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Evaluating The Effects Of Temperature And Photoperiod On The Flowering Responses Of Poinsettia, Michael John Alden

All Theses

During greenhouse production of poinsettia, flower initiation can be delayed by exposure to supra-optimal temperatures; this phenomenon is termed “heat delay.” Poinsettias that are delayed by high temperatures may mature too late to be shipped in time for the Christmas market. This can lead to a significant loss of revenue on a crop that is considered to be marginally profitable. The increasing global temperatures brought on by climate change are expected to amplify the magnitude of heat delay in susceptible regions and spread this problem to new areas previously unaffected by heat delay. The goal of this thesis was to …

The Mechanisms And Consequences Of Shrub Encroachment On The Virginia Barrier Islands, Lauren K. Wood

Theses and Dissertations

Shrub encroachment is a global phenomenon driven by direct and indirect anthropogenic influence which alters plant communities and ecosystem function. Many studies have investigated drivers and consequences of woody plant establishment, but mesic landscapes are underrepresented in the literature. My objective was to assess the mechanisms of Morella cerifera encroachment into coastal mesic grassland, the potential for self-reinforcement, and consequences on community composition, nutrients, and landscape productivity. I studied temperature and water microclimate modification by Morella cerifera presence and removal to understand ecosystem engineering and community composition changes. Additionally, I examined the influence of shrubs on surrounding grassland species traits …

Optimizing Species Selection For Forest Restoration In The Lower Rio Grande Valley, Faeqa Mohsin

Theses and Dissertations

Over the past four decades, the Lower Rio Grande Valley has been reforested with over 3.3 million native thornscrub plants in old agricultural land through transplanting native species. However, assessments of LRGV forest restoration efforts are scarce, and to address the knowledge gap, this study examined species-specific responses to restoration interventions (RIs) aimed at minimizing seedling mortality for optimizing species selection. A critical period for forest restoration in old croplands is the seedling stage, where high mortality occurs due to the interactive effects of abiotic stress, compromised soil nutrient status from intensive agriculture, and mammalian herbivory. So, we evaluated seedling …

Carbon And Nitrogen Dynamics In Plants Grown At Low Co2 Conditions Of The Past, Andre Galvao Duarte

Electronic Thesis and Dissertation Repository

For most of the recent evolutionary history of plants, atmospheric CO₂ concentrations have been far below modern values. However, little is known about how plants grown in a low CO₂ environment balance their carbon demand for growth while meeting their requirement for nitrogen acquisition, the establishment of mycorrhizal fungal associations, and the production of defense compounds. Here, I investigated how low CO₂ affects Elymus canadensis and Picea mariana by comparing their growth at low and current CO₂ concentrations. I found that reduced N availability exacerbated low CO₂ effects on growth, and reduced stomatal index and …

Greening Rates And Photosynthetic Development Of Leaves In C3 And C4 Plants, Tayler J. Kriss

Master's Theses

To study chlorophyll development time and overall photosynthetic development in C3 and C4 leaves, seeds were germinated in complete darkness and achlorophyllous leaves were then allowed to develop in lighted conditions. Corn (Zea mays, C4), sorghum (Sorghum bicolor, C4), green bean (Phaseolus vulgaris, C3), broad bean (Vicia faba, C3), and wheat (Triticum aestivum, C3) were investigated for the first ten days of sunlight exposure. Chlorophyll concentration, chlorophyll fluorescence, and CO2 gas exchange measurements were conducted daily on the first leaf that emerged after the embryonic leaves of each plant. The first five days of the experiment, days zero to four …

Structure And Function In Petioles Of Pelargonium, Dustin M. Ray

Doctoral Dissertations

As the connection between lamina and stem, petioles are essential for plant survival. Petioles serve two major functions in service to the leaf blade. First, they hold the leaf blade away from the stem to reduce self-shading and optimize light interception, a mechanical function. Second, petioles serve as the bridge between the stem and lamina allowing water to move up the plant body and photo-assimilates to move down to the plant body from the leaf blade, a physiological function. While mechanics and physiology have been studied independently, the petiole could be a space-limited structure leading to tradeoffs between the two …

Linking Climate Change And Mortality In Piñon-Juniper Woodlands, From Leaf To Ecosystem, Amanda I. Liebrecht

