Theses and Dissertations Collection

Symbiotic of Ventenata dubia, Bromus tectorum, Boechera stricta, and Phoenix dactylifera investigates the intricate nature of plant symbiosis as the relationship between specific plant species (four plant species V. dubia, B. tectorum, B. stricta, and P. dactylifera,) in specific contexts (northwest USA and Saudi Arabia), utilizing laboratory experimental design and literature review methodologies.

Symbiosis is a relationship between organisms of different species, and the interaction may be beneficial or harmful. There are three types of symbiotic relationships: mutualism, commensalism, and parasitism. Mutualism is a relationship between organisms of different species with each benefiting. Commensalism is a relationship between organisms of different species without any harm but benefiting one organism and this relationship applies to chapter 3, A bottleneck for microbes in seeds of Ventenata dubia, Bromus tectorum, and Boechera stricta, as endophytes have benefit and no effects on the three-plant species V. dubia, B. tectorum, B. stricta. Endophytes are microorganisms that live in the interior of the plant and have no apparent of damage to their host. Endophytes play essential roles in plant protection, act against herbivores, insects, and pathogens of the host and may even increase plant resistance to pathogens, biotic, and abiotic stresses.

Lastly, parasitism involves two organisms, for one benefit and the other, which is considered a host is harmed. For example, plant pathogens cause disease to plants. For example, P. dactylifera (date palm) is parasitized by Aspergillus tubingensis (Chapter 4), and we are setting the groundwork to search for a biological control agent for V. dubia (Chapter 2).

The dissertation addresses four plant species that can be categorized as native, introduced, and invasive. Boechera stricta is native to North America and is widespread and has a great potential for studies involving symbiosis. The second category, introduced, is represented by date palm (Phoenix dactylifera L.), intentionally introduced by humans to a new area where it was not previously found. Date palm is native to the arid Arabian Peninsula, North Africa, and the Middle East however to date palm has been introduced to many countries including Australia, India, Pakistan, Mexico, South Africa, and the United States. Dates have been a staple food in the Middle East region for years. Dates are the primary source of income and basic food for the local population in many countries where they are grown and have played essential roles in the economy, society, and environment of those countries.

The final relationship involves Ventenata dubia and Bromus tectorum and these two species are invasive. Invasive is defined as a non-native species that changes how an ecosystem functions. Invasive plant species are one of the main and most rapidly developing threats to food security, animal, human health, and biodiversity. The transportation of these invader plants can be through global travel, transport, tourism, and trade, timber products, and ornamental flora. When a new and aggressive species is brought into an ecosystem, it might be in a stage of enemy release leaving all its enemies in their native range, and this helps the invader to spread quickly and to take over an area from the native plants. They can change the plant community by competing with native species in the light, water, or nutrient resources. Invasive plants are threats to native wildlife. Prevention, eradication, and management of invasive species are a costly challenge. For example, in this dissertation V. dubia and B. tectorum are choosen because they are especially damaging the native plants. These two are threatening many of the plant communities in the Pacific Northwest, and they are creating economic and ecosystem losses. The reason to be concerned about losing any native species is that loss of a single species can affect the interconnected in life on earth. If enough "living connections" are broken, entire ecosystems in the earth could fail, and balance of nature be forever changed. Additionally, the diversity of animals and plants could change as well, and when species were lost humans would lose the benefits of them as food and medicines forever.

European settlers introduced many plants to North America from their homelands, for food, medicinal, ornamental, and other purposes. Introductions of non-native plants continue today, and are even increasing due to elevated worldwide travel and expanded worldwide trade. Many introduced plants have become naturalized over the continent, and a few are replacing North American native plant species.

Parallel to overpopulation and global immigration, we also contend with impact from climate change on invasive plant species and an overall change of ecosystems. It is hard to know the immediate measurable effects of climate change because we are uncertain about how the invasive species will respond to diverse parameters of climate change, such as temperature and precipitation. However, there is more than one reason to believe that most climate change will have an impact by increasing the frequency and severity of invasive species in any given geographic region. Invasive species will increase in abundance and emergence because the changing climate becomes unsuitable for the native species. With high nutrition resources, invasive species are well suited to succeed in new environments. Climate change leads to warmer temperatures, and higher CO2 concentration. Severe storms become more common due to climate change and may disperse invasive plant seeds more widely.

Presented are four chapters: all chapters are related to the concept of plant symbiosis. All of the four plant species, V. dubia, B. tectorum, B. stricta, and P. dactylifera, have symbiotic relationships with microorganisms. However, each chapter has a different experimental design, and the objectives for each are not the same. The first and second chapters focus on V. dubia, an invasive plant in PNW that is affecting ecosystems by reducing native species abundance and diversity and causing an economic loss in the area infected by V. dubia. The species likely is in a state of enemy release, and thus a biological control would assist in its management. The native range of V. dubia had to be specified so that biological control discovery could be carried out within the native range, and we can look for a control agent.

The third and fourth chapters involve symbiosis of the four plants species mentioned above. The third chapter tests a hypothesis of a bottleneck and exclusionary interactions for microbes in seeds of invasive plant species V. dubia, B. tectorum, and native plant species B. stricta and builds on prior research. Experimental design in this chapter was different than Newcombe et al. (2018) to see if this could make any difference. In this experiment, different factors were used: varied age of seed, surface-sterilization protocol, and isolation medium, inoculated versus uninoculated during flowering stage and plant genotypes.

The fourth chapter is about date palm seeds and the hypothesis that Aspergillus tubingensis affects the emergence of date palm seedlings. In the beginning, we examined the seeds' endophytes, and we noted that there is an effect of Aspergillus to the seedlings of the date palm and no impact to the seedlings by the other endophytes that were found in the seeds of the date palm.

This dissertation’s style is each chapter follow by its references, tables, and figures for better organization. Full credit is given to the dissertation author for tables in chapter 2 synthesizing literature review around V. dubia as all tables were compiled by her.