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Encore azaleas are popular ornamental plants for their full sun tolerance, coldhardiness, low maintenance requirements, and reblooming habit in spring, summer, and fall. With their varying growth rates and multiple blooms during a growing season, there is limited information on the nutrient and irrigation requirements of Encore azalea cultivars. The objectives of this study were to investigate the optimum nitrogen (N) requirement of Encore azalea ‘Chiffon’ during a growing season and determine how irrigation frequency and fertilization practices (rates, methods, and timing) affect plant growth and nutrient uptake using both a traditional plastic container and a paper biocontainer. One-year-old liners of Encore azalea ‘Chiffon’ were treated with different N fertigation rates, irrigation frequencies, and sprayed with 3% urea or water in late fall. Plants were investigated for their growth responses and flower production, and analyzed for nutrient and carbohydrate status in different studies when they were grown in both a traditional plastic container and a biodegradable container made from a mix of recycled paper. The biocontainers increased plant growth index, plant dry weight, leaf area, root growth, and uptake of both macro- and micronutrients using N rates of 10, 15, and 20 mM. During a growing season, the biocontainer-grown plants had three flushes of growth while the plastic container-grown plants had only two. The third flush of growth on the biocontainer-grown plants occurred in mid-September, resulting in greater dry weight and N uptake than with plants grown in plastic containers. One irrigation per day resulted in higher flower count and greater root length and surface area. Foliar urea application in late fall was effective in improving plant N status by increasing plant N concentration and content without affecting plant dry weight, but decreased tissue concentrations of glucose, fructose, sucrose, and starch to varying degrees.

The literature was reviewed for information regarding anatomical studies of secondary xyqlem - particularly information pertaining to <u>Acer Nigrum, Platanus occidentalis</u>, and <u>Rhododendron maximum</u>. / Master of Science

Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape. / Master of Science

Rosebay rhododendron (Rhododendron maximum L.) is an ericaceous shrub commonly found in riparian areas of the Appalachian Mountains. After more than a century of fire exclusion in the U.S., the distribution of R. maximum and its dominance of forest understories have increased. Rhododendron expansion has caused a decline in overstory regeneration and the potential for dangerous fuel conditions around suburban structures near the wildland-urban interface. The purpose of this study was to determine the effects of seven silvicultural treatments on both the fuel loading within an R. maximum thicket and the control of R. maximum as a forest weed. The final objective of the project was to determine the cost effectiveness of each implemented treatment. Due primarily to moisture conditions, a single prescribed burn was relatively ineffective in reducing fuel loading and causing R. maximum mortality. Mechanical cutting caused a drastic shift in the size-class distribution of R. maximum but resulted in heavy sprouting and increased fuel loading. Herbicide application did not reduce or increase fuel loading and was important in R. maximum control only when combined with other treatments. The prescribed burning treatment was the least expensive individual treatment while mechanical cutting was the most expensive. Combination treatments showed increased effectiveness in controlling R. maximum but were more expensive than the individual treatments. The results of the treatments from this study will be used over the long term to demonstrate to land managers the effects of vegetation control on rhododendron. / Master of Science

The goal of this thesis was molecular analysis of rhododendron plants obtained after transformation by Agrobacterium tumefaciens and subsequent selection on kanamycin. Presence of incorporated genes gusA and nptII was determined by polymerase chain reaction (PCR) and Southern analysis. GUS activity was determined by fluorimetric and histochemical assay too.

Purple-flowered rhododendron (Rhododendron ponticum L.) and yellow-flowered rhododendron (R. flavum Don.) are two dominant shrub species of the eastern beech (Fagus orientalis L.) understories in the eastern and western Black Sea Region (BSR), respectively. These invasive woody species significantly reduce beech growth and can preclude tree regeneration. The ecological consequence is an aging beech overstory with little or no regeneration to replace the mature trees. Great rhododendron (R. maximum L.) has been increasing in the forests of the Southern Appalachians of the United States, reducing tree regeneration and growth. The BSR and Southern Appalachians bear noteworthy similarities in climate, topography, and the forest flora. Purple-flowered and great rhododendrons also show important similarities in their ecology and the forest vegetation problems they can cause. Current rhododendron-dominated and threatened BSR forests may provide an advanced ecological picture of the forests of the Southern Appalachians in which great rhododendron now thrives. Therefore, new information gained on the ecology and effective and cost-efficient control of purple-flowered rhododendron may significantly improve forest management practices, not only for the current rhododendron-invaded BSR ecosystem, but also for other parts of the world. This dissertation consists of five separate yet related chapters. The first gives relevant literature reviewed for the dissertation. The second chapter focuses on various environmental and disturbance factors that may have shaped the current purple-flowered rhododendron-dominated beech forests of the BSR of Turkey. Chapter 3 assesses the effects of various manual and herbicidal woody control techniques on purple-flowered and yellow-flowered rhododendron in two field experiments in the BSR. The fourth chapter relates a study of uptake and translocation behavior of triclopyr ester and imazapyr in great rhododendron. This information is used to determine the optimum herbicide-surfactant combinations for the greatest active ingredient uptake and root translocation in great rhododendron. The last chapter is a synthesis of the information gained in all of these different experiments. / Ph. D.