Biology ETDs

As global climate changes, the Southwestern US is predicted to experience more frequent and intense drought events. Extreme droughts can drive decreases in both physiological and ecosystem function, and can result in widespread tree mortality. Piñon-juniper (PJ) woodlands are a prevalent ecosystem in the region, co-dominated by two tree species, piñon (Pinus edulis) and juniper (Juniperus monosperma). Drought-induced piñon mortality has occurred over the past few decades, coinciding with outbreaks of a piñon-specific bark beetle. Piñon and juniper have different hydraulic strategies (isohydry and anisohydry, respectively) that should affect the way each species responds to drought. …

Mejora En Los Procesos Actuales De Producción Y Comercialización Del Abono Orgánico Derivado De La Lombriz En El Centro De Investigación Agropecuaria Y Plantulacion Vegetal En Fómeque, Laura Daniela Medina Ruíz, Angie Natalia Bohada Ortega

Ingeniería Industrial

No abstract provided.

The Effects Of Root-Absorbed Glyphosate On Physiology And Growth Of Select Ditch Plants, Lyndsay Erin Saunders

Electronic Theses and Dissertations

Hundreds of thousands of hectares of agricultural lands are drained by edge-of-field ditches that flow into surface waters. Vegetation within agricultural ditches is subject to the effects of agrochemicals in runoff. Glyphosate, the world's most widely used herbicide, has been detected in agricultural runoff where it may interact with plant roots. Laboratory and greenhouse experiments were conducted to evaluate the effects of root-zone glyphosate exposure on plant functioning including growth, physiology, morphology, and survival. Investigations included identifying a sublethal concentration of root-zone glyphosate exposure for use in subsequent experiments, quantifying the physiological effects of a range of sublethal glyphosate exposures, …

Studies On Nitrogen And Silicon Deficiency In Microalgal Lipid Production, Curtis Adams

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Microalgae are single celled plants that inhabit aquatic and terrestrial environments across the planet. Many species are oleaginous, which means they are capable of producing oils, similar to many higher plants we are familiar with like canola, safflower and coconut. Different from higher plants, however, algae have simple structures that allow them to grow at very high rates. Due to these characteristics—oil production and rapid growth rates—algae are considered a promising future source of oil. Algal oils could be useful for production of food for people, feed for animals, biodiesel, detergents, and many other applications.

Algae have not been heavily …

Evaluating Native Wheatgrasses For Restoration Of Sagebrush Steppes, Jayanti Ray Mukherjee

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Pseudoroegneria spicata and Elymus wawawaiensis are two native perennial bunchgrasses of North America's Intermountain West. Frequent drought, past overgrazing practices, subsequent weed invasions, and increased wildfire frequency have combined to severely degrade natural landscapes in the region, leading to a decline in the abundance of native vegetation. Being formerly widespread throughout the region, P. spicata is a favorite for restoration purposes in the Intermountain West. Elymus wawawaiensis, which occupies a more restricted distribution in the Intermountain West, is often used as a restoration surrogate for P. spicata. However, since most restoration sites are outside the native range of …

Physiological And Molecular Function Of Hap3b In Flowering Time Regulation And Cold Stress Response, Mingxiang Liang

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Heme-activated proteins (HAPs) are transcription factors that have multiple roles in plant growth and development, such as embryogenesis, flowering time control, and drought tolerance.

In the present study I found that HAP3b was also involved in controlling response to cold stress. Transcript profiling and gene expression analyses indicated that HAP3b repressed the CBF3 regulon under normal growth conditions. As a result, plants with HAP3b-overexpressed showed decreased survival rates while plants homozygous for the null allele hap3b showed an improved freezing tolerance compared to wild-type plants.

To understand the mechanism of HAP3b in Arabidopsis, i.e. whether it also acts …

Remediation Of An Oil Contaminated Wetland And The Effects Of Crude Oil And Brine On Two-Year Old Loblolly Pine (Pinus Taeda) Seedlings., Dean Anthony Goodin

LSU Historical Dissertations and Theses

The goal of this project is to introduce a successful remediation and restoration plan for a wetland and pine forest contaminated by an oil well blowout. A field study focused on the effectiveness of ammoniated bagasse (ABG) to enhance the bioremediation of the contaminated wetland. A comprehensive soil and vegetation greenhouse study investigated the effects of oil and brine on loblolly pine tree seedlings and the effectiveness of ABG to remove and remediate oil contaminated forest soils. The most effective, ecologically sound, and economical plan to remove the oil from the wetland was to burn the area. Once the area …

