Life Sciences Commons^™

Investigating The Impacts Of Drought On Turfgrass (Festuca Arundinacea) Chlorophyll-A Fluorescence Emission, Ayanna S. Hatton

Honors Projects

When photons from sunlight are absorbed by plants, they can take paths of photosynthesis, fluorescence, or energy dissipation. Instruments to quantify fluorescence have expanded in scale to allow measurements from satellites and flux towers using Solar-Induced Chlorophyll Fluorescence (SIF). Studies have found a positive correlation between SIF and gross primary productivity (GPP; representative of photosynthesis), suggesting SIF is a proxy for GPP. This conclusion encourages the use of SIF to inform decisions about carbon budgets and responding to climate change. Studies of fluorescence on the single-leaf scale have revealed that SIF measurements do not account for all variables nor is …

Climate Interactions Drive Tree Physiology And Growth In A Northeastern Forest Ecotone, Alexandra M. Barry

Electronic Theses and Dissertations

Climate change is a threat to global forest ecosystems. In the northeastern United States, forest trees are facing rising temperatures and increasingly inconsistent moisture regimes. In addition to long-term changes in climate conditions, there is concern about the potential for more frequent and intense climate extremes, which can have severe and rapid negative effects on tree physiology and growth. Further, climate extremes may co-occur to produce a greater magnitude of effect than the sum of their parts, with a prominent example being hot droughts, which are increasing in occurrence and severity. The impact of these and other extreme climate interactions …

Evaluation For Using Expended Bioelectrochemical Systems As Soil Amendments For Improved Corn Plant Growth And A Drought Resistant Soil., Jackson Lee Sauers

Theses and Dissertations

A long-held practice is to mix agricultural soil with a soil amendment to improve growing conditions in crops. A common soil amendment is biosolids produced from both municipal and dairy wastewater due to the macro- and micronutrients within it. Both the agricultural and wastewater industries are participating in the Circular Economy concept (CEC). Two experiments explored using expended bioelectrochemical systems (BES) that treated either synthetic dairy wastewater (DWW) or synthetic municipal wastewater (SWW) as soil amendments to improve corn plant growth when treated with three different nutrient treatments: 100%- 50%- and 0% Hoagland Nutrient Solutions. Biochar and used terracotta clay …

Transcriptional Analysis Of Maize Under Drought Stress And The Impact Of Plant Maturity, Oliver J. Oviedo

Biology ETDs

Climate change related drought is projected to harm maize production. Water use strategies can help mitigate the impact of drought on crop yield. However, little is known about maize metabolic response to drought at different developmental stages. To shed light on this, drought conditions were applied to maize at the six-leaf stage (V6), twelve leaf stage (V12), and tassel stage (VT). V6 and VT took eight days to achieve a low stomatal conductance threshold, but V12 took 16 days. Differential gene expression analysis of the transcriptome indicates that V6 showed the most response with 53 impacted metabolic pathways, many of …

Breeding Soybean [Glycine Max (L) Merr.] Under Reduced Irrigation, Francia Seconde Ravelombola

Graduate Theses and Dissertations

Soybean [Glycine max (L) Merr.], a legume species native to East Asia in the Fabaceae family, ranks among the most important food crops in the world. It is widely grown and known for its high protein and oil concentration. Soybean is valuable because its seeds have multiple applications in food, feed, pharmaceutical, and industrial enterprises. Even though seed yield is the most important trait, breeders have recently given a significant attention to quality traits, such as high protein or modified oil concentration. Soybean seed protein inheritance has been extensively studied; however, genetics of high-protein ‘BARC-7’ soybean are still unknown.On the …

Improving Water And Plant Growth Regulator (Pgr) Management Practices In Cotton: Cultivar Physiological Responses And Pgr Rates, Kurt Wedegaertner

Masters Theses

Cotton (Gossypium hirsutum L.) is grown in an increasingly unpredictable climate and often under rainfed conditions. Without irrigation to alleviate common drought conditions, cultivar selection becomes a primary tool in mitigating the negative effects of water-deficit stress. Cultivars can differ in water use under water-limited environments, which can affect crop performance. Moreover, cotton management must involve balancing vegetative and reproductive growth through the use of plant growth regulators (PGR) due to the plant’s perennial growth pattern. The efficacy of PGRs are dependent on many variables including environmental conditions, irrigation, and genetics (cultivar). In 2020 and 2021, a series of …

