Biology Commons^™

Seed Longevity And Climatic Tolerance Of San Joaquin Wooly-Threads (Monolopia Congdonii; Asteraceae) An Endangered Plant From The San Joaquin Desert, California, Paul Excoffier

Master's Theses

San Joaquin wooly-threads (Monolopia congdonii; Asteraceae) is a federally-listed, endangered annual plant species from the desert areas of the San Joaquin Valley. Its limited range puts it at risk of extinction if the climate changes in such a way as to hinder its growth and reproduction. The primary aims of the study were to 1) determine how long-lived the seeds of the M. congdonii are, a key determinant of survival of desert annual plant populations through long droughts and 2) determine how severely hotter, drier conditions impact the ability of emerged plants to grow and reproduce. Secondarily, I …

A Comparison Of Natural, Living, And Hardened Shorelines Ability To Prevent Coastal Erosion And Maintain A Healthy Ecosystem, Gabrielle Spellmann

Master's Theses

It is important to find a suitable method to protect the U.S. Gulf Coast shoreline, since its’ low elevation and the Loop current make it vulnerable to sea level rise. I focused on two manmade methods, hardened, and living shorelines, of coastal protection for when the natural marsh suffers excess erosion rates. Living shorelines are a suite of shoreline conservation and restoration techniques that usually involve some sort of hardened structure that dampens wave energy so that the native vegetation behind it can take root and stabilize the shoreline. This study looked at six different sites, all containing a natural, …

Effects Of Water Table Depth And Edaphic Characteristics On Plant Diversity In A Southern Mississippi Pitcher Plant Bog, Patrick Kirby

Master's Theses

This study examined the effects that water table depth and soil characteristics have on plant species richness and species composition within pitcher plant bogs across seasons. Eight piezometers were installed at random distances to monitor long-term water table depth and pressure fluctuations along a ~710-meter line transect traversing upland and bog habitats. Vegetation sampling quadrats (n=128) were set up near each piezometer. Cover data and water table depths were collected in spring and late summer. Soil samples collected from each treatment group were used to obtain soil texture and nutrient data. The summer collection period yielded a total gdiversity of …

Influence Of Shaded Conditions On Development Of Asteraceae Species Native To Kansas, Aline Rodrigues De Queiroz

Master's Theses

to the heterogeneity of habitats, all plants are exposed to at least some degree of shade during their lifetime. Reduced light intensity, drops in R:FR ratio, and limited blue light are cues for plants to perceive competition; the shade avoidance syndrome (SAS) is common for grassland species while shade tolerance (ST) is common for forest species when competition is perceived. SAS is characterized by elongation of stems and petioles, reduced branches, decreased leaf area, decreased shoot biomass, and increased number of ramets. ST is characterized by little elongation of stems and petioles, high chlorophyll content and high chlorophyll a/b ratio …

Greening Rates And Photosynthetic Development Of Leaves In C3 And C4 Plants, Tayler J. Kriss

Master's Theses

To study chlorophyll development time and overall photosynthetic development in C3 and C4 leaves, seeds were germinated in complete darkness and achlorophyllous leaves were then allowed to develop in lighted conditions. Corn (Zea mays, C4), sorghum (Sorghum bicolor, C4), green bean (Phaseolus vulgaris, C3), broad bean (Vicia faba, C3), and wheat (Triticum aestivum, C3) were investigated for the first ten days of sunlight exposure. Chlorophyll concentration, chlorophyll fluorescence, and CO2 gas exchange measurements were conducted daily on the first leaf that emerged after the embryonic leaves of each plant. The first five days of the experiment, days zero to four …

The Population Genetics Of Morro Bay Eelgrass (Zostera Marina), Julia Gardner Harencar

Master's Theses

Seagrass populations are in decline worldwide. Zostera marina (eelgrass), one of California’s native seagrasses, is no exception to this trend. In the last 8 years, Morro Bay, California has lost 95% of its eelgrass. Eelgrass is an ecosystem engineer, providing important ecosystem services such as sediment stabilization, nutrient cycling, and nursery habitats for fish. The failure of recent restoration efforts necessitates a better understanding of the causes of eelgrass decline in this estuary. Previous research on eelgrass in California has demonstrated a link between population genetic diversity and eelgrass bed health, ecosystem functioning, and resilience to disturbance and extreme climatic …

Evaluating The Myth Of Allelopathy In California Blue Gum Plantations, Kristen Marie Nelson

Master's Theses

It is widely accepted that allelopathy is not only significant, but more or less singular, in the inhibition of understory vegetation in California Eucalyptus globulus (blue gum) plantations. However, there is no published documentation of allelopathy by blue gums against California native species. Here, we present evidence that germination and early seedling growth of five California native species are not inhibited by chemical extracts of blue gum foliage, either at naturally-occurring or artificially concentrated levels. In the greenhouse, seeds were germinated in field-collected soil from mature blue gum plantations and the adjacent native, coastal scrub communities. In petri plates, seeds …

The Vascular Flora Of Wayne County, Mississippi, Daniel M. Mcnair

Master's Theses

The vascular flora of Wayne County, Mississippi, was surveyed from 2013–2015, and the species of native and naturalized plants are listed. In total, 1,135 species were identified from field collections, previously collected herbarium specimens, and field observations. These belong to 556 genera and 165 families. Four of these species represent first recorded occurrences in the state of Mississippi: Blyxa aubertii Rich., Gomphrena serrata Pav. ex Moq., Isoetes valida (Engelm.) Clute, and Polypogon interruptus Kunth. GPS coordinates are given for important collection sites representing the diversity of plant communities in the county. All voucher specimens from the survey are deposited in …

Photosynthetic Thermal Tolerance And Recovery To Short Duration Temperature Stress In Desert And Montane Plants: A Comparative Study, David William Gallagher

Master's Theses

• Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T₂₅)and photosynthetic recovery (RT₂₅) were quantified in 27 species. We also studied the relationships between T₂₅, RT₂₅ and leaf mass per area (LMA). Leaf temperature was also monitored in the field.
• Leaves used in this study were collected from two distinct …

The Vascular Flora Of Powhatan County, Virginia, Michael Austin Terry

Master's Theses

The project was undertaken with three main goals in mind: to provide as current and complete an account as possible of the flora of Powhatan County in the form of an annotated checklist; to integrate the information obtained from the inventory into phytogeographical and ecological generalizations currently being developed for the state of Virginia; and, to report any significant or anomalous discoveries. There is no previous county-wide inventory of plant diversity for Powhatan County. However, Corcoran (1981) published a list of plants from the Jones and Mill Creek watershed located in the Fine Creek Mills area of northeastern Powhatan.