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1
Wood, Christopher. "Oxidative stress and seed survival." Thesis, Abertay University, 1998. https://rke.abertay.ac.uk/en/studentTheses/79d28b74-9210-4ebd-a3b8-66a610bd8c87.
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Free radical and aldehydic breakdown product content were determined, by EPR and UV / visible spectroscopy, primarily in intermediate (desiccation tolerant) seeds of Carica papaya L. (Papaya) and recalcitrant (desiccation intolerant) seeds of Aesculus hippocastanum L. (Horse chestnut), but also in other species covering a range of desiccation tolerances, with a view to determining the role of oxidative stress as a diagnostic marker for desiccation tolerance. Axes of non-senescent highly viable recalcitrant seeds of horse chestnut were metabolically active, contained products of lipid peroxidation, displayed low levels of enzymatic protection against activated oxygen and peroxides, and a two-peak free radical EPR signal. During fully hydrated storage at 16 °C for up to 18 months, seeds exhibited, sequentially, an increase in germination rate, a transient increase in intensities of both the low field and high field EPR peaks, a significant increase in membrane leakage and decrease in seed viability, germination rate, and SOD and peroxidase activities. Drying 'unstored' seeds below and embryonic axis moisture content of 40 to 50 % initiated viability loss. At < 25 % moisture content all axes were inviable and displayed a 2- to 4-fold increase in solute leakage, lipid peroxidation products and the low field EPR signal. Seed desiccation sensitivity increased with hydrated storage. The accumulation of lipid peroxidation products and free radicals on drying generally occurred to a greater extent, or at a higher moisture content, than observed with unstored seeds. The results indicate a mediating role for oxidative stress in recalcitrant seed viability loss which is differentially expressed during hydrated, 'natural' ageing and desiccation. Similar trends were seen in other recalcitrant species with the increase in lipid peroxidation products occurring around the point of viability loss. However the study of a more orthodox species (papaya) revealed no such trends.
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Butler, Laura Helen. "Seed development, re-hydration and variation in seed survival." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440098.
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Leon-Lobos. "Nothofagus and Fagus seed survival after dessication and storage." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339979.
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Kuprewicz, Erin Kathleen. "The Effects of Large Terrestrial Mammals on Seed Fates, Hoarding, and Seedling Survival in a Costa Rican Rain Forest." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/391.
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Terrestrial mammals affect numerous aspects of plant demography, colonization, and community structure in Neotropical forests. Granivorous mammals destroy seeds via seed predation and seedlings through herbivory, negatively affecting plant fitness. Mammals can also positively affect plants by dispersing or hoarding seeds. Seed fate outcomes are contingent on the interaction between mammal seed handling strategies and the intrinsic anti-predation defenses possessed by seeds. In field experiments at La Selva Biological Station, I investigated how collared peccaries (Pecari tajacu) and Central American agoutis (Dasyprocta punctata) affect five species of large seeds that have various defenses against predation. Overall, peccaries consumed and killed most non-defended and chemically-defended seeds but they could not destroy seeds with physical defenses. Agoutis killed non-defended and physically-defended seeds, but not seeds with chemical defenses. Using seeds of Mucuna holtonii, I investigated how chemical and structural defenses deter mammal and insect seed predation respectively. I also determined how endosperm removal by invertebrates affects seed germination and seedling biomass. Chemical defenses protected seeds from rodents, but not ungulates that digest seeds via pregastric fermentation. Physical defenses protected seeds from invertebrate seed predators, and removal of endosperm negatively affected both seed germination and seedling growth. To determine how scatter-hoarding by agoutis affects seed escape from seed predators, germination, and seedling growth, I created simulated agouti hoards. I also investigated how mammals affect young seedling survival. Hoarding enhanced seed survival, germination, and seedling growth for most species of seeds. Terrestrial mammals killed some seedlings via seed predation rather than by herbivory. Overall, large mammal activity in La Selva negatively affected seed and seedling survival and this likely influences many aspects of forest dynamics.
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De, Villiers Rykie (Rykie Jacoba). "The influence of chemical seed treatment on germination, seedling survival and yield of canola." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/50163.
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Thesis (MScAgric)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The influence of chemical seed treatments on the germination, seedling survival and yield of canola (cv. Varola 44) was investigated in a series of incubation studies, glasshouse experiments, as well as field trials in the canola producing areas in the Western Cape Province. Incubation experiments were conducted to compare germination and seedling growth of untreated (control) seed with that of seed treated at different application rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® and SA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 g a.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The results indicated that seed treatment (all rates of SA-combination and highest rate of Cruiser) delayed germination and seedling growth, especially if the seed was subjected to the Accelerated Ageing Test. Glasshouse studies with pasteurised soil at different water contents, seed sources (storage periods) and planting depths confirmed the phytotoxic effects of the chemical seed treatments in the absence of soil borne pathogens. From the results it became clear that extreme water conditions (very wet or dry) increased the suppressing effect on germination and seedling growth, but that no phytotoxic reactions occurred in moist (favourable soil water conditions) soil, regardless of application rate of the chemicals used, planting depth and seed source. In a second glasshouse experiment conducted in moist soil (kept at 50% of field water capacity to prevent any toxic effects) from seven different localities that were naturally infested with pathogens, both chemicals proved to be effective where soil borne pathogens (Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could however be found due to either chemical or application rates used. Finally, field trials were conducted to study the effect of chemical seed treatments on the plant populations and yield of canola planted in different row widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Results showed that treated seeds produced more plants.rn" and yielded more than untreated seeds at Roodebloem Experimental Farm, while the highest seeding rate produced significantly more plants.rn" (Roodebloem and Langgewens Experimental Farms), but not significantly higher yields than the lowest seeding rate at the same locality. Although row width did not have an effect on plant population, yield (Roodebloem 2003) was significantly less at the wider (34 cm) rows. As in earlier experiments, no consistent differences between the two chemicals used were found. These results clearly illustrated both the negative (in the absence of pathogens) and positive (where soil borne pathogens do occur) effects that chemical seed treatments may have on the germination, seedling growth and even yield of canola under local environmental and soil conditions. Because no significant differences were found between the chemicals used, both chemicals should be regarded as efficient. More research, especially under field conditions and with more cultivars, is needed before the registration of a chemical for seed treatment could be considered.
