Life Sciences Commons^™

Major Fusarium Diseases On Corn, Wheat, And Soybeans In Nebraska, Bo Liu, Loren J. Giesler, Tamra A. Jackson-Ziems, Stephen N. Wegulo, Robert M. Harveson, Kevin A. Korus, Robert N. Klein

Department of Plant Pathology: Faculty Publications

Fusarium species are associated with diseases of corn, wheat, and soybean, causing significant yield loss in Nebraska. Some produce mycotoxins that are harmful to humans and animals.

Taxonomy And Dna Barcoding In The Genus Manfreda (Salisb.) Asparagaceae, William David Ritchie

Graduate Theses and Dissertations

The genus Manfreda Salisb. of Asparagaceae is a genus of potential horticultural interest and is currently subject to breeding efforts at the University of Arkansas. A lack of taxonomic clarity however undermines the classification of potential inter - and intrageneric hybrids. The study aims to assess existing species delimitation within the genus Manfreda employing morphology while investigating the potential utility of Consortium for the Barcode of Life Plant (CBOL) DNA Barcodes for identification of specific taxa and an External Transcribed Spacer (ETS) - Internal Transcribed Spacer (ITS) DNA barcode for developed hybridized taxa.

Observation of 855 herbarium specimens facilitated phylogenetic …

The Biological Control Of Spotted Knapweed In The Southeastern United States, Carey R. Minteer

Graduate Theses and Dissertations

Spotted knapweed is an invasive, short-term-perennial plant that is native to Eurasia. It was accidentally introduced into North America in the early 1890's and has since spread across The United States and Canada. Spotted knapweed degrades rangelands and pastures by negatively impacting native plants, increasing soil surface runoff and stream sediment yields, and reducing soil infiltration. A biological control program for spotted knapweed using Larinus minutus (Coleoptera: Curculionidae), was initiated in Arkansas in 2008. In this dissertation I described the releases of L. minutus and investigated the adult activity in the southeastern United States (Chapter 1), investigated the effects of …

False Smut Of Rice: Histological Analysis Of Infection, Liem Thi Thanh Nguyen

Graduate Theses and Dissertations

False smut of rice, caused by Ustilaginoidea virens (Cooke) Takahashi (Teleomorph: Villosiclava virens), has become a common disease in most major rice growing regions throughout the world. Considerable confusion exists regarding the infection process and the disease cycle. Therefore, a clearer understanding of pathogenesis caused by Ustilaginoidea virens is critical for future efforts to develop genetic and chemical tools to manage false smut in Arkansas and other regions of the world. The overall goal of this research was to clarify the infection process underlying false smut, with emphasis on comparing and contrasting the histological basis of root and foliar infections. …

Evaluation Of The Recombination Efficiencies Of Flp Proteins, Linh Duy Nguyen

Graduate Theses and Dissertations

Site-specific recombination systems are powerful tools for genetic modification. They have been used to integrate a transgene into a pre-defined locus and to remove marker genes from a transgene locus. Two of the most widely used site-specific recombination systems in plants are the Cre/lox system from the bacteriophage P1 and the FLP/FRT system from the yeast Saccharomyces cerevisiae. The Cre/lox system is well-characterized and is the first choice in application of site-specific recombination system. However, some applications such as marker-free site-specific gene integration require the use of two recombination systems. In addition, the availability of alternative recombination systems can offer …

Community Structure And Ecological Specialization In Plant-Ant Interactions, Paola Barriga

Graduate Theses and Dissertations

Positive associations among species have contributed to the maintenance of biodiversity. These interactions are typically studied in pairwise fashion where two interacting organisms are the focus. This dissertation uses network theory to analyze positive plant-ant associations in three Neotropical forests. Obligate plant-ant mutualisms were used, where plants host the ants in domatia and provide food bodies while the ants protect the plants and can feed them. A network approach was used to depict all obligate plant-ant interactions within a community. The main questions asked at the community level were: 1) Do network structure and levels of specialization change geographically and, …

Ecology And Invasive Properties Of Musk Thistle (Carduus Nutans) In The Central Prairies Of Nebraska, Chengchou Han

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Musk thistle (Carduus nutans) is an herbaceous monocarpic herb introduced to the U. S. from Eurasia. The invasion of musk thistle can reduce forage area, soil stability, and reduce recreation and open areas for humans and wildlife.

