Plant Biology Commons^™

Effects Of Photosynthetic Mode On Growth In Closely Related Tillandsia Species, Jeremy L. Read

Electronic Theses, Projects, and Dissertations

To examine the effects of photosynthetic mode (C3 vs CAM) on plant productivity, subjects of the sister taxa Tillandsia confertiflora (a C3 species) and Tillandsia latifolia (a CAM species) were grown under controlled conditions via growth chamber over 30 weeks. These subjects were divided into non-stressed and drought stress groups. Subjects were compared for total biomass gained or lost over the time period as well as physiological stress measures and CAM activity. The primary conclusion is that usage of CAM does not show major differences or tradeoffs for overall productivity. Future work is needed to clarify if this holds true …

Adapting Population Genetics, Practice, And Policy For Plant Conservation In A Changing World, Cooper M. Kimball-Rhines

Graduate Doctoral Dissertations

Biodiversity conservation is an inherently interdisciplinary goal that requires effective collaboration among academics, ecosystem managers, policymakers, and other stakeholders. Codesigning research with these groups ensures experiments are useful and improves adoption of policy and practice recommendations while advancing our understanding of basic science. This dissertation explores the power of codesigned research in shaping plant conservation strategies using stakeholder engagement, causal inference, demographic modeling, and multi-omic sequencing techniques. In chapter 1 I discuss the history of New England ecosystems and the need for research-driven changes to plant conservation policy and practice in the face of global change. In chapter 2, I …

Ecological And Nutritional Drivers Of Floral Fidelity In Wild Pollinators, Adelaide Elise Ergastolo

Master's Theses

Plants must receive pollen from the same species in order to successfully reproduce. For most flowering plants, the transfer of pollen occurs via animal pollinators while they forage on plants to obtain food. Therefore, the fidelity of pollinators to individual plant species during foraging trips is directly related to the amount of conspecific pollen plants receive. Low floral fidelity of pollinators can reduce plant reproductive success, which in turn has the potential to lower food resources for pollinators in the future. While many factors can potentially influence pollinator floral fidelity, several important ones may be the nutritional resources provided by …

Impact Of Land-Use Disturbances On The Composition Of Wetland Plant Communities Across The Conterminous United States, Maya Merchant

Undergraduate Honors Theses

Due to the threat of invasive species on wetland biodiversity, it is critical to assess factors driving their proliferation in wetlands. To address this growing need, this project analyzes relationships between non-native species and known anthropogenic disturbance types associated with increased biological invasions. Using the U.S. EPA’s 2021 National Wetland Condition Assessment, the relationship between non-native species (diversity, richness, and coverage) and surrounding land-use within 500, 1,000, and 3,000-meter buffers was evaluated. To explore patterns across larger spatial scales, mean non-native species diversity, richness, and coverage was calculated at the watershed level and compared to associated percentages of agricultural land …

Bottles, Butterflies, And Biomass: Recycled Glass Sand, Microbial Additions, And Herbivory Effects On Milkweed Growth, Kealey Skinner

Honors Theses

Plant-soil-microbe interactions are integral components of ecological networks and drive ecosystem function from the bottom-up. Whereas herbivores regulate ecosystem function from the top-down, having opposing and potentially complementary effects on ecosystem function. My thesis sought to understand how below-ground microbial communities contribute to herbivore preference and plant biomass across varied soil substrates. My thesis asked: how do substrate and soil microbial communities influence herbivore preference and plant biomass accumulation on swamp milkweed (Asclepias incarnata)? To address this question, seedlings of A. incarnata were sown in 2.5 cm wide × 10 cm deep pots filled with either natural beach sand or …

Evaluating Fungal Endophytes Inoculation As A Mechanism For Salt Tolerance In Juncus Roemarianus, Rani Badve

Honors Theses

Salinity stress is increasing in coastal and estuarine ecosystems due to increasing temperatures and the reduction of freshwater inputs via precipitation pattern changes. Elevated salinity can negatively affect plant survival, threatening the stability of coastal wetlands and the ecosystem services they provide. Juncus roemerianus is a common and dominant marsh plant in the Northern Gulf Coast that lives in varying salinities. Growing evidence suggests that root-associated fungal endophytes may contribute to enhanced stress tolerance; however, the response of fungal communities to salinity remains poorly understood.