AFRIKAANSE OPSOMMING: Die invloed van chemiese saadbehandeling op die ontkieming, saailing oorlewing en opbrengs van canola (cv. Varola 44) is ondersoek in 'n reeks inkubasie studies, glashuis eksperimente en veldproewe in die canolaproduserende gebiede in die Wes Kaap Provinsie. Inkubasie eksperimente is uitgevoer om die ontkieming en saailing groei van onbehandelde (kontrole) saad te vergelyk met dié van saad wat behandel is teen verskillende dosisse (0.5, 1.0 en 2.0 keer die aanbevole) van Cruiser® en SA-kombinasie (wat bestaan uit Thiulin® teen 0.5g a.i.; Apron® teen 0.0815 g a.i.; Gaucho® teen 0.6125 g a.i. en Rovral® teen 0.9975 g a.i.). Die resultate het aangedui dat saadbehandeling (vir alle dosisse van SAkombinasie en die hoogste dosis van Cruiser) ontkieming en saailing groei vertraag, veral wanneer die saad onderwerp was aan die Versnelde Verouderings Toets. Glashuis studies met gepasteuriseerde grond by verskillende waterinhoude, saad bronne (stoor periodes) en plantdieptes, het die fitotoksiese effekte van die chemiese saadbehandelings bevestig in die afwesigheid van grondgedraagde patogene. Vanuit die resultate het dit duidelik geword dat ekstreme water toestande (baie nat of droog) die onderdrukkende effek op ontkieming en saailinggroei verhoog het, maar dat geen fitotoksiese reaksies plaasgevind het in klam (gunstige grondwater toestande) grond nie, ongeag die dosisse of chemikalieë gebruik, plantdiepte en saad bron. In 'n tweede glashuis eksperiment uitgevoer in klam grond (gehou by 50% van veldwaterkapasiteit om toksiese effekte te voorkom) van sewe lokaliteite wat natuurlik besmet was met patogene, was beide chemikalië effektief waar grondgedraagde patogene (Rhizoctonia so/ani en Pythium spp.) voorgekom het. Geen duidelike tendens is egter waargeneem vir enige van die chemikalieë of dosisse nie. Laastens is veldproewe uitgevoer om die effek van chemiese saadbehandelings op plant populasies en opbrengs te bepaal van canola geplant in verskillende rywydtes (17 en 34 cm) en saaidigthede (3, 5 en 7 kg.ha-1). Resultate het aangedui dat behandelde saad meer plante.rn" produseer en 'n groter opbrengs lewer as onbehandelde saad by Roodebloem Eksperimentele Plaas, terwyl die hoogste saaidigtheid betekenisvol meer plante.m" (Roodebloem en Langgewens Eksperimentele Plase), maar nie betekenisvol hoër opbrengste gelewer het as die laagste saaidigtheid by dieselfde lokaliteit nie. AI het rywydte nie 'n effek op plant populasie gehad nie, was opbrengs (Roodebloem 2003) betekenisvol minder by die wyer (34 cm) rye. Soos in vroeëre eksperimente is geen konsekwente verskille tussen die twee chemikalieë gevind nie. Hierdie resultate illustreer duidelik beide negatiewe (in die afwesigheid van grondgedraagde patogene) en positiewe (in die aanwesigheid van grondgedraagde patogene) effekte wat chemiese saadbehandelings op ontkieming, saailing groei en selfs opbrengs van canola onder plaaslike omgewings en grondtoestande kan hê. Omdat geen betekenisvolle verskille tussen die chemikalieë gevind is nie, moet beide chemikalieë as doeltreffend aanvaar word. Meer navorsing, veralonder veldtoestande en met meer kultivars, is egter nodig voordat die registrasie van 'n chemiese middel vir saadbehandeling oorweeg kan word.
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Johansson, Björn. "Stay below water! - a strategy to avoid seed predators : - seed survival and germination of Mauritia flexuosa in southeastern Peru." Thesis, Ecology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19930.
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The tropical palm Mauritia flexuosa has highly nutritious fruits and is an important food resource for both humans and wildlife throughout its geographic range in South America. Unsustainable harvesting threatens wild populations. Mauritia f. occurs primarily in wetlands called Aguajales where it can become the dominating canopy species. Seed predation and dispersal can dramatically affect the survival and distribution of plant species in tropical rainforests (Janzen 1970, Connell 1971, Bleher & Böhning-Gaese 2001, Paine & Beck 2007, Mari et al. 2008). Increased knowledge of seed predation and germination requirements is essential for successful management of this commercially and ecologically important palm. Four experiments were conducted in Manu National Park in southeastern Peru to study: (1) Seed survival in the Aguajal, (2) Quantify seed predators on dry land, (3) Insect visitors and consumers of fruits and seeds, and (4) Germination in greenhouse experiments. Seed survival was significantly higher below water compared to on dry micro sites within the Aguajal. Seeds and fruits placed on dry land were preyed upon by both insects and mammals. Terrestrial insects were the most important predators. Different insects visited fruits and seeds, indicating a successive breakdown of different tissues. Seed survival was also higher below water and/or soil in the greenhouse experiment. This may suggest that the distribution of Mauritia f. is highly influenced by seed predation and that water protects seeds from their insect enemies.
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Roselli, Sasha Mahani. "The role of seed dispersal, seed predation and drought in the restoration of Ngel Nyaki Forest, Nigeria." Thesis, University of Canterbury. School of Biological Sciences, 2014. http://hdl.handle.net/10092/9967.
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The restoration of degraded landscapes has become one of our most valuable tools for conservation, however there are many factors which can restrict natural regeneration and impede active restoration attempts. The purpose of this study was to investigate three key processes which commonly limit the establishment of forest tree species into abandoned pasture in tropical forests: i) dispersal limitation, ii) seed predation, and iii) competition from the grass sward.
