ETD Search Results: instcode:ohiou

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1. Albrecht, Matthew A. Reproductive Biology of Medicinal Woodland Herbs Indigenous to the Appalachians.

Degree: PhD, Plant Biology (Arts and Sciences), 2006, Ohio University

► Eastern deciduous forests include a remarkable number of plants that are utilized… (more)

▼ Eastern deciduous forests include a remarkable number of plants that are utilized widely for their medicinal properties. However, the long-term sustainable use of medicinal forest plants requires that methods be developed for restoring and cultivating them in natural and semi-natural settings. This study examined the seed regeneration biology of several perennial forest herbs that are internationally traded in the increasingly lucrative botanical medicines industry. Specific objectives were to: (1) determine how environmental cues (temperature, light, substrate, and burial) regulate dormancy-break and carry-over in seed populations of Actaea racemosa (black cohosh), Hydrastis canadensis (goldenseal), and Sanguinaria canadensis (bloodroot); (2) experimentally evaluate seedling recruitment probabilities of A. racemosa, H. canadensis, S. canadensis, and Panax quinquefoliusin different forest microenvironments defined by varying levels of leaf litter and opposing topographic positions; (3) classify seed dormancy and determine optimum germination temperatures for Collinsonia canadensis (stoneroot) and Dioscorea villosa (wild yam); and (4) quantify survival rates and dormancy-levels of A. racemosa and H. canadensis seed populations stored in artificial conditions. Results from these studies showed that: (1) germination probabilities can vary widely when seeds experience different environmental cues, although temperature is the primary factor regulating dormancy-break and germination; (2) some perennial forest herbs can form persistent seed banks and spread germination across time; (3) leaf litter and topographic position can act as ecological filters during early life-history stages; and (4) storing seed populations prior to outplanting reduces viability in H. canadensisseeds and deepens dormancy levels in A. racemosa seed. Recommendations are made for cultivating, managing, and restoring these species in the eastern deciduous forest landscape. Advisors/Committee Members: McCarthy, Brian C.

Keywords: nontimber forest products; regeneration niche; seed dormancy; germination; woodland herb; seedling recruitment

2. Chiang, Jyh-Min. Aboveground Carbon Storage and Net Primary Production in Human Impacted Forests Under Current and Future Climate Scenarios.

Degree: PhD, Plant Biology (Arts and Sciences), 2007, Ohio University

► Forested ecosystems contain the largest terrestrial carbon pools and fluxes on earth.… (more)

▼ Forested ecosystems contain the largest terrestrial carbon pools and fluxes on earth. Thus, forest ecosystem disturbances can result in large perturbations in global carbon cycling and subsequently climate. The objective of my dissertation was to investigate the role of forest burning and thinning, changing climate, and changing species compositions on carbon cycling in a subset of forests in the eastern United States. I examined processes that influenced net primary production (NPP) of forested ecosystems at different scales: First, I examined the sensitivity of budburst phenology on simulations of NPP and, based on the Harvard Forest phenology database, I optimized a subroutine, which included a chilling factor, for the prediction of budburst dates. Budburst phenology was a sensitive variable in PnET model simulations but leaf-off date was not. The phenology subroutine, when applied to southern Ohio forests, exhibited geographic specificity, highlighting the importance of local phenological data. Second, I examined the effects of mechanical thinning, prescribed burning, and multiple environmental factors on specific leaf weight (SLW) and leaf nitrogen content (Nmass) of seven common tree species. Increases in both leaf traits were positively associated with increases in potential NPP. Thinning increased SLW at the lower canopy by 22% and resulted in an 8% increase of modeled NPP. The effects of burning were not significant. Variations of both leaf traits were primarily explained by species differences. Third, I assessed the impacts of thinning and burning on aboveground carbon stocks and NPP using both field measurements and PnET model simulations in southern Ohio. Only thinning affected NPP (> -30%); however, the thinning effect on NPP was transient (1-2 years) according to both field and model results. Lastly, at a larger spatio-temporal scale, I used the PnET-II model to simulate the NPP consequences of potential tree species redistribution and future climate in four selected focal areas (40,000 km2 each). The effects of potential species redistribution predicted in 2100 had moderate effects (-12% to 8%) on NPP compared to the impacts of future climatic change (-60% to 25%). As increasing temperatures negatively impact NPP, the reduction in forest carbon uptake capacity could accelerate changing climate. Advisors/Committee Members: Brown, Kim J.

