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Articles 271 - 300 of 377
Full-Text Articles in Biology
Soil Microbial Community Composition As Affected By Restoration Practices In California Grassland, Rebecca E. Drenovsky, Martin Pothoff, Kerri L. Steenwerth, Louise E. Jackson, Rainer G. Joergensen, Kate M. Scow
Soil Microbial Community Composition As Affected By Restoration Practices In California Grassland, Rebecca E. Drenovsky, Martin Pothoff, Kerri L. Steenwerth, Louise E. Jackson, Rainer G. Joergensen, Kate M. Scow
Biology
Agricultural practices have strong impacts on soil microbes including both the indices related to biomass and activity as well as those related to community composition. In a grassland restoration project in California, where native perennial bunchgrasses were introduced into non-native annual grassland after a period of intensive tillage, weeding, and herbicide use to reduce the annual seed bank, microbial community composition was investigated. Three treatments were compared: annual grassland, bare soil fallow, and restored perennial grassland. Soil profiles down to 80cm in depth were investigated in four separate layers (0–15, 15–30, 30–60, and 60–80cm) using both phospholipid ester-linked fatty acid …
Exploring The Role Of Sac9 In Arabidopsis Thaliana Stress Response And Phosphoinositide Signaling, Elizabeth J. Drake
Exploring The Role Of Sac9 In Arabidopsis Thaliana Stress Response And Phosphoinositide Signaling, Elizabeth J. Drake
Biology
The SAC9 gene in Arabidopsis thaliana encodes a protein, Sac9, which is a putative 5-phosphatase involved in phosphoinositide stress signaling pathways in plants. The SAC domain of Sac9 has sequence homology with yeast and mammalian phosphoinositide phosphatases that catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2]. The loss of the Sac9 protein in A. thaliana leads to an increase in the quantity of PtdIns(4,5)P2 in the plant. This increase in PtdIns(4,5)P2 in the sac9-1 mutant A. thaliana likely causes plants grown under non-stress conditions to exhibit several phenotypes normally associated with stress. The focus of this thesis …
Systematics Of The Sympetrine Dragonflies With Emphasis On The Phylogeny, Taxonomy, And Historical Biogeography Of The Genus Sympetrum (Odonata: Libellulidae), Erik M. Pilgrim
Biology
Within dragonflies and damselflies, the family Libellulidae is the largest. The systematics have never been analyzed in a phylogenetic context. Using both molecular and morphological characters, this dissertation is the first study to address the phylogenetics of the Libellulidae, the phylogenetics and historical biogeography of Sympetrum, and several species-level disputes within Sympetrum. Phylogenetic study of the family Libellulidae revealed that many of the libellulid subfamilies (Brachydiplactinae, Leucorrhininae, Sympetrinae, Trameinae, Trithemistinae, and Urothemistinae) were paraphyletic. Wing venation characters were not useful for delineating the hierarchy of taxa within Libellulidae. Study of the systematics of Sympetrum shows that S. navasi …
Genetic And Phenotypic Variability Of Metarhizium Anisoplae For Virulence And Tolerance To Uv-B Radiation And Heat, Drauzio E. N. Rangel
Genetic And Phenotypic Variability Of Metarhizium Anisoplae For Virulence And Tolerance To Uv-B Radiation And Heat, Drauzio E. N. Rangel
Biology
The fungus Metarhizium anisopliae is an important agent for biological control of insects and has great advantages over chemical insecticides. However, ultraviolet radiation and heat from sunlight are serious obstacles for the use of M. anisopliae in agriculture, where the conidia may be impaired in a matter of a few hours in the field. Therefore, isolate selection and/or generation of conidia with increased tolerance to UV radiation and heat are a major goal of this dissertation. High variability in heat and UV-B tolerance was found among 17 isolates of M. anisopliae from different geographic origins, but there was very low …
Creating Mechanistic Ion Channel Models Using Genetic Algorithms, Jonathan Neal Hurst
Creating Mechanistic Ion Channel Models Using Genetic Algorithms, Jonathan Neal Hurst
Biology
Modeling ion channel function is often problematic, especially for channels that have not been physically characterized, because transitions between many conformational states cannot be directly observed. Myriad voltage clamp protocols have been developed to study these transitions, but model parameterization remains difficult because either all transitions must be culled from one protocol, or the data from multiple protocols must be non-redundantly combined. One solution to this problem is to use a genetic algorithm to create models that fit all desired voltage clamp data. This method has the distinct advantage of producing accurate ion channel models without manipulating the voltage clamp …
