Plant Sciences electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Division of Plant Sciences. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item Biosystematics of the Lupinus mexicanus complex(University of Missouri--Columbia, 1976) Rafaill, Barbara L; Dunn, David B."Lupinus mexicanus was the first taxon in the genus Lupinus named for Mexico; therefore, the establishment of its identity and description became of substantial importance to the taxonomy of the complex it represented, as well as to the systematics of the genus in Mexico. Work was formally initiated on the Lupinus mexicanus complex after Dunn (1972) probed into the perplexing question of the taxon, L. mexicanus, and proposed the illustration in Edward’s Botanical Register (#457; 1820) serve as the type. The present monograph represents an effort to reveal the limits of the complex beginning with the previously ignored taxon, L. mexicanus. It also attempts to resolve the systematic and nomenclatural problems which resulted from such an investigation. Pursuit of a complete understanding of the Lupinus mexicanus complex involved reviewing taxonomic literature and correlating and comparing it with as many herbarium specimens as could be obtained relating to the complex. Distribution, ecology, and plant associations of the populations under study were noted. Morphological studies were performed. In addition to these traditional approaches to taxonomy, alkaloid thin-layer chromatography and breeding studies, including pollen viability, were also incorporated. Thus, a biosystematic approach was utilized in evaluating the Lupinus mexicanus complex of Mexico."--Introduction.Item Fine structural analysis of Sorangium cellulosum(University of Missouri--Columbia, 1970) Jackson, Michael Eugene"Two cell types are found in the Order Myxobacterales; the fine structure of the long, thin, flexuous rods found in the Genus Myxococcus has been well characterized. However, the fine structure of the proportionately short, blunt, rigid rods of the Genus Sorangium is relatively unknown. Therefore, a critical fine structure analysis of the Sorangium—type cell was appropriate. Isolates of Sorangium cellulosum, probably the best known representatives of this group, were selected. Three primary goals were established for the study reported in this thesis. The first was to compare the structure of S. cellulosum which is a Gram-negative bacterium, with other Gram-negative true bacteria in general and, specifically, with other myxobacteria. Second, the structure of the vegetativ e cells was to be compared with those of the cells found in the resis tant structures, the fruiting bodies, which myxobacteria form as part of their life cycle. The third primary goal was to elucidate the nature of certain phase-dense, moving inclusions which had been observed in these cells on many occasions. In addition, it was hoped that' such a study might shed light on some aspects of the numerous questions, such as slime production, movement, and morphogenesis, as yet unanswered about the myxobacteria in general, and S. cellulosum specifically."--Introduction.Item The biosystematics of the Lupinus argenteus complex and allies(University of Missouri--Columbia, 1969) Hess, Lloyd William; Dunn, David B."Introduction: For many years there has been great confusion in the nomenclature of Lupinus. Many authors have contributed numerous names as they interpreted the morphological variations. Since the work of Sereno Watson (1873) there has not been an attempt to make a monographic study of the perennial lupines of the United States. Individual authors have attempted to work up the treatment of Lupinus for their particular state without reference to the taxa described in neighboring areas. It was believed that a careful monographic study of related taxa was badly needed and could help clear-up some of the confusion. The large flowered members of the Lupinus argenteus complex and its apparent relatives were selected as a group extending widely in the Rocky Mountain area, which could be studied as a starting point. Since three taxa of this group existed in the Crested Butte area (near the Rocky Mountain Biological Laboratory) it was believed that work on the possible genetic barriers could be utilized in interbreeding studies to shed some additional light on the relationships within the group. No biosystematic technique, such as breeding studies, has been used in the previous studies. The present study then is the first attempt at a monograph on this related segment of Lupinus using both field work and the extensive collections that have been accumulated to date. Field collections were made throughout the extensive range of the Great Basin and western face of the Rockies inhabited by the various members of this group. Collections of various other workers and the major herbaria of the area were also used. The ecology, geography, and especially the monographic comparisons and breeding studies have hopefully given an improved understanding of the relationship within this complex. From this understanding of the genetically significant groups, as biological populations of nature, the taxa are defined and interpreted. An understanding of the extremely varied ecology of the extensive range involved, as well as its cataclysmic geological history is important to an understanding of the evolution and hence the phylogeny of the taxa of the complex. For this reason the geological history, especially glaciation, has been reviewed and related since most of the range has probably been invaded in post glacial times. The basic ecology of the range is also considered. Chromosome numbers have been counted but are of little value in the biosystematics of these lupines since they are octaploid and are extremely small. This and other unique problems pertaining to the interpretation of the speciation of polyploids have also been reviewed."