Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 23 for “"chemical defense"”.
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Hydrogen peroxide from photosynthesis: Theory and experiments linking elevated atmospheric CO2 with C3 plant chemical defense
Elevated atmospheric CO2 alters C3 plant chemical defense for reasons that remain unclear. To explain the influence of elevated CO2 on plant chemical defense, this dissertation proposes, then tests, the hypotheses that: 1. C3 plant chloroplasts exert control over chemical defense against biotic …
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Multi-component chemical defense in seahares (Gastropoda:Opisthobranchia): antipredator compounds act as both honest and deceptive signals to multiple predator species
Many organisms produce chemical defenses to deter predation, yet the behavioral, neurophysiological, and cellular mechanisms of chemical defenses are largely unexplored. Animals do not face a single hypothetical predator, but rather a diversity of predators whose behaviors and sensory systems can …
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Molecular and Functional Characterization of Terpene Chemical Defense in Arabidopsis Roots in Interaction with the Herbivore Bradysia spp. (fungus gnat)
… different strategies such as direct and indirect chemical defense mechanisms. Research has primarily focused on visible aboveground interactions between plants and herbivores. Root-feeding insects, although often overlooked, play a major role in inducing physical and physiological changes in …
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Are Chemical Defenses Allocated within Sponges to Defend Regions Most at Risk to Predator Attack?
The allocation of chemical defenses to regions most at risk to predator attack may provide adequate protection at minimal metabolic cost. This study examined chemical defense allocation within three sponge species from a temperate reef by investigating the predictions that: concentrations of …
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Ecological significance of seed traits in the genus Macaranga
… requirements for germination, investment in seed chemical and physical defense, and seed persistence in the soil. Empirical measurements of germination and seed persistence in the soil were made at Lambir Hill National Park in Borneo, and coupled with analyses of the physical and chemical defense …
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HIDE AND SEEK: AN EXPLORATION OF ANTIPREDATOR AND PREDATOR AVOIDANCE MECHANISMS IN ORTHOPODOMYIA SIGNIFERA IN RESPONSE TO PREDATION FROM TOXORHYNCHITES RUTILUS
… states thoracic setae serve as a physical defense that prevents <em>Tx. rutilus</em> from grasping <em>Or. signifera</em>. The third hypothesis states <em>Or. signifera </em>possess a chemical defense indicated by aposematic coloration. To test the first hypothesis larval <em>Or. …
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Biochemical and Functional Characterization of Induced Terpene Formation in Arabidopsis Roots
… evolved a variety of constitutive and induced chemical defense mechanisms against biotic stress. Emission of volatile compounds from plants facilitates interactions with both beneficial and pathogenic organisms. However, knowledge of the chemical defense in roots is still limited. In this …
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SYNTHESIS OF NATURAL-DERIVED POLYPHENOLS AS POTENTIAL ANTICANCER AGENTS
… focuses on the biosynthesis and the study of chemical properties and biological functions of secondary metabolites. These are organic compounds not ubiquitous in all organisms, and represent an expression of the individuality of the species; secondary metabolites do not exert primary …
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Oxygen Atom Transfer Reactions Catalyzed by Molybdenum and Tungsten Oxo Transferase Mimics
… for advancing selective and sustainable chemical transformations. Nature employs molybdenum and tungsten enzymes to mediate oxygen atom transfer (OAT) reactions, which are critical in biological redox processes. Despite their efficiency, the development of synthetic analogues that …
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Understanding the singlet oxygen reactivity of salarin C through synthesis of a simplified macrocyclic analogue; multicomponent, enantioselective organocatalytic synthesis of tetrahydropyridazinones.
… especially, produce a wide variety of cytotoxic chemical defense agents. The macrolide salarin C is one of those cytotoxic sponge natural products, isolated from a Madagascar sponge. Of particular interest is the marked reactivity of its oxazole moiety with singlet oxygen that converts salarin C …
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Functional Characterization and Evolutionary Analysis of Lepidopteran Cytochrome P450 Genes Involved in Plant -Insect Interaction
… P450 monooxygenases (P450s), to overcome the chemical defense systems of plants. Understanding the driving force behind the evolution of these systems that is promoted by gene duplication will help us elucidate the mechanisms underlying the reciprocal selection between plants and their …
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Constraints on plant resistance and tolerance trade-offs
… and pathogens) have focused on the evolution of chemical and structural traits that reduce or prevent tissue damage by herbivores (resistance) (Simms and Fritz 1990). However, herbivores may also select for traits that allow plants to compensate for tissue loss with little or no detriment in …
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Carbon based secondary metabolites in African savanna woody species in relation to anti-herbivore defense
Chemical defense in African savanna woody species have been inferred from foliar condensed tannin and total phenolic concentrations. However these measures are controversial since condensed tannin chemical heterogeneity compromises its simple quantification and total phenolics, which is a measure …
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Adaptive evolution, sex-linkage, and gene conversion in the voltage-gated sodium channels of toxic newts and their snake predators
… Tetrodotoxin is a potent neurotoxin used as a chemical defense by various animals, including toxic newts. Snakes have evolved resistance through mutations in voltage-gated sodium channels, the protein targets of tetrodotoxin, sparking an evolutionary arms race between predator and prey. In this …
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Exploring Chemically Mediated Interactions Between Spotted Lanternfly, Lycorma delicatula, and Its Host Plants in the Mid-Atlantic Region of the United States
… which L. delicatula sequesters quassinoids for chemical defense. Yet how volatile semiochemicals and sequestration dynamics shape behavior and inform management remains unresolved. This dissertation integrates behavioral ecology, analytical chemistry, and transcriptomics to connect mechanisms …
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Ecology of chemical defenses of algae against the herbivorous snail, Littorina littorea, in the New England rocky intertidal community
… first direct evidence that these algae produce chemicals which inhibit feeding by the snails. Polyphenols in Fucus vesiculosus and Ascophyllum nodosum were shown to be effective chemical defenses against the snails. Feeding experiments demonstrated that the presence in the diet of as little as …
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Consequences of global redistribution on the ecology and evolution of the invasive weed Pastinaca sativa and its associated insect fauna
… as it occurs. In Chapter 1, I examined the chemical mediation of wild parsnip pollination to understand selection pressures imposed by both florivores and pollinators. In Chapter 2, I evaluated phenotypic evolution in wild parsnips after six years of webworm infestation (2004 – 2009) in a …
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Identification, Characterization, and Functional Analysis of Terpenoid Specialized Metabolism in Switchgrass (Panicum virgatum) and Carrot (Daucus carota)
… leaves and roots in response to herbivory or defense hormone treatments and the application of drought. With a focus on volatile terpene metabolites, I functionally characterized over thirty genes (terpene synthases, TPSs), of which one third could be correlated with the production and release …
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Isolation and structure elucidation of bioactive secondary metabolites from marine sponges and sponge-derived fungi
… of new lead structures for medicinals and agrochemicals. In the search for bioactive compounds from marine sponges and sponge-associated fungi, this research work resulted to the isolation of twenty-six compounds, eight of which are new metabolites. The sponges were collected from the …
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Marine natural products as antimicrobial chemical defenses and sources of potential drugs
… The heterogeneous presentation of antimicrobial chemical defenses on host surfaces suggests the potential importance of spatial scale in understanding host-pathogen interactions, and illustrates the capacity of mass spectrometry imaging in understanding chemically-mediated biological processes. …
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