Plant Biology Commons^™

Analysis Of Alternative Oxidase In Non-Angiosperm Plants, Anissa M. Francis

Theses and Dissertations (Comprehensive)

Alternative oxidase (AOX) is a mitochondrial terminal oxidase that provides an alternative pathway for electron transport, allowing plants to maintain respiratory flexibility under environmental stress conditions. While AOX has been extensively studied in angiosperms (flowering plants), little is known about its distribution and conservation in non-angiosperms. Based on gaps identified in the literature, this thesis investigated the distribution of AOX across non-angiosperm plant lineages. Although AOX is present in many green algae and is therefore considered to be an ancient protein that originated before the existence of non-angiosperm plants, it remains unclear whether the protein is uniformly distributed across these …

Characterizing The Targeting Of Toc159 Receptors To The Chloroplast Outer Envelope Membrane And Their Role In The Assembly Of Distinct Toc Complexes, Michael Fish

Theses and Dissertations (Comprehensive)

Global agriculture and food security face challenges from climate change, population growth, and other human-driven pressures. Enhancing our understanding of plant biology, particularly chloroplast function, is critical for improving crop yield and stress resilience. As the sites of photosynthesis and key regulators of plant responses to environmental cues, chloroplasts depend on the precise import of thousands of nuclear-encoded proteins to maintain their biogenesis and function. While much is known about the core translocon components in the chloroplast outer envelope membrane that form the TOC complex, the mechanisms underlying their targeting, assembly, and regulation remain incompletely understood.

Plastids, including chloroplasts, evolved …

Npr1 As A Temperature-Sensitive Regulator Of Pipecolic Acid-Mediated Plant Systemic Immunity, Spencer Tout

Theses and Dissertations (Comprehensive)

Healthy plant development requires balancing both abiotic (e.g. climate) and biotic (e.g. pathogen) challenges, which intercept important signaling pathways in plants. For example, climate change-associated elevated temperature can negatively modulate various aspects of plant immunity, including the production of central immune signals salicylic acid (SA) and N-hydroxypipecolic acid (NHP). Since SA and NHP signaling both require the master immune co-activator protein NON-EXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1), it is important to investigate NPR1 as a potentially temperature-regulated molecular hub. Although the NPR1 gene is not transcriptionally downregulated at elevated temperatures (28° C vs. 23° C), little is known about …

Natural Variation In Temperature-Modulated Immunity To Pseudomonas Syringae Pv. Tomato (Pst Dc3000) In Arabidopsis Thaliana Plants, Christina A. M. Rossi

Theses and Dissertations (Comprehensive)

Studies conducted on the model plant-pathogen system Arabidopsis thaliana-Pseudomonas syringae pv. tomato (Pst) showed that elevated temperature suppresses the pathogen-induced production of salicylic acid (SA), which is a key plant defence hormone. This increased host vulnerability at higher temperatures is due to downregulated expression of CALMODULIN BINDING PROTEIN 60-LIKE G (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1), which encode master regulators of SA production. Collectively, these previous studies only focused on one natural accession of Arabidopsis called Columbia-0 (Col-0). However, the intraspecific variation in Arabidopsis immunity phenotypes under elevated temperature remains unknown. To fill this critical knowledge gap, my …

Winter Dynamics Of Storm Water Management Ponds And Winter Tolerance In Three Aquatic Plant Species, Patrick Strzalkowski

Theses and Dissertations (Comprehensive)

The vast majority of the research into the performance of stormwater management ponds (SWMPs) has been performed in warm regions or during the warmer seasons in temperate regions. It is presumed that SWMPs are inactive in the winter as any potential stormwater is trapped in snow and ice. The main goal of this thesis was to test this presumption and to study the dynamics and performance of three SWMPs during the winter. Remote water level loggers were installed into the three SWMPs and daily grab samples from the influents and effluents were taken and analyzed for total phosphorus (TP), chloride, …

Diversity And Evolution Of Inflorescences In Cuscuta, Morgan Glofcheskie

Theses and Dissertations (Comprehensive)

Cuscuta (dodder) includes ca. 200 species of plant obligate stem parasites with both ecological and economical significance. Inflorescences have been historically used in Cuscuta for species descriptions and identification keys, but no comprehensive study exists to date. The main objective of this study was to survey the diversity of inflorescences, and to understand their evolution and possible form-function relationships. The inflorescence architecture of 132 Cuscuta taxa was analyzed using herbarium specimens, and eight species were grown to study their inflorescence development. Inflorescence traits were mapped into a genus phylogeny obtained from a combined analysis of nuclear ITS and plastid trnL-F …

Changes In Plant Community Composition, Structure, And Function In Response To Permafrost Thaw, Katherine Standen

Theses and Dissertations (Comprehensive)

