Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item MAKING APPLES BLUSH: UNDERSTANDING HOW THE COMBINED USE OF REFLECTIVE GROUNDCOVERS AND PLANT GROWTH REGULATORS IMPACT RED SKIN COLORATION AND QUALITY OF ‘HONEYCRISP’ APPLES IN THE MID-ATLANTIC US(2024) Miah, Md Shipon; Farcuh, Macarena; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Apples are among the most valuable fruits globally, with 'Honeycrisp' ranking as the top sales-producing cultivar in the US. However, challenges such as insufficient red skin coloration and increased preharvest fruit drop significantly diminish their market value. Reflective groundcovers have been reported to enhance apple skin coloration, while the application of the plant growth regulator AVG reduces fruit drop but may negatively impact skin coloration. Research on the impacts of these practices in mid-Atlantic US-grown apples remains limited. In this two years study, our aims were 1) to evaluate the effect of reflective groundcovers on solar radiation (PPFD, UV) distribution; 2) to assess the combined effect of reflective groundcovers and ethylene inhibitor (AVG) on preharvest fruit drop, ethylene production, red blush percentage, and overall fruit quality; 3) to investigate the combined effect of reflective groundcovers and ethylene inhibitor (AVG) on expression level of key anthocyanin and ethylene biosynthesis related genes; 4) to determine the combined effect of reflective groundcovers and ethylene inhibitors (AVG) in the accumulation of total anthocyanin. Apples underwent four treatment combinations of reflective groundcover (Extenday) and AVG (130 mg L−1). Our findings revealed that Extenday significantly enhanced skin coloration (>75% blush) through increased reflectance of PPFD and UV radiation, along with increased IEC, while also accelerating fruit maturity, i.e., overripening. In fact, Extenday-only treated fruit exhibited the highest upregulation of ethylene and anthocyanin biosynthetic-related genes, as well as total anthocyanins. Conversely, AVG notably reduced fruit drop and decreased IEC, delaying fruit maturity while significantly diminishing red coloration (30–48% blush). AVG treated fruit significantly suppressed the expression of key ethylene and anthocyanin biosynthetic structural and regulatory genes, as well as total anthocyanins. The combined application of Extenday and AVG synergistically decreased fruit drop while enhancing skin coloration (>50% blush), but without inducing overripening. This combination fine-tuned the transcript accumulation of ethylene and anthocyanin biosynthetic-related genes, as well as total anthocyanins, enabling 'Honeycrisp' fruit to exceed 50% blush, while moderately increasing IEC (compared to Extenday-only and control fruit), thus enhancing fruit economic value. Therefore, combining Extenday and AVG can boost the market value for 'Honeycrisp' apples in the mid-Atlantic US.Item THE USE OF ORGANIC WASTE PRODUCTS AS SOIL AMENDMENTS FOR TURFGRASS ESTABLISHMENT: EFFECTS AND REGULATORY INFLUENCES(2024) Morash, Jennifer Dawn; Lea-Cox, John; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The use of organic waste products as soil amendments in highly disturbed urban soil is poised to grow due to rising fertilizer costs, waste-management issues, and greater emphasis on creating sustainable circular economies. Despite the advantages of using waste products as organic amendments to enhance fertility, their incorrect use may result in short-term unintended consequences such as nutrient losses or the immobilization of plant-essential nutrients, which could diminish efforts to establish vegetation on disturbed soil. To avoid these consequences, transportation authorities – cited as the largest users of compost in some states – have implemented measures to improve product specifications. This research details the efforts of one such organization, the Maryland Department of Transportation State Highway Administration (MDOT SHA), and the results of an initiative to increase the quality of manufactured topsoil and compost use through agency topsoil specifications. After determining which products were most likely to be incorporated into manufactured topsoil (finely shredded wood mulch and composted leaf yard waste), two greenhouse microcosm experiments were conducted to evaluate plant growth responses and the efficiency of nutrient uptake compared to leachate losses when those amendments were used in accordance with MDOT SHA specifications. Composted yard waste provided excellent results while wood mulch suppressed growth in the short-term studies. A biosolids treatment was included in the experiments due to widespread availability and growing interest. Biosolids improved soil fertility and plant growth. However, the difference between nitrogen (N) uptake and leachate mass losses required a second set of experiments, to quantify the effects of four biosolids amendments on plant growth, nutrient uptake, and leachate losses. Treatments were applied at the rate recommended by UMD for turfgrass establishment (2.54 cm, incorporated) and included fresh biosolids, biosolids that were stockpiled for two years, two blended products made from either the fresh or aged biosolids and fine wood mulch, an inorganic fertilizer, and a control. Aging and wood fines reduced N leaching losses but at the expense of N inputs to soil. The cumulative N leachate mass loss from the new biosolids treatment was 63 times greater than the