Plant Sciences Commons^™

Characterization Of Radiotolerance In Potato And Development Of A Gamma Radiation Phytosensor., Robert Graham Sears

Doctoral Dissertations

As humans pursue space travel and nuclear energy, the risk of harm from ionizing radiation increases. On Earth or in space, plants are essential to our personal and environmental health. Plants serve as sentinels, bioremediators and food sources in areas of high ionizing radiation, therefore it is essential to understand how ionizing radiation affects plant biology. This work aimed to understand plant responses to ionizing radiation in the potato chassis and apply that knowledge to generate novel phenotypes for nuclear energy and space applications. The first gamma radiation phytosensor was developed for monitoring at standoff distances greater than three meters. …

Characterization Of Lignin Structural Variability And The Associated Application In Genome Wide Association Studies, Nathan D. Bryant

Doctoral Dissertations

Poplar (Populus sp.) is a promising biofuel feedstock due to advantageous features such as fast growth, the ability to grow on marginal land, and relatively low lignin content. However, there is tremendous variability associated with the composition of biomass. Understanding this variability, especially in lignin, is crucial to developing and implementing financially viable, integrated biorefineries. Although lignin is typically described as being comprised of three primary monolignols (syringyl, guaiacyl, p-hydroxyphenyl), it is a highly irregular biopolymer that can incorporate non-canonical monolignols. It is also connected by a variety of interunit linkages, adding to its complexity. Secondary cell wall …

Regulation Of Protein Synthesis In Arabidopsis Thaliana Through A Bioinformatic And Mathematical Lens, Ricardo Andres Urquidi Camacho

Doctoral Dissertations

Organisms exist under constantly varying environmental and internal conditions, which necessitate the differential regulation of gene expression. To synthesize proteins, the ribosome translates the information encoded in the nucleotide sequence of an mRNA into the final, functional amino acid sequence. Knockouts of ribosomal proteins lead to lethality. One such protein is the ribosomal protein 6 of the small subunit (eS6/RPS6). We confirmed that the knockout of either one of two eS6 paralogs in Arabidopsis leads to stunted growth and chlorosis. Here, these phenotypes have been further characterized in seedlings by precisely quantifying the ribosome loading of mRNAs as well as …

A Robust Agroinfiltration Method, Bryce N. Trull

Masters Theses

Stable transformation of soybean (Glycine max) is a markedly slow and laborious process. Thus, a tool that enables rapid evaluation of genetic elements in planta is critical to advance complex research and genetic engineering in soybean. To that end, a substantially robust agroinfiltration method was innovated in this work. Agroinfiltration is a technique that leverages Agrobacterium-mediated transient transformation to deliver genetic elements to the cells of whole plant tissues, usually leaves. Several factors were found to be relevant to successful soybean leaf agroinfiltration, including genotype, surfactant, developmental stage, and Agrobacterium culture medium. The research represents not only …

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 …

Bioregenerative Dietary Supplementation: Optimizing Brassica Production For Space Travel Through Light Intensity, Photoperiod, And Harvest Methodology, Ethan W. Darby

Masters Theses

Bioregenerative dietary supplementation, a component of bioregenerative life support, will be necessary for the success of future exploration-length space endeavors. Plants, as autotrophic producers of calories, nutrients, and oxygen, will be indispensable in the development of these systems. Previous work has identified leafy greens from the genus Brassica as promising candidates for in-flight production of necessary human nutrients such as vitamins C, B₁, and K₁, in addition to β-carotene, the primary vitamin A precursor in the human diet. These plants also produce lutein and zeaxanthin, two compounds important in protecting the eye from radiation-induced damage, as …

The Influence Of Spectral Quality On Primary And Secondary Metabolism Of Hydroponically Grown Basil, Hunter Albright Hammock

Doctoral Dissertations

This dissertation explores the influence of spectral quality from supplemental lighting and seasonal changes on primary and secondary metabolism in hydroponically grown greenhouse basil. It aims to enhance understanding of plant/light interactions and provide practical insights for light emitting diode (LED) manufacturers and commercial growers. The research is premised on the hypothesis that altering spectral quality can significantly impact primary and secondary metabolism, potentially improving flavor and increasing phytonutrients with health benefits. This project involved four phases, each building on the results of the previous ones. In Phase 1, different basil varieties were evaluated to determine aroma volatile profiles and …