On The Geomorphology, Hydrology, And Biogeochemistry Of Stream-Lake Interactions In The Sawtooth Mountains, Idaho, Usa, Christopher D. Arp
On The Geomorphology, Hydrology, And Biogeochemistry Of Stream-Lake Interactions In The Sawtooth Mountains, Idaho, Usa, Christopher D. Arp
Biology
This dissertation focuses on the geomorphology, hydrology, and biogeochemistry of streams and lakes as coupled, interacting ecosystems in the Sawtooth Mountains, Idaho, USA. The study design used intensive field studies of several ecosystems nested within a broader comparative study of many ecosystems. Stream geomorphology was affected by lakes due to the glacial legacy of lakes and subsequent modification of water and sediment flux. Hydrologically, streams below lakes had more frequent and longer duration floods, and lakes were shown to attenuate summer floods, but not spring snowmelt floods. Biogeochemically, nutrient uptake among streams showed high phosphate and low nitrate uptake downstream …
Evolutionary Consequences Of An Introduced Predator: Adaptive Change In Daphnia Melanica In Response To Exotic Salmonids In The Sierra Nevada, Debra L. Fisk
Biology
The introduction of exotic species into a novel habitat, like all drastic environmental alterations, can lead to rapid evolution of both native and exotic species. Few studies have focused on the rapid adaptive evolution of native species to the introduction of a foreign species. Therefore, I wanted to determine if the introduction of exotic size-selective predators (salmonids) to alpine lakes in the Sierra Nevada, CA, has led to an adaptive response in the native prey species, Daphnia melanica. I conducted two common garden experiments with D. melanica from multiple populations, and collected data for morphological and life-history traits. With …
Mycobacterium-Plant Interactions In Bioremediation Of Polycyclic Aromatic Hydrocarbon Compounds, Robert D. Child
Mycobacterium-Plant Interactions In Bioremediation Of Polycyclic Aromatic Hydrocarbon Compounds, Robert D. Child
Biology
Five mycobacterium isolates that degrade polycyclic aromatic hydrocarbons colonize the surface of barley roots from a seed inoculum. Colonization was maintained in the presence of an aggressive root-colonizing pseudomonad. All five of the mycobacterium strains utilized components in root washes for growth but they differed in their potential for biofilm formation. Components in the barley root washes did not impede the mineralization of pyrene. An inexpensive, portable, flexible microcosm chamber system was constructed and implemented in pyrene mineralization experiments. The system facilitated control of sterile conditions, air flow-through, and collection of volatilized radiolabeled compounds. Mineralization rates of pyrene were higher …
A Survey Of The Bees Of Grand Staircase-Escalante National Monument, Southern Utah: Incidence, Abundance, And Community Dynamics, Olivia Messinger
A Survey Of The Bees Of Grand Staircase-Escalante National Monument, Southern Utah: Incidence, Abundance, And Community Dynamics, Olivia Messinger
Biology
A survey of the bees of Grand Staircase-Escalante National Monument, southern Utah, was conducted over a period of four years. Six hundred and fifty-six species were discovered within the monument, including numerous range extensions, several new species, and three genera new to the state of Utah. This is the richest bee landscape studied to date; reasons for the high diversity include the large elevation gradient, the richness of flowering plants, many of which are limited in distribution and require specific pollinators, and the many small local populations of species. To test the significance of these features on patterns of bee …
Anurans Of The Solomon Islands, Gerald W. Scoville
Anurans Of The Solomon Islands, Gerald W. Scoville
Biology
Studies of Northern Melanesia have contributed prominently to our understanding of evolution, but knowledge of the distribution, abundance, and diversification of amphibians of the region remains poor. In 2004, I accompanied members of the American Museum of Natural History to the New Georgia group, Western Province of the Solomon Islands, to conduct an investigation of the anurans of the area. Data consist of descriptions of morphology, behavioral traits, ecological settings, and relative abundance and diversity, as well as a review of historical information. Platymantines of the Solomon Archipelago are exceedingly distinctive, and are likely the product of an autochthonous radiation.