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. …

Genetic And Environmental Regulation Of Plant Growth, Kirk J-M Mackinnon

Doctoral Dissertations

Field grown crops are continually exposed to a variety of external stimuli that influence plant responses. Light, temperature, and water availability interact to affect many economically important traits including growth rate, size, and lifespan. My research is focused on the intersection of genetic and environmental factors influencing plant growth. Specifically, I am interested in elucidating the regulation of rhythmic genes in response to photo- and thermocycles and identifying novel candidate genes associated with growth and drought traits. Understanding the gene regulatory networks that mediate time-of-day signaling is vital to identifying candidate genes across the pan-genome associated with traits of interest.

Comparing Organic And Conventional Yield Responses To Climate Variations, Joost Wilken Meyer

Graduate Theses and Dissertations

This thesis compares the responses of organic yields and conventional yields towards climate variations. To achieve this objective, weather variables such as growing season weather conditions (average temperature, precipitation, cloud cover, relative humidity, drought index), weather anomalies, the occurrence of severe or extreme droughts and excessive rainfalls, are combined with 23 data sets gathered from previous studies that compare organic and conventional yields from the same location and time periods. To narrow the scope, the thesis focuses on soybean, maize, and wheat production in Europe and North America. Study-level fixed-effects models are used to control for any time-invariant factors such …

Hybrid Bermudagrass And Kentucky Bluegrass Response Under Deficit Irrigation In A Semi-Arid, Cool Season Climate, Hanna R. Burgin

Theses and Dissertations

As average global temperatures rise, cool-season C3 turfgrasses, such as the most commonly grown Kentucky bluegrass (Poa pratensis L.; KBG), struggle to tolerate extreme summer heat and increase their water consumption. Hybrid Bermudagrass (Cynodon dactylon [L.] Pers. × Cynodon transvaalensis Burtt Davy; HBG) is a warm-season C4 grass that may be increasingly suited for northern ecosystems traditionally classified as transition or cool-season climate zones. Glasshouse and field studies were conducted to compare HBG and KBG water use. The objective of the glasshouse study was to evaluate plant health and growth for two HBG cultivars (‘DT-1’ and ‘NorthBridge’) compared to a …

Loblolly Pine (Pinus Taeda) Leaf-Level Physiology And The Influence Of Genotype, Drought, And Thinning, Norman Jesse Cone Iv

Master's Theses

The Southeastern U.S. is known as the “Wood Basket” for producing the vast majority of U.S. timber, but projected increases in the frequency of severe drought events could threaten timber plantations. Loblolly pine (Pinus taeda) is the principle timber species of the southeast and is distributed across the Atlantic Coastal Plains and west into Texas. Western Gulf states (LA, TX, AR, and OK) lie at the edge of the range for loblolly pine and are particularly vulnerable to any changes in precipitation or temperature. Current research suggests two main methods to increase plantation drought resistance: plant drought resistant seedlings or …

Identifying Drought Tolerance Traits In Tennessee Soybean Genotypes: Recovery From Severe Water Deficit Stress, Samuel W. Purdom

Masters Theses

Ninety-four percent of U.S. grown soybeans are produced under rainfed conditions with intermittent droughts occurring late in the season during reproductive growth stages. Due to the temporary nature of drought, the ability of a crop to survive and recover effectively from water deficit stress is important for ensuring yield stability. In 2019 and 2020, two greenhouse experiments and two field studies were conducted to screen eleven soybean genotypes for transpiration response and recovery from water deficit stress and high vapor pressure deficit (VPD). In the first greenhouse study, soybean plants were grown in pots sealed to prevent evaporation and plants …

Assessing Short-Term Microalgal Community Responses Over Altering Hydrological Conditions In Experimental Wetlands Of Costal Georgia, Maggie M. Kuhn