Increasing Productivity And Biodiversity Of Tall Fescue Swards By Intercropping Cool And Warm-Season Forage Species, Michael Dereck Corbin

Doctoral Dissertations

Mixed pastures are known to produce greater biomass yields and higher nutritive value than monocultures. Intercropping biologically N fixating legumes, along with the use of intercropping warm-season annual grasses, such as crabgrass [Digitaria ciliaris Retz.], provides the potential to aid tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] productivity. To determine the benefits of intercropping species into tall fescue forage systems in the Southeastern U.S., two studies were developed. The first study consisted of 9 tall fescue paddocks, in which 3 paddocks contained red clover (Trifolium pratense L. [TRC]) mixed with tall fescue, 3 paddocks contained sunn …

Methods To Hasten Zoysiagrass Establishment From Sprigs, Tyler Carr

Doctoral Dissertations

Zoysiagrasses (Zoysia spp. Willd.) are commonly used on golf course fairways and tees in addition to residential and commercial lawns due to lower input requirements relative to bermudagrass (Cynodon spp.). This has led to increased interest in using zoysiagrass for golf course putting greens; however, zoysiagrass establishment from sprigs is prolonged compared to bermudagrass. A series of experiments were conducted in glasshouses in Knoxville, TN in 2022 to evaluate the effects of environmental conditions and management practices on the establishment of Prizm zoysiagrass from sprigs. To determine the optimal soil temperature for Prizm zoysiagrass establishment, sprigs were exposed …

Understanding Host-Microbe Interactions In Maize Kernel And Sweetpotato Leaf Metagenomic Profiles., Alison K. Adams

Doctoral Dissertations

Functional and quantitative metagenomic profiling remains challenging and limits our understanding of host-microbe interactions. This body of work aims to mediate these challenges by using a novel quantitative reduced representation sequencing strategy (OmeSeq-qRRS), development of a fully automated software for quantitative metagenomic/microbiome profiling (Qmatey: quantitative metagenomic alignment and taxonomic identification using exact-matching) and implementing these tools for understanding plant-microbe-pathogen interactions in maize and sweetpotato. The next generation sequencing-based OmeSeq-qRRS leverages the strengths of shotgun whole genome sequencing and costs lower that the more affordable amplicon sequencing method. The novel FASTQ data compression/indexing and enhanced-multithreading of the MegaBLAST in Qmatey allows …

A Field Guide To Foodways And Foraging In Southern Appalachia, Aeryn Lorraine Longuevan

Chancellor’s Honors Program Projects

No abstract provided.

Impact Of Cover Crop Species Diversity On Soil Nutrient Availability And Crop Productivity, Amanda Kramer

Masters Theses

Cover crops provide multiple environmental benefits that improve both soil and water quality; however, farmers only utilize them on approximately 5% of harvested U.S. cropland. Low adoption rates are attributed to yield impact concerns, seed and planting costs, and lack of advocacy. This study, which began in October 2019, assessed the effects of nitrogen rate and cover crop diversity on weed biomass, soil coverage, in-situ residue decomposition, soil nitrogen and phosphorus availability, and cash crop yield to better understand the costs and benefits of cover crop adoption at two locations in Tennessee (Milan and Spring Hill). Treatments were replicated 4 …

Characterization And Management Of Auxin-Resistant Palmer Amaranth In Tennessee, Delaney C. Foster

Doctoral Dissertations

Palmer amaranth has a long history of evolving resistance to herbicides to the point it has become a significant row crop production obstacle. Cotton and soybean growers were offered new technologies in 2016, expanding in-crop herbicide options to include dicamba or 2,4-D. Within three years of commercialization, dicamba use in these crops increased ten-fold and growers began to report Palmer amaranth escapes in west Tennessee auxin-tolerant production systems. A survey of Palmer amaranth escapes in dicamba and 2,4-D-tolerant cotton and soybean fields in Tennessee was conducted in the fall of 2021 with the objective of determining if poor control was …