Subjects: Biology, Ecology

Keywords: net primary production; leaf traits; leaf nitrogen; specific leaf weight; SLW; SLM; LMA; budburst; phenology; thinning; burning; climate change; community change

3. Glasgow, Lance S. THE EFFECTS OF PRESCRIBED BURNING ON INVASIBILITY AND UNDERSTORY COMPOSITION IN A SOUTHEASTERN OHIO FOREST.

Degree: MS, Plant Biology (Arts and Sciences), 2006, Ohio University

► Fire and fire surrogate treatments (hot burn, cool burn, litter removal, increased… (more)

Subjects: Biology, Ecology

Keywords: fire, invaisve species, forest composition

4. Graham, John B. Forest Fuel and Fire Dynamics in Mixed-oak Forests of Southeastern Ohio.

Degree: MS, Plant Biology (Arts and Sciences), 2005, Ohio University

► In eastern deciduous forests, prescribed fire and thinning are used as tools… (more)

Keywords: Quercus; Litter; Coarse woody debris; Silviculture; Fire ecology; Thinning; Hardwood forests

5. Havran, J. Christopher. Ecology and Evolution of the Hawaiian Violets.

Degree: PhD, Plant Biology (Arts and Sciences), 2008, Ohio University

► The Hawaiian violets represent a monophyletic lineage of angiosperms restricted to the… (more)

Subjects: Biology; Botany; Ecology

Keywords: adaptive radiation; parallel evolution; reproductive isolation; Hawaiian Islands; Violaceae; Biogeography

6. House, Denise L. Genetic Variation of Batrachospermum gelatinosum (Batrachospermales, Rhodophyta) from Eastern North America.

Degree: MS, Plant Biology (Arts and Sciences), 2008, Ohio University

► Batrachospermum gelatinosum (L.) DC. is a commonly reported freshwater red alga from… (more)

Subjects: Biology; Botany; Environmental science; Molecular biology

Keywords: phylogeography; COI; rbcL; Batrachospermum; freshwater; red alge

7. Jacques, Rochelle R. Effects of Microstegium vimineum (Trin.) A. Camus (Asian stiltgrass; Poaceae) on native hardwood seedling growth and survival.

Degree: MS, Plant Biology (Arts and Sciences), 2007, Ohio University

► Microstegium vimineum (Trin.) A. Camus (Poaceae) is an annual C4 invasive grass… (more)

▼ Microstegium vimineum (Trin.) A. Camus (Poaceae) is an annual C4 invasive grass threatening most of the eastern United States. Microstegium vimineum has been observed to overtake native species and dominate the understory of many hardwood forests, resulting in a depauperate regeneration layer. While information regarding the invasion, spread, and general ecology of M. vimineum is readily available, few studies exist regarding habitat restoration following M. vimineum invasion. I examined the effects of M. vimineum removal on the growth and survival of planted hardwood seedlings. Two-year-old native hardwood seedlings (Acer saccharum, Quercus rubra, and Liriodendron tulipifera) and one-year-old invasive tree seedlings (Ailanthus altissima) were planted in a split-plot (open vs. closed forest canopy) block (replicates) design at Crummies Creek Tree Farm, Calhoun County, West Virginia, in an area that had been heavily invaded by M. vimineum. Within each block (N = 10), three treatments were employed: chemical (Sethoxydim), mechanical (hand pulling), and no removal (control). The growth (height and basal diameter) and survival of planted seedlings were assessed within each treatment over a 2-year period. Hemispherical photographs were taken to quantify canopy cover, and soil was sampled to determine soil nutrients and moisture. Hardwood seedling height and diameter differed significantly as a function of forest canopy type (open vs. closed) and among species; however, no significant treatment effects were detected. Mechanical removal of M. vimineum increased the survival of native hardwood seedlings relative to the control but did not differ from the chemical treatment. The lack of treatment effect on hardwood seedling growth, as well as the high rate of survival, is promising in regards to restoring habitats invaded by M. vimineum. My data suggest that restoration of forested habitats invaded by M. vimineum can be achieved by a bottom-up approach that utilizes planted native hardwood seedlings with little additional expenditure of resources for control. Restoring a mid-story regeneration layer will likely shade out M. vimineum and further erode its dominance in the stand. However, the impact of M. vimineum on natural hardwood regeneration via seedling recruitment still warrants further investigation. Natural regeneration of hardwood species from seed will not likely occur until M. vimineum density is reduced to a minimum threshold. Advisors/Committee Members: McCarthy, Brian C.

