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The Relationship Between Riparian Zone Width And Floristic Quality In Shenandoah County, Virginia, Jamie D. Smith

Masters Theses, 2010-2019

Riparian zones harbor an above average plant biodiversity. This biodiversity is threatened by invasive species and increasing human disturbance, the latter of which includes deforestation from agriculture and urban development. In this study, I examine relationship between the width of a forested riparian zone and the vegetation growing there. By using floristic quality assessment as a measure of anthropogenic disturbance, one can determine if wider riparian zones foster exclusion of non-native species while providing higher quality habitats for native plants. A randomized block design was used with three forested riparian treatments: deforested, moderately forested (woody vegetationstream), and extensively forested (woody …

Potential Effects Of Elevated Co2 On Pitcher Plant Nectar Composition, Prey Capture, And Inquiline Communities, Deirdre Courtney

Honors Theses

Human activities such as fossil fuel burning and deforestation have contributed significantly to the increasing levels of CO₂ in the atmosphere since the industrial revolution. Under the IPCC A1FI emission scenario, we are expected to reach levels as high as 1000 ppm by the end of the century. On average, C₃ plants experience a 27% increase in carbon to nitrogen (C:N) ratio under elevated CO₂. As a result, C₃ plants typically exhibit an increase in carbon-based secondary compounds. Carnivorous plants are a rare type of C₃ plant that has adapted to survive in low …

Inheritance Of Virulence In The Root Rot Pathogen Phytophthora Sojae, Sirjana Devi Shrestha

Electronic Thesis and Dissertation Repository

The oomycete Phytophthora sojae causes stem and root rot of soybean plants. The interaction of pathogen avirulence (Avr) and host resistance (R)-genes determine the disease outcome. The Avr3a mRNA transcript level is variable among P. sojae strains and determines virulence towards the R-gene Rps3a. To study the inheritance of virulence, genetic crosses and self-fertilizations were performed. A cross between P. sojae strains ACR10 and P7076 causes transgenerational gene silencing of Avr3a allele, and this effect is meiotically stable up to the F₅ generation. However, test-crosses of F₁ (Avr3a^ACR10/Avr3a …

Effect Of Photoperiod On Redox Regulation Of Phenotypic Plasticity And Cellular Growth In Chlorella Vulgaris, Lauren E. Hollis

Electronic Thesis and Dissertation Repository

Photoautotrophs are predisposed to maintain a balance between light energy absorption with the capacity to consume this energy through metabolism. An imbalance in energy flow may be a consequence of increased light intensity and is sensed as modulation of excitation pressure (EP). Chlorella vulgaris acclimated to continuous high EP exhibits a yellow-green phenotype characterized by reduced chlorophyll content and high chlorophyll a/b ratio with reduced light-harvesting complex abundance relative to the dark green phenotype of low EP-acclimated cultures. Previous studies on acclimation to EP in green algae have been conducted under constant growth light. To determine the role of EP …

Thylakoid Phosphorylation And Cell Morphology In The Antarctic Psychrophile, Chlamydomonas Sp. Uwo241, Beth Szyszka-Mroz

Electronic Thesis and Dissertation Repository

The unicellular green microalga, Chlamydomonas sp. UWO 241, was isolated from Lake Bonney, Antarctica. A unique characteristic of this algal strain is its inability to undergo state transitions combined with an altered thylakoid protein phosphorylation profile, which suggests the absence of LHCII phosphorylation, and preferential phosphorylation of a set of novel proteins. Examination of the unique phosphoproteins revealed that they are associated with a large pigment-protein supercomplex, which contains components of both photosystem I and the cytochrome b₆/f complex and likely functions in cyclic electron flow (CEF).

The absence of phosphorylation of LHCII proteins, associated with state …

Arabidopsis Chromatin Remodeler Brahma: Its Functional Interplay With Polycomb Proteins And The Ref6 Histone Demethylase, Chenlong Li

Electronic Thesis and Dissertation Repository

BRAHMA (BRM) is a SWI/SNF-type chromatin remodeling ATPase that plays an important role in regulation of gene expression. Tri-methylation of lysine 27 on histone H3 (H3K27me3) is a histone modification that is associated with transcriptionally repressed genes and catalyzed by Polycomb Group (PcG) proteins. BRM has been proposed to antagonize the function of PcG proteins but the underlying molecular mechanism is unclear. To understand how BRM regulates the function of PcG proteins during plant development, a genome-wide analysis of H3K27me3 in brm mutant was performed using chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq). Loss of BRM leads to increased …