Seed dispersal
I identified 59 species of birds that were using the grassland habitat. Through 216 hours of focal tree observations I established that isolated trees in the grassland that had larger canopies, and those that were providing a food source (i.e. flowers or fruit) had significantly higher bird visitation rates and average stay lengths. I found evidence of the “perch effect” as patches of remnant trees encouraged more birds into areas of grassland, and the density of seedlings under tree canopies was significantly positively correlated with bird visitations. 95% of the seedlings found beneath tree canopies in grassland were of a different species to that of the tree canopy above them, demonstrating the dispersal of seeds from elsewhere into these microhabitats. 98% of these seedlings are grassland or forest edge species showing forest core species are still dispersal or microsite limited despite the effect of these trees.
Seed predation
Removal rates of seeds from experimentally laid out seed piles varied among seed species, the habitat the pile was in, and the predator guild able to access the piles. Preliminary results indicate that these trends are driven by the ecology of the seed predator. Removal of seeds by vertebrates was highest in the core forest, while ant predation was constant across all habitats. Vertebrates removed the larger seeds (Entandrophragma angolense and Sterculia tragacantha) while ants preferred the smaller Celtis gomphophylla and Croton macrostachyus. Overall predation rates in grassland were lower than those in the forest, and the presence of remnant trees did not influence predation rates, a positive sign for regeneration and the survival of seeds dispersed into these areas.
Competition from the grass sward
While the grass sward provides shade for seedlings of forest tree species it is also a harsh environment for them, as the grass competes with seedlings for water. Removing the grass and covering planted seedlings with artificial shading structures significantly increased both the survival and growth of these seedlings.
Recommendations
From this study I was able to make recommendations for a low input restoration program at Ngel Nyaki. Planting seedlings in small „islands‟ takes advantage of the natural increase in dispersal of seeds under isolated trees, while low seed predation rates increase the chance of survival of these seeds to germination. Planting these seedlings under shade will lead to increases both their growth rates and their survival. Once the secondary forest develops, under-planting seedlings of core forest trees will introduce them to the system, as the natural establishment of these seeds appears to be limited in the current environment. This study has also served to remind us how little we know about this particular forest-grassland system, and has led to the development of ideas for further investigations into several more aspects of regeneration.
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Weatherall-Thomas, Clayton Richard. "Seed dynamics and seedling survival in mainland thicket of the Eastern Cape." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1048.
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Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.
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Melifronidou, Anthemis Ioanni. "Influence of storage conditions and fungal activity on the survival of vegetable seeds." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308208.
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Santos, Marta Sofia Sousa. "Efeito de pré-tratamentos na germinação de sementes da espécie Corema album L.(subsp. album)." Master's thesis, ISA, 2013. http://hdl.handle.net/10400.5/6462.
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Mestrado em Engenharia Agronómica - Hortofruticultura e Viticultura - Instituto Superior de AgronomiaCorema album (Ericaceae) endemic of the Atlantic dunes of the Iberian Peninsula has the possibility to become a new niche berry crop. Considering the agronomic and market possibilities for this specie we characterized C. album populations along its biogeographical area. The results show that different seeds characteristics differ significantly between sites. We also tested the effect of pretreatments on the germination of C. album seeds (subsp. album). Seeds were collected from Duna de Quiaios in 2011, from Comporta in 2011 and Aldeia do Meco in 2011 and in 2012. The results show that there is site-to-site variation in the same year and year-to-year variation in a particular site in percentage of germinated seeds. Acid scarification (30, 60 and 120 minutes) followed by 1000 ppm of gibberellic acid was the most effective pretreatment in breaking dormancy of C. album and this pretreatment promote the best germination from seeds collected from Aldeia do Meco 2011 (30.3%) after 175 days. Our results suggest that the seeds had morphophysiological dormancy. Considering the 4600 seeds collected: 54.5% had ruptured the seed coat, 7.4% had germinated and seedling survival was 0.1%.
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Mallinson, Julian Robert. "The impact of herbivores on the natural regeneration of temperate deciduous woodland." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4591/.
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Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment.
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Lönnberg, Karin. "Effects of seed size and habitat on recruitment patterns in grassland and forest plants." Doctoral thesis, Stockholms universitet, Botaniska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-82384.
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A trade-off between seed size and seed number is central in seed ecology, and has been suggested to be related to a trade-off between competition and colonization, as well as to a trade-off between stress tolerance and fecundity. Large seeds endure hazards during establishment, such as shading, drought, litter coverage and competition from other plants, better than do small seeds, due to a larger amount of stored resources in the seed. Small seeds, however, are numerous and small-seeded species are therefore more fecund. Moreover, a pattern with small-seeded species being associated with open habitats and large-seeded species being associated with closed habitats has been reported in the literature. In this thesis I assess effects of seed size on recruitment, and how relationships between seed size and recruitment may relate to habitat conditions. Seed sowing experiments were performed in the field to assess inter- and intra-specific relationships between seed size and recruitment in open and closed habitats (Paper I and II). Seed removal experiments were performed in the field to assess what effects seed predation may have on a relationship between seed size and recruitment (Paper III). A garden experiment was performed based on contests between larger-seeded and smaller-seeded species, in order to examine different models on co-existence of multiple seed size strategies. The results showed that there was a weak positive relationship between seed size and recruitment in the field, and that this relationship was only weakly and inconclusively related to habitat (Paper I and II). Seed removal was negatively related to seed size in closed habitats and unrelated to seed size in open habitats (Paper III). This indicates that any positive relationship between seed size and recruitment may be an effect of higher seed removal in small-seeded species. However, when grown under controlled conditions in a garden experiment, there was a clear advantage of larger-seeded species over smaller-seeded species (Paper IV). This advantage was unaffected by seed density, indicating that there was no competitive advantage of the larger-seeded species. Instead, indirect evidence suggests that larger-seeded species exhibit higher tolerance to stress.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.
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Hobani, Ali Ibrahim Bokar. "The effect of strong water absorbers on the survival of pelleted seed in the arid areas." Thesis, Cranfield University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358021.
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Willis, Blake D. "Burning, Flaming and Herbicides for Control of Jointed Goatgrass (Aegilops cylindrica Host.)." DigitalCommons@USU, 1990. https://digitalcommons.usu.edu/etd/4682.
