Life Sciences Commons^™

Deep Learning Can Be Used To Classify And Segment Plant Cell Types In Xylem Tissue, Reem Al Dabagh, Benjamin Shin, Sean Wu, Fabien Scalzo, Helen Holmlund, Jessica Lee, Chris Ghim, Samuel Fitzgerald, Marinna Grijalva

Seaver College Research And Scholarly Achievement Symposium

Studies of plant anatomical traits are essential for understanding plant physiological adaptations to stressful environments. For example, shrubs in the chaparral ecosystem of southern California have adapted various xylem anatomical traits that help them survive drought and freezing. Previous studies have shown that xylem conduits with a narrow diameter allows certain chaparral shrub species to survive temperatures as low as -12 C. Other studies have shown that increased cell wall thickness of fibers surrounding xylem vessels improves resistance to water stress-induced embolism formation. Historically, these studies on xylem anatomical traits have relied on hand measurements of cells in light micrographs, …

Developmental Staging And Morphological Comparisons Of Four Fern Gametophyte Species From The Santa Monica Mountains, Tristan Furlong

Seaver College Research And Scholarly Achievement Symposium

The fern life cycle alternates between two distinct phases: a diploid sporophyte phase consisting of the “adult” fern, and a haploid gametophyte phase. Early events and changes in gametophyte development can have considerable consequences in the morphologies of these different fern species and may facilitate the various adaptive strategies employed by the gametophytes in their different habitats. This study investigates early developmental events in the gametophytes of four different fern species found in the Santa Monica Mountains, Adiantum jordanii (chaparral understory, summer deciduous sporophyte), Woodwardia fimbriata (riparian stream), Dryopteris arguta (chaparral understory, evergreen), and Pentagramma triangularis (chaparral understory, resurrection sporophyte). …

Substrate Type Affects The Drying Speed And Desiccation Tolerance Of Fern Gametophytes, Jordyn D. Regier, Mayra J. Hernandez, Camille K. Sicangco, Stephen D. Davis, Helen I. Holmlund

Seaver College Research And Scholarly Achievement Symposium

Although most ferns require abundant water to thrive, some ferns can survive in habitats with limited water. Previous studies have examined the adaptations that allow xeric ferns to thrive in mediterranean-type ecosystems such as southern California. However, the large fern sporophyte only represents one stage of the fern life cycle; the independent gametophyte phase must also survive water stress, including the six-month summer drought periods of the Santa Monica Mountains. Some fern gametophytes have been reported to be desiccation tolerant (capable of recovery from near-complete drying), and this trait is believed to be dependent on the plant’s drying speed. In …

Does The Fungal Pathogen (Botryosphaeria Dothidea) Exceed The Dehydration Tolerance Of Its Chaparral Host?, Cristian M. Garcia

Seaver College Research And Scholarly Achievement Symposium

We tested the hypothesis that an opportunistic endophytic fungus Botryosphaeria dothidea that frequently infects and causes dieback in several different species of chaparral shrubs in the Santa Monica Mountains continues to elongate and grow in host tissues at dehydration levels that exceed host survival. This was done by collecting several large branches from the field from three dominant species of co-occurring chaparral shrubs, Malosma laurina, Ceanothus spinosus, and Ceanothus megacarpus. We allowed branches to dehydrate at increasing lengths of time, from a few days to one week, in an air-conditioned laboratory, then sealed in plastic bags to allow tissuewater equilibration, …

Investigation Of Antimicrobial Properties Of Rhus Ovata Extracts, Sydney T. Adams

Seaver College Research And Scholarly Achievement Symposium

Native peoples of Southern California historically used a variety of local plants as remedies for illnesses. Chaparral species such as Rhus ovata (sugar bush) were widely available and were used to ease headaches, coughs and chest pains, and colds. In light of the historical importance of this plant and other chaparral species, recent fungal pathogen-induced diebacks of Malosma laurina, a species closely related to R. ovata, have raised questions regarding the innate defenses of these plants against fungal pathogens. We attempted to scientifically evaluate the traditional medicinal use of R. ovata and its antifungal resistance by testing two …

Testing For The Presence Of Botryosphaeria Dothidea In Branches Of Ceanothus Spinosus Undergoing Dieback, Katarina Carter

Seaver College Research And Scholarly Achievement Symposium

Botryosphaeria dothidea is an opportunistic pathogen found in some of the cavitated branches of the chaparral vegetation in the Santa Monica Mountains. In this study, we focused on investigating the presence of Botryosphaeria dothidea in Ceanothus spinosus located on Pepperdine University’s campus. We wanted to test this hypothesis because we had observed a large amount of dieback in the Ceanothus spinosus population and wanted to identify a possible contributor. Because of the large number of cavitated branches in the Ceanothus spinosus we tested, we hypothesized that they contained fungus. To test this, we took twenty samples of twenty different Ceanothus …

Potential Spread Of The Fungal Pathogen Botryospharea Dothidea From Chaparral Shrubs To Grape Vineyards In The Santa Monica Mountains, Alexandra N. Case, Natalie M. Aguirre, Rodney L. Honeycutt, Stephen D. Davis

Seaver College Research And Scholarly Achievement Symposium

We tested the hypothesis that an opportunistic endophytic fungus, Botryosphaeria dothidea, that frequently infects and causes dieback in species of chaparral shrubs in the Santa Monica Mountains during drought events, may spread to grape vineyards in the Santa Monica Mountains. Recently a dominant chaparral species in coastal exposures of the Santa Monica Mountains, Malosma laurina, has undergone extensive dieback in low elevation, dry sites, in response to historic drought in California, but less dieback in high elevation moist sites. M. laurina frequently grows adjacent grape vineyards. Thus we hypothesized that fungal isolates from a low elevation, dry vineyard …

