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N-acylethanolamines (NAEs) are fatty acid derivatives that occur naturally in plant and animal systems. In mammals, they regulate physiological functions, including neurotransmission, immune responses, vasodilation, embryo development and implantation, feeding behavior, and cell proliferation. NAEs are metabolized by fatty acid amide hydrolase (FAAH), which belongs to the amidase signature family. It is hypothesized that putative FAAH functions as the catalyst in the metabolism of N-acylethanolamine in tomato plants. To test the hypothesis, FAAH protein homologs were identified in tomato via in silico analysis. Among the six homologs identified, FAAH1 and FAAH2 were selected for further validation. This study is focused on 1) in silico analyses of SlFAAH2, 2) quantification of transcript levels for SlFAAH2, 3) determination of FAAH activity at various developmental stages of tomato, and 4) isolation of and synthesis of SlFAAH2 cDNA for cloning. Putative SlFAAH2 showed high homology to Arabidopsis FAAH1. Transcript levels, as measured by qPCR using RNA extracted from various developmental stages, were highest at 0 days and lowest at 4 days. Enzyme activity at certain developmental stages coincided with SlFAAH2 transcript levels. In order to confirm that putative SlFAAH2 encodes for an enzyme that hydrolyzes NAEs, SlFAAH2 gene was isolated from total RNA of tomato, cDNA was synthesized by reverse transcription and the gene was amplified by PCR for further cloning in a heterologous expression system for biochemical characterization. To gain better molecular and biochemical understanding of FAAH and determine its broader functions, it is pertinent to characterize FAAH in other plant species.

Lily leaf spot, a fungal foliar disease caused by Pseudocercosporella inconspicua, leads to premature senescence of aboveground tissues in Lilium grayi. At Roan Mountain, North Carolina/Tennessee, the disease was most prevalent and most severe in seedlings and juveniles. In the two growing seasons assessed, 59 and 70% of mature plants experienced disease-induced premature senescence. Plants with disease lesions on seed capsules matured fewer capsules and had fewer seeds per capsule, and seeds had reduced viability. Disease prevalence over the growing season followed a sigmoidal pattern typical of polycyclic epidemics. Plants with low and high disease severity occurred in clusters whose locations were stable across growing seasons. Prior to the recent description of lily leaf spot, L. grayi was already considered threatened or endangered in each of the three states where it naturally occurs. Therefore, this infectious disease poses conservation and management difficulties because increases in plant density can be expected to lead to enhanced disease transmission. Lily leaf spot of L. grayi is best characterized as an annually recurring epidemic because of high prevalence rates, strong impacts on all life stages, and reductions in seed production and viability.

An examination of previously unaccessioned and overlooked specimens has added 16 species to the vascular flora of the 3800 ha Rocky Fork Tract in northeastern Tennessee. One species was deleted because of a prior misidentification for a net gain of 15 species and a total of 764 species. One species, Solidago lancifolia (Torr. ex A. Gray) Chapm., is listed as Endangered in Tennessee. All additions except two, represent county records. ©2018 Botanical Research Institute of Texas.