Resistance of warm season and cool season perennial grass communities to musk thistle invasion is important for land managers to consider, especially where disturbance has made an area particularly susceptible. Our results show that disturbances, such as overgrazing can open up niches in canopies of warm season grass communities and facilitate invasion but not in cool season grass communities. The mechanism …

Challenges In Predicting The Future Distributions Of Invasive Plant Species, Chad C. Jones

Botany Faculty Publications

Species distribution models (SDMs) are increasingly used to predict distributions of invasive species. If successful, these models can help managers target limited resources for monitoring and controlling invasive species to areas of high invasion risk. Model accuracy is usually determined using current species distributions, but because invasive species are not at equilibrium with the environment, high current accuracy may not indicate high future accuracy. I used 1982 species distribution data from Bolleswood Natural Area, Connecticut, USA, to create SDMs for two forest invaders, Celastrus orbiculatus and Rosa multiflora. I then used more recent data, from 1992 and 2002, as validation …

Plant Classification And Nomenclature In Ndumba, Papua New Guinea Highlands, Terence Hays

Terence Hays

Traditionally, the terms "ethnobotany" and "ethnozoology" have designated little more than the study of plant and animal utilization. In the past two decades, however, the ways in which the components of given biological environments are locally perceived and categorized have received increasing attention. Not only has the study of ethnobiological classification been recognized as essential to a wide variety of ethnographic concerns (cf. Frake 1962; Bulmer 1967), but the discovery of possible universals in folk classification systems promises to enrich our understanding of human cognitive processes as well (Berlin et al. 1973; Brown 1977).

The paucity of comprehensive studies of …

Marketing Contracts, Overconfidence, And Timing In The Canadian Wheat Market, Fabio L. Mattos, Stefanie A. Fryza

Department of Agronomy and Horticulture: Faculty Publications

This paper investigates factors that impact marketing performance in the Canadian wheat market. Using data provided by the Canadian Wheat Board (CWB) for six crop years, results indicate that producers were not able to profitably use all marketing contracts offered by the CWB, earlier pricing tended to generate better performance, there was a negative relationship between activeness and performance (suggesting overconfidence in marketing skills), and performance was generally worse in volatile crop years. Further analysis reveals some of these findings differ when outperforming and underperforming producers are investigated separately, particularly with respect to activeness and volatility.

Streptomycin Resistance Of Erwinia Amylovora, Causal Agent Of Fire Blight, Claudia Nischwitz

All Current Publications

No abstract provided.

A Proposed Mechanism For Nitrogen Acquisition By Grass Seedlings Through Oxidation Of Symbiotic Bacteria, James F. White Jr., Holly Crawford, Mónica S. Torres, Robert Mattera, Ivelisse Irizarry, Marshall Bergen

All Faculty Scholarship for the College of the Sciences

In this paper we propose and provide evidence for a mechanism, oxidative nitrogen scavenging (ONS), whereby seedlings of some grass species may extract nitrogen from symbiotic diazotrophic bacteria through oxidation by plant-secreted reactive oxygen species (ROS). Experiments on this proposed mechanism employ tall fescue (Festuca arundinaceae) seedlings to elucidate features of the oxidative mechanism. We employed 15N₂ gas assimilation experiments to demonstrate nitrogen fixation, direct microscopic visualization of bacteria on seedling surfaces to visualize the bacterial oxidation process, reactive oxygen probes to test for the presence of H₂O₂ and cultural experiments to assess conditions …

Functions Of The Arabidopsis Kinesin Superfamily Of Microtubule-Based Motor Proteins, Chuanmei Zhu, Ram Dixit

Biology Faculty Publications & Presentations

Plants possess a large number of microtubule-based kinesin motor proteins. While the kinesin-2, 3, 9, and 11 families are absent from land plants, the kinesin-7 and 14 families are greatly expanded. In addition, some kinesins are specifically present only in land plants. The distinctive inventory of plant kinesins suggests that kinesins have evolved to perform specialized functions in plants. Plants assemble unique microtubule arrays during their cell cycle, including the interphase cortical microtubule array, preprophase band, anastral spindle and phragmoplast. In this review, we explore the functions of plant kinesins from a microtubule array viewpoint, focusing mainly on Arabidopsis kinesins. …