Electronic Theses and Dissertations

Wetlands provide valuable ecosystem services such as nutrient cycling and carbon storage. Microalgae (i.e., diatoms) provide the foundation of primary production and determine rates of energy transfer throughout the system. Climate change models predict an increase in frequency of intense storms and severe drought conditions that pose a threat to known hydrological regimes and wetland ecosystem stability. The purpose of my study was to assess the effects of water permanence (i.e., duration of flooding) on diatom community structure in experimental wetlands. I predicted that wetlands with prolonged periods of flooding (i.e., permanent) would harbor a consistent diatom community throughout flooding …

Fruit Tree Responses To Water Stress: Automated Physiological Measurements And Rootstock Responses, William D. Wheeler

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

New orchard plantings utilize trees grafted to dwarfing rootstocks planted close together to facilitate larger harvests. These dwarfing rootstocks have not been comprehensively studied for their ability to withstand drought. This is of special importance in the Intermountain West which has limited rainfall. Additionally, orchard growers face competition for water from a growing population and increased uncertainty in rainfall from climate change. My research examined the use of dendrometers, which measure changes in trunk diameter, and sap flow sensors, which measure how quickly sap moves, as methods to inform growers about tree water status. I also used a weighing lysimeter …

Molecular Genetic Analysis Of Drought Resistance And Productivity Traits Of Rice Genotypes, Yheni Dwiningsih

Graduate Theses and Dissertations

Rice (Oryza sativa L.) is the staple food for a majority of the world’s population, and uses 30% of the global fresh water during its life cycle. Drought at the reproductive stage is the most important abiotic stress factor limiting grain yield. The United States is the third largest exporter of rice, and Arkansas is the top rice-producing state. The Arkansas rice-growing region in the Lower Mississippi belt is among the 10 areas with the highest risk of water scarcity. Adapted U.S. rice cultivars were screened for drought resistant (DR) traits to find sources for breeding U.S. rice cultivars for …

Genetic Architecture Of Salt And Drought Tolerance In Cowpea, Waltram Second Ravelombola

Graduate Theses and Dissertations

Cowpea [Vigna unguiculata (L.) Walp.] is a diploid and nutrient-dense legume species. It provides affordable source of protein to human. Cowpea cultivation is prevalent in Africa, Asia, the western and southern U.S., and Central and South America. However, earlier reports have shown that drought and salt stress can be devastating to cowpea production. The objectives of this study were to screen for salt and drought tolerance in cowpea and to identify molecular markers associated with these traits. Simple methodologies to screen for drought (Chapter 2) and salt tolerance were developed (Chapter 3). Results suggested that: 1) a total of 14, …

Genetics Of Physiological Traits Associated With Drought Tolerance In Soybean (Glycine Max), Sumandeep Kaur Bazzer

Graduate Theses and Dissertations

Soybean (Glycine max L.) is one of the major row crops in the United States, and its production is often limited by drought stress. Physiological traits from exotic germplasm that confer drought tolerance may be useful in improving commercial soybean production. For example, carbon isotope ratio (δ13C) is positively correlated with water use efficiency (WUE), and nitrogen isotope ratio (δ15N) is negatively correlated with N2 fixation; canopy temperature (CT) is an indicator for genetic variation in transpiration and stomatal conductance. Therefore, the objectives of this research were to identify the genomic regions associated with: (1) δ13C and δ15N using a …

Characterization Of Squamosa Promoter Binding Protein Like (Spl), And Its Role In Drought Stress Tolerance In Medicago Sativa (Alfalfa)., Alexandria K. Hanly

Electronic Thesis and Dissertation Repository

Traditional breeding involving Medicago sativa (alfalfa), has resulted in minimal yield increases. Moreover, extreme environmental conditions threaten to further limit production. Strategies that make use of molecular tools – such as small non-coding RNA, miR156 – represent an innovative means by which to influence tolerance to abiotic stress. miR156 functions, at least in part, through the SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) family of transcription factors. In this study, the role of SPL9 in regulating alfalfa development and drought tolerance is evaluated. Examination of alfalfa plants with RNAi-mediated SPL9 (SPL9-RNAi) showed that plant height, stem thickness, and internode …

Aboveground-Belowground Interactions: Roles Of Soil Biotic And Abiotic Factors On Switchgrass's (Panicum Virgatum) Growth, Defense Against Herbivory And Cell Wall Chemistry., Binod Basyal

