Life Sciences Commons^™

Establishing And Optimization Of Tissue Culture Work With Erigeron Canadensis, Robert Petursson

Masters Theses

Glyphosate resistance among weed species has been an increasing problem in crop production over the past two decades. Glyphosate resistant Erigeron canadensis (horseweed) has been found on multiple continents and 20 U.S. states. It appears that the resistance is of non-target type, with mechanisms of action that have yet to be elucidated at the gene level. For the first portion of the study, I focused on reproducing the original indirect organogenesis protocol but discovered biotype variability can influence regeneration success. An improved indirect organogenesis method was then developed using the previously published methods that could be used across biotypes. A …

Protein, Methionine, And Cysteine Upregulation In Phaseolus Vulgaris ‘Black Turtle Bean’ Seeds Through Sulfur Fertilization At V2 And R2 Stages Of Growth, Hannah Paige Barry

Masters Theses

The purpose of this research was to increase protein, methionine, and cysteine content in Phaseolus vulgaris L., common bean in relation to the inhibitory compound tannin. Previous research has shown that sulfur fertilization increases total protein, methionine and cysteine content in various crops, but always in tandem with inhibitory compound increases. If successful, the resulting bean seed will have a better nutrient profile for malnourished populations around the world.

Granular gypsum was applied at 0 kg S ha^-1 [kilograms of sulfur per hectare], 10 kg S ha^-1, 20 kg S ha^-1, 40 kg S ha …

Evaluation Of Hall’S Panicgrass (Panicum Hallii Vasey) As A Model System For Genetic Modification Of Recalcitrance In Switchgrass (Panicum Virgatum (L.)), Joshua Nathaniel Grant

Masters Theses

While switchgrass (Panicum virgatum (L.)) has long been recognized as a viable bioenergy feedstock, it and other plants have cell walls with recalcitrance to processing. Recalcitrance is recognized as a major barrier to broad adoption of switchgrass and other feedstocks for cellulosic bioenergy. In an effort to reduce recalcitrance, transgenic plants have been generated with altered cell wall phenotypes such as reduced lignin. Unfortunately, stable transformation of switchgrass and other C4 grasses is time intensive, costly, and genetic analysis is further complicated by polyploid genomic structures. Unlike switchgrass, which can be tetraploid to octoploid, a closely related species, Hall’s …

Comparison Of Mesophyll Protoplast Isolation And Transformation Between Panicum Virgatum And Panicum Hallii, Andrea Grace Collins

Masters Theses

Protoplasts are appropriate targets for genome editing, DNA functional screens and transgenesis. This project focuses on the comparison of inexpensive mesophyll protoplast isolation via the use of food-grade enzymes and transformation between diploid Panicum hallii Vasey (PAH) and polyploid cellulosic feedstock Panicum virgatum L (switchgrass), a relative of PAH. PAH has great potential as a C4 model species for crop and bioenergy research. Here an inexpensive switchgrass and PAH mesophyll protoplast isolation and transformation system was developed; the first protoplast system for PAH. Using low-cost commercial food-grade enzymes, a cost reduction of ~1000-fold was achieved compared to traditional protoplast isolating …

Testing The Temporal Stability Of The Climate Response Of Tree Species At Norris Dam State Park, Tennessee, U.S.A., Allison Elizabeth Ingram

Masters Theses

Temporal stability of the climate-tree growth relationship means that over time, tree species were responding to a specific climate variable and continue to respond to that variable into the present. The stability of this response is important to test prior to attempting to reconstruct past climate. In this study, I sampled oaks (white oak = Quercus alba L. and chestnut oak = Quercus montana Willd.) and pines (Virginia pine = Pinus virginiana Mill. and shortleaf pine = Pinus echinata Mill.) growing in Norris Dam State Park in eastern Tennessee and tested the temporal stability of these species and their potential …

Rooting Characteristics And Antioxidant Pigment Responses Of Three Hybrid Bermudagrass [Cynodon Dactylon (L.) Pers. × Cynodon Transvaalensis Burtt- Davy] Cultivars Exposed To Drought, Cory Alan Yurisic

