Plant Biology Commons^™

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. …

Evaluating The Roles Of Pollinators In Shaping The Floral Color Variation Of Phacelia Dubia, Katherine Riddle

All Theses

Floral color variation within a species is a common occurrence and its maintenance has been a long-standing question in evolutionary biology. Differences in flower color between populations can be shaped by pollinator-mediated selection. Pollinators can exhibit innate and learned preferences for color that may influence floral color variation. These preferences may be molded by the visual environment in which pollinators forage. Most current understanding of how pollinators shape floral color variation involves dramatic differences in dominant pollinators between populations (e.g., hawkmoth vs. bee) and most behavioral work utilized model pollinators like honeybee and bumble bee. However, less is known about …

Investigating The Adaptive Potential Of Leaf Variegation In Two Dimorphic Hexastylis Species, Cierra N. Sullivan

All Dissertations

Variegated leaves with disjointed, patterned coloration of the leaf blade are often hypothesized to have decreased photosynthetic capacity in comparison to uniformly colored leaves. Yet, many forest understory plants in tropical, subtropical, and temperate climates possess leaf variegation. Moreover, mixed findings from previous research on the physiological impacts of leaf variegation suggest variegation is adaptative under certain environmental conditions despite decreased photosynthetic tissue area. I take an eco-physiological approach to investigate agents of selection maintaining a leaf variegation polymorphism in Hexastylis, which has both quantitative and qualitative variation in variegation. First, I conduct field surveys of morph frequencies, quantitative …

I’M A Forest, Not A Saltmarsh, Captain: Carbon And Sap Flow Dynamics In Coastal Forested Wetlands Of The Southeastern United States, Chris Shipway

All Theses

Coastal forested wetlands are identified as some of the highest-priority ecosystems for climate change mitigation. Here, we present two studies conducted in these unique ecosystems.

The first assessed changes in aboveground vegetative C stocks along the estuarine-riverine gradients of the Winyah Bay in South Carolina and the Savannah River in Georgia, using a space-for-time substitution to increase understanding of the impacts to upper estuarine forested wetlands from relative sea level rise. Standing C stocks on the Savannah River averaged 183.6 Mg C ha^-1, while sites on the Winyah system averaged 162.3 Mg C ha^-1. The largest …

Enhancing Crop Resilience: Physiological And Omics Approaches For Drought And Heat Stress Tolerance In Soybean And Peanut, Jyoti Prasad Kakati

All Dissertations

Soybean and peanut are two major crops globally grown for oil and protein. Climate change-associated factors like drought and increased temperature (heat stress) challenge the global production of soybeans and peanuts. Though the United States is the second-largest producer of soybean and the fourth-largest producer of peanuts, it still faces production constraints associated with drought and heat stresses. In the present study, we have examined the responses of soybean and peanut plants to drought and heat stresses during germination and reproductive phases. We conducted field and controlled environmental studies to elucidate the impact of drought stress on germination and seedling …

Germination Trends Of American Chaffseed, Schwalbea Americana L., And Factors Affecting First-Year Seedling Development, Trenton Miller

All Theses

Following centuries of exploitation and fire suppression, longleaf pine systems are now the focus of many conservation efforts. Efforts to restore populations of Schwalbea americana L. in longleaf pine savannas have been met with frustratingly low recruitment. While past studies have briefly quantified germination rates for Schwalbea, there have not been any studies yet that truly investigate this plant’s germination requirements. Additionally, there has been little research into characterizing the parasitic relationship between Schwalbea and its various host species. We conducted a germination study in a growth chamber that investigated Schwalbea’s germination rate and time to germinates as …

Survey And Prevalence Of Palmer Amaranth Herbicide Resistance In South Carolina, Mitchell Williams

All Theses

Palmer amaranth is a troublesome weed for growers to control, not only due to its aggressive growth characteristics that limit row-crop production, but because of its resistance to different herbicide modes of action. The first case of herbicide resistance in Palmer amaranth was detected in 1989 and has since grown to nine different herbicide classes throughout the United States. New herbicide modes of action have not been developed since the 1980s, so proper stewardship of the remaining modes of action is important for effective control of Palmer amaranth. Increased herbicide resistance from states bordering South Carolina have been reported; therefore, …

Meta-Analysis Of The Effects Of Endophytes And Their Secondary Metabolites On Herbivory From Insects, Derrick Taylor