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Winter wheat stubble and dried plant residue in Conservation Reserve Program (CRP) fields were burned in the fall and spring to evaluate effects on jointed goatgrass (Aegilops cylindrica Host.) seed survival and germination. Laboratory studies were also conducted to determine minimum temperatures and heat duration needed to reduce jointed goatgrass seed viability. Maximum air temperatures attained during various field burns reached from 74 C to over 700 C. Temperatures 2.5 em above the soil surface remained above 400 C for over 10 seconds and above 600 C for 2 to 8 seconds in burning CRP stubble. Results for the winter wheat stubble location were similar with temperatures sustained above 400 C for over 30 seconds.
Seed exposure in the lab to 400 and 600 C flames for 1 second reduced germination to 20 and 15 percent, respectively. Germination was reduced to zero with exposures of 10 seconds or more. Oven temperatures of 150 C reduced germination to 85, 57.5, 17.5, 0 and 0 percent for exposures of 20, 30, 60, 120 and 300 seconds, respectively. At 275 C oven temperature germinability dropped to 50% after a 10 second exposure and 0% after a 20 second exposure.
Jointed goatgrass plant populations were reduced 54 to 92% after field burning in the spring or fall. Fall burning provided 70 to 85% control of goatgrass the following spring. In non-burned non-disked plots over 90% of emerging plants germinated from seeds on the soil surface. In burned non-disked plots few seeds germinated from on the surface, with 80 to 90 percent of surviving plants having germinated from buried seed.
Herbicides provided limited control of jointed goatgrass. None of the herbicides provided greater than 50% control.
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Serafim, João Afonso Machado Pinto de Aguiar. "Assessing the role of macro- and microclimate on Holm oak performance in Mediterranean drylands." Master's thesis, ISA, 2019. http://hdl.handle.net/10400.5/21285.
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Mestrado em Biologia dos Recursos Vegetais / Instituto Superior de Agronomia / Faculdade de Ciências. Universidade de LisboaMediterranean drylands are expected to become drier due to climate change. This may aggravate desertification by increasing dryland susceptibility to land degradation, leading to the loss of biodiversity and ability to provide ecosystem services. In Mediterranean Basin drylands, a large area is occupied by oak woodlands, a semi-natural agro-silvopastoral system called Montado in Portugal. In the drier areas, where Montado seems to act as a buffer against desertification, the dominant tree species is Holm oak (Quercus ilex subsp. rotundifolia), However, in the last decades, a declining trend has been reported for Holm oak woodlands, mostly attributed to unsustainable land management, biotic factors and to an increase in aridity at a regional scale. Also, at a local scale, it has been shown that microclimate conditions driven by topography have a major influence on this species natural regeneration rates. Over the last decades, many (re)afforestation with Holm oak have been implemented to revert Montado’s decline and combat desertification, although not always successful. The aim of this work was to study the effect of macro- and microclimate on Holm oak performance, specifically on acorn germination and first summer seedling survival. Holm oak acorns were collected along a climatic gradient based on long-term precipitation (30 yrs.), resulting in 6 macroclimate provenances. In 2 sites, the driest and the wettest sites of the gradient, areas with contrasting microclimates were selected using Potential Solar Radiation (PSR) as a proxy of microclimate conditions. Holm oak performance was, thus, studied along a macroclimate gradient and in microclimate contrasting conditions. Holm oak acorns from each provenance where characterized biometrically and acorn production evaluated. Germination of acorns and seedling survival were evaluated under greenhouse similar conditions and in the field under contrasting macro- and microclimate conditions. We found that macro- and microclimatic provenance influences acorn size and germination. Drier sites and more exposed areas (higher PSR) had bigger acorns with higher germination. Field conditions did not seem to affect germination but rather the first summer seedling survival. The survival of Holm oak seedlings to the first summer was significantly higher in the wetter site and in less exposed areas than in the drier site and in more exposed areas. This work provides guidelines to increase Holm oak seedling quantity and quality in nurseries to be used in (re)afforestation plans and to improve Holm oak young seedling survival, either by focusing (re)afforestation in microclimatic favorable areas (using remote sensing derived information like PSR), or by providing additional assistance to seedlings growing in drier and/or more exposed areas. In addition, it may also help to better understand Holm oak seedling mortality and/or natural regeneration patterns. Hence, these findings may contribute to improve the success of Holm oak (re)afforestation as a critical restoration tool to combat desertification in Portuguese drylands, and revert Holm oak Montado’s decline, particularly under a climate change scenario
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Taylor, Matthew Gary. "Impact of Planting Date, Cultivar, Phosphorus, Potassium, and Fungicide Seed Treatments on Winter Wheat Survival and Yield." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27261.
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Field experiments and greenhouse studies were conducted to evaluate the effects of phosphorus (P), potassium (K), and fungicides on winter survival, and yield of winter-wheat in North Dakota. The study was conducted as a RCBD with a split-plot of planting date, and a factorial combination of cultivars and seed treatments. Of the factors included, cultivar was the most contributing factor for fall emergence, spring stand count, and yield. Planting date was confounded by insufficient autumn soil moisture, delaying emergence approximately 50% at Minot, Williston, and Hettinger. Phosphorus, K, and fungicide treatment effects were not consistent across locations, but fungicide, priming and selected P and K treatments increased stand count or yield at Hettinger, Williston, and Lisbon. These data indicate the use of winter-hardy cultivars, fungicides, and favorable conditions in the fall for emergence are critical factors for growing winter wheat in North Dakota.
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Pace, Brian A. "Maternal effects on multiple generations of Helianthus annuus crop-wild hybrid seed: overwinter germination, dormancy and survival." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354696610.
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Holm, Stig-Olov. "Reproductive patterns of birches (Betula spp.) in northern Sweden." Doctoral thesis, Umeå universitet, 1994. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96884.