This study evaluated how salinity influences the abundance and diversity of culturable root-associated fungal communities …

Degradation And Metabolic Analysis Of Synthesized Quorum-Sensing Signals By The Model Eukaryote Chlamydomonas Reinhardtii, Adam Josef Bach

Theses and Dissertations

Bacterial organisms can “talk” with one another on a colony-wide scale using a communication system known as quorum-sensing (QS) via chemical signals. These signals are produced at a basal rate throughout the life of the bacteria and are classified as autoinducers, which diffuse across the cell membrane. Once the critical concentration is reached, they begin to diffuse back into the cell and initiate a phenotypic change. As these signals exist outside the membrane of their producer, they are also accessible to other organisms. It has already been noted that some plant species uptake these compounds through their roots and break …

Discovering The Genetics Underlying Speciation Traits In Heuchera (Coral Bells), Tajinder Singh

Honors Theses

Hybridization is a key evolutionary mechanism for generating biological diversity, ultimately shaping diversification and adaptation of plant lineages in natural and agroecosystems.  Our understanding of the frequency, distribution, and significance of hybridization is rapidly increasing, but the external driving forces that dictate why certain species hybridize, and others do not remain obscure. The physical traits that shape gene flow and trait sharing among species are likely to be among the key factors that directly control hybridization. Gene flow in most plants is mediated by pollinating insects and thus by pollination syndromes, which are suites of floral traits that have evolved …

Testing The Intermediate Disturbance Hypothesis On Anthropogenic Pressure In Central Alabama, Gavin Terrell

Theses

Biodiversity is fundamental to maintaining ecosystem structure and function globally. Prior to the late 20th century, ecological theory generally predicted that biodiversity would be highest in systems experiencing minimal disturbance. However, Joseph H. Connell challenged this view with the Intermediate Disturbance Hypothesis (IDH), which posits that species diversity peaks at intermediate levels of disturbance and declines under conditions of both low and high disturbance. Although widely cited, the applicability of the IDH to natural systems remains debated, particularly in the context of anthropogenic disturbances and when diversity is measured beyond species richness alone.

This study evaluated the predictions of the …

Alabama Prairie Reconstruction: Comparing Management Pathways For A Southeastern Landscape, Cecelia R. Geyer

Theses

Southeastern prairies are highly biodiverse yet increasingly threatened by land-use change, fire suppression, and habitat fragmentation. These disturbance-dependent systems rely on periodic fire and grazing to maintain plant diversity and ecosystem function. This study evaluates prairie restoration strategies by testing predictions from the Intermediate Disturbance Hypothesis and the Patch Mosaic Burn Hypothesis. The study site was divided into three treatments: prescribed burned only (B), prescribed burned with mowing (BM) to simulate grazing, and an undisturbed control (C). A standardized mix of native plant seeds was broadcast across all treatments. Ecosystem health and function were evaluated using plant community diversity and …

Succession And Alpine Plant Habitat Of A Recently Deglaciated Foreland In The Trinity Alps, California, Sebastian Evans

Cal Poly Humboldt theses and projects

The recent extinction of the Salmon Glacier in the Trinity Alps, California, provides a rare opportunity to examine post-glacial succession in a region of high endemism experiencing climatic stress. Using a chronosequence spanning ~150 years since deglaciation, I investigated (1) vegetation successional trajectories in the foreland, (2) whether the foreland functions as a climate refugium for alpine specialists, and (3) whether facilitative interactions between the dominant vascular plant (DVP) and bryophytes occur and persist through succession. I surveyed 100 plots across 11 transects within the foreland and 40 randomized plots in adjacent ecosystems. Successional patterns and refugial potential were analyzed …

Evaluating Source Material And Seed Propagation Techniques For Spartina Alterniflora To Enhance Salt Marsh Restoration In Coastal Georgia, Maygan Palacios

College of Graduate Studies: Theses & Dissertations

Salt marshes provide critical ecosystem services, including carbon sequestration, flood attenuation, and habitat for diverse aquatic and terrestrial species. Despite their ecological importance, these habitats are increasingly threatened by anthropogenic activities and rising sea levels. To protect and restore salt marshes and their ecosystem services, restoration efforts using living shorelines (LS) have become more common. Along the Eastern and Gulf coasts of the United States, the native grass Spartina alterniflora is commonly used in LS installations for its key role in salt marsh food webs, resilience to abiotic stress, and ability to stabilize and build sediment. Previous studies have documented …

Soil Nutrient Sufficiency Versus Plant Nutrient Status In Compost-Amended Soils: Plant Tissue Analysis As A Diagnostic Tool, Chandralekha Joga Miss