All Theses

Endophyte-infected plants have reduced the level of herbivory. The defense to herbivory can vary due to the metabolites in the plant and the method of feeding from the pest. Secondary metabolites produced by the endophytes are mainly alkaloids. The associations between endophytes and some alkaloid groups are studied in greater detail. The lack of research of certain alkaloid groups ultimately means that some alkaloids had more data that could be analyzed. As a result, the alkaloid groups were not evenly represented in the meta-analysis. The meta-analysis analyzed the relative effectiveness of the metabolites or endophytes in each of the articles …

In Vitro Rooting Techniques In Prunus Spp. For Propagation And Disease Screening For Armillaria Root Rot (Arr) Resistance, John Lawson

All Theses

Prunus is a genus widely cultivated to produce edible fruit including almond (P. amygdalus), peach (P. persica (L.) Batsch), cherries (P. avium and P. cerasus), among others. The cultivation of Prunus is economically important for several regions of the United States and relies on appropriate cultivars and rootstocks that are adapted to a growing region. Encroaching plant pathogens are forcing breeders to use sexually compatible germplasm from related species for introgression of novel alleles that confer tolerance or resistance. This is especially true in the rootstock breeding where interspecific hybridization is often used …

Etiology And Epidemiology Of Mini-Ring In Ultradwarf Bermudagrass Putting Greens, Lukas Dant

All Dissertations

Mini-ring is a disease in ultradwarf bermudagrass (UDBG) [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)] putting greens caused by Waitea zeae (Voorhees) J.A. Crouch & Cubeta, (formerly Rhizoctonia zeae). Symptoms typically resemble frog-eye patches that are 10 to 40 cm in diameter with a bronze to orange outer ring and green center. In the southeastern United States, mini-ring symptoms appear in late-summer and generally persist until UDBG dormancy in late-fall. Mini-ring is often problematic in UDBG when nitrogen (N) fertility is reduced to manage organic matter production and improve putting green performance and perceived green speed. While …

The Influence Of Water Stress And Rootstocks On Nutrient Uptake And Gas Exchange Of Young Peach Trees, Naif Alshammari

All Theses

Young peach trees are often rainfed in the southeastern U.S. and periods of dry weather can cause tree water deficit that can be detrimental to orchard productivity. There is a lack of understanding of the influence of water regimes and rootstocks on the nutritional status and gas exchange of the peach tree. Most peach growers in Southeastern United States do not irrigate their young peach trees because they do not produce fruit until the third leaf. In this region, peach growers use Guardian as a rootstock, although MP-29 is also interesting for growers with orchards that have Armillaria root rot …

Floating Treatment Wetlands For Brackish Waters: Plant Selection And Nutrient Uptake Potential., Andrea Landaverde

All Theses

Brackish water bodies in coastal regions provide critical ecosystem services that support human and environmental health. Anthropogenic activities such as agricultural and industrial activities, construction, urban settlements, and tourism contribute to increased inputs of nitrogen (N) and phosphorus (P) in brackish coastal ecosystems. Excess nutrients can lead to impaired water quality and affect marine organisms. Floating treatment wetlands (FTWs) are a vegetated-base technology used to remove contaminants from water column, that has been mainly studied and applied in freshwater systems. Application of FTWs in brackish systems requires further investigation, as high salinity in brackish waters could result in toxicity to …

Elucidating The Cellular Physiology Of Glyphosate Resistance In Palmer Amaranth (Amaranthus Palmeri) Using Integrated Omics Approaches, Pawanjit Kaur Sandhu

All Theses

The evolution of resistance to herbicides in weeds poses a major threat to agricultural production systems. To date, herbicide resistance has been reported against 21 modes of action in 266 weed species across 71 countries. More than 50 weed species have developed resistance against glyphosate, the most widely used herbicide worldwide. Although several mechanisms of glyphosate resistance have been discovered, our understanding of alterations in the cellular physiology of glyphosate-resistant weed biotypes, and the induction of the resistance mechanisms remains limited. This knowledge is critical to developing sustainable weed management practices and for a comprehensive understanding of plant stress adaptations. …

Biology, Ecology, And Control Of Doveweed (Murdannia Nudiflora [L.] Brenan), Jeffrey Atkinson

