Growth and element assimilation was investigated in post oak seedlings exposed to four different treatment combinations of fertilization and ectomycorrhizal inoculation. Element concentration in excised leaves was analyzed via particle induced X-ray emission spectrometry with a 1.8 MeV proton macrobeam. Mean growth was significantly different across the treatment groups as well as mean concentration of Mg, Al, S, K, Ca, Fe, Cu, and Zn. The data suggest that fertilization rather than mycorrhizal inoculation had a stronger influence on plant growth and nutrient uptake. A follow up study was conducted with a 3 MeV microbeam. A 850 μm2 scanned area of a post oak leaf produced topographical maps of 11 elements.

N-Acylethanolamines (NAEs) are endogenous plant lipids hydrolyzed by fatty acid amide hydrolase (FAAH). When wildtype Arabidopsis thaliana seeds were germinated and grown in exogenous NAE 12:0 (35 µM and above), growth was severely reduced in a concentration dependent manner. Wildtype A. thaliana seeds sown on exogenous abscisic acid (ABA) exhibited similar growth reduction to that seen with NAE treatment. AtFAAH knockouts grew and developed similarly to WT, but AtFAAH overexpressor lines show markedly enhanced sensitivity to ABA. When low levels of NAE and ABA, which have very little effect on growth alone, were combined, there was a dramatic reduction in seedling growth in all three genotypes, indicating a synergistic interaction between ABA and NAE. Notably, this synergistic arrest of seedling growth was partially reversed in the ABA insensitive (abi) mutant abi3-1, indicating that a functional ABA signaling pathway is required for the full synergistic effect. This synergistic growth arrest results in an increased accumulation of NAEs, but no concomitant increase in ABA levels. The combined NAE and ABA treatment induced a dose-dependent increase in ABI3 transcript levels, which was inversely related to growth. The ABA responsive genes AtHVA22B and RD29B also had increased expression in both NAE and ABA treatment. The abi3-1 mutant showed no expression of ABI3 and AtHVA22B, but RD29B expression remained similar to wildtype seedlings, suggesting an alternate mechanism for NAE and ABA interaction. Taken together, these data suggest that NAE metabolism acts through ABI3-dependent and independent pathways in the negative regulation of seedling development.

