) Available on microfilm from Pro Quest Information and Learning.