cumulative fertilizer total. Aging did not reduce phosphorus (P) leaching losses but wood fines did by diluting the concentration of P in blends. However, biosolids mostly retained P in the soil and cumulative fertilizer losses were 2 times higher. Overall, growth measurements showed that biosolids enhanced growth during the first and second growing seasons. However, based on the results of this research, 2.54 cm of pure biosolids is not required to enhance turfgrass establishment. An application of 1.27 cm of pure biosolids or 2.54 cm of a biosolid/wood fine blend should provide comparable enhanced turfgrass growth results while reducing overall nutrient leachate losses.Item An Investigation of Maize at Four Sites (LA 20241, LA 38597, LA 112766, and LA 131202) in Eddy County, New Mexico(2022) Granados, Suzan Marie; Palus, Matthew; Hockersmith, Kelly; Anthropology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A topic of interest for many New Mexico archaeologists is the introduction and domestication of maize in the Southwest. This investigation adds to the archaeological record of when and to what extent maize was integrated into the subsistence of southeastern New Mexico prehistoric groups. Currently, the accepted date range for the introduction of maize in southeast New Mexico is 500–200 BC (Vierra 2020). Preliminary results of this investigation indicate the presence of maize in the Permian Basin of southeastern New Mexico dating to 2501 +/-125 calibrated (cal) BC; 1000 years prior to the earliest maize site recorded in the archaeological record for the area. The significance of this early date is twofold 1) the Middle Archaic date in comparison to other old maize sites in the area; and 2) the Middle Archaic date challenges the currently accepted migration patterns of maize into southeastern New Mexico. Dr. Jonathan Mabry’s 2008 study suggest that maize was introduced no later than 2100 BC in the southwest; however, Mabry states that maize use did not become common in the North American southwest until around 1400 BC (Mabry 2008). This investigation focuses on a case study of four sites, LA 20241, LA 38597, LA 112766, and LA 131202, in what is now known as Eddy County within the Permian Basin of southeastern New Mexico. I chose these sites because of my direct involvement in the data recovery field investigation and curation. I spent several weeks directing the excavation at Sites LA 112766 and LA 131202. and served as the laboratory manager for processing the artifact collections and flotation samples for all four sites. Evidence recovered from these four archaeological sites in southeast New Mexico, specifically Eddy County, suggest that maize use was low through the Archaic period and did not increase until AD 700–850 (Diehl 1996, Miller 2016, Railey 2016). This thesis demonstrates that maize was present much earlier in the archaeological record than previously reported for southeastern New Mexico. The analysis of macrobotanical, phytolith, and starch remains, and ceramics, and radiocarbon dates from cultural features at Sites LA 20241, LA 38597, LA 112766 and LA 131202 were examined to answer the question: when and to what extent was maize integrated into the subsistence of southeastern New Mexico prehistoric groups? A radiocarbon date from Feature 5, at Site LA 112766, indicates evidence of maize as early as 2501 +/-125 calibrated (cal) BC. Additionally, radiocarbon dates identified six Late Archaic features and thirteen Early Formative features that contained maize residue collectively from Sites LA 20241, LA 38597, LA 112766, and LA 131202. Lastly, Site LA 20241 had a single Late Formative feature that yielded maize residue. This thesis will focus on the signature of maize in the archaeological record of Archaic and Formative groups of southeastern New Mexico.Item IMPROVING IRRIGATION MANAGEMENT AND ROW COVER USE IN STRAWBERRY PRODUCTION IN THE MID-ATLANTIC REGION(2020) Belayneh, Bruk Eshetu; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Irrigation strategies that reduce water application and improve water use efficiency could be useful in strawberry production, to save water and reduce the environmental impact of nutrient leaching. Therefore, the effect of moisture availability on the physiology, growth, yield and fruit quality of strawberry (Fragaria X ananassa) was studied under field and greenhouse conditions by implementing deficit irrigation at decreasing matric potentials. Incremental drought stress significantly affected crop physiology, growth and yield, but not fruit quality. The results revealed both physiological and morphological adaptations of strawberries to incremental drought stress that are typical of isohydric plants. Since reduced irrigation applications led to proportional yield losses, there was no significant improvement in the irrigation water use efficiency/water productivity of the crop. Economic analysis showed that the loss of revenue as a result of reduced yields was of a much higher magnitude than the savings associated with reduced irrigation application, making adoption of reduced irrigation strategies such as deficit irrigation unlikely. Nevertheless, results revealed that soil moisture measurement-based irrigation management can be used to improve current (excess irrigation) grower practices, without impacting revenue. The effect of row covers on canopy and soil temperature, was studied in plasticulture strawberry production to more quantify