Subjects: Biology, Ecology

Keywords: Asian stiltgrass; hardwood regeneration; invasive species; Microstegium vimineum; restoration; split-plot block ANOVA; survival

8. Joesting, Heather M. Physiology and Leaf Characteristics of American Chestnut ( Castanea Dentata (Marsh.)Borkh.) Seedlings, Saplings, and Mature Trees in Ohio and Wisconsin.

Degree: MS, Plant Biology (Arts and Sciences), 2005, Ohio University

► The restoration of the American chestnut to U.S. forests is currently a… (more)

Subjects: Biology, Plant Physiology

Keywords: American Chestnut; Photosynthesis; Leaf Moss Per Area; Nitrogen Content; Light Availability; Growth Stages

9. Keppler, Brian D. IRX14 and IRX14-LIKE: Two Glycosyl Transferases involved in Glucuronoxylan Biosynthesis in Arabidopsis.

Degree: MS, Plant Biology (Arts and Sciences), 2010, Ohio University

► IRX14 and IRX14-LIKE are two closely related glycosyl transferases in the glycosyl… (more)

Subjects: Botany; Genetics; Molecular biology

Keywords: Irregular Xylem; Cell Wall; Glycosyl Transferase; Glucuronoxylan; Drought Tolerance; Arabidopsis

10. Larrimer, Audrey K. Biological diversity associated with bigtooth aspen patches in a mixed oak forest.

Degree: MS, Plant Biology (Arts and Sciences), 2004, Ohio University

► This study assessed the ability of bigtooth aspen (Populus grandidentata Michx.) patches… (more)

Subjects: Biology, Ecology

Keywords: Populus grandidentata; Aspen; Overstoy - understory Interactions; Herbaceous; Understory

11. Lombardo, Jeffrey A. SILVICULTURAL TREATMENT EFFECTS ON OAK SEED PRODUCTION AND ACORN WEEVIL DIVERSITY IN SOUTHEASTERN OHIO.

Degree: MS, Plant Biology (Arts and Sciences), 2007, Ohio University

► Oak regeneration failure in the hardwood forests of eastern North America has… (more)

Keywords: prescribed burning; thinning; fire surrogate; silviculture; oak regeneration; masting; seed production; acorn weevils

12. Longbrake, A. Christina W. Ecology and Invasive potential of Paulownia Tomentosa (Scrulariaceae) in a Hardwood Forest Landscape.

Degree: PhD, Plant Biology (Arts and Sciences), 2001, Ohio University

► Introduction of non-native species is the oldest form of human-induced global change.… (more)