Murray State Theses and Dissertations

This study evaluated whether Mehlich III soil nutrient sufficiency ratings reliably predict plant nutrient status and chlorophyll response across contrasting compost application histories. A greenhouse pot experiment was conducted with Chijimisai (Brassica rapa) planted in three treatment soils that had no compost (T1), moderate compost history (T2), and long-term hog manure compost application (T3). Plant performance was assessed through weekly shoot length and chlorophyll content (SPAD) measurements, leaf number at maturity, and leaf tissue nutrient analysis conducted at harvest. Soil test results indicated adequate to high nutrient levels across all three treatments. Leaf tissue analysis, however, revealed substantial …

Investigating Microbe-Mediated Temperature Tolerance In Lemna Minor, Matthew Thomas Farbaniec

Honors Theses and Capstones

Temperature limits plant growth and survival more than many other environmental variables, and increases in the frequency of extreme hot or cold weather events pose significant challenges for plant growth and crop yields. Previous studies have shown that bacteria, fungi, and other microorganisms associated with plants ( i.e., the plant microbiome) can influence host response to temperature stress. These same microbes have their own temperature tolerances. We investigated whether microbial temperature tolerance correlates with plant resilience using an aquatic plant model, Lemna minor, and isolates derived from its microbiome. Microbial isolates were assessed at −10°C, 4°C, and 32°C for …

Analysis Of Alternative Oxidase In Non-Angiosperm Plants, Anissa M. Francis

Theses and Dissertations (Comprehensive)

Alternative oxidase (AOX) is a mitochondrial terminal oxidase that provides an alternative pathway for electron transport, allowing plants to maintain respiratory flexibility under environmental stress conditions. While AOX has been extensively studied in angiosperms (flowering plants), little is known about its distribution and conservation in non-angiosperms. Based on gaps identified in the literature, this thesis investigated the distribution of AOX across non-angiosperm plant lineages. Although AOX is present in many green algae and is therefore considered to be an ancient protein that originated before the existence of non-angiosperm plants, it remains unclear whether the protein is uniformly distributed across these …

Characterization Of The Genetic Diversity Of Curlyleaf Pondweed (Potamogeton Crispus L.) In The Contiguous United States And Canada And Analysis Of Possible Hybrid Potamogeton Crispus Lineages, Mallory M. Kaiser

All Graduate Theses, Dissertations, and Other Capstone Projects

Curlyleaf Pondweed (Potamogeton crispus L.) is a prolific invasive species that has spread across the United States and into parts of Canada since its introduction to North America in the 1840s. It causes extensive economic and environmental damage across its invasive range, and its control and eradication are of utmost importance to agricultural, ecological, recreational, and transportational stakeholders. Developments in molecular ecology and invasive management have found that genetic diversity and hybridization of aquatic macrophytes may affect their susceptibility to herbicide treatments, and genotype or lineage identification are important control variables that must be considered in field and …

Evaluating Soil And Plant Health In A Wide-Row Maize (Zea Mays L.) Production System Integrated With Perennial Cover Crops And Turkey (Meleagris Gallopavo), Sovika Bhattarai

All Graduate Theses, Dissertations, and Other Capstone Projects

In regions dominated by intensive maize (Zea mays L.) production systems, such as the US Midwest, sustainable agricultural practices such as cover crops and livestock integration are gaining interest for their potential to improve soil, plant, and environmental health. Traditionally, annual cover cropping systems (ACCs) have been used to maintain soil quality and crop performance without compromising ecosystem services. However, the high establishment and management costs of ACCs highlight the need for alternative approaches, such as perennial cover crops (PCCs). Grown as companion crops with maize, PCCs provide extended soil cover and can improve soil biochemical properties (e.g., total C …

From Theory To Ecosystems: Exploring Biodiversity And Ecosystem-Function In Pitcher Plant (Darlingtonia Californica) Microbial Communities, Gavin Sutter

Cal Poly Humboldt theses and projects

The relationship between biodiversity and ecosystem-function (BEF) has been a central focus of ecological research for the last three decades, yet the role of space in shaping BEF relationships remains relatively unknown. Research has shown that community diversity and composition can strongly influence productivity, nutrient cycling, and decomposition, but much of this work treats communities as spatially isolated, leaving open how dispersal and other spatial processes shape BEF at broader scales. To begin addressing this gap, I used microbial communities inhabiting Darlingtonia californica pitcher plant leaves to evaluate how spatial organization and successional change shape biodiversity and ecosystem-functioning. I quantified …

