Browsing by Subject "Flowering"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Analysis of the U.S. Department of Agriculture's regulation of genetically engineered crops and reproductive biology of Carex pensylvanica (Lam.)(2013-08) McGinnis, Esther EbataThis dissertation is divided into two parts. Chapters 1 through 3 are interdisciplinary and focus on legal and scientific perspectives regarding the regulation of genetically engineered crops. Chapters 4 and 5 evaluated the environmental factors that control flowering in Pennsylvania sedge (Carex pensylvanica Lam.). The commercial potential of genetically engineered (GE) crops has not been fully realized in the United States due to environmental litigation that dramatically affected the pace of GE crop development and deregulation. The USDA's Animal and Plant Health Inspection Service (APHIS) regulates GE crops. However, litigation initiated by nongovernmental organizations exposed APHIS's vulnerability to lawsuits under the National Environmental Policy Act. We concluded in chapters 1 and 2 that APHIS did not adequately evaluate the environmental risks of novel crops, and thus left itself open to litigation. In Chapter 3, we described how the biotechnology industry is attempting to avoid regulation of GE crops through the creation of a non-plant pest loophole.Pennsylvania sedge is an upland forest sedge with horticultural potential as a low maintenance groundcover. For large plantings, achenes are preferred, but Pennsylvania sedge typically produces few achenes in its native habitat. As a first step in improving achene production, Chapter 4 evaluated the effect of vernalization and photoperiod on floral initiation and development. We concluded that Pennsylvania sedge is an obligate short day plant that does not require vernalization for flowering. Plants flowered when exposed to daylengths of 6 to 12 hours. Flowering was completely inhibited with 14-hour photoperiods. Chapter 5 examined the environmental factors that control floral gender sequence and inflorescence culm heights. Plants were found to be determined and florally initiated in the fall in the northern United States. A post-floral induction chilling treatment (winter) was necessary to produce protogynous flowering and normal inflorescence culm elongation.Item Phenological responses of herbaceous plants, shrubs, and tree seedlings to experimental climate change conditions in northern Minnesota(2016-08) Rice, KarenChanging climate has been linked to changes in phenology, the timing of biological events such as leaf out and flowering. Phenological changes of herbaceous plants and shrubs remain less studied and thus less understood. This study takes place within the Boreal Forest Warming at an Ecotone in Danger (B4WarmED) project in Minnesota, examining phenological responses of herbaceous plants, shrubs, and tree seedlings to warming and reduced rainfall over. Warming extended the growing season, primarily through earlier leaf unfolding in the spring. Flowering advanced under warming, though more so for fall blooming species than for spring blooming species. Warming did not alter senescence for most species, though several species did delay senescence with warming. Community level phenological responses of the groundlayer and tree seedlings were not altered by rainfall treatments. Fall blooming species altered flowering phenology to rainfall manipulation. Two species diverged in flowering time in the warmest, driest treatment.Item The role of SHORT HYPOCOTYL UNDER BLUE 1 in Arabidopsis seed and seedling development.(2010-01) Zhou, YunSHORT HYPOCOTYL UNDER BLUE 1 or SHB1 was previously identified as a negative regulator of the cryptochrome-mediated blue light response in Arabidopsis early seedling development. shb1, a T-DNA insertional loss-of-function allele, showed a short hypocotyl phenotype only under blue light, whereas shb1-D, a gain-of-function over-expression allele, showed a long hypocotyl phenotype under blue as well as red or far red light. SHB1 is a nuclear protein and contains a N-terminal SPX domain and a C-terminal EXS homologous to yeast SYG1 protein family. Using a biochemical approach, I found that SHB1 is anchored to a large protein complex through both of its SPX and EXS domains. In a genetic screen, I identified five mis-sense mutations within or nearby its N-terminal SPX domain and these mutation impaired its biological function and proper assembly into a protein complex. In contrast, the C-terminal EXS domain, when over-expressed, created a dominant negative phenotype and interfered with the assembly of the endogenous SHB1 into a native protein complex. SHB1 also functions in flowering timing control and this involvement is likely related to its light signaling activity. In addition, SHB1 plays a specific role in a quite different developmental phase, seed development. SHB1 regulates the timing of endosperm cellularization and promotes the subsequent embryo development through its control over both cell division and cell expansion. SHB1 associates with the promoters of MINISEED3 (MINI3), a WRKY transcription factor gene, and HAIKU2 (IKU2), an LRR receptor kinase gene in vivo, and activates the expression of these two genes required for endosperm development. In summary, SHB1 plays a novel signaling role in both Arabidopsis seed and early seedling development, and this conserved function may be implicated for some SHB1-like proteins in many other organisms.