Masters Theses

With recent changes in global climate, water use and its conservation have become important topics of discussion. Turfgrasses for lawns, parks, and other recreational areas are often perceived negatively due to the need for irrigation. The identification of turfgrasses possessing an improved ability to withstand water deficit is an important goal in science to curb irrigation requirements in the landscape. Newly released cultivars of hybrid bermudagrass (C. dactylon L. x. C. transvaalensis Burtt-Davy) have demonstrated improved tolerance to stresses such as cold, traffic, and water deficit; however, drought resistance mechanisms of these new cultivars have been largely uninvestigated. Drought …

Rare Occurrences Of Free-Living Bacteria Belonging To Sedimenticola From Subtidal Seagrass Beds Associated With The Lucinid Clam, Stewartia Floridana, Aaron M. Goemann

Masters Theses

Lucinid clams and their sulfur-oxidizing endosymbionts comprise two compartments of a three-stage, biogeochemical relationship among the clams, seagrasses, and microbial communities in marine sediments. A population of the lucinid clam, Stewartia floridana, was sampled from a subtidal seagrass bed at Bokeelia Island Seaport in Florida to test the hypotheses: (1) S. floridana, like other lucinids, are more abundant in seagrass beds than bare sediments; (2) S. floridana gill microbiomes are dominated by one bacterial operational taxonomic unit (OTU) at a sequence similarity threshold level of 97% (a common cutoff for species level taxonomy) from 16S rRNA genes; …

Distribution Of Abc Transporter Genes Across The Plant Kingdom, Thomas Scott Lane

Masters Theses

The ATP-binding cassette (ABC) transporter gene superfamily is ubiquitous among extant organisms. ABC transporters act to transport compounds across cellular membranes and are involved in a diverse range of biological processes and functions including cancer resistance in humans, drug resistance among vertebrates, and herbicide resistance in weeds. This superfamily of genes appears to be larger and more diverse in the plant kingdom—yet, we know relatively less about ABC transporter function in plants compared with mammals and bacteria. Therefore, we undertook a plant kingdom-wide transcriptomic survey of ABC transporters to better understand their diversity.

We utilized sequence similarity-based informatics techniques to …

Evaluating Pollination Ecology Of The Endangered Pityopsis Ruthii (Small) Small (Asteraceae), Philip Anthony Moore

Masters Theses

Pityopsis ruthii (Small) Small, also known as Ruth’s golden aster, is a federally endangered herbaceous perennial, endemic to two river systems, the Hiwassee and the Ocoee, within the Cherokee National Forest, Polk County, Tennessee. There are approximately 13,000 individuals that may be at high risk of short-term extirpation (Thompson and Schwartz, 2006). Little is known of the basic reproduction and life history of P. ruthii. Clebesh and Sloan (1993), Cruzan (2001), Park (1998), and Wadl et al. (2014) found evidence that seed production and seed viability are highly variable. Clebesh and Sloan (1993) indicated that pollinator visitation was highly temporal …

Use Of Capacitance Sensors For Development Of Conservative Irrigation Regimes, Ethan Daniel Hagen

Masters Theses

Several experiments were conducted to further develop capacitance sensor-based automated irrigation systems. The first experiment tested whether the photosynthetic response to decreasing volumetric water content (VWC) differed among four species tested. A sigmoidal curve best described the relationship for all species (r² [r-squared]>0.86). The VWC that maintained maximum photosynthesis at 90% was selected as a potential conservative irrigation set point and values were not different between species, nor were 100% container capacity values. This indicates that a single set point is adequate to initiate irrigation and that a common upper threshold for VWC can be used for this …

Distribution And Growth Of Autumn Olive In A Managed Landscape, Matthew Ruddick Moore

Masters Theses

Invasions by exotic plant species result in significant challenges for forest managers. Disturbance and increased light have been shown to facilitate the successful establishment and invasion of exotic, invasive plant species. Several studies have sought to determine which key factors lead to greater abundance of exotic, invasive plants on certain sites and this information is important for determining the likelihood for exotic plant invasions at broad scales. Site characteristics that may promote autumn olive (Elaeagnus umbellata) were studied. Our goal was to identify variables associated with forest road edges most important in explaining autumn olive abundance and growth. …

Impacts Of Preemergence Herbicides On Hybrid Bermudagrass Morphology, Patrick Alan Jones

Masters Theses

Preemergence (PRE) herbicides were evaluated in multiple experiments to determine their impacts on hybrid bermudagrass morphology [(C. dactolyn (L.) Pers. x C. transvaalensis (Burtt Davy)]. First, indaziflam and prodiamine were applied to hybrid bermudagrass rooted to various depths in either sand or silt loam mini-rhizotrons. Results indicated that prodiamine (a mitiotic inhibitor) and indaziflam (a cellulose biosynthesis inhibitor) both significantly reduced root length density compared to a non-treated control; however, indaziflam treated plants exhibited foliar injury (i.e., reddening, necrosis) while those treated with prodiamine did not.

