Browsing by Subject "plant physiology"

Now showing 1 - 5 of 5
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    Costs and Benefits of Extended Leaf Phenology in Invasive Shrubs
    (2019-01) O'Connell, Erin
    Many woody invasive plants in North America develop leaves earlier and retain leaves later than their native associates, which could result in greater carbon gain. However, freezing temperatures and low light levels at northern latitudes constrain growing season length, potentially reducing the importance of spring and fall carbon gain. To investigate the costs and benefits of extended leaf phenology, I observed two years of leaf phenology and for one year estimated total carbon gain, measured growth, and tested the freezing tolerance of four native and four invasive woody shrubs growing in Duluth, MN. I conducted my study in a disturbed forest with greater canopy openness than commonly studied late successional forests, in order to explore these traits in a habitat typical of invasive species. The invaders leafed out simultaneously with native species in the spring and demonstrated an equally high freezing tolerance, but retained their leaves later in the autumn. In addition, invasive species assimilated less carbon during the summer than the native species. Therefore, extended fall phenology in invaders was critical to maintaining competitive levels of carbon gain and did not provide an advantage over native species. These findings suggest that invasive species may be able to take advantage of lengthening growing seasons and that freezing temperatures do not currently limit their northern expansion. Continued research should consider geography and latitude when studying woody invasive species phenology and physiology.
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    Effects of Flooding and Light on the Performance of Potential Replacement Species in Black Ash Wetland Forests
    (2022-04) Keller, Gwendolen
    Within black ash wetlands in the western Great Lakes region, black ash (Fraxinus nigra Marshall) is a foundational species that controls hydrologic regime, nutrient cycling, and wildlife habitat. The role of black ash in these stands makes them particularly vulnerable to the invasive emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae). One strategy that has been suggested to mitigate the impact of this invasive insect is the increase of tree species diversity through artificial regeneration, however, there is limited information available on how potential replacement tree species respond to shade and flooding. We used controlled greenhouse and field experiments that manipulated flooding duration and intensity as well as shade to explore early survival, growth, and physiology of 23 different tree species that vary in shade and flood tolerance. Measurements of seedling physiology, growth, and survival were taken throughout the growing seasons of 2020 and 2021. Results indicate that bald cypress was able to tolerate the most extreme flooding conditions simulated in the study: water table at the soil surface for 15 weeks. American elm, sycamore, and river birch were tolerant of water tables between 0 and 14 cm below the soils surface for up to 15 weeks. Northern white cedar, red maple, tamarack, swamp white oak, and yellow birch had high survival and growth rates with the water table at the soil surface for up to 6 weeks. Finally, black walnut, sugar maple, white spruce, white oak, red pine, and bitternut hickory responded poorly to flooding of any duration. Results indicate that water table depth has a greater influence on seedling growth and gas exchange rates than light reduction, especially at light levels likely to be found in black ash wetlands. Since shade treatments were generally not a significant impediment to early growth, survival, and gas exchange rates, natural resource managers should focus on matching the flood tolerance of potential replacement species to local site hydrology.
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    Investigation of vascular limitations on floral water loss in temperate woody species
    (2018-12) McMann, Natalie
    In temperate biomes, limitations imposed by vascular physiology may influence floral water use in woody species. Freeze-thaw induced embolism in the xylem can reduce vascular transport capacity in the early spring, potentially limiting growth. To investigate whether xylem transport capacity impacts floral physiology, I quantified inflorescence water loss rates and stem hydraulic conductivity of five woody species that flower before producing leaves. I found inflorescence size and ambient temperature at flowering positively correlated with water loss. However, I detected no correlation between branch level floral water loss and stem hydraulic conductivity within species. Furthermore, a comparison of branch level water loss rates from inflorescences and leaves showed that leaf water loss is 2–4 orders of magnitude greater than that of flowers. To evaluate whether flowers were primarily phloem or xylem hydrated, I modeled the amount of water brought in during floral development and full bloom. Despite their relatively low rates of water loss, the model indicates that flowers in this study obtain the majority of their water from the xylem. Overall, the data suggest that within species floral water loss may not be limited by the xylem during flowering, but large differences in floral water loss and stem conductivity among species could explain hydraulic trait variation between large and small flowered plants.