Stomatal Conductance Trends Of The Jade Plant (Crassula Ovata) In Relation To Circadian Rhythm Entrainability, Katie Cahoon, Martin Garcia, Matthew Pierga

Featured Research

The effect of an inverse light cycle on a Crassulacean acid metabolism (CAM) plant was observed in the study. CAM plants are unique in that they open their stomata at night in order to conserve water, an evolution that has come about because these plants primarily exist in very arid climates. By placing a plant in a chamber in which the lights could be programmed to turn on when it was dark out, and to turn off during normal daylight hours, the stomatal conductance of the leaves of a jade plant (Crassula ovata) were recorded several times a day over …

Is There A Correlation Between Water Potential And Mechanical Strength Of Stems Of Malosma Laurina?, William Chang, Lauren Price, Nicolas Pak

Featured Research

The purpose of this experiment was to see if there was a correlation between water potential and the stem mechanical strength of the Malosma laurina. This experiment was conducted with the use of a Scholander-Hammel pressure chamber to find water potential and the Instron 5500 to test the mechanical strength of the stems. After analysis of the data, there was no direct correlation between water potential and the mechanical strength of stems of Malosma laurina.

Photosynthetic Advantage Of Invasive Species, Gabby Gurule-Small, Alis Sokolova, Patrick Stephens

Featured Research

Californians have greatly benefited from the introduction of plant and animal species necessary for food or other human pursuits; however, there are many other introduced species that can wreak havoc on the state’s environment and economy. Invasive species threaten the diversity and abundance of native species by both competing for resources and causing changes to the natural habitat. We hypothesize that invasive species will have higher photosynthetic and conductance rates which contribute to their success. Through their impacts on natural ecosystems, agricultural lands, and water delivery systems, invasive species may also negatively affect human health and possibly even the economy.

The Effect Of Riparian And Arid Environments On Stomatal Conductance In Baccharis Salicifolia And Heteromeles Arbutifolia, Danalit Rangel, Vicki Mac, Ariel Lan

Featured Research

A riparian environment is characterized by higher moisture levels than an arid environment; therefore they have different species of plants that can adapt to their natural habitats. It is critical that we explore the characteristics plants have in relation to their native environments. We propose to test the hypothesis that Baccharis salicifolia would have a higher stomatal conductance rate to water vapor loss compared to Heteromeles arbutifolia because Baccharis salicifolia thrives in a riparian environment in which water abundance would increase stomatal opening thereby contributing to the greater conductance. Using the LI-6400, we measured the conductance rate, photosynthetic rate, CO2 …

Effect Of Ambient Air Temperature On Leaf Size In Raphanus Sativus, Matthew Fleming, Michael Mccormack

Featured Research

Global warming is an increasing problem in today’s society. Thus, it is important to know how plants, specifically those that are cultivated for human consumption, react to rising average temperatures. This experiment tested how the leaf size of a common crop plant, Raphanus sativus (radish), is affected by two different temperatures. It is hypothesized that as temperature rises, the leaf size will increase, giving the leaf greater ability to cool via transpiration because of an larger surface area for stomatal conductance. This hypothesis was tested by growing two samples of plants in separate incubators. One sample was grown at a …

The Relationship Between Leaf Mechanical Strength And Photosynthetic Rates, Aaron Van Loon, Brianna Manes, Taylor Stucky, Thomas Addington

Featured Research

Photosynthesis is the process by which plants convert light energy to chemical energy, helping sustain life in the biosphere. There are many factors that affect the rate of photosynthesis such as atmospheric CO2 concentration, temperature, and sunlight. In this experiment, we attempt to determine what effect, if any, the mechanical strength of a plant has on its rate of photosynthesis. To perform this experiment we used both the LI-COR 6400 and the Instron Mechanical Testing Device. With the LI-COR we measured photosynthetic rate of our plant subjects in real time during the prime photosynthetic hours, 10-12am. The Instron allowed us …

The Effect Of Dirt On Inhibition Of Light Absorption In Musa Leaves, Lorelle Knight, Alexis Carrington, Angela French, Roxanne Barker