Leveraging Mass Spectrometry-Based Proteomics And Post-Translational Modifications For System-Wide Understanding Of Bioenergy Plants And Their Environment, Him K. Shrestha

Doctoral Dissertations

Bioenergy research focuses on utilizing renewable biomass feedstocks to produce biofuels and bioproducts to address growing concerns about energy security and climate change. To better understand the details of bioenergy crop production and conversion to bioproducts, it is essential to characterize bioenergy plants and their environments at a molecular systems level. Mass spectrometry has emerged as a promising technique for detailed proteomic information, including post-translational modifications (PTMs), of molecular processes and cellular functions of biological systems. In this dissertation, proteomic approaches have been optimized and implemented to deepen our understanding of the interaction of plants and their environment in a …

Functional Analysis Of Soybean Proteinase Inhibitor Genes And Cyst Nematode-Inducible Synthetic Promoters For Insects And Nematode-Resistance In Plants, Mst Shamira Sultana

Doctoral Dissertations

Proteinase inhibitors (PIs) from legumes have the potential for use as protectants in response to pests and pathogens. Soybean (Glycine max) contains two trypsin inhibitors (TIs): Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI). In this study, the possible role of soybean TIs in plant defense against insects and nematodes was investigated. In addition to the three known TIs (KTI1, KTI2 and KTI3), novel inhibitors KTI5, KTI7, and BBI5 were identified in soybean. Their functional role was further examined by overexpression in soybean and Arabidopsis. In vitro enzyme inhibitory assays showed significant increase in trypsin and chymotrypsin inhibitory …

Winter Wheat Cover Crop Increased Subsoil Organic Carbon In A Long-Term Cotton Cropping System In Tennessee, Rounak Patra, Debasish Saha, Sindhu Jagdamma

Biosystems Engineering and Soil Science Publications and Other Works

Long-term cover-cropping and no-tillage practices can facilitate soil organic carbon (SOC) accumulation in agroecosystems for soil health and climate mitigation benefits. However, the contribution of these conservation management practices to SOC gain from the subsoil layers is not been extensively studied. To understand this knowledge gap, it is essential to determine the distribution of total SOC and SOC fractions in response to management practices across the soil profile. Therefore, this study was conducted by leveraging a 40-year replicated field experiment in a continuous cotton (Gossypium hirsutum) system. The management treatments examined included three cover crop treatments: 1) hairy vetch, HV …

Corn (Zea Mays L.) Production In Living Mulch Systems, Grazing Potential, And Economic Viability, Marcia Peireira Quinby

Doctoral Dissertations

Living mulch (LM) is a practice in which forages are grown simultaneously with the main crop, serving as a living cover throughout the growing season. The LM systems were developed to alleviate concerns of soil depletion and finding ways to reduce tillage negative effects on soil productivity. In addition, when legumes are use can decrease the reliance on N fertilizer. The use of corn in LM have been previously studied due to the crop being a large commodity in the U.S.; In addition, the ability to graze the LM after corn production can increase the land use efficiency. To determine …

Better Understanding Genomic Architecture With The Use Of Applied Statistics And Explainable Artificial Intelligence, Jonathon C. Romero

Doctoral Dissertations

With the continuous improvements in biological data collection, new techniques are needed to better understand the complex relationships in genomic and other biological data sets. Explainable Artificial Intelligence (X-AI) techniques like Iterative Random Forest (iRF) excel at finding interactions within data, such as genomic epistasis. Here, the introduction of new methods to mine for these complex interactions is shown in a variety of scenarios. The application of iRF as a method for Genomic Wide Epistasis Studies shows that the method is robust in finding interacting sets of features in synthetic data, without requiring the exponentially increasing computation time of many …

Genome Evolution In The Salicaceae: Genetic Novelty, Horizontal Gene Transfer, And Comparative Genomics, Timothy Yates

Doctoral Dissertations

Genome evolution is a powerful force which shapes genomes over time through processes like mutation, horizontal transfer, and sexual reproduction. Although questions which aim to explore genome evolution are broad, they are all understood through the discovery and comparison of genetic variation. For example, genetic diversity may explain differences in phenotypes, etiology of disease, and is essential for phylogenomic analysis. Recently, the democratization of next generation and third generation DNA sequencing technologies have allowed for genomics to produce large amounts of sequence data. This has facilitated the capture of genetic variation at species and population scales.