Electronic Theses and Dissertations

Plants constantly interact with their biotic and abiotic soil environments. Most terrestrial plants form beneficial associations with soil microbes such as arbuscular mycorrhizal (AM) fungi, which are widely known for their ability to transfer soil phosphorus and nitrogen to the host plants. They help plants tolerate drought stress and improve plant defense against herbivores such as plant-parasitic nematodes (PPNs). This dissertation investigates the role of AM fungi on switchgrass’s (Panicum virgatum) growth, cell wall chemistry, and defense against PPNs using a combination of growth chamber and field studies. Switchgrass is a native warm-season species which is gaining traction as candidate …

Microrna156: A Short Rna With A Major Role In Abiotic Stress Tolerance In Alfalfa, Biruk Ayenew Feyissa

Electronic Thesis and Dissertation Repository

The highly conserved plant microRNA156, miR156, affects various aspects of plant development and stress response by silencing SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors. Our understanding of the role of miR156 and its mode of action in alfalfa’s (Medicago sativa L.) response to drought and flooding is still elusive, and thus this study was aimed at filling this gap in knowledge. Physiological parameters, metabolite and transcriptional analyses showed an interplay between miR156/SPL13 and WD40-1/DFR to mitigate drought stress. Low to moderate levels of miR156 overexpression suppressed SPL13 and increased WD40-1 to fine-tune the DIHYDROFLAVONOL-4-REDUCTASE (DFR) level for …

Drought Effects On Germination Rate Of Two Sagebrush Species, Artemisia Cana And Artemisia Arbusula, And Comparison Of Seed Counts Using A Photography App And Weighing, Sam S. Kelly, Cessair E. Mckinney

Environmental Science & Management Senior Capstones

Sagebrush steppe ecosystems have been impacted by climate change, grazing, and invasive plants. While some widespread sagebrush species have been well-studied, including big sagebrush (Artemisia tridentata), others like silver sagebrush (Artemisia cana) and low sagebrush (Artemisia arbuscula) are understudied. To learn more about how to restore these important ecosystems, we conducted a germination study of two sagebrush species. We germinated seeds from A. cana in petri plates and in soil to compare the rates of germination in both methods, while A. arbuscula seeds were germinated only in petri plates. We also tested the efficiency …

Subalpine Forest Tree Seedling Response To Drought, Alex Goke

Electronic Theses and Dissertations

Knowledge of tree species’ ability to tolerate drought is necessary to anticipate future forest dynamics with climate change, especially at the seedling stage given their role in shaping forest structure. We used precipitation reduction shelters to mimic drought for subalpine conifer seedlings (A. lasiocarpa and P. engelmannii) in the Rocky Mountains and compared survivorship and morphological and physiological responses to assess relative degrees of drought tolerance. We detected no significant investment in morphological tolerance traits (e.g. root biomass, leaf:stem area ratio) but substantial reductions in net photosynthesis. While shading partially ameliorated drought effects when precipitation reduction was moderate, …

Determining Water Requirements In Turfgrass Systems, Tyler Quinn Carr

Graduate Theses and Dissertations

Turfgrass lawns are commonly utilized for home and commercial applications because of the aesthetic, environmental, and recreational benefits grasses provide, but many people perceive turfgrass as solely an aesthetic benefit that requires significant water inputs. It is important to identify and use turfgrass cultivars that have known drought tolerance, and also fine-tune and throughout development. A series of field experiments were conducted to determine the water requirements of turfgrass lawn systems with the following objectives: 1) investigate differences in chronic drought resistance and irrigation recommendations among cultivars of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) 2) …

Studies On Pathogenesis Of The Diseases Caused By Macrophomina Phaseolina And Phomopsis Longicolla On Soybean, Marcio Leizer Zaccaron

Graduate Theses and Dissertations

Soybean (Glycine max), a legume, is an economically important crop in many parts of the world, including the USA, Brazil, Argentina, China, and India, currently the top five producing countries. Soybean is primarily used as feed, with incising markets for food and biodiesel. Similar to most crops, soybean yield and quality are affected by a diverse group of plant pathogens. In particular, several species of filamentous fungi have been the cause of severe yield losses in most growing regions world-wide. The soil born fungus Macrophomina phaseolina, causal agent of charcoal rot, has been found to be endemic to several soybean …