Featured Research

Dirt can be transported by wind, human activity and many other factors. It was hypothesized that dirt particles collected on leaves will decrease leaf reflectance and thus make the leaf less healthy. The rationale for this is that the more dirt present on the leaf, the more inhibited photons will be in reaching leaf pigments. The leaf will therefore be less healthy as it will be less able to perform photosynthesis. To test this hypothesis, eight leaf samples with varying amounts of dirt present, were collected from the plant, Musa. A Unispec spectrophotometer was used to test the reflectance of …

The Relationship Of Stomatal Conductnace To Mechanical Strength In Leaves Of Santa Monica Plants, Russell P. Mott, Steven R. Fleming, John R. Macbeth

Featured Research

The Santa Monica Mountains ecosystem has a high diversity of plants with different lifestyles that produce different physiological characteristics individual to all plants. Studies in Australia, another Mediterranean ecosystem, have shown that mechanical strength of leaves is relatable to soil stress. This experiment seeks to determine whether mechanical strengths of leaves correlate to stomatal conductance of leaves across different species in the Santa Monica Mountains. Four species of plants are tested for their stomatal conductance in the field, and the leaves are tested for tensile strength using Young’s Modulus for comparison across leaves. These data show that there was no …

The Effect Of Leaf Trichome Density On Stem Mechanical Strength In Salvia Leucophylla, S. Mellifera, And S. Apiana, Brieanna English, Jeff Scanlon, Anushree Mahajan

Featured Research

Salvia species in southern California exhibit a variety of leaf trichome densiIes. S. mellifera, S. leucophylla, and S. apiana were chosen as study organisms because they exhibit varying trichome densiIes. A UniSpec was used to measure NDVI in leaves and an Instron was used to measure stem mechanical strength. This study provides preliminary evidence that suggests plants with high leaf trichome density have less stem mechanical strength, and those with low leaf trichome density have greater mechanical strength. Data generated from this study supports the idea that this may be a general and loose trend amongst plant families similar to …

A Comparison Of Brittlebush (Encelia Farinosa) Productivity And Health During Drought And Post Rainfall, Gabi Diciolli, Karre Lawson, Anders Reimer

Featured Research

Encelia farinosa is well adapted for drought tolerance as its leaves transform color based on water availability. We were puzzled by a question that any desert botanist must consider. How does the photosynthetic efficiency of E. farinosa fluctuate as it transitions from a state of drought to a state of soil saturation within a 72 hour period? In this experiment we looked at the effects of irrigation on the health and quantum yield of the brittlebush by looking at photosynthetic rates using the portable photosynthesis system LI-COR 6400 when applied to two leaves on a given plant and water potential …

Fuzzy Clustering Of Cpp Family In Plants With Evolution And Interaction Analyses, Tao Lu, Yongchao Dou, Chi Zhang

Center for Plant Science Innovation: Faculty and Staff Publications

Background: Transcription factors have been studied intensively because they play an important role in gene expression regulation. However, the transcription factors in the CPP family (cystein-rich polycomb-like protein), compared with other transcription factor families, have not received sufficient attention, despite their wide prevalence in a broad spectrum of species, from plants to animals. The total number of known CPP transcription factors in plants is 111 from 16 plants, but only 2 of them have been studied so far, namely TSO1 and CPP1 in Arabidopsis thaliana and soybean, respectively.

Methods: In this work, to study their functions, we applied …

Evolution On The Hawaiian Hotspot: Biogeography And Divergence Time Estimation Of Kadua (Rubiaceae), Kenneth L. Parker

Biological Sciences Theses & Dissertations

Recent studies on the colonization time of Hawaiian plant and animal lineages have suggested certain lineages arrived to the archipelago before the formation of the extant islands. Kadua, a recently resurrected genus, is mostly endemic to the Hawaiian Archipelago, with many member taxa autochthonous to individual islands. This work investigates the colonization time of Kadua to the Hawaiian Islands. Sequence analyses of the quickly evolving nuclear regions ITS, ETS and 5s-NTS regions for 20 Hawaiian and 7 French Polynesian species of Kadua were used to create dated phylogeny calibrated with island ages. The phylogeny suggests a single colonization of Hawaii …