Populus and Salix are …

Evaluating Current And Future Potential Distribution Of Epiphytic Orchids In The Congo Basin With Ecological Niche Models, Michael L. Ngoh

Masters Theses

The Congo Basin Forest harbors a rich diversity of epiphytic communities, with the Orchidaceae alone making up more than 50% of all epiphytes in the region. Despite the huge diversity of epiphytes, many species, including epiphytic orchids, are at risk to a diverse array of threats. Climate change for instance poses severe threats to epiphytic orchids due to elevated temperatures, prolonged periods of droughts, as well as reduced rainfall across the Congo Basin Forest. In this study, we used ecological niche modeling and GIS techniques to identify spatial patterns of species richness, potential future climate refugia, and novel climatic suitability …

Poa Annua: An Annual Species?, Devon E. Carroll

Doctoral Dissertations

Poa annua L. is ranked the most troublesome turfgrass weed but can also be a highly desirable turfgrass species. As the Latin name annua implies, the species is thought to persist via an annual life cycle; yet there are many reports in literature of P. annua persisting perennially. Considering that P. annua senescence patterns do not align with other true annual species such as Triticum spp. and Zea mays L., we hypothesized that P. annua presents itself similarly to other perennial, cool-season, turfgrass species that are subject to a confluence of environmental factors in summer that can cause mortality. …

Evaluation Of Cotton Management Decisions: Cover Crops, Weed Control, And Injured Stands, Savana D. Denton

Doctoral Dissertations

Herbicide-resistant weed species have altered the challenges faced by Tennessee cotton (Gossypium hirsutum, L.) producers. While the weed control and environmental benefits of cover crops have been well-documented, the integration of cover crops into cotton production systems has presented management challenges. In-season broadcast postemergence weed control options are limited in cotton. Furthermore, off-target movement of 2,4-D and dicamba can result in additional management challenges if susceptible cotton is injured. Studies were conducted from 2018 to 2021 to evaluate: 1) cotton response to cover crop termination timings and methods; 2) postemergence weed control programs in cotton without the use of …

Improved And Sustainable Management Of Economically Important Plant-Parasitic Nematodes Of Field Crops And Fungal Diseases Of Soybean And Hemp In Tennessee, Rufus J. Akinrinlola

Doctoral Dissertations

Nematodes and diseases can limit field crops and hemp production in Tennessee. Therefore, seven research objectives were undertaken to improve the management of the crops: First, the prevalence and density of plant-parasitic nematode populations were evaluated across many field crop acreages in Tennessee through a survey from 2018 through 2020. Second, the virulence phenotypes of soybean cyst nematode (SCN), (Heterodera glycines [HG]), populations were assessed in Tennessee fields using the HG types test. Third, the impact of the virulent SCN HG type 1.2.5.7 on soybean nitrogen fixation activity and growth was evaluated on different soybean genotypes in the greenhouse. …

Native Soil Virus Abundance, Composition, And Mobility Under Natural And Managed Agricultural Conditions, Regan Mcdearis

Doctoral Dissertations

Soil viruses are ubiquitous in the environment and important for their influence on host community composition and function. Viral infection influences host evolution, metabolism, function, diversity, community evenness, and more. As host bacteria play critical roles in agricultural systems, including nutrient cycling and soil aggregate formation, the influence which soil viruses have on their hosts makes them key players in these systems. However, many important questions remain regarding virus abundance and distribution under human imposed and natural conditions in agricultural systems. Understanding how these conditions impact virus abundance, transport, and community structure is critical for a broader understanding of soil …

Effect Of Herbicide Concentration On Atrazine, Pyroxasulfone, And Saflufenacil Dissipation Under Field And Lab Conditions, Randall Lee Landry