Although there are several fragments of vegetation in Semiarid, a lack of techniques for its recovery is observed. Most of the studies about degradation is based on the identification of the locations and degrees of desertification, and recovery practices are few, and when done, they only aim economic aspects, leaving the ecological in second plan. In this context, the present study was accomplished with the objective of evaluating the development of five species of woody plants of Caatinga under different water regimes, in a stretch of ciliary forest of the Upper Wilderness Sergipano. For this, a method of artificial vegetation recovery was applied in an environment with high degradation degree, located in Natural Monument Grota do Angico, Poço Redondo, Sergipe. In the implantation of the experiment the design was done in randomized blocks (DBC), in scheme fatorial with four repetitions, using the spacing 3x3 between the plants. In each block make up the planting of 40 seedlings of Aspidosperma pyrifolium Mart., Erythrina velutina Willd., Geoffroea spinosa Jack., Myracrodruon urundeuva Allemão and Spondias tuberosa Arruda, being 8 individuals for species. After three months, there was division of the blocks in 8 similar areas, which were randomly select. Base on this result, two treatments were used (irrigated I. and without irrigation W.I.) with four individuals for species in each block. With these data, seedling survival and growth characteristics (height, diameter at the stem and relative growth rate) were evaluated. It was verified that the general average of survival of the species after 7 months was 91,22%. Two species presented superior survival to the general average, A. pyrifolium, with 96,8%, and S. tuberosa, with 93,7%. Erythrina velutina presented higher RGR in both treatments (I. and W.I.), followed by M. urundeuva (I.), which had superior development to other species and treatments. For the growth rate in diameter, it was observed that M. urundeuva (W.I.) had higher RGR (29.30%), followed by the G. spinosa (I.) with RGR (27.52%), being observed the lowest rate of growth in stem diameter for E. velutina (W.I.), with RGR (16,93%). In the increment in height stood out the species S. tuberosa (55,63 cm (I.) and 55,50 cm (W.I.)) and E. velutina (55,16 cm (I.) and 52,03 cm (W.I.)), that presented higher development to the other species. Erythrina velutina (I. (19,0 mm) and W.I. (17,5 mm)) and Spondias tuberosa (I. (8,7 mm) and W.I. (9,3 mm)) had higher absolute values for diameter. In this study, the selected species showed high survival and development; being recommended for the recovery of riparian vegetation in that area. / Apesar de existirem muitos fragmentos de vegetação no Semiárido, observa-se uma carência de técnicas para a recuperação daqueles que se encontram em processo de degradação. A maioria dos trabalhos sobre degradação está baseada na identificação de locais e graus de desertificação, sendo que práticas de recuperação são poucas, e quando realizadas, buscam apenas aspectos econômicos, deixando o ecológico em segundo plano. Neste contexto, o presente estudo foi realizado com o objetivo de avaliar o desenvolvimento de cinco espécies de plantas lenhosas da Caatinga sob diferentes regimes hídricos, em um trecho de mata ciliar do Alto Sertão Sergipano. Para isso, foi aplicado um método de recomposição vegetal artificial em um ambiente com alto grau de degradação, localizado no Monumento Natural Grota do Angico, município de Poço Redondo, Sergipe. O delineamento na implantação do experimento foi feito em blocos casualizados (DBC), em esquema fatorial com quatro repetições, utilizando o espaçamento 3x3 m entre as plantas. Em cada bloco foi efetuado o plantio de 40 mudas de Aspidosperma pyrifolium Mart., Erythrina velutina Willd., Geoffroea spinosa Jack., Myracrodruon urundeuva Allemão e Spondias tuberosa Arruda, sendo 8 indivíduos por espécie. Após três meses, realizou-se a divisão dos blocos em 8 áreas similares, as quais foram sorteadas. Com base nesse resultado, foram empregados dois tratamentos (com irrigação C.I. e sem irrigação S.I.) com 4 indivíduos por espécies em cada bloco. Com esses dados, avaliou-se a sobrevivência das mudas e as características de crescimento (altura, diâmetro à altura do colo e taxa de crescimento relativo). Foi constatado que a média geral de sobrevivência das espécies após 7 meses foi 91,22%. Duas espécies apresentaram sobrevivência superior à média geral, A. pyrifolium, com 96,8%, e S. tuberosa, com 93,7%. Erythrina velutina apresentou maior taxa de crescimento relativo em altura nos dois tratamentos (C.I. e S.I.), seguida de M. urundeuva (C.I.), que por sua vez teve desenvolvimento superior às demais espécies e tratamentos. Para a taxa de crescimento em diâmetro do colo, observou-se que a M. urundeuva (S.I.) apresentou maior TCR (29,30%), seguido do G. spinosa (C.I.) com TCR (27,52 %). No incremento em altura destacaram-se as espécies S. tuberosa (55,63 cm (C.I.) e 55,50 cm (S.I.)) e E. velutina (55,16 cm (C.I.) e 52,03 cm (S.I.)), que apresentaram desenvolvimento superior às demais espécies. Erythrina velutina (C.I. (19,0 mm) e S.I. (17,5 mm)) e Spondias tuberosa (C.I. (8,7 mm) e S.I. (9,3 mm)) apresentaram maiores valores absolutos para diâmetro do colo. Neste estudo, as espécies selecionadas apresentaram índices de sobrevivência e desenvolvimento inicial satisfatórios, sendo indicadas para a recomposição de vegetação ciliar na referida área.

Dans le contexte du changement climatique, l’augmentation de la fréquence et de l’intensité des canicules a un impact négatif sur la physiologie des plantes, du fait de la perturbation structurale des protéines et des membranes par les fortes températures. Au cours de cette thèse, nous avons développé et caractérisé un système expérimental original dans lequel des plantules d’Arabidopsis thaliana sont arrêtées dans leur développement du fait d’une carence minérale. Ces plantules présentent une grande plasticité métabolique, notamment au niveau énergétique, qui leur permet de survivre pendant des semaines en état stationnaire. Nous avons ensuite réalisé une étude intégrative des processus qui permettent à ces plantules de survivre à un stress thermique normalement létal (43°C, 2 h), grâce à l’application d’un prétraitement à une température non létale (38°C, 2 h). Le pré-traitement à 38°C permet la protection du métabolisme énergétique ainsi que la reprise de la dynamique des organites lors de la phase de récupération. Au niveau transcriptionnel, les plantules pré-acclimatées surexpriment notamment des protéines chaperones et des gènes impliqués dans la photosynthèse et la régulation de l’expression des génomes mitochondriaux et plastidiaux. Au niveau protéique, l’accumulation d’HSPs et d’autres protéines de stress favorisent la récupération des plantules, tandis qu’en l’absence d’acclimatation, le choc thermique provoque la diminution des protéines ribosomales et l’accumulation de protéines impliquées dans la dégradation des protéines. Cette étude illustre l’intérêt de l’analyse multi-échelle pour décrypter les mécanismes de réponse des plantes aux stress. / In the context of climate change, the increased frequency and intensity of heat waves will likely have a negative impact on plant physiology, due to the structural destabilization of proteins and membranes caused by high temperatures. As part of this thesis, we developed and characterized an original experimental setup in which Arabidopsis thaliana seedlings are arrested in their development because of mineral starvation. These seedlings exhibit a high metabolic plasticity, especially for energy metabolism, which allows them to survive in a steady state for weeks. Then, we performed an integrative analysis of the processes that allow these seedlings to survive an otherwise lethal heat stress (43°C, 2 h), thanks to a priming treatment at a nonlethal temperature (38°C, 2 h). Priming protects the energy metabolism and permits the recovery of organelle dynamics after stress. At the transcriptional level, primed seedlings overexpress many chaperone proteins and genes involved in photosynthesis, and in the regulation of the expression of mitochondrial and plastidial genomes. At the protein level, the accumulation of HSPs and other stress proteins favour seedling recovery, whereas in the absence of acclimation, heat shock provokes the decrease of ribosomal proteins and the accumulation of proteins implicated in protein degradation. This study highlights the relevance of multi-scale analysis to decipher mechanisms of stress response in plants.