▼ Introduction of non-native species is the oldest form of human-induced global change. From the exchange of agricultural crops and domestic animals, to the accidental introduction of weeds and microbes, non-native species have been incorporated into the floras and faunas of all continents and most oceanic islands. These organisms can have marked effects on ecosystems. I wanted to address the following facets of non-native species invasion: (1) What characteristics of ecosystems make them more susceptible to non-native species invasion? and (2) What characteristics of the invader allow invasion? To address these questions, I used a gradient of anthropogenic disturbance common in southeastern Ohio forests: intact secondary forest, forest edge, and aggrading clear cuts. Paulownia tomentosa is a tree native to Asia and thought to have been introduced to North America in the 1840's. The species has naturalized throughout Appalachia. I studied the growth, allocation, establishment, and seed persistence across habitats. I also became interested in the basic ecology of P. tomentosa, particularly the ability of the species to resprout and phenotypic plasticity in naturalized populations. The most important factors in determining the invasive potential of P. tomentosa were disturbance and herbivory. Paulownia tomentosa is an early successional species that can grow rapidly under high light conditions. Seed ecology suggests that the species can form a persistent seed bank. However, light is required for germination and seeds responded positively to soil disturbance. Large gaps may be sufficient to allow seeds in the seed bank to germinate and grow to the canopy. However, the species is very susceptible to herbivory. Plants had to be protected from mammals in order to persist. Even though above- and below-ground competition affected plant growth and allocation, it did not affect the overall success of plants. Paulownia tomentosa can resprout at an early age and initially invests heavily in below-ground biomass. Naturalized populations showed some variability in traits, particularly in those associated with below-ground biomass and growth of roots. Paulownia tomentosa has potential to remain a part of the mixed mesophytic forests of North America since it can form a seed bank, disperse seeds to great distances, and grow quickly once established. Advisors/Committee Members: McCarthy, Brian C.

Keywords: terrestrial biological invasions; non-native plant; disturbance hypothesis; clear cut habitat; forest edge habitat

13. McEwan, Ryan W. Tree-Ring Based Reconstructions of Disturbance and Growth Dynamics in Several Deciduous Forest Ecosystems.

Degree: PhD, Plant Biology (Arts and Sciences), 2006, Ohio University

► Forests are characterized by dynamism in species composition, structure and function. These… (more)

▼ Forests are characterized by dynamism in species composition, structure and function. These dynamics, in turn, are often related to disturbance. These disturbances, therefore, are intrinsically linked to the biology of forest ecosystems. In order to understand and ultimately manage forest ecosystems, the role of disturbance in the systems must be ascertained. Disturbances that occur in forests rarely kill all of the existing trees. Therefore evidence of disturbance in the surrounding landscape is often recorded as a growth response in the surviving trees. In this dissertation I present four projects that were executed to develop an understanding of disturbance and growth dynamics in deciduous forest ecosystems of eastern North America. In each project, analysis of tree-rings (dendroecology), was used as the primary data source in the analyses. The first project focuses on the growth of American chestnut (Castanea dentata) in a Wisconsin oak forest. Castanea dentata exhibited a range of growth responses suggesting plasticity in ecological response that 1) offers promise for restoration efforts and 2) may have contributed to its dominance prior to the chestnut blight. The second dissertation project addresses anthropogenic disturbance and the formation of oak savanna in central Kentucky. Because of the > 300 year depth of the chronology in this project, I was able to develop a hypothetical model linking human population dynamics, land use eras, and ecosystem structure. The third and fourth projects work in tandem. The third project presented a vetting of the commonly employed technique of fire-history reconstruction using fire scars in oak samples. In this project we show that 1) scarring occurs from sources other than fire in the landscape, and 2) that multiple annual fires may not be recorded in the tree-ring record. Overall, the tree-ring record proved effective in fire history reconstruction. In the final project of the dissertation, I used this technique to develop a fire history of oak communities in eastern North America. I demonstrated that fire was a frequent and widespread occurrence during the formation of oak communities. I also isolate a variety of features in the historical regime that are appropriate for application in modern stands. Advisors/Committee Members: McCarthy, Brian C.

Keywords: tree-ring; dendrochronology; white oak; Quercus alba; fire scar; fire history; bur oak; Quercus macrocarpa; dendroecology; fire; American chestnut; Castanea dentata; Quercus velutina; forest

14. Nadella, Ramya. Biosynthesis of Xyloglucan in Grasses and Identification of Endosperm Developmental Phases in Wheat Seeds.