Assessing The Genetic Diversity Of The Genus Viburnum Using Simple Sequence Repeats, Deborah Dean

Doctoral Dissertations

The genus Viburnum was established in 1753 by Linnaeus and is the largest genus in the Adoxaceae and consists of approximately 160 species. Viburnum species are small trees which grow throughout the temperate regions of the Northern Hemisphere (Hoch, 1995). While this genus shares little variety in fruit and flower morphology, it is diverse in many other traits. As molecular studies advance, this large genus continues to undergo reclassification. Here three SSR libraries were constructed to discern additional molecular insight into this vast genus.

Microsatellite markers were developed to characterize Viburnum on several different levels. V. dilatatum is an introduced …

Pore Selectivity And Gating Of Arabidopsis Nodulin 26 Intrinsic Proteins And Roles In Boric Acid Transport In Reproductive Growth, Tian Li

Doctoral Dissertations

Plant nodulin-26 intrinsic proteins (NIPs) are members of the aquaporin superfamily that serve as multifunctional channels of uncharged metabolites and water. They share the same canonical hourglass fold as the aquaporin family. The aromatic arginine (ar/R) selectivity filter controls transport selectivity based on size, hydrophobicity, and hydrogen bonding with substrates. In Arabidopsis thaliana, NIP II subclass proteins contain a conserved ar/R “pore signature” that is composed of Alanine at the helix 2 position (H2), Valine/Isoleucine at the helix 5 position (H5), and an Alanine (LE1) and an invariant Arginine (LE2) at the two loop E positions. In this study, …

Evaluation Of Traits Associated With Breeding For Improved Biomass And Ethanol Yield In Switchgrass, Virginia Roseanna Sykes

Doctoral Dissertations

Switchgrass (Panicum virgatum L.) is a perennial, warm season grass that can be used as a biofuel. A greater understanding of the relationship of biomass yield and ethanol yield with disease susceptibility and morphological traits, estimation of the underlying genetic parameters of these traits, and the efficacy of selection at different maturity and under different production conditions could help breeders more effectively develop improved biofuel switchgrass cultivars. To examine these issues, three studies were performed. The first examined switchgrass leaves exhibiting low, medium, and high severity of rust symptoms, caused by infection with Puccinia emaculata. Results indicate P. …

Integration And Management Of Winter-Annual Cover Crops And Herbicides To Control Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri S. Wats), Matthew Scott Wiggins

Doctoral Dissertations

The main objective of this research was to evaluate the integration of high residue winter-annual cover crops with herbicides, both preemergence and postemergence, to control glyphosate-resistant Palmer amaranth. The results of these trials indicated that winter-annual cover crops improved early-season weed suppression. However, cover crops alone or as part of an integrated weed management system including only preemergence or only postemergence herbicides was not sufficient to control of glyphosate-resistant Palmer amaranth. Therefore, winter-annual cover crops should be used in conjunction with existing weed control tactics to achieve adequate glyphosate-resistant Palmer amaranth control, where applicable.

Pacific Plug & Liner Crop Shrinkage Evaluation, Jillian Balli

Horticulture and Crop Science

Crop Shrinkage has a major impact on a company’s bottom line. There are many ways to combat shrinkage. This report focuses on shrinkage reduction by adjusting buffer planting numbers to reflect the actual number of plants lost in production. Inaccurate buffer can cause the cost of production to be inaccurate as well. This report evaluates crop shrinkage of a greenhouse located in Watsonville, CA called Pacific Plug & Liner.

Using Avifauna To Access The Functional Success Of The Restored Beaver Creek Wetlands Near Cave Run Lake, Menifee County, Kentucky, Brian D. Wulker

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science in Biology by Brian D. Wulker on December 1, 2014.