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The aim of this thesis was to study patterns of reproduction of Betula pendula and B. pubescens coll. along an altitudinal, coastal-inland, gradient in northern Sweden. The altitudinal variation was related to the distribution of the birch taxa along the gradient. Six years field data showed a steep decrease of seed germinability of B. pendula towards its altitudinal range limit in the Scandes every year. In contrast, B. pubescens ssp. pubescens showed significant positive correlations between seed germinability and altitude in three of the six years. Furthermore, there was a highly significant positive correlation between seed weight and altitude for B. pubescens coll., but not for B. pendula. Production of viable seeds fluctuated strongly between years in most populations, except in marginal B. pendula populations in the mountain area where it was constantly very low. On average 15 - 41 % of the seeds produced in B. pendula populations above 400 m altitude were attacked by gall midges (Semudobia ssp.). Corresponding values for B. pendula populations below 400 m altitude were 4 - 7 %. In B. pubescens populations, the seeds attacked by Semudobia ssp. never exceeded 3 %. The high frequency of Semudobia attackes in high altitude marginal B. pendula populations was suggested to be due to limited resources for defense against the seed predator. A 3-yr study documented large variations in pollination and seed quality between taxa, high and low altitude populations, and between years. Empty seeds (without embryos) dominated among the sampled seeds in most cases. This proportion was decreased by pollen addition, in both B. pendula and B. pubescens, in mountain populations, but not in coastal populations. The high percentage of empty seeds was therefore suggested to be partly caused by pollen-limitation, but failure of pollen tube penetration - fertilisation, or maternal resource supply could also have had an influence. A laboratory experiment showed increased pollen germination and length of the longest pollen tube per style after increased pollination. The correlations between number and length of pollen tubes per style were however mostly low in natural populations, suggesting low probability of pollen competition in the natural situation. Sowing experiments indicated that differences in initial seedling density between B. pendula and B. pubescens was more affected by interspecific differences in seed quality than by interspecific differences in survival of seedlings after establishment A study of the age structure of a B. pendula stand, planted about 250 m above its natural altitudinal limit, indicated that this birch may reproduce above its recent range limit during temporally warmer periods. It was concluded that the level of accumulated resources in B. pendula in marginal sites in the Scandes would mostly be too low for completion of the reproductive cycle. In contrast, B. pubescens ssp. pubescens is able to accumulate enough rescources for reproduction also at relative high altitudes.Diss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 5 uppsatser.
digitalisering@umu
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Sagra, Javier, Daniel Moya, Pedro Plaza-Álvarez, Manuel Lucas-Borja, Raquel Alfaro-Sánchez, Las Heras Jorge De, and Pablo Ferrandis. "Predation on Early Recruitment in Mediterranean Forests after Prescribed Fires." MDPI AG, 2017. http://hdl.handle.net/10150/625399.
Full textAbstract:
Wildfires play a significant role in many different elements of Mediterranean forest ecosystems. In recent years, prescribed fires have started being used more often as a fuel reduction tool, and also as silvicultural treatment to help the regeneration and health improvement of stands. Apart from the fact that fire may alter microsite conditions, very little is known about the impact of prescribed burning on natural regeneration or plant species renewal in Mediterranean pine forests. Likewise, knowledge about the influence of seedling predators on post-fire regeneration is still scarce. In this study, we aimed to compare the effects of seedling predation on recruitment in earlier stages after prescribed burnings in three pine stands in Central Spain: a pure stand of Pinus nigra; a mixed stand of Pinus halepensis and Pinus pinaster and a mixed stand P. nigra with P. pinaster. In situ we superficially sowed seeds from two different species. In the sowing experiment, we tested two different seed provenances (drier and more humid spanish regions) for each species. In all, 60 plots (30 burned, 30 unburned) per site, with 10 seeding units per plot and more than 20,000 seeds, were used in the whole study. Seedling predation was evaluated by replicating the seeding units inside and outside a wire cage as protection for rodents and birds. Our results showed that prescribed fires alter initial seedling predation intensity: predation was significantly higher in the seedlings grown in the plots affected by prescribed fire. The individuals sown before the fire passed showed slightly more predation than those sown after fire passage. Provenances did not appear as an important predation drive. Understanding the role of the predation associated with these treatments can help improve Mediterranean pine forest management.
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Rowan, Lisa S. "Effects of Asphondylia borrichiae, Simulated Herbivory, and Nutritional Status on Survival, Flowering, and Seed Viability in Sea Oxeye Daisy (Borrichia frutescens)." UNF Digital Commons, 2014. http://digitalcommons.unf.edu/etd/500.
Full textAbstract:
Although herbivory and other types of plant damage typically are viewed as detrimental to plant survival and performance, vigorous regrowth, greater seed set, and fitness benefits may be possible when damage to the apical meristem, or actively growing stem terminal, is involved. Such damage releases apical dominance, or the hormonal suppression of lateral buds, activates dormant lateral buds, and enables lateral shoots to grow. Since in plants with terminal flowers, each stem may bear a flower, removal of the apical meristem may result in stem bifurcation and ultimately increase the number of flowers and seeds, thereby increasing potential fitness. In the current study, possible overcompensation in response to apical meristem damage caused by simulated herbivory (clipping) and the gall midge Asphondylia borrichiae Rossi and Strong (Diptera: Cecidomyiidae) (galling) was investigated in the native coastal halophyte, sea oxeye daisy Borrichia frutescens (L.) DC. (Asteraceae), in relation to nutrient supplementation. Results suggest a strong correlation between stem count and gall count at the study site; moreover, apical dominance was relatively weak early in the growing season and stronger in short plants that were shaded by taller neighbors later in the season. Results also indicate that overcompensation or even full compensation is an unlikely response to apical meristem damage in B. frutescens. Stem count was similar across all stem treatments, but increased significantly with nutrient supplementation, which all supports weak apical dominance in sea oxeye daisy. Nearly all measures of fitness also were either slightly or significantly lower when clipped and galled compared to plants with stems intact, while seed count responded positively to nutrient supplementation.
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Munro, Sioban Lucille. "Seedling growth and survival, in relation to seed size and phosphorus content, of six Fynbos Proteaceae species deprived of single mineral nutrients." Thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26312.