Floral Ontogeny And Phylogeny In Malvaceae., Teresa Shuff Crozier

LSU Historical Dissertations and Theses

Floral ontogeny in representatives of Malvaceae was compared using scanning electron microscopy. Many aspects of floral development have been resolved by this research, including the presence of a petal-stamen ring meristem in malvaceous taxa. There are several ontogenetic pathways to the formation of this ring meristem; in addition, common petal-stamen mounds are usually present during some stage of development. Stamen proliferation is achieved by partitioning of the ring meristem and furcation of common stamen primordia. Time of initiation overlaps between the corolla and the androecium, and between the androecium and the gynoecium. Helical initiation occurs in the outer organ whorl …

Heritability Of Waterlogging Tolerance In Wheat., Agron Collaku

LSU Historical Dissertations and Theses

Waterlogging stress is one of the factors depressing wheat yield. Study of heritability for yield and yield components under waterlogging is important in determining the influence of genetic factors accounting for waterlogging tolerance as compared to environmental stress. The objectives of this study were: (1) to study the effect of waterlogging on yield and yield components of soft red winter wheat; (2) to estimate losses from waterlogging; (3) to estimate heritability of waterlogging tolerance in early generations of wheat for yield and yield components, and (4) to provide selection criteria for waterlogging tolerance in wheat breeding. Linear reduction in yield …

Intraspecific Variation In Three Marsh Grasses In Response To Increased Flooding And Salinity., Jeannine Marie Lessmann

LSU Historical Dissertations and Theses

Intraspecific variation in response to moderate levels of flooding and salinity stress was identified in Spartina patens, S. alterniflora, and Panicum hemitomon. This analysis enabled genotypes of each species to be selected for desired traits to enhance their function in restored systems, such as increased belowground biomass to stabilize soil substrates or increased aboveground biomass to enhance sedimentation. It was also determined that increased flood tolerance conferred a greater advantage for plant growth at moderate stress levels than did increased salt tolerance. However, this growth advantage was overridden by high salinity stress, and was greatly reduced by excessive flooding stress. …

Cloning And Identification Of Chlamydomonas Reinhardtii Genes And Proteins Upregulated Under Low Carbon Dioxide Conditions., Aravind Somanchi

LSU Historical Dissertations and Theses

A mechanism that concentrates CO$\sb2$ in cells of Chlamydomonas reinhardtii, is induced when cells are grown at low CO$\sb2$ conditions. This mechanism increases the CO$\sb2$ concentration at the site of RuBisCO, and thereby improves the efficiency of C$\rm\sb{i}$ uptake and fixation. Cells adapting to low CO$\sb2$ show significant physiological changes. Few of the genes encoding proteins needed to produce these changes have been identified. A cDNA library has been constructed from C. reinhardtii to identify genes involved in these changes. The cloning and identification of several cDNAs that are upregulated under low CO$\sb2$ conditions are reported here. The possible roles …

Etiology And Biological Control Of Seedling Disease In Water-Seeded Rice., Se-Chul Chun

LSU Historical Dissertations and Theses

In order to assess the potential of biological control of rice seedling disease, detailed etiological information was required, i.e. when and for how long are seedlings susceptible and which portions of the seed and seedling are susceptible. Contaminant-free seeds were required for these studies. For this purpose, rice seeds were soaked for 2 hrs in freshly prepared 2.6% sodium hypochlorite adjusted to pH 7.0 with a final concentration of 0.5 M potassium phosphate. This treatment was not only very effective in disinfesting seeds but also seemed to promote seedling growth. On the basis of this observation, a study was conducted …

A Physiological Study Of Common Carpetgrass (Axonopus Affinis) Subjected To Cultural And Environmental Stress., Edward Wayne Bush

LSU Historical Dissertations and Theses

Common carpetgrass (Axonopus affinis Chase) is a low maintenance stoloniferous grass widely distributed throughout the southern coastal plains of the United States. This study investigated seed germination enhancement, seedhead suppression, waterlogging tolerance, winter hardiness, and maintenance practices for common carpetgrass. Pre-soaking common carpetgrass and centipedegrass (Eremochloa ophiuroides (Munro.) Hack.) seed was beneficial at the 30C germination temperature. Priming seed in KNO$\sb3$ solutions significantly accelerated seed germination of both centipedegrass and carpetgrass at 30C, and increased total germination percentage of centipedegrass. At 20 and 25C, seed priming significantly improved mean time of germination for both grass species and total germination percentage …