Degree: MS, Plant Biology (Arts and Sciences), 2007, Ohio University

► Xyloglucans are the major hemicellulosic polysaccharides in the primary cell walls of… (more)

▼ Xyloglucans are the major hemicellulosic polysaccharides in the primary cell walls of dicots and non-graminaceous monocots but small amounts are also seen in the walls of grasses. They serve as cross-linkers of cellulose microfibrils and maintain the structural integrity of the cell.Xyloglucan biosynthesis mechanism is well understood and many biosynthetic genes have been identified in dicots. However this process is not known in grasses where structural differences in xyloglucan exist. Thus, this study aimed to investigate xyloglucan biosynthesis in grasses by functionally characterizing some xyloglucan biosynthetic genes, particularly the xylosyltransferases from wheat and rice. Wheat (TaGT34-7) and rice (OsGT34-3) homologs of Arabidopsis xyloglucan-xylosyltransferase (AtXT1) gene were previously identified using a bioinformatic script developed by Faik et al. (2006). The full-length cDNAs encoding TaGT34-7 and OsGT34-3 proteins were expressed in Pichia pastoris and Drosophila S2 expression systems, but the proteins did not show xylosyltransferase activity in Pichia pastoris and a low activity in Drosophila S2 cells. Further optimization is required to fully identify the function of these two proteins. In another study, the endosperm developmental phases were identified in developing wheat seeds using sectioning and light microscopy. Cell walls of wheat endosperm have ~70% (w/w) of arabinoxylan (AX), 20% (w/w) of mixed linked glucan (MLG), and only 5% (w/w) of cellulose. MLG and AX are deposited during cellularization and differentiation phases of the endosperm development, respectively. To identify the putative glycosyltransferase genes involved in the biosynthesis of these polymers (AX, MLG), it was necessary to first identify the endosperm developmental phases namely cellularization and differentiation phases at which they are deposited. Fresh wheat seeds were collected and their endosperm developmental phases were investigated using sectioning and light microscopy methods. Also, starch deposition was monitored using polarized light microscopy. Advisors/Committee Members: Faik, Ahmed.

Subjects: Biology, Plant Physiology

Keywords: Xyloglucan; Grasses; Wheat; Rice

15. Pai, Aswini. The Population Ecology of a Perennial Clonal Herb Acorus calamus L. (Acoraceae) in Southeast Ohio, USA.

Degree: PhD, Plant Biology (Arts and Sciences), 2005, Ohio University

► Acorus calamus L. (Sweetflag, family Acoraceae) is an economically important helophyte… (more)

▼ Acorus calamus L. (Sweetflag, family Acoraceae) is an economically important helophyte found in temperate and subtropical wetlands. I examined edaphic factors influencing distribution of A. calamus populations; potential of the rhizome in wetland restoration; genetic diversity of populations; and, environmental factors influencing seed germination. Redundancy analysis (RDA) indicated that rhizome length and biomass, total number of leaf scars and leaf scars per unit length in A. calamus are positively related to a soil calcium content gradient. Shoot density is influenced most by a silt and nitrogen gradient but negatively related to organic matter. Multivariate Analysis of Variance indicated that light (λ = 0.762, P < 0.001), nutrient (λ = 0.449, P < 0.001) and moisture (λ = 0.508, P < 0.001) had significant effects on rhizome growth. A. calamus grows best in open light, waterlogged conditions and is best planted at the very onset of a wetland mitigation project. I estimated genetic diversity in populations of Acorus calamus L. in southeast Ohio using Intersimple sequence repeats. Indices of genetic diversity, evenness, expected heterozygosity and percentage of polymorphic loci were low. Analysis of Molecular variance (AMOVA) indicated that most of the variation (58%) is among populations and a moderate amount (42%) is within populations. Cluster analysis, Principal Coordinates Analysis and the coefficient of genetic variation among populations (G st = 0.7188) and gene flow (N m = 0.1956) indicated little gene flow among populations. My results suggest that A. calamus populations in southeast Ohio are primarily clonal in nature. Seed germination occured only in light and varied significantly ( F = 8.42, p < 0.0001) across temperatures with seeds germinating maximally in spring (15/25°C) and summer (20/35°C) in submerged conditions. Ger mination velocity (Timson's Index) was greater in moist acidic conditions in spring temperatures. There was no significant difference in seed germination after storage for 24 months. Results indicate that A. calamus seeds are adapted to germinate in wide variety of wetlands in summer and spring but are limited by light availability. They can create persistent seed banks. Seeding of A. calamus in wetland restoration projects is best conducted at the very onset when there is more light at the soil surface. Advisors/Committee Members: McCarthy, Brian.