Low Leaf N And P Resorption Contributes To Nutrient Limitation In Two Desert Shrubs, Rebecca E. Drenovsky, J. H. Richards
Low Leaf N And P Resorption Contributes To Nutrient Limitation In Two Desert Shrubs, Rebecca E. Drenovsky, J. H. Richards
Biology
Both water and nutrients are limiting in arid environments, and desert plants have adapted to these limitations through numerous developmental and physiological mechanisms. In the Mono Basin, California, USA, co-dominant Sarcobatus vermiculatus and Chrysothamnus nauseosus ssp. consimilis are differentially N and P limited. We hypothesized that low leaf N resorption contributes to N-limitation in Sarcobatus and that low leaf P resorption contributes to P-limitation in Chrysothamnus. As predicted, Sarcobatus resorbed proportionally 1.7-fold less N than Chrysothamnus, but reduced leaf P in senescent leaves to lower levels than Chrysothamnus (8.0–10.8-fold lower based on leaf area or mass, respectively), consistent with N, …
Oaz Regulates Bone Morphogenetic Protein Signaling Through Smad6 Activation, Manching Ku, Shavonne Howard, Weihua Ni, Giorgio Lagna, Akiko Hata
Oaz Regulates Bone Morphogenetic Protein Signaling Through Smad6 Activation, Manching Ku, Shavonne Howard, Weihua Ni, Giorgio Lagna, Akiko Hata
Biology
The intensity and duration of activation of a signal transduction system are important determinants of the specificity of the cellular response to the stimulus. It is unclear how different cells can generate a signal of varying intensity and duration in response to the same cytokine. We investigated the role of the transcriptional activator and Smad1/4 cofactor OAZ in regulating bone morphogenetic protein (BMP) signaling. We demonstrate that upon BMP4 stimulation, an OAZ-Smad1/4 complex binds to and activates the gene encoding Smad6, a specific inhibitor of the BMP pathway. Removal of endogenous OAZ from pluripotent embryonal carcinoma cells prevents the induction …
Ecotypic Variation In Phosphorus Acquisition Mechanisms Within Marine Picocyanobacteria, Lisa Moore, M. Ostrowski, D. J. Scanlan, K. Feren, T. Sweetsir
Ecotypic Variation In Phosphorus Acquisition Mechanisms Within Marine Picocyanobacteria, Lisa Moore, M. Ostrowski, D. J. Scanlan, K. Feren, T. Sweetsir
Biology
ABSTRACT: Prochlorococcus and Synechococcus are major prokaryotic primary producers in the oligotrophic oceans that may be affected by the climate-related increases in nitrogen fixation and subsequent phosphorus (P) limitation in some parts of the oceans. Evidence that Prochlorococcus populations in the North Pacific subtropical gyre (NPSG) have increased over the past decades, possibly due to having a competitive advantage under conditions of P limitation, suggests aspects of their Pphysiology that are important for dictating their in situ success. Here, we compared the physiology of P acquisition and response to P stress (indicated by alkaline phosphatase activity, APA) among isolates of …
Physiological And Molecular Genetic Mechanisms Of Tetrodotoxin Resistance In The Garter Snake, Thamnophis Sirtalis, Shana L. Geffeney
Physiological And Molecular Genetic Mechanisms Of Tetrodotoxin Resistance In The Garter Snake, Thamnophis Sirtalis, Shana L. Geffeney
Biology
The focus of this project was the identification of physiological and molecular genetic mechanisms of tetrodotoxin resistance in the common garter snake, Thamnophis sirtalis. Tetrodotoxin, a neurotoxin, specifically blocks the activity of voltage-gated sodium channels. Some populations of garter snake have evolved geographically variable resistance to tetrodotoxin in a coevolutionary arms race with their tetrodotoxic prey, newts of the genus Taricha. Variation in tetrodotoxin resistance among snake populations is extreme and spans three orders of magnitude. Here I describe a physiological mechanism of whole-animal tetrodotoxin resistance in four populations of snake that represent two independent evolutionary origins of …
A Qualitative And Quantitative Characterization Of Emergent, Distributed Computation As A Possible Mechanism For Biological Information Processing In Stomatal Networks, Susanna M. Messinger
A Qualitative And Quantitative Characterization Of Emergent, Distributed Computation As A Possible Mechanism For Biological Information Processing In Stomatal Networks, Susanna M. Messinger
Biology
This research presents an exploration of the qualitative and quantitative properties of emergent, distributed computation in artificial cellular networks with the goal of better understanding the same computational mechanism as it might occur in biological systems, particularly plants. Stomata are tiny pores on the surface of a plant. As the sole pathway for the exchange of gasses between a plant and the atmosphere, stomata are responsible for both CO2 assimilation and water loss. By adjusting their pore size in response to environmental conditions, stomata appear to maximize carbon assimilation while minimizing water loss—a constrained optimization problem. Stomata interact with …