All Dissertations

Doveweed (Murdannia nudiflora [L.] Brenan) is a summer annual in the Southeastern United States with an expanding geographic range. The light green color and texture of doveweed is problematic for turfgrass managers as it contrasts with the color and texture of desirable turfgrasses. Limited research is available concerning the biology, ecology, and herbicide control options for doveweed. Therefore, experiments were conducted to improve the understanding of how environmental conditions effect doveweed germination, how cultural practices and environmental resource availability effect doveweed growth and development, to identify pre- and postemergence herbicides with efficacy for doveweed control, and to improve the understanding …

Factors Influencing The Distribution And Structure Of Tropical Vascular Epiphyte Communities At Multiple Scales, Carrie Woods

All Dissertations

Understanding the factors that determine species distributions is a central question in ecology. Niche-based theories stress the importance of environmental heterogeneity in influencing species distributions while neutral-based theories emphasize the effects of dispersal limitation. The relative importance of these factors in influencing species distributions may depend on spatial scale - deterministic factors may be more important at small spatial scales where fine-scale habitat factors become more relevant and stochastic factors may be more important at larger spatial scales where dispersal limitation becomes more relevant. I examined the influence of deterministic and stochastic factors on the distribution and structure of vascular …

Functional Characterization Of A Jacalin-Like Lectin Domain-Containing Protein In Arabidopsis Thaliana, Shane Reighard

All Theses

Jacalin-related lectins (JRLs) are proteins that bind carbohydrates. Functionally, JRLs are thought to be involved in a diverse array of functions including biotic stress defense, intracellular storage, abiotic stress response, and plant development. Recent Arabidopsis thaliana microarray data indicate that a Jacalin-like domain-containing protein (JLL1) exhibits highly root specific expression. Previous transcriptomic and proteomic studies indicate that JLL1 may have a dual role in planta as a biotic stress defense protein and in plant development. In order to better understand the physiological function of JLL1 in Arabidopsis, several different analyses were conducted examining its regulatory sequences, spatial expression, responsiveness to …

Cloning, Expression Analysis, And Transformation Vector Construction Of Dam Homologs In Peach And Poplar, Yuhui Xie

All Theses

Genetic fine mapping and sequencing of the EVG locus in peach [Prunus persica (L.) Batsch] identified six tandem arrayed Dormancy-Associated MADS-box (DAM) genes as candidates for regulating growth cessation and terminal bud formation in the non-dormant evergrowing (evg) mutant. Since the mutant is lacking expression of six genes in the mapped locus, further functional analysis is needed to narrow the list of gene candidates for the non-dormant evg phenotype. Here I report three sets of experiments designed to functionally test DAM genes in peach and their homologs in a model tree, hybrid poplar.
First I constructed overexpression and knockdown vectors …

Enhancing The Ability Of Panicum Virgatum To Survive Flooding And Its Effects On Soil Activity When Used For Lakeshore Stabilization, Lee Edwards

All Dissertations

Reservoirs in upstate South Carolina are subject to erosion and vegetation has been placed to help stabilize banks, but soils are nutrient-poor and have high bulk densities. Panicum virgatum L. (switchgrass) has been planted in several sites, and it is hypothesized that over time, changes in microbial activity and soil quality will occur in response to the planting. As vegetated sites aged, acid phosphomonoesterase, nitrate reductase, and dehydrogenase activity increased. Low values of nitrogen fixation and substrate-induced respiration were measured at all sites with no statistical differences between sites. Fatty acids indicative of Gram negative bacteria were found in vegetated …

Maestra2: A Model For Simulating Spatially Explicit Carbon Dioxide Exchange Rates Among Species' Water Stress Response, Robert Reynolds

All Theses

MAESTRA2, a species specific mechanistic model, was parameterized to estimate water use, carbon accumulation and organ specific respiration of five deciduous tree species under both irrigated and water stressed conditions. The model was validated using temporally and spatially explicit ecophysiological data to account for seasonal changes in species physiology. The following tree species: Acer rubrum L. 'Summer Red' (A. rubrum), Betula nigra (B. nigra), Paulownia elongata (P. elongata), Quercus nuttallii (Q. nuttallii), and Quercus phellos (Q. phellos) were intensively measured and organ specific destructively harvested samples were compared to modeled estimates of carbon accumulation. Among species, we observed variability in …