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Guindal, Estévez Guillermo. "Impacts of hydropower dams operations on plants : A greenhouse experiment on the response of germination and performance and survival of plant seedlings to direct and indirect effects of hydrological alterations resulting from hydropower dam operations." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105157.
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This work helps increasing our general understanding of how plants behave under altered hydrological conditions which occur along rivers regulated by hydropower dams. Usually, natural-real environments are highly unpredictable. Consequently, research based on field data becomes challenging and results may contain uncertainty. Here, an experimental design in a greenhouse is developed. Several measured attributes of selected plant species related to germinability, performance and survival were used as indicators of the impact of watering treatments which mimic hydrological regime spilled through hydropower dams. Specifically, direct effect
of water availability changes, water fluctuation and water flooding, and indirect effect through derived erosion, were tested. Results benefitted from indoors controlled conditions. They showed significant different responses depending on species and hydrological changes. In general, Helianthus annuus was slightly affected. It deal well flooding conditions, and was comparatively more affected by water fluctuation and stress. Carex and Filipendula species showed the highest sensitivities to flow. They hardly germinated under any water treatment (few germinations under flooding for Carex and few under water fluctuation for Filipendula) and performance was very low for germinates. Betula pubescens was in between. Contrarily to Helianthus, it was severely affected by flooding, and also for water fluctuation. It survived water stress better than Helianthus, but looked unhealthy. All species seeds but Helianthus were highly eroded. However, erosion resulting from water fluctuation was relatively higher than from prolonged flooding. Differing responses are the result of morphological and physiological characteristics of the species which enable them to success under certain stressful conditions, such as water scarcity and anoxia. These results objectively inform about tolerance limits of selected species to key hydrological conditions and are useful for riparian areas management and environmental flows designs.
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Kulakkattolickal, Augusthy Thevasia. "The effects of surface access and dissolved oxygen levels on survival time of a water-breathing and an air-breathing fish species exposed to a plant toxin (Croton tiglium, Euphorbiaceae, seed extract) /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66223.
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Bekele, Tesfaye. "Plant Population Dynamics of Dodonaea angustifolia and Olea europaea ssp. cuspidata in Dry Afromontane Forests of Ethiopia." Doctoral thesis, Uppsala universitet, Institutionen för evolutionsbiologi, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-493.
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Human disturbance has led to excessive deforestation and to a very limited forest cover in the Afromontane zone of Ethiopia, which forms a large part of the country. Thus urgent conservation measures are required to ameliorate the situation. Understanding the natural regeneration processes and the dynamics of plant populations of tree and shrub species has a practical application in the restoration of these habitats. The present study focuses on the population dynamics and regeneration of an early successional shrub Dodonaea angustifolia and a late successional tree Olea europaea ssp. cuspidata in southern Wello, Ethiopia. Population structure and dynamics, regeneration and seed banks in dry Afromontane habitats were considered. For both species, three population structure patterns were identified: 1) high density, reversed J-shape structure with many seedlings and few large individuals, 2) lower density, unimodal structure with higher proportions of plants of intermidiate size, 3) high density with higher proportions of large plants , in some cases bimodal with small and large individuals. Vegetation type and protection time were found to have a significant effect on the population structure of both species. Dodonaea can establish itself on degraded land, once the disturbance has ceased Projection matrix analysis on observations from permanent plots in Dodonaea populations in protected and unprotected sites resulted in one declining population, and one increasing in the protected site and declining populations at the unprotected site. The overall projected growth rate in Dodonaea calculated from a pooled matrix indicated positive population growth. The factors influencing the population growth, recruitment and survival are discussed. The persistence of Olea populations seems to depend on the more stable environmental conditions in later successional stages of forest vegetation. There are possibilities of natural regeneration of Olea if regenerating individuals still occur in the area. Rainfall seasonality is a dominant factor in regulating establishment, recruitment, survival and growth, particularly during the seedling stage. Moreover, shade and herbivory are factors that need consideration. Since Olea grows better under shade than in the open sun, successful regeneration for this species relies on shade from other plants and on protection from grazing, at least during the seedling stage. Most of the species that germinated from the seed banks were herbs and grasses with very few shrub and tree species. There was low correspondence between species composition of the seed banks and that of the standing vegetation. Spatial and temporal variation in demographic parameters among populations of Dodonaea and Olea can be attributed to human and environmental influence. Under protection, both Dodonaea and Olea seem to have a possibility to regenerate naturally. Further research should consider factors mentioned in detailed investigations of other dominant Afromontane forest species.
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Azevedo, Iábita Fabiana Sousa. "Modelos de dose-resposta com censura intervalar aplicados a dados de germinação de sementes." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-09112016-112017/.