Responses Of Stream-Breeding Amphibians To Riparian Buffers In Headwater Streams: Ameliorating The Effects Of Regeneration Harvest, Kathleen Louise Pollett
Responses Of Stream-Breeding Amphibians To Riparian Buffers In Headwater Streams: Ameliorating The Effects Of Regeneration Harvest, Kathleen Louise Pollett
Biology
This study focused on steep (>10 °) headwater streams in a volcanic geologic region in southwestern Washington. The presence and abundance of Rhyacotriton cascadae, Ascaphus truei, and Dicamptodon spp. (D. copei and D. tenebrosus) were assessed in four treatment types (unbuffered (clearcuts), buffered (12 to 23 m wide), second-growth (35 to 50 years old stands), and unmanaged (not previously logged)). No difference among treatments for R. cascadae or Dicamptodon spp. presence was found. R. cascadae abundance did not differ statistically between buffered and second-growth streams or between buffered and unbuffered streams. R. cascadae densities did …
Functional Diversity In Autotrophic Ammonia-Oxidizing Bacteria From Agricultural Soils, Teresa E. Koper
Functional Diversity In Autotrophic Ammonia-Oxidizing Bacteria From Agricultural Soils, Teresa E. Koper
Biology
Ammonia-oxidizing bacteria carry out the first step of nitrification, producing nitrite that is subsequently converted to nitrate, which may contribute to environmental pollution. The objective of this study was to gain insight into the functional diversity of ammonia-oxidizing bacteria in agricultural soils. We investigated the urease encoding gene sequences of several nitrifying bacteria and the kinetics of nitrification of soils treated with different nitrogen sources. Many, but not all, ammonia-oxidizing bacteria produce urease and are capable of hydrolyzing urea for their source of ammonium. The urease operons were sequenced from the betaproteobacterial Nitrosospira sp. NpAV and the gammaproteobacterial Nitrosococcus oceani. …
Biotic And Abiotic Determinants Of Species Distribution: Desert Horned Lizards (Phrynosoma Platyrhinos) And Ants In A Shrub-Steppe Ecosystem, T. A. Scott Newbold
Biotic And Abiotic Determinants Of Species Distribution: Desert Horned Lizards (Phrynosoma Platyrhinos) And Ants In A Shrub-Steppe Ecosystem, T. A. Scott Newbold
Biology
The primary objective of this study was to attempt to disentangle the relative importance of biotic vs. abiotic factors on the distribution and abundance of desert horned lizards (Phrynosoma platyrhinos). Research was conducted along a Great Basin shrub-steppe bajada that examined interactions among P. platyrhinos, ants, plants, and soil characteristics. Studies focused on: (1) pattern description and habitat associations of P. platyrhinos, and (2) evaluating specific biotic and abiotic pathways underlying observed patterns of lizard abundance and distribution. Examination of lizard habitat associations along the elevational gradient revealed that unvegetated spaces and cryptobiotic crust cover were …
Evolutionary History Of The Clitellariinae And Stratiomyidae (Insecta: Diptera) Using Molecular, Morphological, And Total Evidence Approaches, Colin A. Brammer
Evolutionary History Of The Clitellariinae And Stratiomyidae (Insecta: Diptera) Using Molecular, Morphological, And Total Evidence Approaches, Colin A. Brammer
Biology
Stratiomyidae is a diverse, cosmopolitan family of Diptera (true flies). One of its twelve subfamilies, Clitellariinae, is distributed in all major biogeographic regions except Antarctica. Understanding the evolutionary history of Clitellariinae is key to reconstructing the phylogeny of Stratiomyidae as a whole because Clitellariinae is united only by shared ancestral characters, and, thus, may not be a natural group. This research investigates the relationships between the genera currently placed within Clitellariinae and the subfamilial relationships of Stratiomyidae using morphology, molecules, and combined data. Morphology was analyzed with the method of parsimony using 97 adult characters. Molecular analyses were performed with …
A Kinetic Analysis Of Bluetongue Virus Messenger Rna And Protein, Margaret K. Buccambuso
A Kinetic Analysis Of Bluetongue Virus Messenger Rna And Protein, Margaret K. Buccambuso
Biology
Bluetongue virus (BTV) of the family Reoviridae has a segmented double-stranded RNA (dsRNA) genome with ten dsRNA segments which encode seven structural proteins and four nonstructural proteins. Previous studies have revealed that newly synthesized RNA transcripts during viral replication were found in equimolar ratios within BTV virions. However, synthesized mRNA transcripts intended for translation into viral proteins are not equimolar. The levels of expression of these BTV mRNAs are still unknown although the number of viral proteins present in each BTV virion had been defined. The purpose of this research was to establish a kinetic analysis of the ten BTV …