Identification Of Root-Knot Nematodes (Meloidogyne Spp.) Of Arkansas Using Molecular Diagnostics, Churamani Khanal

Graduate Theses and Dissertations

Root-knot nematodes (Meloidogyne spp.) are highly-adaptable, obligate plant parasites distributed worldwide. In addition, root-knot nematodes are an economically important genus of plant-parasitic nematodes. Meloidogyne incognita, M. arenaria, M. javanica, M. hapla and M. graminis have been reported from Arkansas during 1964 to 1994. Previous identifications were based primarily on morphological characters and host differentials. In this study, identification using molecular diagnostics methods was performed to identify Meloidogyne species present in Arkansas. A total of 106 soil and root samples from 36 of the 75 counties were collected and processed to obtain root-knot nematodes. Polymerase chain reaction (PCR) was performed …

Evaluation Of Medicago Truncatula Accessions For Triterpene Saponins And Their Potential Impacts On Plant Pests, Samantha Roberson

Graduate Theses and Dissertations

Plants have developed numerous ways to protect themselves from microbes and insects, including producing secondary metabolites that negatively impact an invading pathogen or pest. Saponins are specialized metabolites found in many plant species and may play a role in protecting the plant. Though saponins are found in many plant species, triterpene saponins are found primarily in dicotyledons, including legumes. Medicago truncatula is a model system for studying legume biology and some accessions accumulate high concentrations of saponins. Accessions of M. truncatula known to have differing levels of saponins in both foliar and root tissues were tested for their suitability as …

The Phenotypic Effects And Transcript Response Of Salt Stress, The Impact Of Viral Infection On Salt Stress Symptoms, And The Effect Of Salt Stress On Soybean Virus Vector Activity In Soybean Varieties That Vary In Chloride Uptake, Alma Glenn Laney

Graduate Theses and Dissertations

With the increase in saline soils worldwide, understanding the mechanisms for salt tolerance in plants is important to reduce yield loss due to salt stress. Soybean, Glycine max (L.) Merr., genotypes differ in chloride uptake with genotypes that take up chloride into foliar tissues tending to be salt-sensitive whereas those that partially exclude chloride from the leaves are more salt-tolerant. Transcriptional and physiological responses were measured in two soybean cultivars, Clark and Manokin, which differ in chloride uptake in response to salt stress and in combination with Soybean mosaic virus (SMV) and its aphid vector, Aphis glycines . The interaction …

Characterization Of A Novel Fungal-Specific Gene, Fug1, In Fusarium Verticillioides, John Byron Ridenour

Graduate Theses and Dissertations

Filamentous fungi are responsible for numerous plant and animal diseases. The filamentous ascomycete Fusarium verticillioides is a globally important pathogen of maize, capable of causing severe yield reductions and economic losses. Also of substantial concern is the contamination of infected kernels with fumonisins, toxic secondary metabolites linked to toxicoses in humans and livestock. The number of sequenced fungal genomes is rapidly increasing. However, functional characterization of fungal genes has not progressed at a comparable rate. In pathogenic fungi, uncharacterized genes represent a source for novel virulence factors or anti-fungal targets. Therefore, to fully understand the genetic mechanisms underlying fungal pathogenesis, …

Reniform Nematode (Rotylenchulus Reniformis) Manipulation Of Host Root Gene Expression During Syncytium Formation In Upland Cotton (Gossypium Hirsutum), Wei Li

All Theses

Background: The semi-endoparasitic reniform nematode (Rotylenchulus reniformis) is a major yield-limiting pest of multiple crops in the tropics and sub-tropics, including upland cotton (Gossypium hirsutum). Reniform-resistant cotton varieties are urgently needed, but genes that confer resistance to reniform nematode have not been identified in any species. Parasitism by reniform nematode involves significant developmental changes in plant roots, leading to the formation of multicellular feeding structures called syncytia. Here, we present de novo transcriptomes assembled from syncytial and non-syncytial cotton roots on three sampling dates across a 12-day time course. Results: Total mRNA samples extracted from reniform-infected …

Consumer Acceptance And Willingness To Pay For Genetically Modified Rice In China: A Double Bounded Dichotomous Choic Contingent Valuation Survey Calibrated By Cheap Talk, Jing Jin

Graduate Theses and Dissertations

Considering population growth, limitations on land and water resources, and contamination to the ecosystem due to agricultural activities, current rice production in China is facing pressure to fulfill national demand. Self-sufficiency of rice has been a long-held political objective of the Chinese government and it is national goal to maintain the equilibrium between the national production and consumption or even achieve a supply surplus in rice. With the developing bio-technology of genetic modification (GM), scientists believe that using genetically modified cultivars may ease the pressure mentioned above. However, both the government and the people are very cautious about large-scale cultivation …