Doctoral Dissertations

Widespread herbicide resistant weeds over the last several years have fueled a renewed interest in the utility of soil-applied residual herbicides. Residual activity of a herbicide is based on a myriad of factors within and among environments. A common assumption used in simulation models examining herbicide persistence is that herbicide degradation is independent of application rate. These studies compared herbicide concentration on dissipation with three commonly used residual herbicides under field and lab conditions. Atrazine, pyroxasulfone, and saflufenacil represent herbicides with a relative field persistence of medium, high, and low, respectively. Field studies were conducted over two years where herbicides …

Nodulin 26 Like Intrinsic Proteins: Structurally Similar Membrane Channels With Diverse Functions In Plant Hypoxia Stress, Metalloid Nutrition & Toxicity, Zachary Beamer

Doctoral Dissertations

Plant nodulin 26 intrinsic proteins are categorized into three groups (NIP I, II, and III) based on pore architecture. NIP II and III participate in metalloid nutrition, whilst the function of a third (NIP I) is less understood. Here we investigate the physiological function of one NIP I protein (Arabidopsis thaliana NIP2;1) as a lactic acid channel, and also explore the structural basis for metalloid and water permeability of NIP I and NIP II proteins in general. In addition, a strategy was developed for the purification and crystallization of soybean nodulin 26 as a step towards structure determination of a …

Multi-Omic Systems Biological Analysis Of Host-Microbe Interactions, Piet Jones

Doctoral Dissertations

Systems biology offers the opportunity to understand the complex mechanisms of various biological phenomena. The wealth of data that is produced, at an increasing rate, provides the potential to meet this opportunity. Here we take an applied approach to integrate multiple omic level data sources in order to generate biologically relevant hypotheses. We apply a novel analysis pipeline to model both, in concert, the microbial and transcriptomic signature from COVID-19 positive patients. We show patients may suffer from an increased microbial burden, with an increased pathogen potential. Gene expression evidence further shows patients may exhibit a compromised barrier immunity, owing …

Plant Community Responses To Interactive Anthropogenic Disturbances Along A Natural-Wildland-Urban Gradient And Undergraduate Students’ Attitudes Toward Disturbances, Mali M. Hubert

Doctoral Dissertations

Anthropogenic disturbances are defined as any change caused by human activity that alters biodiversity. Wildfire and urbanization disturbances are among the most influential on the landscape because of their individual and interactive properties. Areas deemed wildland-urban interfaces (WUI; area where environment intermingles with human-built structures) are increasing near protected lands because of human population growth and movement, which often facilitates fire ignitions by humans. Houses that are adjacent to or overlap with wildland vegetation can complicate protection of urban development and wildlands from fires. The expansion of the WUI due to population growth will exacerbate fire risk, which can ultimately …

Improving Water And Plant Growth Regulator (Pgr) Management Practices In Cotton: Cultivar Physiological Responses And Pgr Rates, Kurt Wedegaertner

Masters Theses

Cotton (Gossypium hirsutum L.) is grown in an increasingly unpredictable climate and often under rainfed conditions. Without irrigation to alleviate common drought conditions, cultivar selection becomes a primary tool in mitigating the negative effects of water-deficit stress. Cultivars can differ in water use under water-limited environments, which can affect crop performance. Moreover, cotton management must involve balancing vegetative and reproductive growth through the use of plant growth regulators (PGR) due to the plant’s perennial growth pattern. The efficacy of PGRs are dependent on many variables including environmental conditions, irrigation, and genetics (cultivar). In 2020 and 2021, a series of …

A Bioassay To Determine Poa Annua Responses To Indaziflam, Benjamin D. Pritchard

Masters Theses

Herbicide resistance within Poa annua is widespread in managed turfgrass systems. In 2020, a P. annua collection from a golf course in the southeastern United States was reported to be resistant to indaziflam as well as six other mode-of-action groups. Considering P. annua is the most troublesome weed in turfgrass, a bioassay to screen other collections with putative indaziflam resistance is needed. A dose-response experiment was conducted with ten concentrations of indaziflam (0, 250, 500, 750, 1000, 1250, 1500, 2000, 4500, and 9000 pM) in Gelrite® culture during 2021 and 2022. An herbicide-susceptible (S1) collection of P. annua, a …