Testing Species Disputes And Population Genetics In The Genus Phragmatopoma Using Molecular Characters, Carrie A. Drake
Testing Species Disputes And Population Genetics In The Genus Phragmatopoma Using Molecular Characters, Carrie A. Drake
Biology
Phragmatopoma californica (found in the Pacific Ocean) and P. caudata (found in the Atlantic Ocean) are intertidal, marine reef-building polychaete worms that have been found to produce viable larvae in a laboratory setting, but are otherwise geographically isolated. The first study was aimed at determining their specific status by analyzing the DNA sequences of cytochrome c oxidase subunit I (COI) and the first internal transcribed spacer region (ITS-1). Phylogenetic analyses revealed that P. californica individuals shared no COI haplotypes or ITS-1 sequences with P. caudata individuals and formed well supported separate clades. The molecular data therefore supports the status of …
Characterization Of Monoclonal Antibodies That Recognize Myxobolus Cerebralis, The Causative Agent Of Whirling Disease, Carey A. Wicks
Characterization Of Monoclonal Antibodies That Recognize Myxobolus Cerebralis, The Causative Agent Of Whirling Disease, Carey A. Wicks
Biology
Twenty-five monoclonal antibodies produced against myxospores and triactinomyxon spores of M. cerebralis, the causative agent of whirling disease of salmonids, were selected in the initial screening for their reactivity to myxospores. Twelve were found to be effective and accordingly they were characterized fully for their potential as diagnostic reagents for isolated myxospores, pre-spore stages, and spores in frozen sections. Comparative detection assays using enzyme linked immunosorbent assay (ELISA), immunofluorescent assay (IFA), and immuno dot-blot were conducted. Six antibodies bound to developing stages and mature spores of the parasite. Localization of antibody binding in IFA was affirmed by electron microscopy. …
Hypoxia Signaling In Arabidopsis Thaliana, Julie C. Johnson
Hypoxia Signaling In Arabidopsis Thaliana, Julie C. Johnson
Biology
The oxygen level at or below which respiration is limited is termed hypoxia. Hypoxia can be induced by several different environmental factors, including flooding and microgravity. Plants have developed mechanisms to survive and acclimate to these conditions through changes in morphology, metabolic pathways, and protein synthesis. One mechanism used by plants to signal stress environments is a signal transduction pathway involving membrane phospholipids that can induce calcium mobilization, or the movement of calcium into the cytosol from extracellular or in-tracellular stores. However, the data from this study indicates that hypoxic stress did not result in phosphoinositide accumulation or calcium mobilization …
The Effect Of Wildfire On Populations Of The Jemez Mountains Salamander (Plethodon Neomexicanus) With Consideration To Arthropod Prey Availability Following The Cerro Grande Fire Of Northern New Mexico, Michelle R. Cummer
Biology
Fire regimes in North America, including the American Southwest, have undergone relatively dramatic shifts in the last century, resulting in novel stand-replacing fires that are changing landscapes in unprecedented ways. Some possible effects of these novel landscape changes on a terrestrial plethodontid salamander (Plethodon neomexicanus) were investigated. Microhabitat temperatures in four burn-severity types following recent fires were measured. Temperatures were significantly greater in high-severity and moderate-severity burn areas than in low-severity and unburned areas. Salamander presence/absence data from four burn-severity types that were documented as having salamanders prior to wildfire are considered. The proportions of presence and absence …
Ecology And Physiology Of Tetrodotoxin Toxicity In The Newt Genus Taricha: Ramifications For A Coevolutionary Predator-Prey Interaction, Charles T. Hanifin
Ecology And Physiology Of Tetrodotoxin Toxicity In The Newt Genus Taricha: Ramifications For A Coevolutionary Predator-Prey Interaction, Charles T. Hanifin
Biology
I examined the ecology and physiology of tetrodotoxin (TTX) toxicity in the newt genus Taricha (family Salamandridae) to understand the forces that have shaped the adaptive evolution of TTX toxicity in this group. In particular, this work sought to explore how coevolution with a TTX-resistant predator (the garter snake, Thamnophis sirtalis) has shaped patterns of phenotypic diversity in TTX toxicity among populations of Taricha. I developed a set of techniques to directly measure levels of TTX in the skin of newts, and used those measurements to estimate the amount of TTX a snake predator would be exposed to …
