Browsing by Subject "Plant"

Now showing 1 - 5 of 5
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    Minnesota Taconite Workers Health Study: Environmental Study of Airborne Particulate Matter in Mesabi Iron Range Communities and Taconite Processing Plants - Taconite Processing Facilities Particulate Matter Collection and Gravimetric Analysis
    (University of Minnesota Duluth, 2019-12) Monson Geerts, Stephen D; Hudak, George J; Marple, Virgil; Lundgren, Dale; Zanko, Lawrence M; Olson, Bernard
    The Minnesota Taconite Workers Health Study (MTWHS) was initiated in 2008 and included a multicomponent study to further understand taconite worker health issues on the Mesabi Iron Range (MIR) in northeastern Minnesota. Approximately $4.9 million funding was provided by the Minnesota Legislature to conduct five separate studies related to this initiative, including:  An Occupational Exposure Assessment, conducted by the University of Minnesota School of Public Health (SPH);  A Mortality (Cause of Death) study, conducted by the University of Minnesota SPH;  Incidence studies, conducted by the University of Minnesota SPH;  A Respiratory Survey of Taconite Workers and Spouses, conducted by the University of Minnesota SPH; and  An Environmental Study of Airborne Particulate Matter, conducted by the Natural Resources Research Institute (NRRI) at the University of Minnesota Duluth (UMD). NRRI’s “Environmental Study of Airborne Particulate Matter” comprises a multi-faceted characterization of size-fractionated airborne particulate matter (PM) from MIR community “rooftop” locations, background sites, and all taconite processing facilities active between 2008 and 2014. Characterization includes gravimetric determinations, chemical characterization, mineralogical characterization, and morphological characterization. This report specifically discusses the methods and gravimetric results of multiple aerosol PM sample collections from active (operating) and inactive (temporarily, but completely, shut down) taconite plants on the MIR. Taconite plant samples were collected in 2009 and 2010.
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    Multiple scale spatial dynamics of the moose-forest-soil ecoystem of Isle Royale National Park, MI, USA
    (2008-11) De Jager, Nathan R.
    Moose (Alces alces) make foraging decisions at scales that range from plant stems (centimeters) to home ranges (kilometers). These decisions determine the spatial distribution of forage consumption and the consequent impacts on plant communities and nutrient cycles. From the fine scale changes in the size and density of plant stems to the distribution of plant patches and community assemblages across landscapes, the effects of moose browsing at one spatial scale may amplify spatial heterogeneity at scales that are orders of magnitude larger than the scales at which the interactions originally took place. In this thesis, I focused on how gradients of moose browsing in two valleys at Isle Royale National Park, MI, USA influenced plant fractal geometry and how such changes to plant geometry feedback to moose foraging across larger previously browsed landscapes. I also examined changes in larger scale patterns of forage availability, plant community composition, and soil fertility in response to recent declines in island-wide moose population density. Increasing moose browsing influenced the geometry of deciduous and conifer species differently. The fractal dimension of bite density, bite mass, and forage biomass of aspen saplings all responded quadratically to increasing moose browsing and were greatest at intermediate browsing rates. In contrast, fractal dimension of bite density, bite mass, and forage biomass of balsam fir all declined steadily with increasing moose browsing. These different responses of plant canopies to increased browsing as well as seasonal changes in bite mass altered the distribution of foraging mechanisms across larger previously browsed landscapes. At the larger scale, recent (2005-2007) landscape patterns of available and consumed browse became decoupled from each other and distributions of available forage, plant species composition, and soil fertility were qualitatively different from patterns documented in the early 1990's. These changes are coincident with and likely driven by recent declines in the island-wide moose population of Isle Royale. Collectively, these two studies suggest that large scale landscape patterns of browse availability, species composition, and soil fertility may emerge from finer scale impacts of browsing on plant geometry and the feedbacks to larger scale foraging decisions that moose make in addition to population density. The long-term dynamics of landscape patterns in boreal forests are therefore dependant on both fine scale foraging decisions and large scale population dynamics.
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    Structure-function relationship of plant sucrose transporters (SUTs)
    (2012-07) Sun, Ye
    Sucrose transporters (SUTs or SUCs) are membrane proteins that transport sucrose and H+ into the cytoplam at a ratio of 1:1. They are important for the long-distance transport of sucrose in plants. However, little is known about the structure-function relationship of SUTs. In this thesis, the transport activity and substrate specificity of rice SUTs were measured using [14C] sucrose yeast uptake and oocyte electrophysiology. More importantly, a 3D structural model of rice sucrose transporter OsSUT1 was built using known crystal structures of transporters from E.coli as templates. Based on the predicted model, six charged amino acids in transmembrane spans were selected for mutagenesis, five of which turned out to be essential for the SUT transport function. One mutant, R188K, caused a complete loss of sucrose transport activity, and showed a H+ leak that could be blocked by sucrose. Based on electrophysiology experiments results, a putative binding interaction between Arg188 of OsSUT1 and hydroxyl groups of sucrose was proposed. A role of Arg188 in the substrate transport process was also suggested. In addition, methods to identify amino acids important for SUT substrate specificity were explored.
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    Theoretical evolutionary genetics of plant mating system and self-incompatibility
    (2020-12) Harkness, Alexander
    The mating system of a diploid eukaryote is an outcome of intragenomic coevolution. Close relatives are more likely to share recessive deleterious mutations at many locations, so an allele at another locus that reduces the probability of inbreeding will increase offspring’s expected fitness. Self-incompatibility in flowering plants, which acts through a polymorphic locus (an S-locus) that rejects pollen when pollen and pistil haplotypes match, is a particularly old and widespread inbreeding avoidance adaptation that has persisted through long-term balancing selection among different S-locus haplotypes (S-haplotypes). Intragenomic coevolution occurs between the individual elements of the S-locus: those expressed in pollen and those expressed in pistils. When intragenomic coevolution is disturbed, selection on mating system or on particular mating system adaptations is shifted and the population may adapt in new ways. In this thesis, the theoretical consequences of three disturbances to the intragenomic coevolution of mating system in flowering plants are determined. First, it is shown that isolation of the genetic load in separate inbreeding populations produces a transitory benefit upon secondary contact to a mutation promoting outcrossing, but that this benefit evaporates too rapidly as the populations reassimilate to favor the evolution of greater outcrossing consistently. Second, it is shown that, under the taxonomically widespread ribonuclease-based self-incompatibility system, the evolution of a novel S-haplotype greatly disturbs inter-haplotype coevolution, and may either lead to coexistence of all haplotypes (diversification) or extinction of multiple haplotypes (collapse) in a rescue-like process. Third, it is shown that biased patterns of pollen rejection form between non-coevolved S-haplotypes from isolated populations, which may favor the introgression of some haplotypes, prevent introgression of others, and cause some to be lost by swamping introgression.