European Consumers' Attitudes Towards Cisgenic Rice, Anne-Cécile Delwaide

Graduate Theses and Dissertations

The enhancement of existing plant breeding techniques, such as cisgenesis, allows plant breeders to enhance an existing cultivar quicker and with little to no genetic drag. Cisgenesis is the genetic modification of a recipient plant with natural gene(s) from a sexually compatible plant. Unlike transgenesis, which is the genetic modification of a recipient plant with gene(s) from any non‐plant organism, or from a donor plant that is sexually incompatible with the recipient plant, the results of cisgenesis could occur naturally over time. Currently, both cisgenic and transgenic products are classified as genetically modified organisms (GMOs) and are labeled as such …

Potential For Optical Sensor-Based Nitrogen Fertilization In Grain Sorghum (Sorghum Bicolor L. Moench) In Arkansas, Kamil H. Rosales Rodriguez

Graduate Theses and Dissertations

Ground-based active-optical (GBAO) crop sensors have become an effective tool to improve nitrogen (N) use efficiency and to predict yield early in the growing season, particularly for grass crops. Commercially available canopy sensors calculate the normalized difference vegetative index (NDVI) by emitting light in the red and near infrared range of the electromagnetic spectrum. The NDVI is used to evaluate vigor status and to estimate yield potential. However, few studies have been conducted to compare the performance of commercially available sensors. Therefore, a study was conducted using the most common crop canopy sensors: i) N-Tech's GreenSeeker^TM (GS), ii) Holland …

Use Of Remote Imagery And Object-Based Image Methods To Count Plants In An Open-Field Container Nursery, Josue Nahun Leiva

Graduate Theses and Dissertations

In general, the nursery industry lacks an automated inventory control system. Object-based image analysis (OBIA) software and aerial images could be used to count plants in nurseries. The objectives of this research were: 1) to evaluate the effect of an unmanned aerial vehicle (UAV) flight altitude and plant canopy separation of container-grown plants on count accuracy using aerial images and 2) to evaluate the effect of plant canopy shape, presence of flowers, and plant status (living and dead) on counting accuracy of container-grown plants using remote sensing images. Images were analyzed using Feature Analyst® (FA) and an algorithm trained using …

Assessing Net Returns To Blueberry Production Using A Decision Support Tool, Sokha Sok

Graduate Theses and Dissertations

The purpose of this study was to develop and assess the profitability of four highbush blueberry farming systems in the south: organic field production, conventional field production, organic high tunnel production and conventional high tunnel production. Four baseline budget scenarios, one for each system, are developed for a 15 year production period. The results suggest that under expected production and price conditions for Northwest Arkansas, while all four production systems generated positive present value of net returns, the conventional field production produced the highest present value of net returns across the 15 years. The breakeven years of production were 7 …

The Mechanism Of Lhcp Insertion Into Thylakoid Membranes, Larae Brown

Graduate Theses and Dissertations

The light harvesting chlorophyll a/b-binding proteins (LHCPs) are the most abundant membrane proteins. LHCP is a nuclear encoded protein which is targeted to the thylakoid membranes by chloroplast signal recognition particles (cpSRP). Insertion into thylakoid membranes is facilitated by the cpSRP receptor cpFtsY and the Alb3 translocase. Work here focused on understanding the molecular events of LHCP insertion into the thylakoid membranes. Specifically, we sought to develop a tool to detect the insertion of the lumen-localized loop of LHCP into thylakoid membranes, which relies on cleavage of the loop by a thylakoid lumen processing protease. We also sought to understand …

Dissection Of Gray Leaf Spot Of Maize Through Functional Genomics, Robert Louis Hirsch

Graduate Theses and Dissertations

Gray leaf spot, caused by Cercospora zeae-maydis, is a devastating disease of maize that reduces yields and increases management costs. C. zeae-maydis penetrates maize leaves through stomata, but the biological and molecular bases of this process are poorly understood. The goal of this research was to elucidate the biological parameters of stomatal infection in C. zeae-maydis, and to identify and characterize novel genetic pathways involved in stomatal sensing and pathogenesis. Histopathological observations of a GFP-expressing strain of C. zeae-maydis during infection of maize indicated that the fungus responded to host-derived stomatal cues during the infection process. C. zeae-maydis was observed …