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O crescimento de investimentos em biotecnologia na agricultura tem sido um elemento primordial para a segurança alimentar global. Isso tem levado a uma reorganização da indústria mundial de sementes na busca por técnicas mais adequadas de cultivo, mecanização, uso de fertilizantes, defensivos agrícolas e a utilização de sementes. O Brasil por ser um dos ambientes mais sólidos nesse contexto tem contribuído com o crescimento e a diversificação da produção de sementes levando as lavouras brasileiras a atingirem um novo patamar de produtividade. Diferentes metodologias estatísticas têm sido utilizadas para analisar o comportamento da germinação de uma população de sementes. Entretanto, usar abordagens estatísticas que analisam os dados de germinação da melhor maneira possível permitirá uma maior confiabilidade dos resultados, bem como, ganho de informações pertinentes. Como em testes de germinação de sementes estuda-se o tempo até a ocorrência do evento, que envolve medidas repetidas feitas no mesmo lote e não se conhece o tempo exato da germinação da semente, propõe-se o uso de modelos de dose-resposta com censura intervalar, que permitem a interpretação biológica dos parâmetros usados para medir o processo germinativo e refletem o desenho experimental dos dados. Neste trabalho foram utilizadas duas metodologias estatísticas usuais na análise de dados de germinação de sementes e seus resultados foram comparados com os da abordagem de modelos dose-resposta com censura intervalar. Foram utilizados os modelos de dose-resposta Weibull 2 e log-logístico para explicar o processo germinativo de sementes de Brachiaria e Citrumelo Swingle respectivamente, com diferentes tempos de observação. Os experimentos foram realizados em delineamento inteiramente aleatorizado e os procedimentos dos testes de germinação de acordo com as Regras para Análise de Sementes (RAS). As conclusões obtidas a partir da análise dos dados por meio da metodologia proposta, em geral, divergiram das conclusões obtidas por abordagens tradicionais (modelos de regressão não-linear considerando a distribuição normal e índices de germinação com o uso da análise de variância) utilizadas para analisar dados de germinação. Os modelos de dose-resposta com censura intervalar apresentaram ajustes satisfatórios e sendo portanto uma análise mais adequada que as abordagens usuais.The growth of investment in biotechnology in agriculture has been a vital element for global food security. This has led to a reorganization of the world seed industry in the seeking of the most appropriate techniques of cultivation, mechanization, use of fertilizers, pesticides and seeds. The Brazil for being one of the most solid in the world context of the seed industry has contributed to the growth and diversification of seed production, leading Brazilian crops to a new level of productivity. Different statistical methodologies have been used to analyze the germination behavior. However, using statistical approaches that analyze germination data as efficiently as possible will allow a greater reliability of the results, as well as relevant information gain. As in seed germination test studies the time until the occurrence of the event, involves repeated measurements on the same experimental unit and do not know the exact time of germination, we propose the use of dose-response models with interval censured that allow biological interpretation of parameters used to measure the germination process and reflect the experimental design of the germination data. In this work we used two methodologies of usual statistical analysis and their results were compared with those of the approach that uses the dose-response models with interval censured. We used the dose response models Weibull 2 and log-logistic to explain the process of seed germination of Brachiaria and Citrumelo Swingle with different observation times. The experiments were carried out in completely randomized design and testing procedures according to the rules for seed analysis (RAS). The conclusions obtained from the analysis of the data by the proposed methodology in general diverged from the conclusions obtained by traditional approaches (regression models nonlinear considering normal distribution and germination indices using analysis of variance) used to analyze data germination. The dose-response models with interval-censored showed satisfactory adjustments and therefore a more accurate analysis than the usual approaches.
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Bultitude, J. M. "The survival of seeds and seedlings on colliery spoil." Thesis, University of York, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373312.
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Cordazzo, Cesar Vieira. "Comparative population studies of four dominant plants of southern Brazilian coastal dunes." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241475.
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Ratcliffe, Sophia Emma Thirza. "Competition and coexistence in experimental annual plant communities." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/11515.
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Taïbi, Khaled. "Integrated approach for addressing assisted population migration programs in forest management to climate change: out-planting performance, genotype by environment interactions, physiological and molecular response." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48467.
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Abstract
Forest ecosystems are likely to shift faster in response to climate
change than their maximum natural rate at which they can migrate and
establish. This thesis introduces an interdisciplinary approach to develop a
proactive management strategy towards climate change through assisted
populations’ migration for two pine species; Aleppo pine (Pinus halepensis
Mill.) and Black pine (Pinus nigra ssp. salzmannii).
The main objectives of this study were to (1) evaluate plantation
performance and phenotypic plasticity in the broad context of genotype by
environment interaction (GEI) of these pine seed sources out-planted in
contrasting trial sites to test a hypothetical northwards migration for further
selection under specific conditions, (2) compare the efficiency of joint
regression and Additive Main effect and Multiplicative Interaction (AMMI)
models in elucidating seed sources adaptation patterns in each site then, (3)
explain the basis of the differential response of seed sources to induced
drought and cold stresses through the physiological, metabolomic and
proteomic analyses. This study reproduced real conditions of reforestation
in potential future climatic conditions either in field or under phytotron
controlled conditions.
The selective use of the intraspecific variability was demonstrated to
have a potential contribution to alleviate adverse climate change impacts on
forest ecosystems. For both species, certain seed sources were able to cope
better with specific climate perturbations than others in response to the
northwards shifts; seedlings not belonging to the target site could be
selected for facing current climate irregularities in different environments.
Abstract
Here, provenances moved from slightly different transfer distance metrics
were the best performers. The main problem is the high expected seedlings
mortality due to freezing events and drought stress mainly for seedlings
belonging to warmer provenances. Seed sources phenotypic plasticity was
low to moderate for height and diameter growth and the environmental
effect had a great influence on their performance variation. The AMMI
models demonstrated higher adequacy to analyse complex GEI than the
joint regression analysis. An important finding is that specific adaptation to
adverse environmental conditions was coupled with low phenotypic
plasticity responses.
Differences among Aleppo pine seed sources subjected to induced
drought conditions were significant for chlorophyll fluorescence, pigments
and soluble sugars contents. However, induced cold stress changes
transpiration rate, stomatal conductance, pigments and glucose contents.
The decrease in photosynthesis under drought, unlike to cold stress, was
due to stomatal closure. At the considered metabolomic level, drought
tolerance was related to the decrease of glucose and fructose and the
increase of sucrose contents in needles. However, the cold tolerance was
associated to the decrease of glucose and the increase of sucrose and
fructose contents. At the proteomic level, most of the identified proteins
were related to the transcriptional machinery and sugar metabolism. The
presence of enzyme related to the sulphur amino-acids metabolism could be
the limiting factor for drought stress in Aleppo pine.
Keywords
Assisted population migration, Reforestation, Pinus halepensis, Pinus nigra ssp.
salzmannii, Seed Sources, Out-planting performance, Survival, Growth,
Phenotypic Plasticity, Genotype by Environment Interaction, Adaptation,
Physiology, Metabolomic, Proteomic.Taïbi, K. (2014). Integrated approach for addressing assisted population migration programs in forest management to climate change: out-planting performance, genotype by environment interactions, physiological and molecular response [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48467
TESIS
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Newton, Rosemary Jean. "Development, dormancy, germination and ex-situ survival of seeds of selected Amaryllidaceae species." Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.567701.