Effect Of Drought On Resin Production In Woody Stems Of Rhus Ovata, Sydney T. Adams, Melody Young, Moriah Hall

Seaver College Research And Scholarly Achievement Symposium

Resin production in stems of woody plants is generated from resin canal secretions and is thought to play a significant role in protection from fungal infection and spread. This may be one of several factors associated with fungal infection and fungal induced dieback in plants during severe water stress or drought. We set out to determine if reduction in resin production in a chaparral shrub, Sugar Bush (Rhus ovata), was associated with severe drought in southern California. We hypothesized that dehydrated R. ovata would produce less resin than hydrated plants. Our null hypothesis was that there is no …

Comparison Of Leaf Water Potential, Stomatal Conductance, And Chlorophyll Fluorescence Between An Invasive Weed, Schinus Molle, And A Native Chaparral Shrub, Ceanothus Spinosus, In The Santa Monica Mountains, Adam L. Fahey, Harry Zhou, Katie Callahan

Seaver College Research And Scholarly Achievement Symposium

The Peruvian peppertree, Schinus molle, is an invasive species in California that has escaped cultivation to competitively exclude native species in the landscape. One example of such competition is between a dominant member of the chaparral shrub community, greenbark ceanothus (Ceanothus spinosus), and S. molle. The mechanism of competitive displacement of chaparral by S. molle is not understood nor has it been previously studied. We hypothesized that during severe drought, such as occurred during the sumer/fall of 2016, S. molle would have a more favorable water balance then its native competitor C. spinosus, eventually leading to higher survival and species …

Hydraulic Mechanisms Of Fungal-Induced Dieback In A Keystone Chaparral Species During Unprecedented Drought In California, Natalie M. Aguirre, Marissa E. Ochoa, Helen I. Holmlund, Frank E. Ewers, Stephen D. Davis

Seaver College Research And Scholarly Achievement Symposium

Between 2012-2016, southern California experienced unprecedented drought that caused dieback in Malosma laurina, a keystone species of chaparral shrub communities. Dieback was especially severe in coastal exposures of the Santa Monica Mountains, leading to whole plant mortality exceeding 50% at some sites. We hypothesized that the endophytic fungus causing the dieback, Botryosphaeria dothidea, was successful in invading the xylem tissue of M. laurina because of protracted water stress, carbon starvation, or a combination of the two. We tested these possibilities in a controlled pot experiment by comparing three treatments, each inoculated with the fungus: (1) irrigated controls (2) …

A Comparison Of Water Potential, Photosynthetic Rate, Electron Transport Rate, And Stomatal Conductance Between Native Malosma Laurina And Exotic Schinus Molle, Karagan L. Smith, Agatha C. Heng, Viridiana Hernandez-Lopez

Seaver College Research And Scholarly Achievement Symposium

A Comparison of Water Potential, Photosynthetic Rate, Electron Transport Rate, and Stomatal Conductance between Native Malosma laurina and Exotic Schinus molle

Karagan L. Smith, Agatha C. Heng, and Viridiana Hernandez-Lopez

First-year Students as Scholars Program

Mentors: Natalie M. Aguirre, Kaitlyn E. Sauer, and Stephen D. Davis

Schinus molle is a relatively new invasive species in chaparral shrub communities of the Santa Monica Mountains, and has only recently been observed to displace native species of shrubs, such as Malosma laurina. To investigate the probably cause of S. molle’s invasiveness and mechanisms of competitive displacement of M. laurina, we compared …

Root Hydraulic Conductance In Malosma Laurina Experiencing Severe Dieback In The Santa Monica Mountains, Natalie M. Aguirre 5861995, Avery Davis, Sarah Nelson

Seaver College Research And Scholarly Achievement Symposium

Malosma laurina is a dominant species in coastal chaparral ecosystems The deep root systems of M. laurina provide structural support for the steep Santa Monica Mountains and allow M. laurina to tap into the deep water table. M. laurina dieback is prevalent in coastal exposures of the SMM, presumably due to historic drought predisposing plant tissues to infection by the fungal pathogen Botryosphaeria dothidea. In ecosystems that experience annual dry periods, a high hydraulic conductance in roots is necessary to provide plants with sufficient water. A recent study has examined the effect of Botryosphaeria on the hydraulic conductance of M. …

An Individual-Based Model Of Chaparral Vegetation Response To Frequent Wildfire, Timothy Lucas, Dayna Mann, Reanna Dona

Seaver College Research And Scholarly Achievement Symposium

In recent years, the Santa Monica Mountains (SMM) have been plagued by frequent wildfires which threaten the native chaparral species. Nonsprouting chaparral species are completely killed by a fire, but their seeds germinate in response to fire cues. Facultative sprouters both resprout after a wildfire and release seeds that germinate post-fire. This project is based on data collected since 1986 at a biological preserve adjacent to the Malibu campus of Pepperdine University with an average fire return interval of 7.5 years. We present a spatial model that simulates the growth, seed dispersal and resprouting behavior of individual shrubs that compete …

Extracts Of Trichostema Lanatum Inhibit The Growth Of Gram-Positive Bacteria And An Escherichia Coli Δtolc Mutant Strain, Matthew C. Fleming

Seaver College Research And Scholarly Achievement Symposium

The Chumash Native Americans of Southern California have well-documented traditions of using plants for medicinal purposes. If a specific plant has traditionally been used for the treatment of cuts, wounds and infections, it may contain chemicals with anti-bacterial properties. One plant that fits these criteria is Trichostema lanatum (woolly blue curls). We tested extracts of T. lanatum for their ability to inhibit the growth of a variety of bacteria. Because of the widespread use of antibiotics over the past sixty years bacteria are evolving greater resistance to known antibiotics, but unfortunately the rate of antibiotic discovery has diminished during the …