their effects on crop phenology and frost mitigation. Row cover use increased the average temperature measured in the canopy and soil by 6.9 and 9.8%, respectively. Although this seems relatively insignificant, these temperature increases translated to an 84 and 122% increase in growing degree-day accumulation at the canopy and in the soil during a fall study period. In addition, increases in soil temperature were positively correlated with soil moisture. These results indicate the advantages that row covers can provide to growers, as a tool to enhance plant growth and for freeze and frost protection of plants. However, growers need to monitor environmental conditions at canopy level under row covers and in the ambient air in order to gain these benefits without negative consequences for yield.Item Frontiers in Lattice Cryptography and Program Obfuscation(2017) Apon, Daniel Christopher; Katz, Jonathan; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation, we explore the frontiers of theory of cryptography along two lines. In the first direction, we explore Lattice Cryptography, which is the primary sub-area of post-quantum cryptographic research. Our first contribution is the construction of a deniable attribute-based encryption scheme from lattices. A deniable encryption scheme is secure against not only eavesdropping attacks as required by semantic security, but also stronger coercion attacks performed after the fact. An attribute-based encryption scheme allows ``fine-grained'' access to ciphertexts, allowing for a decryption access policy to be embedded in ciphertexts and keys. We achieve both properties simultaneously for the first time from lattices. Our second contribution is the construction of a digital signature scheme that enjoys both short signatures and a completely tight security reduction from lattices. As a matter of independent interest, we give an improved method of randomized inversion of the G gadget matrix, which reduces the noise growth rate in homomorphic evaluations performed in a large number of lattice-based cryptographic schemes, without incurring the high cost of sampling discrete Gaussians. In the second direction, we explore Cryptographic Program Obfuscation. A program obfuscator is a type of cryptographic software compiler that outputs executable code with the guarantee that ``whatever can be hidden about the internal workings of program code, is hidden.'' Indeed, program obfuscation can be viewed as a ``universal and cryptographically-complete'' tool. Our third contribution is the first, full-scale implementation of secure program obfuscation in software. Our toolchain takes code written in a C-like programming language, specialized for cryptography, and produces secure, obfuscated software. Our fourth contribution is a new cryptanalytic attack against a variety of ``early'' program obfuscation candidates. We provide a general, efficiently-testable property for any two branching programs, called partial inequivalence, which we show is sufficient for launching an ``annihilation attack'' against several obfuscation candidates based on Garg-Gentry-Halevi multilinear maps.Item Chromosome studies in Verbena with special reference to the commercial varieties(1938) McCann, Lewis Paul; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item Seed production in Lilium regale E. H. Wils(1949) Rappleye, Robert D.; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Item Local lettuce: heat tolerant romaine cultivars and vermicompost soil amendment to increase sustainability in the Mid-Atlantic(2014) Wallis, Anna Elizabeth; Walsh, Chris S; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Local production of lettuce in the Mid-Atlantic utilizing heat-tolerant romaine cultivars and vermicompost soil amendment has the potential to significantly increase sustainability of agriculture. Heat tolerant cultivars would facilitate season extension into the summer. Vermicompost, compost produced using earthworms, may increase yield and quality of lettuce crops. This research tested a system incorporating these two practices. Success was assessed on lettuce yield and quality of lettuce across three seasons (spring, summer, and fall) and food safety risk of vermicompost. Several of the heat tolerant cultivars showed marketing potential when grown in the summer. Vermicompost did not significantly increase lettuce performance, but trends indicate that it may help, especially at higher rates. No food safety risk was associated with tested materials.Item Spring Seedbed Characteristics after Winterkilled Cover Crops(2013) Lounsbury, Natalie; Weil, Raymond R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tillage is the common practice for seedbed preparation prior to early spring vegetables. To investigate the possibility of eliminating the need for spring tillage through the use of cover crops, spring seedbed characteristics after winterkilled cover crops forage radish (Raphanus sativus L.) and oat (Avena sativa L.) were monitored prior to and during growth of no-till and rototilled plantings of spinach (Spinacia oleracea var. Tyee) over four site years in Maryland's Coastal Plain and Piedmont regions. Results indicate that forage radish can facilitate no-till planting of spring vegetables in the mid-Atlantic without herbicides or fertilizer. Forage radish increases soil nitrate and sulfate in early spring and is best suited as a cover crop before the earliest planted main crops.