Air temperature is increasing at three or more times the global average in high latitudes, causing widespread permafrost thaw across the boreal biome. Since the boreal biome stores 30-40% of global terrestrial carbon (C), of which about 30-45% is found in permafrost soils, this temperature increase could cause a large efflux of C to the atmosphere. Climate warming and permafrost thaw are also expected to alter plant community composition and productivity and, given the link between plant functional traits and ecosystem C fluxes, may alter overall ecosystem function. Across the boreal biome of western Canada, we know surprisingly little about …

Wildlife Forage Recovery Following Boreal Wildfire, Alexis Jorgensen, Jennifer Baltzer

Theses and Dissertations (Comprehensive)

Climate change is altering the boreal wildfire regime through increases in the extent and severity of burning and reductions in fire return intervals. These changes can alter the regeneration trajectory of canopy species and ground vegetation, with implications for wildlife habitat. There is some uncertainty about the timelines of when different animal species will use burned areas as their preferred forage taxa recover following fire, and how such recovery is mediated by environmental factors. Here, we aim to address these knowledge gaps through the following questions: 1) What are the main forage types consumed by boreal wildlife and how much …

Context Is Everything: An Investigation Of Spanish River Carbonatite And Its Effects On Soil-Plant-Microorganism Systems, James Mc Jones

Theses and Dissertations (Comprehensive)

With growing concerns about agricultural sustainability and food security, the use of rock fertilizers and agrominerals is receiving renewed interest. A wide variety of geological resources have been proposed as crop nutrient sources, with silicate rocks the predominant focus. Carbonatite rocks are known to weather more readily than silicate rocks; yet, they have received relatively little attention as it is thought their high Ca and Mg contents hinder effective nutrient release. However, there is strong evidence that the nutrients within carbonatite rocks are easily accessible to plants, and that these rocks have noticable effects on crop plant growth. Here I …

Going Back To The Soil: An Integrated Approach To Farming., Renée V. Christie

Theses and Dissertations (Comprehensive)

Agricultural productivity is often constrained by nutrient availability; as such, copious amounts of synthetic fertilizers are applied to maintain productivity. However, the intensive use of synthetic fertilizers has reduced the capacity of the soil to carry out crucial roles such as nutrient cycling because of shifts in the microbial community composition and structure. In addition, much of the applied synthetic fertilizers become lost to the environment through run-off, which contributes to soil degradation. With the increasing demand on agricultural systems to provide food and fibre and the adverse impacts of agricultural production on the soil resource, amendments that support soil …

Diversity And Evolution Of Seeds In Cuscuta (Dodders, Convolvulaceae): Morphology And Structure, Magdalena Olszewski

Theses and Dissertations (Comprehensive)

Cuscuta is a genus of nearly 200 obligate stem parasites with a nearly cosmopolitan distribution and considerable agricultural and ecological significance. Dodder seeds are considered “unspecialized”, with no morphological adaptations towards particular dispersal vectors; however, the seed coat anatomy has recently suggested an adaptation to endozoochory. This is the first attempt to provide a genus-wide overview of the diversity in morphology and anatomy of Cuscuta seeds, together with an assessment of the water gap and exploration of various form-function relationships. I surveyed 104 species belonging to all four Cuscuta subgenera. Seeds of the species of the first infrageneric dodder …

Competition Or Facilitation: Examination Of Interactions Between Endangered Sida Hermaphrodita And Invasive Phragmites Australis, Samantha N. Mulholland

Theses and Dissertations (Comprehensive)

Virginia Mallow (Sida hermaphrodita) is a perennial herb of the Malvaceae family that is native to riparian habitats in northeastern North America. Throughout most of its geographical distribution however, it is considered threatened and only two populations are known from Canada. The biology and ecology of S. hermaphrodita are still poorly understood and although few studies have been performed to determine the factors that contribute to the species rarity, it is considered threatened potentially due to the loss of habitat caused by exotic European Common reed (Phragmites australis subsp. australis) invasion. Allelopathic and phytotoxic conditioning of …

Influence Of Topography And Moisture And Nutrient Availability On Green Alder Function On The Low Arctic Tundra, Nt, Katherine Louise Black Ms., Jennifer Lynn Baltzer Dr.

Theses and Dissertations (Comprehensive)

The Arctic has warmed by at least 3^°C over the past 50 years and this rapid warming is expected to continue. Climate warming is driving the proliferation of shrubs across the tundra biome with implications for energy balance, climate, hydrology, nutrient cycling, and biodiversity. Changes in tundra plant water use attributable to shrub expansion are predicted to increase evapotranspirative water loss which may amplify local warming and reduce run-off. However, little is known about the extent to which shrubs will enhance evapotranspirative water loss in these systems. Direct measures of shrub water use are needed to accurately predict …

Spanish River Carbonatite: Its Benefits And Potential Use As A Soil Supplement In Agriculture, James J

Theses and Dissertations (Comprehensive)