Characterization Of Physiological Changes In Roots Grown In Spaceflight Conditions: A Comparison Of Nutrient Delivery Technologies., David Marshall Porterfield

LSU Historical Dissertations and Theses

The best strategy for providing food and maintaining the environment on long-duration space missions is a bioregenerative life support system based on the growth of higher plants. Before such a system can be implemented, a better understanding of plant growth in space will have to be achieved. Little is known about the role of gravity-dependent physical processes in normal physiological function. A series of ground-based and spaceflight experiments was conducted to examine root oxygen availability in microgravity nutrient delivery systems. In spaceflight experiments Arabidopsis thaliana (L.) Heynh. plants were analyzed for changes in root medium redox potential and root alcohol …

Submergence Impacts On Selected Wetland/Bottomland Tree Species., Jian Sun

LSU Historical Dissertations and Theses

Flooding is a common natural stress occurring in wetland/bottomland forests. Submergence, total immersion, is a special case of flooding, which has received limited attention in the literature. This study provides information on the impacts of three submergence treatments on three bottomland tree species. The results indicated that submergence would inhibit shoot and root growth for the three tested species during the submergence period. However, the survival of these species under submergence conditions were different. Taxodium distichum (L.) Rich survived even after 30 days of water coverage and survival continued to be high during the recovery period. Quercus nuttallii Palmer was …

Arsenic Characterization In Soil And Arsenic Effects On Canola Growth., Michael Scott Cox

LSU Historical Dissertations and Theses

Reactions of soil arsenic with arsenic addition and the effects of soil arsenic on canola were studied because of a lack of information on this subject. The reactions of different pools of soil arsenic to arsenic addition were studied. The effects of soil arsenic and arsenic form and concentration in solution on canola growth and nutrient uptake were also investigated and an attempt to model arsenic uptake with a mechanistic computer model was made. In a solution study, rate of inorganic arsenic did not appear to effect arsenic accumulation in roots and shoots of canola. However, shoot and root arsenic …

Intraspecific Variation In Salt Tolerance In Panicum Hemitomon, Spartina Patens, And Spartina Alterniflora: Population Differentiation And Investigations Of Underlying Factors., Mark Warner Hester

LSU Historical Dissertations and Theses

Although it is known that wetland plant species exhibit considerable interspecific variation in salt tolerance across coastal plant communities, very little is known concerning the amount of intraspecific variation in salt tolerance within plant species. Panicum hemitomon, Spartina patens and Spartina alterniflora are dominant emergent macrophytes of fresh, brackish and salt marshes, respectively. To investigate intraspecific variation in salt tolerance, plant material was collected from Gulf Coast populations of each of these species and subjected to a salinity screening protocol. All three of the plant species displayed significant intraspecific variation in lethal salinity level and plant morphology. Lethal salinity levels …

Changes Of Amylases And Carbohydrates In Sweetpotatoes During Storage And Their Effects On Viscosity Of Sweetpotato Puree., Xiangyong Liu

LSU Historical Dissertations and Theses

A critical problem associated with the production of sweetpotato puree is the inconsistency of final product. Two possible factors, amylase activity and carbohydrate content in sweetpotatoes during storage, were investigated. It was found that $\alpha$- and $\beta$-amylase activities do not significantly change during storage, and have no significant effects on viscosity of sweetpotato puree. The inconsistent products in sweetpotato puree processing are mostly due to the change of alcohol insoluble solids (AIS) in sweetpotatoes during storage. The decrease of AIS is partially due to respiration that converts starch into CO$\sb2$ and H$\sb2$O. A new bio-processing method was proposed to improve …

Interactions Of The Soybean Looper, Pseudoplusia Includens (Walker), And Soybean, Glycine Max (L.) Merrill, Involving Nitrogen: Effects On Host Symbiotic Nitrogen Fixation And Larval Development And Survival., Alan Thomas Wier

LSU Historical Dissertations and Theses

Acetylene reduction and nitrogen difference assays were used to evaluate effects of defoliation by soybean looper, Pseudoplusia includens (Walker), during reproductive growth stages on symbiotic nitrogen fixation by soybean. Defoliation (50-55%) of group VI cultivar Lee from full bloom into pod development stages caused up to 85% reduction of nitrogenase activity, whereas lower defoliation levels (32%) during seed development did not affect nitrogenase activity. Defoliation (74-94%) of group IV cultivar Clark caused 80-100% reduction of nitrogenase activity, regardless of whether defoliation occurred during bloom and pod development or during seed development. The nitrogen difference assay identified a reduction in the …

