• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Adaptation of an invasive grass to agriculture: ecological and genomic evidence

Smith, Alyssa Laney 06 June 2017 (has links)
Species vary phenotypically and genetically across their environmental range limits, and this variation can influence ecological processes. Ecologically meaningful intraspecific variation might be particularly important in the context of agricultural weeds and exotic invaders, because intraspecific variation in these species might allow them to rapidly adapt to their unusually dynamic and variable environments. In a greenhouse study, we explored intraspecific variation in the size, rhizome production, and competitive ability of the global invader, Johnsongrass (Sorghum halepense), representing populations from agricultural and non-agricultural habitats across its introduced North American range. We also used these populations to explore the relationship between phenotypic variation and genomic endoreduplication responses to the common stresses herbicides, competition, and clipping. Endoreduplication occurs when plants increase their genome size by increasing their nuclear chromosome number, with some evidence showing correlations with stress response. We found that Johnsongrass plants from agricultural habitats were larger than plants from non-agricultural habitats, but there was no difference between habitats in either rhizome production or competitive ability. Two of the five herbicides we tested, primisulfuron and imazethapyr, had the strongest suppressive effects on Johnsongrass, and also stimulated the greatest rates of endoreduplication. Furthermore, agricultural populations showed higher levels of endoreduplication. We found no overall effect of competition on endoreduplication, although endoreduplication was higher for non-agricultural populations than agricultural populations. When competing with corn, but not with conspecifics, Johnsongrass roots increased endoreduplication by 13%. Clipping induced substantial endoreduplication, but there was no difference between agricultural and non-agricultural populations. Our results suggest that endoreduplication may play a role in some, but not all, stress responses in Johnsongrass. Furthermore, our results indicate that Johnsongrass has adapted in some phenotypic and genomic ways to agricultural habitats in North America. Such adaptation may play a role in this species' success as both an agricultural weed and an exotic invader. / Master of Science in Life Sciences
2

Patterns and biological implications of DNA content variation in land plants

Bainard, Jillian D. 21 October 2011 (has links)
DNA content varies significantly over land plants, and is known to correlate with various aspects of plant form and function. In the present study, two measures of DNA content were examined in taxa across the land plant phylogeny: genome size (or C-value) and endopolyploidy (or endoreduplication index, EI). Additionally, the relationships between DNA content and various morphological and ecological traits were assessed. DNA content was determined for 64 liverwort species from 33 families. There was a large range in 1C-values from 0.27 to 20.46 pg, but no endopolyploidy was observed. There was no correlation between genome size and breeding system (monoecy vs. dioecy). Genome size and degree of endopolyploidy were determined for 74 moss species from 21 families. Genome sizes were constrained in this group, with 1C-values ranging from 0.25 to 1.21 pg. Endopolyploidy was high in all species except from the Sphagnaceae. Additionally, 1C-value was negatively correlated with desiccation tolerance but was not correlated with breeding system. DNA content variation was determined in 31 monilophyte (fern) species (including three horsetails) and 6 lycophyte (clubmoss) species. There was a wide range in 1C-values from 2.79 to 26.90 pg, and there was no indication of endopolyploidy in any of the species. Multivariate analyses were used to explore the relative contribution of traits and phylogenetic placement to DNA content varation in 41 angiosperm species. Six measures of DNA content (2C-value, 1Cx-value, leaf EI, stem EI, petal EI and root EI) were assessed. Phylogeny explained more of the variation observed in the six measures of DNA content than 21 ecological and morphological traits. However, many of the traits were able to explain some of the variation in DNA content, both with and without phylogeny included as a covaraite. One trait that was consistently correlated with DNA content was the association with arbuscular mycorrhizal (AM) fungi. In a controlled experiment, the EI in root cells colonized by AM fungi significantly increased compared to non-mycorrhizal plants. This thesis increases our knowledge regarding the extent and significance of variation in DNA content in land plants.

Page generated in 0.0724 seconds