A critical problem facing agriculture today is being able to consistently and sustainably provide plants with adequate nutrients for growth. With this problem being exacerbated by the ever-increasing human population, new perspectives and techniques are required to ensure global food security. In order to fully realize potential solutions, however, plant growth and nutrition cannot be exclusively focused upon. The soil-microorganism-plant system is comprised of many interconnected and interdependent processes that together support plant growth: it is upon these processes that the focus must be placed. In this work, the agromineral Spanish River Carbonatite (SRC) is characterized using the framework of …

Morphology, Structure, Function And Evolution Of Infrastaminal Scales In Cuscuta (Convolvulaceae), Stephanie Riviere

Theses and Dissertations (Comprehensive)

Cuscuta (dodder, Convolvulaceae) is a genus of about 200 species of obligate stem parasites of cosmopolitan distribution. Infrastaminal scales (IFS) are staminode-like formations that surround the ovary in the flowers of dodders. Their morphological diversity has historically provided some of the most useful taxonomic diagnostic characters at the species-level, however, their function had not been determined. I performed a comparative study of the IFS in 147 taxa using light, scanning and transmission electron microscopy, and results were analyzed in relation to a Cuscuta phylogeny obtained from a combined analysis of rbcL and 26S rDNA gene sequences. To test the hypothesis …

The Role Of The Acidic Domain Of The Toc159 Protein Import Receptor Family In Toc Complex Assembly In Arabidopsis Thaliana, Yi Chen

Theses and Dissertations (Comprehensive)

Most chloroplast proteins are encoded in the nucleus and translated in the cytosol with an N-terminal cleavable transit peptide, which can be recognized by the translocon at the outer envelope membrane of chloroplasts (Toc complex). The core Toc complex is composed of two GTPases, Toc159 and Toc34, and the Toc75 channel. atToc159, atToc132 and atToc120 are homologues of the Toc159 family in Arabidopsis, and have been shown to assemble into structurally and functionally distinct Toc complexes. Targeting of atToc159 to the chloroplast outer membrane is mediated by its GTPase (G-) domain. However, the role of the acidic (A-) domain in …

Molecular Studies Of 5-Azacytidine-Induced Early-Flowering Lines Of Flax, Megan A. House

Theses and Dissertations (Comprehensive)

Several early-flowering flax (Linum usitatissimum L.) lines were derived from treatment of germinating seeds with 5-azacytidine in 1990. These lines are also shorter, have fewer leaves, and their DNA is hypomethylated, relative to their corresponding controls. The work presented in this thesis used early-flowering and control lines of the Royal (R) flax genotype, and the Large (L) flax genotroph. Firstly, levels of cytosine methylation were measured over a 24-hour period in the early-flowering line RE2 and its control (RC), using an HPLC method. Secondly, to determine the response of the flax lines to short-day conditions, control and early-flowering …

Insights Into The World Of Pea Nodulation Using The Low Nodulator R50, Scott Clemow

Theses and Dissertations (Comprehensive)

Cytokinin oxidase (CKX) is the enzyme responsible for the degradation of cytokinin, a class of adenine-based plant hormones that stimulate cell division, among other physiological processes. The pea mutant R50 is characterized by having a pale leaf phenotype, dwarf stature, few lateral roots, low nodule formation, and elevated levels of endogenous cytokinins in its shoots, roots and nodules. When compared to that of the wild-type Sparkle, total CKX activity is low but the transcript levels of PsCKX1 are significantly higher. In this study, I investigated the expression of PsCKX1 throughout the development of a nodule and the localization of PsCKX1 …

Evolution And Systematic Significance Of Reproductive Structures In The Genus Cuscuta (Dodders, Convolvulaceae): Pollen And Gynoecium, Mark Welsh

Theses and Dissertations (Comprehensive)

The genus Cuscuta (dodders, Convolvulaceae) is one of the most significant lineages of parasitic plants from economic, conservation, and anthropogenic perspectives. Members of the genus are twining stem parasites with no roots, lacking almost completely chlorophyll or its function, and gather required nutrition from their host via specialized haustorial connections. While there are almost 200 described species, problems with species identification exist because many diagnostic characters are restricted to their tiny flowers. Probably contributing to this identification difficulty is the fact that the group has not received taxonomic attention for over 75 years; even knowledge of its basic reproductive biology …

Vegetation Pattern And Disturbance Effects In The Subalpine-Alpine Interface, Valley Of The Ten Peaks, Alberta, Katherine J. Miller

Theses and Dissertations (Comprehensive)

There have been several recent calls in the biogeography and vegetation ecology literature to investigate more thoroughly the role of recurrent disturbance or perturbation in the dynamics of subalpine communities, by assessing persistence and change in the dominant species population. In order to study the relationship between conifer regenerative effectiveness, disturbance effects, and the nature of the vegetation pattern, a field study was made of the vegetative cover (composition, abundance, dominance) and its performance (survival, vigour, and reproductive mode) in the upper subalpine zone in the Valley of the Ten Peaks, Banff National Park, Alberta. The occurrence of stresses and …