Subjects: Biology, Ecology

Keywords: Acorus Calamus; Clonal Plant; Helophyte

16. Sanders, Heather Louise. Developmental Changes in the Evolution of Fundamental Plant Organography.

Degree: PhD, Plant Biology (Arts and Sciences), 2007, Ohio University

► The fossil record provides structural fingerprints of development from which we can… (more)

Subjects: Biology, Botany

Keywords: ontogenetic changes; evolution of leaves; ab-adaxial identity; KNOX proteins; Ceratopteris; bipolar growth

17. Schelling, Lisa R. Soil Seed Banks in Mixed Oak Forests of Southeastern Ohio.

Degree: MS, Plant Biology (Arts and Sciences), 2006, Ohio University

► The effects of common forest management practices (burning and thinning) on the… (more)

Keywords: soil seed bank; spatial autocorrelation; forest management; disturbance

18. Small, Christine Jodie. Herb Layer Dynamics and Disturbance Response in the Mixed Mesophytic Forest Region of Southeastern Ohio.

Degree: PhD, Plant Biology (Arts and Sciences), 2001, Ohio University

► Understory herbaceous vegetation is a vital component of eastern deciduous forests, typically… (more)

▼ Understory herbaceous vegetation is a vital component of eastern deciduous forests, typically comprising the largest proportion of forest diversity. Understory composition is often correlated with microenvironmental and site conditions such as topography, light availability, and edaphic conditions and provides important indications of site quality, overstory regeneration patterns, and ecosystem health. To better understand understory dynamics and disturbance response, this study examined herbaceous vegetation in managed and mature mixed-mesophytic forests of southeastern Ohio. Specific objectives were to examine: (1) spatial and temporal variability of understory vegetation in an old-growth mixed-mesophytic forest; (2) herb layer dynamics relative to site quality in recently logged and mature oak forests; (3) the relationship of understory vegetation to seasonal soil nitrogen availability in logged and mature stands; (4) the role of the seed bank in post-harvest forest succession; and (5) effects of post-harvest light and soil physical properties on understory forest herbs. Sampling season, topographic aspect, and spatial scale (micro- vs. meso-scale) strongly influenced old-growth understory composition and diversity. In recently clearcut and mature forests, age, sampling season, aspect, and fertility significantly influenced understory composition. Soil C:N ratio was a strong predictor of understory richness in mature forests but weakly related in clearcuts. Seed bank composition differed markedly from aboveground vegetation, but both showed strong topographic and disturbance responses. Experimental treatments simulating post-harvest light and soil compaction conditions caused reduced growth in most study species while patchy, intermediate light levels mimicking mature forest understories often enhanced growth. Results suggest that: (1) forest understories may be frequently undersampled, with sample size, area, and season critical considerations for diversity assessment; (2) understory disturbance response varies seasonally and with site quality, factors important to our understanding of forest management impacts; (3) given the strong relationship of soil nitrogen and forest understory diversity, changes in nitrogen availability may dramatically influence understory dynamics, diversity, and disturbance response; (4) a better understanding of environmental and sampling influences is needed to clarify the role of the seed bank in forest recovery; and (5) management approaches mimicking natural light, soil, and disturbance properties may be essential to the maintenance of eastern forest herbs. Advisors/Committee Members: McCarthy, Brian C.

Subjects: Biology, Botany

Keywords: Understory herbaceous layer vegetation; Eastern deciduous forest; Soil seed bank; Spatial and temporal diversity patterns; Clearcut harvesting disturbances

19. Stewart, Sarah Anna. PHYLOGENETIC AFFINITIES OF AUSTRALASIAN SPECIMENS OF BATRACHOSPERMUM (BATRACHOSPERMALES, RHODOPHYTA) INFERRED FROM MOLECULAR AND MORPHOLOGICAL DATA.

Degree: MS, Plant Biology (Arts and Sciences), 2006, Ohio University

► The phylogenetic affinities of five Australasian species of the freshwater red algal… (more)

Subjects: Biology, Botany

Keywords: Batrachospermales; Batrachospermum; phylogenetics; systematics; freshwater red algae; Rhodophyta; molecular systematics; morphometrics; algae

20. Tomescu, Alexandru Mihail Florian. Late Ordovician – Early Silurian terrestrial biotas of Virginia, Ohio, and Pennsylvania: an investigation into the early colonization of land.