Rhododendron tomentosum is an evergreen shrub with a high content of secondary metabolites, particularly essential oils with antimicrobial effects. Diversity of endophytic fungi in this species and their possible adaptation to growth in the essential oil environment is not much explored. Therefore, the first aim of this thesis was to reveal the diversity of endophytic fungi colonising leaves of R. tomentosum on seven localities in the Czech Republic and one in Estonia. I isolated and determined (using comparison of ITS1 and ITS2 rDNA with the sequences from GenBank and morphological signs) 37 species of endophytic fungi. Among them the ubiquitous species colonising the most of the plants as endophytes were dominant. The second aim of my thesis was to explore whether the essential oil from R. tomentosum influences its endophytic fungi. The hypothesis that the strains obtained from R. tomentosum would be adapted to growth in the environment of the essential oil was postulated. I supposed that they would grow better on mediums with different concentrations of these chemical compounds added, in comparison with strains of the same species obtained from different substrates. Within four of seven species tested, the strains obtained from R. tomentosum grew better, but also on the medium without the...

We analyzed soils in Alder Bald, Grassy Bald, and Rhododendron Bald communities on Roan Mountain to infer the influence of vegetation on soil and to help guide management strategies. In all vegetation types, soils were acid (pH = 4–5) sandy loams. We found vegetation-associated differences for organic content, cation exchange capacity, acidity, two plant macronutrients (K, Mg), and three cations (Fe, Na, Zn). We predicted that nitrogen compounds would be highest in the Alder Bald because Alnus viridis ssp. crispa (Green Alder) can harbor nitrogen-fixing bacteria. Organic content was highest at the alder-bald sites, ammonium was similar among vegetation types, and nitrate was high at only some sample sites. The unique soil properties of the Alder Bald community, its likely role in primary succession, and its documentation as a long-standing community type on Roan Mountain suggest that management should be directed towards its conservation.

The contamination of seafood with methylmercury (MeHg) is a global health issue, as MeHg is a well known neurotoxin. Since dietary nutrients may interact with MeHg toxicity, and oxidative stress is one of the primary mechanisms underlying MeHg neurotoxicity, we characterized dietary antioxidant-MeHg interactions. Firstly, we used an ethnobotanical study to confirm the antioxidant activity of Northern Labrador Tea, Rhododendron tomentosum ssp. subarcticum (Tea), for the Canadian Inuit, a population with elevated MeHg exposure. Secondly, we determined the ability of Tea to ameliorate MeHg-induced toxicity in a rat perinatal exposure study. MeHg exposure (2 mg/KgBW/d) was associated with perturbed development and behaviour, elevated brain N-methyl-D-aspartate receptors, and serum lipid peroxidation. Surprisingly, Tea co-exposure (100 mg/KgBW/d) modulated MeHg’s effects on brain NMDA-R levels and lipid peroxidation, but also increased mercury serum concentrations. Thirdly, using a toxicogenomics approach we determined that MeHg exposure caused the down-regulation of Nr4a2 and its protein product Nurr1. These novel MeHg targets are implicated in developmental learning functions and were corrected with MeHg + Tea co-exposure. Lastly, we conducted a risk assessment survey and cross-sectional dietary epidemiology study in Costa Rica to further investigate dietary nutrient-MeHg interactions. Costa Rica is a Central American country with multiple sources of Hg and a high per capital fish consumption. Here, 5 of the 14 populations we studied exceeded the recommended MeHg provisional tolerable daily intake (pTDI) of 0.2 µg/KgBW/d. In Heredia the pTDI was exceeded by 34% of woman participants, primarily associated with canned tuna consumption. Interestingly, we detected that Hg body burden was significantly reduced by the consumption of antioxidant-rich dietary items. Considering our collective results, we hypothesized that MeHg toxicokinetics may be altered by dietary nutrients at the site of intestinal absorption from the disruption of gut flora, or at the site of cellular demethylation in tissues from the improvement of cellular redox state. The interaction of dietary nutrients on MeHg outcomes has a large impact on risk assessment and may provide a public health approach for managing the risk associated with MeHg exposure without reducing local fish consumption.