Sex In Plants: Birth, Death, And Trying To Survive In Changing Climates, Elena M. Meyer

Theses and Dissertations

Plant mating systems are key determinants of fitness. Angiosperms exhibit a wide variety of reproductive strategies, including self-fertilization (or selfing), outcrossing, and mixed mating. It has been estimated that up to 43% of plant species are capable of selfing, and selfing has been hypothesized to provide reproductive assurance where opportunities for mating may be limited, such as in marginal environments. However, questions regarding the overall distribution of selfing rates across angiosperms, the maintenance of mixed mating in the face of inbreeding depression, and the impact of self-fertilization on diversification rates remain incompletely resolved. Here, we explore the dynamics of self-fertilization …

American Elderberry's Next Top Pollinator: Evaluating The Role Of Arthropods In Pollination, Jenny K. Burrow

Graduate Theses/Dissertations

American elderberry (Sambucus nigra subsp. canadensis) is a woody deciduous shrub native to eastern North America. In addition to its long history of use by indigenous peoples, there is renewed interest in cultivating and consuming American elderberry, primarily driven by expanding health supplement markets. Despite recent advances in horticultural development of American elderberry, its pollination ecology remains poorly understood. In this field study, I evaluated the contribution of arthropod visitors to pollination of American elderberry. To do this, I first characterized the identities and abundances of arthropod visitors via timed arthropod collections and floral observations during peak flowering …

Root Analysis Of Glechoma Hederacea, Austin Z. Shiner

Theses/Capstones/Creative Projects

Glechoma hederacea, or commonly referred to as ground ivy, is a weed that can be found in many places such as parks, yards, and landscapes. A mutant genotype of Glechoma hederacea that was exhibiting virescence was collected from a single mutant branch of the wildtype ground ivy. The collected mutant has delayed chloroplast development, and this appears to impact plastidial terpenoid synthesis resulting in damage to leaf tissue. Since a range of plant hormones include isoprene units, altered IPP synthesis may have visible impacts beyond the green tissues of the plant, so this study aimed at addressing this question. …

The Evolution And Reproduction Of Andean Miconia (Melastomataceae), Juan Angulo

Dissertations, Theses, and Capstone Projects

Understanding the factors that shape diversification and distribution in tropical plant lineages is central to explaining the origins of Neotropical biodiversity. Assessing evolutionary history with trait evolution and climatic niche dynamics provides key insights into the drivers of diversification and biogeography, while natural history data remains critical for these evolutionary studies. The Tropical Andes, with its exceptional biodiversity and environmental heterogeneity, offers an ideal setting to explore these processes. In this dissertation, I investigate how reproductive systems, climatic niche dynamics, and pollination strategies influence the evolution and biogeography of Miconia III, a large and ecologically diverse clade in the …

Plant Reproductive Strategies Shift In Response To Restoration Using Beaver Dam Analogs, Laurel F. Martinez

Biology ETDs

As riparian communities become increasingly degraded, restoration treatments are being implemented in streams to recover ecosystem functions. In the Jemez Mountains, beaver dam analogs (BDAs) are used to restore degraded streams by connecting the floodplain and increasing the extent of anoxic soil conditions. These environmental disturbances are expected to alter how riparian plants recruit, particularly their allocation to seed-based and vegetative regeneration strategies. We investigated whether BDAs and associated changes in soil water filled pore space (WFPS) affected riparian plant recruitment. We investigated the number of flowering stems as a proxy for seed-based regeneration and rhizome length and mass as …

The Ecophysiology Of The Enigmatic Namib Succulent, Lithops Ruschiorum, Garrett Macleod Althausen

Environmental Studies Senior Theses

Water availability is the primary constraint for plant survival and reproduction in hyper-arid ecosystems. In such environments, plant fitness depends on an alignment between physiological traits and limited water resources. The Namib Desert of Namibia exemplifies this extreme selection pressure. Within the Namib Desert, Lithops ruschiorum, a succulent endemic to the gravel plains, exhibits habitat specificity and numerous physiological adaptations to cope with the hyper-aridity.

