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Dna-Binding Site Recognition By Bhlh And Mads-Domain Transcription Factors, Joshua R. Werkman

Theses and Dissertations--Plant and Soil Sciences

Herewithin, two transcription factor (TF) regulatory complexes were investigated. A bHLH–MYB–WDR (BMW) DNA-binding complex from maize was the first complex to be studied. R, a maize bHLH involved in the activation of genes in the anthocyanin pathway, had been characterized to indirectly bind DNA despite the presence of a functional DNA-binding domain. Findings presented here reveal that this is only partially correct. Direct DNA-binding by R was found to be dependent upon two distinct dimerization domains that function as a switch. This switch-like mechanism allows R to be repurposed for the activation of promoters of differing cis-element structure.

The …

Transformations, Bioavailability And Toxicity Of Manufactured Zno Nanomaterials In Wastewter, Sewwandi Rathnayake

Theses and Dissertations--Plant and Soil Sciences

In order to properly evaluate the ecological and human health risks of ZnO Manufactured nanomaterials (MNMs) released to the environment, it is critical to understand the likely transformation products in the wastewater treatment process and in soils receiving biosolids. To address this critical knowledge gap, we examined the transformation reactions of 30 nm ZnO MNMs in single component and multi-component systems, with phosphate and natural organic matter (NOM). We also assessed the influence of nano ZnO transformation on the bioavailability, and toxicity of ZnO transformation products to Triticum aestivum. The data revealed that ZnO MNMs react with phosphate at …

Reduced Tillage And Living Mulches For Organic Vegetable Production, Alex G. Hessler

Theses and Dissertations--Plant and Soil Sciences

Reduced tillage and living mulches are alternative management strategies that can improve soil quality by minimizing disturbance and building soil organic matter. Weed suppression by these two practices alone is often insufficient to avoid crop yield losses, but their performance in an integrated system is not well understood. This project investigated the production of bell pepper (Capsicum annuum L.) and dry bean (Phaseolus vulgaris L.) in conventional tillage and strip tillage with a living mulch of teff (Eragrostis tef Zucc.) and Korean lespedeza (Kummerowia stipulacea Maxim.). Yields of pepper and bean were …

Nitrate Reduction Coupled To Iron(Ii) And Manganese(Ii) Oxidation In An Agricultural Soil, Stephanie Pyzola

Theses and Dissertations--Plant and Soil Sciences

New evidence shows iron(II) oxidation is strongly coupled to nitrate reduction under anaerobic conditions in freshwater sediments and agricultural soils. However, the contribution of iron(II) oxidation to nitrate reduction is unknown. Furthermore, oxidation of manganese(II) by nitrate has been largely overlooked. This study investigated nitrate-dependent iron(II) and manganese(II) oxidation in an agricultural soil (Sadler silt loam) using stirred-batch kinetic techniques with native soil organic carbon (SOC) as the electron donor and included addition of amendments (hydrogen gas and wheat residue). In the presence of native SOC, nitrate-dependent Fe(II) and Mn(II) oxidation occurred at early stages of the reaction while organic …

Hybrid, Row Width, And Plant Population Effect On Corn Yield In Kentucky, Chelsea Clay Mcfarland

Theses and Dissertations--Plant and Soil Sciences

Studies were conducted in 2011 and 2012 to determine if narrow row corn (Zea mays L.) and/or greater plant populations could affect yield, time to silking, and other physiological characteristics. Main plots of six hybrids were arranged as a randomized complete bock design with three replications. Split plots were row widths of 76-cm (wide rows) and 20-cm rows on 76-cm spacing (twin rows). Split-split plots were target plant populations of 75 000 and 111 000 plants ha^-1. Corn was no-till seeded into soybean stubble near Lexington, KY in 2011 and 2012. Year interacted with most factors analyzed …

Evaluating The Sustainability Of Four Organic Vegetable Production Systems, Delia W. Scott

Theses and Dissertations--Plant and Soil Sciences

A field study evaluating the sustainability of four organic vegetable production systems was conducted in Lexington, Kentucky in 2006 and 2007. The four systems included no-till, raised beds covered with biodegradable black mulch, bare ground with shallow cultivation, and bare ground with shallow cultivation and wood chip mulch. The two-year study compared yield, weed control, labor, and costs associated with each system, as well as physical, chemical, and microbiological soil characteristics. In 2006, tomatoes (Lycopersicon esculentum Mill.) were grown in the four systems, with no significant difference in yield. Summer squash (Cucurbita pepo L.) was grown in the …

Twin And Narrow Row Width Effects On Corn (Zea Mays L.) Yield And Weed Management, Grant Mackey

Theses and Dissertations--Plant and Soil Sciences

Corn or maize (Zea mays L.) has been grown in North America for many centuries, and an increase in corn production will continue to be needed. Agriculture producers must meet the demands of feeding and providing for an increasing population of people. In order to meet those needs, different production practices are being investigated as a way to increase grain yield.

Field plots were conducted across the state of Kentucky in 2011 and 2012 to evaluate the interaction between hybrid, row width, and plant density on corn yield. The primary objectives were to test if 1) narrower rows increase …

Control Of Erwinia Tracheiphila In Cucumis Melo, John R. Caudle

Theses and Dissertations--Plant and Soil Sciences

Currently there is no control of bacterial wilt disease, Erwinia tracheiphila, in susceptible cucurbit crops, once infection of the plant occurs. Conventional and organic production systems rely on insecticide applications to kill the vectors, striped and spotted cucumber beetles, Acalymma vittatum and Diabrotica undecimpunctata, respectively, prior to transmission of the pathogen which indirectly controls the disease to some extent. Physical barriers such as row covers are used to exclude the vectors from plants prior to flowering; however, pollination requirements expose plants to potential infection. Experimental field plots were developed to test various enhanced organic production systems in an …

The Role Of Polyadenylation In Seed Germination, Liuyin Ma

Theses and Dissertations--Plant and Soil Sciences

Seed germination has many impacts on the uses of seeds, and is an important subject for study. Seed germination is regulated at both transcriptional and post-transcriptional levels. Therefore, it is important to study how polyadenylation regulates gene expression during seed germination. To this end, a modified Illumina GAIIx sequencing protocol (described in Chapter Two) was developed that allows deep coverage of poly(A) site position and distribution.

Alternative polyadenylation (APA) regulates gene expression by choosing one potential poly(A) site on a precursor RNA consequentially shortening/lengthening the mRNA relative to other possible sites. To further explore this phenomenon, genes affected by APA …

Managing Soil Microbial Communities With Organic Amendments To Promote Soil Aggregate Formation And Plant Health, Shawn T. Lucas

Theses and Dissertations--Plant and Soil Sciences

The effects of managing soil with organic amendments were examined with respect to soil microbial community dynamics, macroaggregate formation, and plant physio-genetic responses. The objective was to examine the possibility of managing soil microbial communities via soil management, such that the microbial community would provide agronomic benefits. In part one of this research, effects of three amendments (hairy vetch residue, manure, compost) on soil chemical and microbial properties were examined relative to formation of large macroaggregates in three different soils. Vetch and manure promoted fungal proliferation (measured via two biomarkers: fatty acid methyl ester 18:2ω6c and ergosterol) and also stimulated …

Ecophysiological Responses Of Tall Fescue Genotypes To Endophyte Infection And Climate Change, Marie Bourguignon

Theses and Dissertations--Plant and Soil Sciences

Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of …