The lipoxygenase (LOX) pathway plays an important role in the oxidative metabolism of polyunsaturated N-acylethanolamines (PU-NAEs). The LOX pathway functions in conjugation with hydrolysis by fatty acid amide hydrolase (FAAH) and to produce oxidized NAEs during seed germination and early seedling development. When Arabidopsis seedlings were grown in low micromolar concentrations of lauroylethanolamide (NAE 12:0), growth retardation and elevated endogenous PU-NAE levels were observed due to the competitive inhibition of LOX by NAE 12:0. The elevated levels of endogenous PU-NAEs were more pronounced in genotypes with reduced NAE hydrolase capacity (faah knockouts), and less evident with overexpression of FAAH. Alterations in PU-NAE metabolism were studied in seedlings of various lox and FAAH mutants. The partitioning of PU-NAEs into oxylipin metabolites was exaggerated in the presence of exogenous linolenoylethanolamide (NAE18:3) and resulted in bleaching of cotyledons. The bleaching phenotype was restricted to a narrow developmental window (3-to-5 days after sowing), and was attributed to a reversible disruption of thylakoid membranes in chloroplasts. Biochemical and genetic evidence suggested that 9-hydro(pero)xy and 13-hydro(pero)xy octadecatrienoylethanolamides (9- and 13-NAE-H(P)OT), but not their corresponding hydro(pero)xy free fatty acids, induced cotyledon bleaching. The LOX-mediated metabolites of NAE18:3 shared some overlapping effects on seedling development with those of linoleoylethanolamide (NAE18:2) such as a reduction in seedling root growth. On the other hand, NAE18:3 oxylipin metabolites also exhibited distinct effects during seedling development such as the inhibition of photomorphogenesis. Biochemical and genetic evidence indicated that a LOX-mediated metabolite of NAE18:2, 9-hydro(pero)xy octadecadienoylethanolamide (9-NAE-H(P)OD), acted as a potent negative regulator of seedling root development, and this depended on an intact abscisic acid (ABA) signaling pathway. Synergistic inhibition of root elongation between 9-NAE-H(P)OD and ABA was restricted to a narrow developmental window (3-to-5 d after sowing) of seedling development. Genetic evidence with Arabidopsis mutants in ABA synthesis (aba1, aba2), perception (pyr1, pyl2, pyl4, pyl5, pyl8) and transcriptional regulation (abi3-1) suggested that negative regulation of growth by 9-NAE-H(P)OD likely was mediated through an increase in ABA synthesis, and this was confirmed biochemically. Induction of a secondary dormancy program in Arabidopsis seedlings by environmental stresses also requires an intact ABA signaling cascade, and our study has shown that this regulatory seedling program is dependent, in large part, on NAE oxylipin formation. Together, results presented here indicated that LOX-mediated metabolites of NAE18:3 and NAE18:2 in Arabidopsis represent a newly-discovered group of bioactive metabolites, and their accumulation during the embryo-to-seedling transition of plant development may act to synchronize seedling establishment with environmental cues.

This dissertation explores the differential effects of fires and rodent communities on native and invasive desert plant communities. Chapter one examines the impacts of fire and repeat fires on fuel loads in two different Utah desert sites, one in the cool Great Basin Desert and one in the hyper-arid Mojave Desert, over the course of four years. We found that both desert sites responded with varying intensities to a single burn, but the effects of a reburn were not as pronounced. We also found that our Great Basin Desert site had a stronger response to fire than our Mojave Desert site, producing a higher plant fuel loads that could potentially exacerbate the changing fire regimes. These data can be used to help map the effects that climate change may have on fuel loads and the fire potential of these deserts. Chapter two uses a full factorial experimental design to compare the effects of rodent herbivory and fire on native versus invasive seedlings at our Mojave Desert field site. We found that rodent herbivory has a more negative impact on the survival of native seedlings than invasive seedlings. This could be because the invasives are grasses that tend to tolerate herbivory better than the native shrubs and forbs. Chapter three again uses a full factorial experimental design to assess the impacts of rodents and fire on the fate of native and invasive seeds at our field site in the Mojave Desert. We found that rodents removed seeds, and they did show preferences for some species of seed over others, but these preferences were not different between native and invasive seeds or seed mass. We propose that the preferences may be influenced by other seed traits such as water content, handling time or physical and chemical defenses. As with the seedlings in chapter two, fire did not have any impact on rodent seed preferences. These data highlight the importance of considering rodent effects on seeds used in restoration effects following wildfires.