Stoichiometric Homeostasis In Two Native And Two Invasive South Dakotan Grasses, Joshua Thonas Harvey

Electronic Theses and Dissertations

Increased nutrient availability has been widely linked to the success of invasive plants, however a general mechanism explaining these observations is lacking. Stoichiometric homeostasis (H), which is the regulation of internal nutrient concentrations, has been used to explain changes in plant community diversity under alterations in nutrient availability. One hypothesis holds that plants with high regulation (larger H) decrease in abundance in nutrient enriched conditions but are stable in nutrient deficient and drought conditions, likely due to extensive root systems. Additionally, plants with low regulation (lower H) increase in abundance under nutrient enriched conditions but are sensitive to drought …

Effect Of Silicon On Wheat Growth And Development In Drought And Salinity Stress, Spencer A. Tibbitts

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Silicon is a major component of most soils, and is found in significant concentration in plant tissue. Plants vary widely in the amount of silicon they take up, with some plants excluding it, and others using transporters to move the silicon from the soil into their roots. Early plant physiology studies were unable to determine conclusively whether silicon was essential to plant growth, but for some plants, most notably rice, it has proved to be important enough to justify fertilizing silicon deficient fields.

Researchers at the USU Crop Physiology Lab tested the effect of silicon on wheat growth and seed …

Quantifying Genetic Responses Of Plants To Drought Stress With A Comparative Transcriptome Approach, Jessica K. Devitt

Electronic Theses and Dissertations

Mentzelia section Bartonia (Loasaceae) commonly occurs in some of the hottest and driest places in North America, but we poorly understand the mechanisms that allow them to tolerate such extreme environments. Morphological and physiological adaptations are well studied in model organisms. The underlying genetic responses to drought stress in non-model organisms like Mentzelia is unknown. To better understand and identify differences and similarities in genetic responses to drought stress between species existing in different habitats with differing water availability, three species from the genus Mentzelia were compared. Species of section Bartonia occur across an environmental gradient, from temperate to arid …

Impact Of Preemergent Herbicides, Mowing Height, And Fertilization On Centipedegrass Root Architecture And Drought Tolerance, Mike J. Adams

LSU Master's Theses

Mowing, N fertilization and the application of preemergence herbicides (PRE) are cultural practices performed on centipedegrass to improve overall turf quality. It is posited that increasing mowing height and application of fertilizers can lead to greater turfgrass rooting and increase drought survival; while the application of PRE is reported to potentially have negative impacts on rooting. At two locations in Louisiana, studies examining the effects of these practices on centipedegrass rooting and drought tolerance were conducted.

In the first 11-week study conducted, centipedegrass was treated with dithiopyr, pendimethalin, prodiamine, simazine, or indaziflam at the manufacturers’ labeled rates. During the 11-wk …

Genomic And Physiological Approaches To Improve Drought Tolerance In Soybean, Avjinder Kaler

Graduate Theses and Dissertations

Drought stress is a major global constraint for crop production, and improving crop tolerance to drought is of critical importance. Direct selection of drought tolerance among genotypes for yield is limited because of low heritability, polygenic control, epistasis effects, and genotype by environment interactions. Crop physiology can play a major role for improving drought tolerance through the identification of traits associated with drought tolerance that can be used as indirect selection criteria in a breeding program. Carbon isotope ratio (δ13C, associated with water use efficiency), oxygen isotope ratio (δ18O, associated with transpiration), canopy temperature (CT), canopy wilting, and canopy coverage …

The Impact Of Climate And Elevation On The Growth And Mortality Of Piñon Pine, Alice M. Fretz

Biology ETDs

The Southwestern United States is currently experiencing severe drought, resulting in the mortality of many tree species. Piñon-juniper woodlands are an extensive biome in the Southwest, and are highly vulnerable to extended periods of drought that lead to tree mortality. Specifically, Pinus edulis populations are decreasing due to increasingly arid conditions. I used dendrochronology to investigate how tree growth rings of Pinus edulis reflect severe drought in living and dead trees. I also investigated how severe drought affects Pinus edulis along an altitudinal gradient. Tree core samples were taken from currently living and dead trees, as well as from trees …