Physiological Variation In Loblolly Pine (Pinus Taeda L.) As Related To Crown Position And Stand Density., Dennis Albert Gravatt

LSU Historical Dissertations and Theses

Physiological parameters were measured under natural light conditions and needle orientation from towers and walkways erected in the crowns of loblolly pine (Pinus taeda L.) trees. Photosynthetic light response curves, chlorophyll content, nutrient content and specific leaf area were determined for current-year foliage on detached branches. Two silvicultural treatments were randomly assigned to the twelve plots in the fall of 1988. Plots were thinned to a density of 731 trees per hectare or left unthinned, at a density of 2990 trees per hectare. The plots were left unfertilized or fertilized with 744 kg per hectare of diammonium triple superphosphate was …

Factors Affecting Asulam Activity On Sugarcane (Saccharum Sp.) Cultivars And Johnsongrass (Sorghum Halepense)., Stacey Alan Bruff

LSU Historical Dissertations and Theses

Studies were conducted to evaluate several factors that may account for the variability in johnsongrass (Sorghum halepense (L.) Pers.) control and sugarcane (Saccharum sp.) cultivar sensitivity observed with postemergence application of asulam, methyl ((4-aminophenyl)sulfonyl) carbamate, herbicide. Johnsongrass at boot stage to 70% seedhead emergence was exposed to simulated rainfall (1.3 cm of water in 15 min) 0, 3, 6, 12, 24, and 48 h after application of asulam at 3.7 kg/ha. Predicted critical rainfree period at which greatest johnsongrass control (65 to 80%) was obtained ranged from 8 to 20 h after treatment, dependent on johnsongrass growth stage and environmental …

Seed Dormancy In Red Rice (Oryza Sativa): Changes In Embryo Ph And Metabolism During The Dormancy-Breaking Process., Steven Footitt

LSU Historical Dissertations and Theses

Hydrated, dehulled, dormant seeds of red rice (Oryza sativa L.) were exposed to chemical treatments (nitrite, propionic acid, methyl propionate, propionaldehyde, and n-propanol) that saturate the dormancy-breaking response. Dormancy-breaking chemicals were (a) metabolized (n-propanol and propionate) by embryos in dormant seeds to weak acids; (b) decreased embryo pH; and (c) increased embryo (Fru 2,6-P$\sb2$) prior to dormancy-breaking. Embryo acidification, but not increased embryo (Fru 2,6-P$\sb2$), was associated with the chemical contact interval required for the onset of dormancy-breaking. During chemical contact, embryo (Fru 2,6-P$\sb2$) increased independent of dormancy-breaking and was inversely correlated with the elapsed time to 30% germination. On …

Effect Of Planting Date And Other Management Inputs On Production Of Wheat., Syed Asif Hussain Shah

LSU Historical Dissertations and Theses

Intensive cereal management (ICM) can optimize the yield and performance of winter wheat (Triticum aestivum L. emend. Thell.). Planting is often delayed beyond the optimum date along the Gulf Coast due to frequent precipitation. Field experiments were conducted at four locations in 1991 and two locations in 1992 to evaluate the effects of intensive management practices on performance of wheat planted at recommended and post-recommended dates. Seeding rates of 84 or 168 kg ha$\sp{-1}$ and topdress N rates of 90 or 90 + 45 kg ha$\sp{-1}$ were evaluated for an early and a late-maturing cultivar planted at a recommended date …

Transgenic Rice Plants Containing A Chlorsulfuron Resistance Gene, A Hygromycin Resistance Gene And The Maizeactivator Transposable Element., Zhijian Li

LSU Historical Dissertations and Theses

A mutant Arabidopsis acetolactate synthase (ALS) gene csr-1-1, conferring chlorsulfuron resistance, was tested in transgenic rice to develop an alternative selectable marker for rice transformation. Up to a 200-fold increase in chlorsulfuron resistance was detected in transgenic rice calli expressing the mutant ALS gene under control of the CaMV 35S promoter. Efficient selection of resistant protoplast colonies was achieved by using 10 to 50 nM of chlorsulfuron after transformation with the 35S/ALS gene. Fertile transgenic rice plants were successfully recovered from 35S/ALS-containing transformants. These results demonstrated that the 35S/ALS gene could be used as a selectable marker gene in rice …