Some Like It Hot, Some Like It Warm: Phenotyping To Explore Thermotolerance Diversity, C. H. Yeh, Nicholas J. Kaplinsky, C. Hu, Y. Y. Charng

Biology Faculty Works

Plants have evolved overlapping but distinct cellular responses to different aspects of high temperature stress. These responses include basal thermotolerance, short- and long-term acquired thermotolerance, and thermotolerance to moderately high temperatures. This ‘thermotolerance diversity’ means that multiple phenotypic assays are essential for fully describing the functions of genes involved in heat stress responses. A large number of genes with potential roles in heat stress responses have been identified using genetic screens and genome wide expression studies. We examine the range of phenotypic assays that have been used to characterize thermotolerance phenotypes in both Arabidopsis and crop plants. Three major variables …

Effects Of Nitrogen Deposition And Empirical Nitrogen Critical Loads For Ecoregions Of The United States, Linda H. Pardo, Mark E. Fenn, Christine L. Goodale, Linda H. Geiser, Charles T. Driscoll, Edith B. Allen, Jill S. Baron, Roland Bobbink, William D. Bowman, Christopher M. Clark, Bridget Emmett, Frank S. Gilliam, Tara L. Greaver, Sharon J. Hall, Erik A. Lilleskov, Lingli Liu, Jason A. Lynch, Knute J. Nadelhoffer, Steven S. Perakis, Molly J. Robin-Abbott, John L. Stoddard, Kathleen C. Weathers, Robin L. Dennis

Frank S. Gilliam

Human activity in the last century has led to a significant increase in nitrogen (N) emissions and atmospheric deposition. This N deposition has reached a level that has caused or is likely to cause alterations to the structure and function of many ecosystems across the United States. One approach for quantifying the deposition of pollution that would be harmful to ecosystems is the determination of critical loads. A critical load is defined as the input of a pollutant below which no detrimental ecological effects occur over the long-term according to present knowledge. The objectives of this project were to synthesize …

Synthesis, Linda H. Pardo, Linda H. Geiser, Mark E. Fenn, Charles T. Driscoll, Christine L. Goodale, Edith B. Allen, Jill S. Baron, Roland Bobbink, William D. Bowman, Christopher M. Clark, Bridget Emmett, Frank S. Gilliam, Tara Greaver, Sharon J. Hall, Erik A. Lilleskov, Lingli Liu, Jason A. Lynch, Knute Nadelhoffer, Steven S. Perakis, Molly J. Robin-Abbott, John L. Stoddard, Kathleen C. Weathers

Frank S. Gilliam

Human activity in the last century has led to a substantial increase in nitrogen (N) emissions and deposition. This N deposition has reached a level that has caused or is likely to cause alterations to the structure and function of many ecosystems across the United States. One approach for quantifying the level of pollution that would be harmful to ecosystems is the critical loads approach. The critical load is dei ned as the level of a pollutant below which no detrimental ecological effect occurs over the long term according to present knowledge. The objective of this project was to synthesize …

Global Assessment Of Nitrogen Deposition Effects On Terrestrial Plant Diversity : A Synthesis, R. Bobbink, K. Hicks, J. Galloway, T. Spranger, R. Alkemade, M. Ashmore, M. Bustamante, S. Cinderby, E. Davidson, F. Dentener, B. Emmett, J. W. Erisman, M. Fenn, Frank S. Gilliam, A. Nordin, L. Pardo, W. Devries

Frank S. Gilliam

Atmospheric nitrogen (N) deposition is a recognized threat to plant diversity in temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems, from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now …

Effects Of Experimental Nitrogen Additions On Plant Diversity In An Old-Growth Tropical Forest, Xiankai Lu, Jiangming Mo, Frank S. Gilliam, Guoyi Zhou, Yunting Fang

Frank S. Gilliam

Response of plant biodiversity to increased availability of nitrogen (N) has been investigated in temperate and boreal forests, which are typically N-limited, but little is known in tropical forests. We examined the effects of artificial N additions on plant diversity (species richness, density and cover) of the understory layer in an N saturated old-growth tropical forest in southern China to test the following hypothesis: N additions decrease plant diversity in N saturated tropical forests primarily from N-mediated changes in soil properties. Experimental additions of N were administered at the following levels from July 2003 to July 2008: no addition (Control); …