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    Leaf and canopy spectra, symptom progression, and physiological data from experimental detection of oak wilt in oak seedlings
    (2019-04-26) Fallon, Beth; Yang, Anna; Nguyen, Cathleen; Armour, Isabella; Juzwik, Jennifer; Montgomery, Rebecca A.; Cavender-Bares, Jeannine; eafallon@gmail.com; Fallon, Beth; University of Minnesota, Department of Ecology, Evolution, and Behavior; University of Minnesota, Department of Forestry; US Forest Service Northern Research Station
    These data were collected as part of an experimental effort to accurately detect oak wilt infections in oak seedlings using remote sensing tools and to differentiate that disease stress from other mechanisms of tree decline. Oak wilt disease causes rapid mortality in oaks in the central and eastern United States. Management of the disease requires early diagnosis and tree removal to prevent fungal spread. Hyperspectral tools provide a potential method of early remote diagnosis, but accurately differentiating oak wilt from other agents of oak decline is integral to effective management. We conducted experiments (2017 and 2018) on two year old seedlings of Quercus ellipsoidalis and Q. macrocarpa in which treatments were 1) maintained as healthy individuals, 2) subjected to chronic drought, or inoculated 3) stems with oak wilt fungus (Bretziella fagacearum, a fungal vascular wilt) or 4) leaves with bur oak blight fungus (Tubakia iowensis, a fungal leaf pathogen). We measured leaf and whole plant hyperspectral reflectance (350 to 2400nm, Spectra Vista HR 1024i spectroradiometer (Spectra Vista Corporation, New York, USA)), gas exchange (LI-6440XT with a leaf chamber fluorometer attachment (LI-COR Environmental, Nebraska, USA)), and tracked symptom development in repeated measures of seedlings over the course of each experiment. In 2018, we explicitly measured spectral reflectance and gas exchange on both symptomatic and green leaves, as available and we also measured collected thermal images of leaves twice during the experiment (2018 only).
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    Viral vector-mediated CRISPR-Cas9 gene editing for fundamental and applied plant research
    (2023-06) Tibebu, Redeat
    Agricultural systems face significant challenges in achieving sustainable and productive growth in light of increasing global population and climate change. In the past decade, advances in genome editing and sequencing technologies have offered promising opportunities for improving various aspects of plant productivity and sustainability. However, while major crops such as maize and rice have been the primary focus of research in this area, regional staple crops also referred to as “underutilized”, “minor” or “orphan” crops have been largely neglected. This has resulted in significant yield gaps for these crops, which could be closed through the application of gene editing techniques. The main challenge in using gene editing technologies for plant improvement is the inefficient delivery of gene editing reagents into plant cells and the subsequent regeneration of an edited plant. This is especially challenging for orphan crops, which often lack reference genomes and efficient plant transformation methods.This thesis comprises three manuscripts and a concluding chapter that address challenges, opportunities, and potential solution in utilizing advanced plant biotechnology tools for fundamental and applied plant research, with a particular focus on orphan crops. The first manuscript reviews biotechnological approaches that have been attempted in Eragrostis tef, a cereal orphan crop, emphasizing the potential of gene editing for crop improvement. In the second manuscript, we demonstrated the use of plant viral vectors to deliver editing reagents into the model plant Nicotiana benthamiana, aiming to regulate stomatal development for functional characterization and enhanced drought tolerance. In the third manuscript, we extended this technique to the orphan fruit crop P. grisea (groundcherry), demonstrating the introduction of domestication trait focused on boosting fruit quality and production. The final chapter concludes the thesis covering the available plant transformation and delivery methods and their potential application in rapid improvement of orphan crops including monocots such as tef. Ultimately, this thesis demonstrates the viability of gene editing technologies to enhance orphan crops and prompts the need for further research aimed at improving the current bottleneck of delivering editing reagents to a wide array of crops thereby supporting global food security and resilient agricultural systems.