Short-Term Effects Of Poultry Litter Or Woodchip Biochar Amendment In A Temperate Zone Agronomic System, Katy Elizabeth Brantley

Graduate Theses and Dissertations

Biochar, a charcoal product produced by the anaerobic thermal decomposition of biomass, can provide agronomic benefits when soil applied. However, research is lacking in temperate region soils investigating specific biochar products and their effects on agronomically important crops. A greenhouse study utilizing poultry litter biochar and a field study utilizing pine woodchip biochar were conducted to observe the effects of biochar application to Northwest Arkansas soils on corn growth and nutrient availability. A third experiment investigated poultry litter and pine woodchip biochar influences on soil water retention. In all three experiments, biochar was applied at three rates (0, 5, and …

Integration Of Herbicide Programs With Cultural And Mechanical Practices For Managing Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri) In Soybean (Glycine Max), Holden Bell

Graduate Theses and Dissertations

Herbicide-resistant Palmer amaranth is the most troublesome weed in Arkansas row crops, causing producers to rely heavily on multiple mechanisms of action to reduce selection pressure for further evolution of herbicide resistance and to successfully produce a profitable crop. It is critical for the sustainability of weed management not only to adequately control this weed but also to reduce the soil seedbank using both non-chemical and chemical practices. Studies were conducted to determine the effect of soybean row spacing, seeding rate, and herbicide program on Palmer amaranth emergence, survival, and seed production in soybean, the effect of drill-seeded soybean population …

Switchgrass Cultivar, Harvest Frequency, Fertilizer Source, And Irrigation Effects On Near-Surface Soil Properties In West-Central Arkansas, Alayna A. Jacobs

Graduate Theses and Dissertations

Switchgrass (Panicum virgatum L.) has been identified as a model bioenergy feedstock crop and is expected to become an important feedstock for future renewable fuel generation. Agronomic management combinations that maximize monoculture switchgrass yield are generally well understood; however, little is known about corresponding effects of differing switchgrass management combinations on near-surface soil properties. The objective of this research was to determine the residual near-surface soil property effects of three years (2008 to 2011) of consistent management combinations to maximize switchgrass biomass production, including cultivar (‘Alamo’ and ‘Cave-in-Rock’), harvest frequency (1-cut and 2-cut systems per year), fertilizer source (poultry …

Spatial Distribution And Genetic Variability Of Reniform And Lance Nematodes In Cotton Agroecosystems, Claudia Holguin

All Dissertations

Rotylenchulus reniformis (reniform nematode) and Hoplolaimus columbus (Columbia lance nematode) are two of the main plant-pathogenic nematode species affecting cotton production in the United States. For the selection and implementation of effective management practices it is important to understand distribution patterns and population genetic structure of these two nematodes in cotton agroecosystems. In a three-year field study, the spatial distribution of reniform nematode was characterized in two commercial fields in South Carolina to determine the effects of relations with soil texture and crop rotation on reniform nematode distribution (Chapter 1). Results of this project suggest that population densities of reniform …

The Response Of Cotton (Gossypium Hirsutum L.) To Slow Release Foliar Fertilization And The Effect Of Environment On Absorption, James Matthews Burke

Graduate Theses and Dissertations

In cotton production, nitrogen (N) is the most limiting nutrient and the demand is substantial. Foliar-N fertilization is regarded as an effective and environmentally sound method of supplying cotton with N during times of deficiency and high demand. In response to the potential benefits of the foliar-N fertilization of cotton, a myriad of foliar-N based fertilizers have been created; each with their own individual chemical technology and constitution. Experiments were performed with the objectives of examining the effects of the slow-release foliar-N fertilizer, Nitamin® (1) on the growth and development of field-grown cotton, (2) on uptake under various environmental conditions, …

Winter Field Pea As A Leguminous Cover Crop In Corn Production, Matthew Carroll Marsh

Graduate Theses and Dissertations

Leguminous cover crops, which fix nitrogen (N) from the atmosphere and add to the N content of the soil, have the potential to replace or partially replace commercial nitrogen fertilizers. In this experiment, field pea (Pisum arvense) was used as the leguminous cover crop in a conventional tilled corn (Zea mays) production system. In a 2-yr experiment (2008 and 2009), conducted at two locations in Arkansas, field pea was planted on half the field in the fall and allowed to grow until late April to early May. Field pea biomass was recorded, N content of biomass determined and then the …