WRINKLED1 (AtWRI1) is a key transcription factor in the regulation of plant oil synthesis in seed and non-seed tissues. The structural features of WRI1 important for its function are not well understood. Comparison of WRI1 orthologs across many diverse plant species revealed a conserved 9 bp exon encoding the amino acids “VYL”. Site-directed mutagenesis of amino acids within the ‘VYL’ exon of AtWRI1 failed to restore the full oil content of wri1-1 seeds, providing direct evidence for an essential role of this small exon in AtWRI1 function. Arabidopsis WRI1 is predicted to have three alternative splice forms. To understand expression of these splice forms we performed RNASeq of Arabidopsis developing seeds and queried other EST and RNASeq databases from several tissues and plant species. In all cases, only one splice form was detected and VYL was observed in transcripts of all WRI1 orthologs investigated. We also characterized a phylogenetically distant WRI1 ortholog (EgWRI1) as an example of a non-seed isoform that is highly expressed in the mesocarp tissue of oil palm. The C-terminal region of EgWRI1 is over 90 amino acids shorter than AtWRI1 and has surprisingly low sequence conservation. Nevertheless, the EgWRI1 protein can restore multiple phenotypes of the Arabidopsis wri1-1 loss-of-function mutant, including reduced seed oil, the “wrinkled” seed coat, reduced seed germination, and impaired seedling establishment. Taken together, this study provides an example of combining phylogenetic analysis with mutagenesis, deep-sequencing technology and computational analysis to examine key elements of the structure and function of the WRI1 plant transcription factor.

A short duration-high intensity grazing trial was conducted in spring of 1985 to determine whether shrub establishment in crested wheatgrass pastures could be enhanced through spring grazing by cattle, or by fertilization of shrub seedlings. Data was collected on diet selection by cattle during spring grazing, and on subsequent shrub growth and survival. Shrubs studied were transplants of sagebrush, Artemisia tridentata, fourwing saltbush, Atriplex canescens, bitterbrush, Purshia tridentata, and one year old bitterbrush seedlings. Cattle did not browse sagebrush or fourwing saltbush transplants, but utilization of bitterbrush transplants and seedlings averaged 15 and 42 percent, respectively. Shrub selection by cattle was unaffected by grazing pressure or fertilization. Fertilization increased growth of sagebrush transplants but had no effect on survival. Trampling of shrubs was greater than anticipated. Trampling reduced growth in sagebrush, and reduced survival of both bitterbrush and sagebrush transplants. Browsing reduced growth of bitterbrush seedlings, but increased growth and survival of bitterbrush transplants. Despite adverse effects from trampling and browsing on some shrubs, the overall effect of spring grazing of crested wheatgrass by cattle was to enhance establishment of fourwing saltbush and bitterbrush transplants. Spring grazing had no measurable effect on establishment of sagebrush transplants or on survival of one year old bitterbrush seedlings.

No description available.

Alteration of river flow regimes due to dams result in modifications of riparian ecosystem, with impacts on vegetation, landforms, and habitats. A key characteristic that differentiates riparian zones from adjacent aquatic and terrestrial environments is the event of periodic flooding and water logging. In the regulated Dalälven and other regulated rivers, the Norway spruce (Picea abies) has been seen to replace deciduous hardwood forests over the years due to decrease in the frequency and duration of floods. This thesis aims to gain knowledge on the inundation duration needed to maintain riparian forests with deciduous hardwood trees along the regulated Dalälven. A laboratory experiment was conducted to assess the sensitivity of spruce seedlings to inundation with treatments varying in duration and depth of inundation and level of oxygenation. My hypotheses were that (1) mortality of spruce seedlings would be higher with complete submergence compared to only soils being waterlogged, and that (2) mortality would increase with duration of inundation, and (3) the mortality of spruce seedlings would be higher without oxygenation of water. The data was analyzed by comparing the plant vitality among treatments using analysis of variance using a binary logistic regression. The results indicated that as inundation time increased, the mortality of the seedlings increased. Since the laboratory experiment showed that a large proportion of spruce seedling died after being inundated for 22 and 44 days, reintroductions of floods shorter than the natural spring floods lasting about 1.5 months may be enough to aid in restore riparian forests dominated by oaks and other deciduous hardwood trees, e.g., in the regulated Dalälven river.