Degree: PhD, Plant Biology (Arts and Sciences), 2004, Ohio University

► An early phase in the colonization of land is documented by investigation… (more)

▼ An early phase in the colonization of land is documented by investigation of three fossil compression biotas from Passage Creek (Silurian, Llandoverian, Virginia), Kiser Lake (Silurian, Llandoverian, Ohio), and Conococheague Mountain (Ordovician, Ashgillian, Pennsylvania). A framework for investigation of the colonization of land is constructed by (1) a review of hypotheses on the origin of land plants; (2) a summary of the fossil record of terrestrial biotas; (3) an assessment of the potential of different continental depositional environments to preserve plant remains; (4) a reevaluation of Ordovician-Silurian fluvial styles based on published data; and (5) a review of pertinent data on biological soil crusts, which are considered the closest modern analogues of early terrestrial communities. The three studied biotas are non-paradigmatic biotas, defined here as biotas whose components escape unequivocal taxonomic assignment because their features preclude assignment to any known group, or compare them to several known groups without allowing further distinction. The Passage Creek biota consists of rich, morphologically and anatomically diverse fossil assemblages. They demonstrate that a well-developed groundcover was already present at the beginning of the Silurian, occupying river floodplains. This groundcover consisted principally of thalloid organisms and the diversity of terrestrial communites included cyanobacteria, as well as organisms characterized by complex internal organization, the affinities of which remain unresolved. The Kiser Lake fossils consist of carbonaceous compressions, one of which compares to liverwort leaves and lichen rhizines. The same sediments yield scraps of cellular tissue and the earliest spores assignable to ascomycetes. These are preserved in peritidal carbonate sediments. The Conococheague Mountain biota includes rich compression assemblages from transitional shallow marine and deltaic facies. Such deposits usually harbor mixtures of marine and continental fossils, rendering interpretation of the ecology of original organisms difficult. These three biotas contain the oldest macrofossils of terrestrial (Passage Creek) and potentially terrestrial (Conococheague Mountain, Kiser Lake) organisms and demonstrate that diverse communities including complex forms were present much earlier than previously thought. The thalloid morphology represents a transitional stage in the evolution of complexity among terrestrial primary producers from exclusively microbial photosynthesizers to complex embryophytes with axial morphology. Advisors/Committee Members: Rothwell, Gar W.

Subjects: Biology, Botany; Paleobotany

Keywords: Fossil; Continental; Fluvial; United States; Evolution; Cyanobacteria; Soil Crusts

21. Withers, John C. CHARACTERIZATION OF TWO NOVEL CYTOCHROME P450S INVOLVED IN GRAVITROPISM IN ARABIDOPSIS THALIANA.

Degree: MS, Plant Biology (Arts and Sciences), 2007, Ohio University

► Understanding gene expression that occurs during gravitropism is important for studying the… (more)

Keywords: Plant gravitropism; Auxin; Flavonoids; Cytochrome P450

22. Zalack, Jason T. Development of a diatom based index of biotic integrity for acid mine drainage impacted streams.

Degree: MS, Plant Biology (Arts and Sciences), 2006, Ohio University

► In Ohio, fish and macroinvertebrates are the organisms of choice for assessment… (more)

Subjects: Biology, Limnology

Keywords: diatoms; streams; acid mine drainage; amd; multimetrics; Index of Biotic Integrity; macroinvertebrates; ICI; DIBI; steam health; algae; indicators; Southeast Ohio

23. Zhang, Jiesheng. Cloning and Characterization of an Invertase Gene From the Garden Pea (Pisum sativum L.).

Degree: MS, Plant Biology (Arts and Sciences), 2003, Ohio University

► The enzyme invertase contributes to sugar unloading, pathogen defense,differentiation and development in… (more)

Subjects: Biology, Plant Physiology

Keywords: Invertase; Pisum Satirum; Gibberellic Acid; cDNA; Expression