The researchers surmised that reductions in root length density with indaziflam may compromise …

Interacting Effects Of Fire Activity, Climate, And Habitat Diversity On Forest Dynamics, El Malpais National Monument, New Mexico, Usa, Alex John Pilote

Masters Theses

The historic effects of fire and climate on stand dynamics in the ponderosa pine-dominated forests of the American Southwest are of increasing concern to land management agencies. Using present forest stand structure, the mixed-conifer forests of the volcanic features in El Malpais National Monument were analyzed at three separate sites: a cinder cone, an ancient basalt flow, and an isolated “island” (kipuka) completely surrounded by basalt flows. Increment cores were collected from 632 trees in 19 plots within the monument to obtain dates of establishment. These dates were compared with historic fire histories and precipitation records to analyze the effects …

Control Of Glyphosate Resistant Horseweed (Conyza Canadensis) With Saflufenacil And Tank-Mixture Partners., Brock Steven Waggoner

Masters Theses

Field and labratory studies were conducted to determine the efficacy of saflufenacil alone and with mixture partners for burndown. Field studies were conducted in 2009 and 2010 to evaluate saflufenacil in mixtures with glyphosate, glufosinate, or paraquat for control of glyphosate-resistant (GR) horseweed prior to planting cotton. Saflufenacil and saflufenacil mixtures were applied 7 days before planting (DBP). Saflufenacil at 25 and 50 g ai ha-1 in mixture with all three non-selective herbicides provided similar GR horseweed control when compared to the current standard of glyphosate plus dicamba. Control of GR horseweed was also not different at the 25 and …

Effects Of Trinexapac-Ethyl And Winter Overseeding On The Morphological Characteristics And Traffic Tolerance Of Bermudagrass Cultivars, William D. Haselbauer

Masters Theses

Common bermudagrass [Cynodon dactylon (L.) Pers.] and hybrid bermudagrass [C. dactylon (L.) Pers. X C. transvaalensis Burtt-Davy] are some of the most common turfgrasses used on athletic fields. Subsequently, the traffic tolerance of commercially available cultivars and the effects of trinexapac-ethyl (TE) on bermudagrass athletic fields with or without perennial ryegrass are often limited. A two year study at the University of Tennessee was conducted under simulated athletic field traffic to evaluate the performance of bermudagrass cultivars as affected by TE and overseeding. Bermudagrass cultivars evaluated were Tifway, Riviera, Patriot, and Celebration. TE treatments consisted of an untreated …

Early Vessel Evolution And The Diversification Of Wood Function: Insights From The Malagasy Canellales, Patrick Joseph Hudson

Masters Theses

Xylem vessels have long been proposed as a key innovation for the ecological diversification of angiosperms by providing a breakthrough in hydraulic efficiency to support high rates of photosynthesis and growth. However, recent studies demonstrated that angiosperm woods with structurally ‘primitive’ vessels did not have greater whole stem hydraulic capacities as compared to vesselless angiosperms. As an alternative to the hydraulic superiority hypothesis, the heteroxylly hypothesis proposes that subtle hydraulic efficiencies of primitive vessels over tracheids enabled new directions of functional specialization in the wood. However, the functional properties of early heteroxyllous wood remain unknown. We selected the two species …

Comparative Ecophysiology Of American Chestnut Under Different Planting Treatments On Reclaimed Mine Sites, Christopher Ryan Miller

Masters Theses

American chestnut was once an abundant species that dominated the Eastern U.S. deciduous forests. Although this species is currently functionally extinct due to the chestnut blight, researchers are working on blight-resistant hybrids in hopes of restoring the species. As one potential vector for chestnut reintroduction and dispersal, the reclamation of mine sites are being considered. Recent research has found that reforestation efforts on these reclaimed mine sites provide productive tree growth while also complying with mine-reclamation laws. Understanding how American chestnut performs physiologically on mine sites will aid in the restoration of this species and reclamation of mine sites.

The …