This research explores the intersection of two fitness strategies for L. ruschiorum: habitat selection and exploitation of alternative moisture sources. The first chapter explores the population dynamics and micro-site habitat conditions preferred by …

Understanding The Role Of Sabp2-Interacting Proteins Sip432: A Premnaspirodiene Oxygenase Enzyme In Stress Signaling, Cristiana F. Martinez

Undergraduate Honors Theses

This study focuses on the characterization of a SABP2-interacting protein (SIP)-432. SIP432 is a putative premnaspirodiene oxygenase-like P450 enzyme. Premnaspirodiene is a 15-carbon compound that can be converted into antimicrobial compounds by a hydroxylation reaction. The interaction of SIP432 with SABP2, a critical component of salicylic acid-mediated plant immunity, implies a role for SIP432 in plant stress signaling. This study uses the T-DNA knockout mutant of Arabidopsis thaliana SIP432 (homolog of NtSIP432) to help understand its role in abiotic and biotic stress responses. Plants were subjected to abiotic and biotic stress to understand their role in stress response pathways. Gene …

Chromosome Evolution Model Reveals Hidden Variation In Karyotype-Driven Speciation In Ferns, Thomas Buchloh

All Theses

Because karyotype change commonly generates reproductive isolation between diverging species, rapid karyotype evolution, like that seen in plants, may increase the total rate of diversification. However, few studies have investigated this predicted relationship. Tests of this prediction have identified a positive correlation between the rate of karyotype change (specifically whole genome duplications) and diversification, but tests have been restricted to relatively small and young clades. Fortunately, novel macroevolutionary models have recently become available to investigate patterns of karyotype evolution in large phylogenies, providing new opportunity to investigate variation in karyotype driven diversification. Ferns are one of the most karyotype rich …

Understanding The Genetic And Metabolic Underpinnings Of Complex Traits In C4 Grasses, Manwinder Singh Brar

All Dissertations

Maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench) are two important cereal crops cultivated worldwide for food, animal feed, and industrial products. Productivity of these crops is significantly impacted by various biotic and abiotic stresses, such as diseases, insect pests, drought, salinity, and heat. Among factors influencing crop performance under stress, the regulation of leaf longevity plays a critical role in determining yield. Leaf senescence is a highly regulated process essential for nutrient remobilization through the degradation of cellular components in aging leaves, but premature or accelerated senescence reduces photosynthetic efficiency and yield. Staygreen, a phenotype …

Investigate The Use Of Nucleic Acids As Pesticides To Manage Major Pests And Pathogens Of Crops In South Carolina, Prasanna Valavanur Shekar

All Dissertations

The sugarcane aphid (SCA, Melanaphis sorghi), first discovered on grain sorghum in late 2013, has gradually become a major insect pest of sorghum. It inflicts significant damage to the crop year after year, causing millions of dollars in losses throughout the sorghum-producing regions of the United States. Similarly, Armillaria root rot—also referred to as oak root rot—is a major cause of decline in peach (Prunus persica) production in the southeastern United States. This disease is caused by Armillaria mellea and Armillaria tabescens. Current management practices for controlling M. sorghi include the use of synthetic pesticides, resistant varieties, and regular scouting. …

Intraspecific Variation In Morphological And Biochemical Responses To Salinity And Flooding In Phragmites Australis, Olivia Hurley

LSU Master's Theses

Phragmites australis is a widespread wetland plant species with numerous haplotypes, several of which are highly invasive. In low-lying coastal marshes of Louisiana, the Delta-type (haplotype M1) dominates across a wide range of salinity and flooding environments. This suggests that Phragmites may be highly adaptable to diverse environmental conditions and that there may be a genetic component, as seen in other coastal wetland plant species. While non-native Phragmites haplotypes are targeted for control and removal in many areas, they are considered beneficial for marsh stabilization and contributing to elevation gain in coastal Louisiana, where several areas experience rapid land loss. …

Assessing Bioactivity Of Green Leaf Volatiles In Various Plant Systems, Fallon S. Tomlin

Senior Theses

Green leaf volatiles (GLVs) are chemical compounds essential in plant communication. Plants emit these volatiles due to abiotic and biotic stressors and, when perceived, these GLVs activate defense responses. Though GLVs play an important role in plant survival, it is still unknown where they localize, how they are perceived, and what structural factors influence perception. To elucidate these structural determinants, we tested the bioactivity of (Z)-3-fatty alcohols with four to nine carbons. Through root growth inhibition assays with tomato (Solanum peruvianum) seedlings, we found that (Z)-3-octenol and (Z)-3-nonenol were more bioactive than (Z)-3 hexenol and (Z)-3-heptenol. Thus, higher bioactivity was …