Florida scrub is a xeromorphic upland shrub community dominated by evergreen oaks that resprout after fire, occurring on moderately to excessively well-drained nutrient-poor sand. Scrub is home to several threatened and endangered animal species (e.g., Florida scrub-jay, gopher tortoise, and indigo snake) and rare and endemic plants. Urban development and agriculture has greatly reduced and fragmented scrub habitat, and because of this Florida scrub is considered one of the most endangered ecosystems in the United States. Climate change is a further threat to Florida scrub. Under a warmer and drier climate, scrub species will be exposed to more frequent and more severe droughts. In order to understand how scrub will respond to a changing climate, we must first have a better understanding of how scrub species respond to climate and water availability. In this dissertation, I use a combination of dendrochronology and plant physiological techniques to examine species responses to climate and water availability. In chapter two, I use dendrochronology to examine the importance of seasonal climate on growth of three co-occurring species in Florida scrub, myrtle oak (Quercus myrtifolia Willd.), Chapman oak (Quercus chapmanii Sarg.), and south Florida slash pine (Pinus elliottii Engelmann var. densa Little & K.W. Dorman). This is the first dendrochronology study on co-occurring scrub species. Therefore, my first goal was to ask whether Chapman oak and myrtle oak put on distinct annual rings with year to year variability that would enable successful crossdating. Because I found that each species does have annual rings that can be crossdated, my second goal was to ask how growth in each species responds to climate and its extremes, drought and extreme precipitation. Growth in both oaks was positively correlated with spring precipitation, while slash pine total and latewood growth was positively correlated with April and September precipitation. Slash pine earlywood growth was positively correlated associated with increased winter precipitation. In all three species, growth was sensitive to both annual and spring droughts. However, only slash pine exhibited increased growth with precipitation associated with tropical weather during July-September. Earlywood growth of slash pine was positively correlated with the Ni[ntilde]o 3.4 index: colder, wetter winters tended to be associated with increased earlywood growth. The between-species differences in response to seasonal climate may be due to differences in growth phenology. For both oaks, the climatic limiting factor was water availability in the spring, which is when the majority of radial growth occurs. By contrast, for slash pine, growth was limited by precipitation in the spring and late summer, its peak growth period. During the period for which we have a dendrochronological record (1920 to present), precipitation in April has become increasingly correlated with growth for all three species; as it has become the driest spring month during this period. In chapter three, I use dendrochronology to determine the climate-growth relationships of the dominant oak in Florida scrub, myrtle oak, for five sites occurring on three different scrub ridges in central Florida. My goals were twofold: 1) to ask whether the climate-growth responses of myrtle oak were robust across sites and 2) to ask how myrtle oak growth was affected by droughts (determined on both seasonal and annual basis). Myrtle oak growth increased with increased spring precipitation; temperature had little effect on myrtle oak growth. The growth response of myrtle oak to moisture availability (measured by the standardized precipitation index (SPI)) in March, April, May, and June, was robust across sites, with the exception of Malabar West. Myrtle oaks at Malabar West grew on poorly drained soils and were less responsive to precipitation and drought than were oaks growing on the other sites. March, April, May, and June SPI explained between 21.5 to 58.3% of the variation in myrtle oak growth for each site. Seasonal droughts explained more of the variation in growth than annual droughts. Spring droughts decreased myrtle oak growth at all sites, and drought during the previous summer decreased growth at Malabar West. Drought impacted growth for a single year; growth was normal or greater than normal during the year after drought. These results suggest that the timing of drought is important for myrtle oak growth, and that seasonal measures of drought are more important than annual measures of drought for determining growth impacts. In chapter four, I examine how the distribution and physiological functioning of scrub species vary along the ridge-swale topography at the Kennedy Space Center. Climatic factors often limit species distributions and plant physiological functions over large elevation gradients. However, on small elevation gradients, hydrologic variation may have strong effects on the distribution of species and the physiological function within a species. I used point-intercept sampling along a ridge-swale gradient at Kennedy Space Center on Merritt Island, Florida, to study how species distribution varied over a 1.2 m elevation gradient. Data from water monitoring wells along the elevation gradient were used to ask whether elevation may serve as a proxy for depth to water table. Elevation served as a good proxy for depth to water table; water table depth increased with elevation. I focused especially on understanding how the distribution and physiological functioning of three co-occurring Florida scrub oak species (Chapman oak, sand live oak (Quercus geminata) and myrtle oak) varied along the elevation gradient. Cover of all three scrub oaks increased with increasing elevation. Only sand live oak exhibited differences in physiological functioning along the elevation gradient; individuals at lower elevations were more sensitive to drought than individuals on the ridge. All three oaks exhibited stomatal regulation of water use efficiency drought. Chapman oak did not exhibit decreased photosynthetic activity during drought. Leaf phenology may play a role in the different responses to drought exhibited.

The genus Scirpus was analyzed according to species occurrence and physiographic distribution in the State of Kentucky. The morphology of three taxonomic problem complexes, Scirpus atrovirens-georgianus, Scirpus validus-acutus, and Scirpus cyperinus-eriophorum-pelius-pedicellatus was evaluated to determine whether or not their components are distinct among the Kentucky specimens. Remaining taxa were likewise evaluated and identified. A key to Scirpus in Kentucky and a taxonomic treatment are presented.

The concentrations of sodium and potassium in the leaves of Euonymus americanus collected from a relict hardwood forest during a four month period showed a possible winter conditioning pattern. Seeds collected from this same relict stand would not germinate, even though they were subjected to a wide variety of germination experiments. Phenotypic differentiation in fully developed leaves was not found; however, differences related to the length of the growing season were noted. Autecological studies of Euonymus americanus should be continued to investigate the role of this plant in relict hardwood stands.

Arceuthobium americanum is a flowering plant which parasitizes Pinus contorta (Lodgepole pine). This study examined branch performance of P. contorta infected to varying degrees with A. americanum.

Heme Oxygenase (HO) is an enzyme universally found in animals, plants and microbes. In plants, the role of heme oxygenase in the synthesis of the phytochrome chromophore is well recognized and has been extensively studied; however its role in regulating reactive oxygen species (ROS) in plants is just beginning to be explored, particularly in legumes. Legumes interact with Rhizobium bacteria to form symbiotic nitrogen fixing nodules. ROS plays an important role in the development of roots as well as symbiotic nodules. In the model legume Medicago truncatula, ROS in the root is regulated in part by the LATD/NIP gene. The M. truncatula giraffe mutant has a deletion that removes the entire HO coding sequence. We have found that the M. truncatula GIRAFFE HO regulates expression of some of the LATD/NIP-regulated ROS genes such as RESPRATORY BURST OXIDASE HOMOLOG C (RBOHC) and a cell wall peroxidase (cwPRX2) in seedlings. This means that the wild-type function of GIRAFFE is to up-regulate expression of RBOHC and cwPRX2 in roots, in contrast to LATD/NIP, which down-regulates them. We also found that LATD/NIP and GIRAFFE do not regulate expression of each other in seedlings. Given that the highest expression of GIRAFFE HO is in a senescing nodule, we tested the expression of ROS-regulatory enzymes in senescing nodules. We found that GIRAFFE up-regulates expression of RBOHC during nitrate-induced nodule senescence. At present, with changing climatic conditions and exposure to various environmental stresses that can alter ROS homeostasis, characterizing the role of GIRAFFE in the antioxidant machinery of legumes can be useful in improving crop productivity and for enhancing soil fertility.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Plant Biology." Includes bibliographical references (p. 45-48).