Yellow Starthistle In Utah: An Investigation Of Centaurea Solstitialis Invasion Patterns, Processes, And Population Dynamics, Julie Patrice Rieder
Yellow Starthistle In Utah: An Investigation Of Centaurea Solstitialis Invasion Patterns, Processes, And Population Dynamics, Julie Patrice Rieder
Biology
In a series of observational studies and experiments in the field, I investigated the general biology of yellow starthistle (Centaurea solstitialis) within a landscape in Utah in light of three main phases of invasion: arrival and establishment, spread, and equilibrium. During the establishment phase, the effect of disturbance on yellow starthistle establishment and performance was context dependent; disturbance positively influenced establishment and fecundity on relatively large disturbed plots that were artificially seeded, but had no significant effect on YST performance on small disturbed plots receiving ambient seed rain. Importantly, disturbance was not essential for establishment of yellow starthistle. …
Antimicrobial Activities Of Lipodepsipeptide Syringopeptins, Mekki F. Bensaci
Antimicrobial Activities Of Lipodepsipeptide Syringopeptins, Mekki F. Bensaci
Biology
Many strains of the plant bacterium Pseudomonas syringae produce two major classes of cyclic lipodepsipeptides, the syringomycins and the syringopeptins. Four groups of small cyclic lipodepsipeptides are well known: the syringomycins, syringostatins, syringotoxins, and pseudomycins. They all have antimicrobial activities and tend to be more active against yeasts than against bacteria. The syringopeptins are lesser-known. The best-studied syringopeptins are SP22 and SP25. They possess antibacterial and antifungal activities, but their mechanisms of action and antimicrobial spectra are less studied. Saccharomyces cerevisiae sphingolipid and sterol biosynthetic mutants were used to investigate the mechanism of action of syringopeptins against fungi. Similarly to …
Investigation Into The Spatial And Temporal Dynamics Of Stomatal Networks To Determine Whether Plants Perform Emergent, Distributed Computation, Jevin West
Biology
This research studies the spatial and temporal dynamics of stomatal patchiness in order to investigate the possibility that plants solve their problem of adjusting stomatal aperture in order to maximize CO2 uptake while minimizing H2O loss through an emergent, distributed computation. An extensive study is done on qualitative and quantitative characteristics of stomatal patchiness, and improved imaging techniques are developed to more fully capture the dynamics. In doing so, soliton-like structures were discovered. Sequences of chlorophyll fluorescence images of Xanthium strumarium leaves were then compared to image sequences of cellular computer simulations that solve problems via emergent, …
Analysis Of Phosphatidylinositol 4,5-Biphosphate And Inositol 1,4,5-Triphosphate In Dehydration And Cold-Stressed Arabidopsis Thaliana, James E. Thompson
Analysis Of Phosphatidylinositol 4,5-Biphosphate And Inositol 1,4,5-Triphosphate In Dehydration And Cold-Stressed Arabidopsis Thaliana, James E. Thompson
Biology
During dehydration and cold stress, Arabidopsis thaliana (A. thaliana) plant cells mobilize calcium into their cytosol to elicit changes in gene expression that enable them to tolerate stress. It has been unclear how dehydration-stressed plant cells receive and transmit the signal that results in promoting increases in intracellular calcium concentration. Previously, phosphatidylinositol 4,5-biphosphate (PtdIns(4,5)P2) and inositol 1,4,5 triphosphate (Ins(1,4,5)P3) have been shown to accumulate and cause calcium mobilization in osmotically stressed A. thaliana. However, it was unknown whether the same occurred in plants exposed to other abiotic stresses. Data presented in this thesis …
Stoichiometric And Environmental Controls Of Consumer-Driven Nutrient Recycling In Steams, John D. Rothlisberger
Stoichiometric And Environmental Controls Of Consumer-Driven Nutrient Recycling In Steams, John D. Rothlisberger
Biology
I investigated the environmental control of consumer-mediated nutrient recycling (CNR) in sub-alpine streams by evaluating the effects of water temperature and food elemental composition on the rates and ratios of nitrogen (N) and phosphorus (P) excretion by macroinvertebrates. I predicted that biomass-specific excretion rates would be positively correlated with temperature whereas N:P ratios would primarily relate to food N:P ratio. I measured nutrient release by heptagenaiid larvae eating periphyton of varying elemental composition grown on nutrient-diffusing substrates. I hypothesized that skewed ratios of N:P release would result from differential retention of nutrients in the food. Excretion rates of N and …