--Page 1.Item Soil health and runoff water quality of broadbase terraces implemented with new tile inlet technologies(University of Missouri--Columbia, 2025) Bansal, Charchit; Singh, Gurbir[EMBARGOED UNTIL 12/01/2026] Soil erosion and waterlogging are persistent challenges in claypan landscapes of northern Missouri, where broad-based terraces are widely constructed to control runoff and sediment loss. However, the process of terrace construction involves extensive soil disturbance that can alter soil physical, chemical, and biological properties. The drainage inlets installed to improve drainage and reduce ponding may facilitate the transport of nutrients and herbicides out of the fields, potentially contributing to downstream water pollution. This research was conducted at the University of Missouri's Grace Greenley Conservation Showcase Research Farm near Leonard, Missouri, to evaluate the short-term impacts of terrace construction on soil health, and fertility, and to assess the performance of different tile inlet technologies, such as standard Hickenbottom riser (HBR), HBR with channel laterals (HBR+CL), water quality inlet (WQI), and blind inlet (BI) on nutrient, sediment, and herbicide transport from farm-scale terraced fields. Geo-referenced soil samples were collected before and after terrace construction from three topographic positions (shoulder, backslope, and footslope) and four depths (0-15, 15-30, 30-45, and 45-60 cm). Terrace construction resulted in substantial alterations in soil properties. Both sand and clay contents increased 32 g kg-1 and 29 g kg-1, while silt decreased 60 g kg-1, indicating a textural class change from silt clay loam to clay. Bulk density at 30-45 and 45-60 cm soil depth increased 7-13%, whereas at 0-15 and 15-30 cm decreased by 8-23% due to topsoil removal and redistribution. After terrace construction, soil temperature in the surface layer (0-15 cm) increased 1.7 °C, permanganate oxidizable carbon increased 12%, and 0.06 g kg-1 net increase in total nitrogen was observed compared to pre-construction values. In contrast, aggregate stability declined by 15-19%, and total carbon decreased by 0.54 g kg-1. Soil enzyme activity was reduced 26-50% including acid phosphatase, β-glucosidase, β-glucosaminidase, and arylsulfatase, confirming biological disturbance from soil mixing and compaction. Terrace construction also altered soil fertility and apparent electrical conductivity (ECa). Total exchange capacity (TEC) and soil test S, Mg, K, Na, and Fe increased, while soil pH, Ca, B, and Cu decreased, indicating both enrichment and dilution processes. An EM38-MK2 was used to record ECa values, which decreased by 19-36% across all four depths after the construction of terraces. Principal component analysis distinctly separated pre- and post-construction values, confirming terrace-induced changes in fertility, texture, and ECa distribution. To address ponding issues in terrace channels after terrace construction, tile inlet technologies were compared under no-till management using a randomized complete block design. Across the 2023-2025 monitoring period, HBR had the highest median daily discharge (2645 L ha-1), followed by HBR+CL (1901 L ha-1), WQI (1443 L ha-1), and BI (997 L ha-1). Additionally, HBR generated the greatest sediment and nutrient losses, while BI and WQI showed significant reductions of sediment and nutrient loads. In 2025, BI reduced TSS by 95% compared with HBR, largely due to adsorption and filtration within limestone gravel medium. Herbicide monitoring during 2024-2025 revealed that the highest chemical loads occurred immediately after the first rainfall following herbicide application, with discharge volume being the primary factor influencing the loads. The HBR and WQI had the highest herbicide losses, while BI consistently reduced loads across all chemicals due to tortuous flow through limestone gravel, resulting in large reductions observed in the 2025 corn season. Atrazine concentrations occasionally exceeded the USEPA maximum contaminant limits for discharge, highlighting potential water-quality risks associated with atrazine and the need for innovative research to reduce loss. Overall, this study demonstrates that terrace construction substantially alters soil physical, chemical, and biological properties across the soil profile, while improved inlet designs, such as BI, effectively reduce nutrient, sediment, and herbicide transport from terraced fields. The WQI effectively reduced sediments while increasing chemical loads compared to the BI. The adoption of these conservation drainage systems, combined with other conservation practices such as residue retention and cover cropping, can help restore soil health and protect downstream water quality in terrace-tile drained, intensively farmed agricultural fields in northern Missouri.Item Smart irrigation management for specialty crops in Missouri : regulated deficit irrigation and sensor-based approach(University of Missouri--Columbia, 2025) B K, Asbin; Neupane, Jasmine[EMBARGOED UNTIL 12/01/2026] Efficient irrigation management is essential for high value specialty crops production in Missouri that require specialized management practices. Additionally, variable climate, within-field variability of soil and topographic properties, and limited water resources have necessitated precise irrigation strategies for sustainable crop production. This research evaluated two irrigation strategies, regulated deficit irrigation (RDI) in blueberries and sensor-based precision irrigation in grapevines to explore the feasibility of smart, data-driven, and sustainable irrigation practices for specialty crops growers in Missouri. A two-year study on two highbush blueberry cultivars (Duke and Legacy) assessed the effectiveness of postharvest RDI as well as feasibility of proximal soil moisture sensing and remote sensing for smart irrigation management. No significant differences in yield, fruit quality, canopy indices and plant water status were observed between RDI and conventional irrigation. Irrigation water productivity increased under RDI for Duke and remained comparable for Legacy. Soil moisture sensors installed at 10 cm depth, combined with pulse-based scheduling, improved monitoring accuracy and maintained stable root-zone moisture. These results indicate that RDI can function as a viable water-saving strategy for blueberry production. Moreover, installation of soil moisture sensors at 10 cm depth and at 15 cm from the drip tape emitters can provide a suitable setup for monitoring soil moisture dynamics for potential precision irrigation management. A complementary study in grapevines compared IoT enabled sensor-based irrigation with conventional grower-managed irrigation across three root systems (101-14, Matador, and own rooted vines). Preliminary results showed improved water use in sensor-based irrigation compared to conventional irrigation (approximately 13 % less water use) while maintaining similar yield, berry weight, canopy indices, and vine water status. Overall, these two studies showed improved water use efficiency with postharvest RDI and sensor-based irrigation, without compromising the yield, quality, and plant water status during the growing season. Hence, the findings from this study indicate the feasibility of using post-harvest RDI and sensor-based irrigation management strategies for improved production profit and sustainability of specialty crops in Missouri.