Full textAbstract:
Seed development, dormancy, germination, desiccation tolerance and survival ex-situ were studied in selected members of the Amaryllidaceae following reports of poor seed germination and storability. Seed dry weight accumulation of temperate woodland European Galanthus nivalis L. and Narcissus pseudonarcissus L. continued until seed dispersal with no subsequent maturation drying phase. Seeds shed at high moisture contents (> 60% FWB). In both species, the ability of seeds to germinate developed before the ability to tolerate desiccation; the latter was not acquired in some seeds at dispersal. Embryo elongation occurred during seed development which continued post-shedding, more rapidly at warmer temperatures similar to summer temperatures of the natural post-shedding environment. Warm temperatures alleviated physiological dormancy gradually; germination occurred in most seeds at subsequent cooler, autumn-like temperatures. This pattern was repeated in seeds which did not germinate initially. Constant temperatures and darkness promoted germination in both species, with darkness a strong requirement for G. nivalis. Desiccation increased dormancy in a proportion of N pseudo narcissus seeds. Seeds 'of European Leucojum aestivum L. and N pseudo narcissus and American Rhodophiala bagnoldii (Herb.) Traub, Rhodophiala advena (Ker Gawl.) Traub and Zephyranthes drummondii D.Don tolerated drying to 4.1 - 5.5% moisture content. Seeds of the American and European species survived sub-zero storage for over four years and six months respectively, and are probably orthodox. Galanthus nivalis seed survival on desiccation varied considerably amongst populations: virtually no seeds survived drying to 7.1 - 7.3 % moisture content while others tolerated desiccation to 12 -18%, suggesting possible intermediate seed storage behaviour. Seeds of these American and European species are estimated to be relatively short-lived in seed bank storage compared with species from other families. Storage of seeds of European species at slightly higher moisture contents may reduce the rate of viability loss.
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Szekely, Ora. "Send lawyers, guns and money: the politics of militia survival in the Middle East." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104551.
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This dissertation considers the sources of variation in the ability of nonstate military actors to both resist and recover from – in short, to survive – confrontations with much stronger conventional militaries. While much of the existing literature on civil war focuses on structural variables, such as initial material or social endowments, this dissertation argues that these resources are less important in determining a non-state actor's resilience than the relationships it builds in order to acquire them and the means it uses to do so. “Resources” may be either material, (e.g., money and arms) or non-material (e.g., legitimacy and influence) and are acquired (from the civilian population and/or a foreign sponsor) through three possible strategies: coercion, service-provision, and marketing. I argue that the first is least effective, as coercion tends to provide only short-term access to material resources, while marketing is the most effective, as it produces the most durable access to both material and non-material resources. Service provision produces a mid-range outcome. Moreover, all three can have significant unintended consequences. I test the argument by comparing the performances of the PLO, Hizbullah and Hamas in their confrontations with Israel over the past four decades. I conclude by considering the implications of my conclusions both for the study of nonstate actors more broadly, and for the dynamics of 21st century Iraq and Afghanistan.Cette thèse considère les facteurs de variation de l'habileté des acteurs militaires non-étatiques à résister à et à se remettre- en bref, à survivre à- des confrontations avec des militaires conventionnels comparativement beaucoup plus forts. Alors que la plus grande partie de la littérature sur les guerres civiles se concentre sur les variables structurelles telles que le matériel initial ou les atouts sociaux, cette thèse soutient que ces ressources sont moins importantes pour déterminer la résilience d'un acteur non-étatique que les relations qu'elles construisent afin de les acquérir ainsi que les moyens qu'elle utilise pour le faire. Les « ressources » peuvent être soit matérielles (par exemple, de l'argent et des armes) ou non-matérielles (par exemple, la légitimité et l'influence) et sont acquises (de la population civile et/ou d'un soutien étranger) à travers trois stratégies possibles : la coercition, la prestation de services, et le marketing. Nous soutenons que le premier est le moyen le moins efficace, puisque la coercition tend à donner seulement un accès à court terme aux ressources matérielles, alors que le marketing est le moyen plus efficace, puisqu'il donne l'accès le plus durable à la fois aux ressources matérielles et non-matérielles. La prestation de service aboutit à un résultat intermédiaire. Qui plus est, les trois peuvent avoir des conséquences inattendues. Nous testons ces arguments en comparant la performance de l'OLP, du Hezbollah et du Hamas dans leur confrontation avec Israël au cours des quatre dernières décennies. Nous concluons en considérant la portée de nos conclusions pour l'étude des acteurs non-étatiques en général, ainsi que pour les dynamiques du 21ième siècle en Iraq et en Afghanistan.
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Pollinger, Maegan. "PLANTING SEEDS OF CHANGE: GARDEN SPACES AND THE SURVIVAL OF HISTORIC HOUSE MUSEUMS IN CRISIS." Master's thesis, Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/442350.
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HistoryM.A.
This study explores the use of gardens and agricultural spaces at historic house museums, and the potential these spaces have for supporting positive change. At the turn of the twenty-first century, house museums grappled with a crisis of limited funding and ever shrinking visitor capacity, which continues to affect the success of these spaces today. I argue that garden spaces can provide interpretive revitalization, community relevancy, and increased income for historic house museums that can positively support a house museum. By surveying house museums throughout New Jersey and Pennsylvania, I show that garden spaces provide a tool for house museums to gain stability amidst crisis.
Temple University--Theses
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Legras, Elaine C. "Microhabitat is critical for sugar pine seedlings emergence and survival in a xeric Jeffrey pine dominated forest /." abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1455660.
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Thesis (M.S.)--University of Nevada, Reno, 2008."May, 2008." Includes bibliographical references (leaves 39-44). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Barnett, Katie. "Fathering the future : masculine survival and paternal restoration in 1990s Hollywood." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4488/.
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The 1990s in the United States saw a particular cultural anxiety manifested in the crisis of masculinity, in which American men were perceived to be suffering from a loss of power and diminished authority. As President Clinton heralded a final push towards the millennium and the creation of a better, brighter future for the nation, concerns emerged over the ability of straight, white, middle-class men to access this same future. In this pre-millennial period, fatherhood is presented as the solution to this state of masculine crisis. Hollywood in particular invests in this notion of masculine crisis and the need for rehabilitation through fatherhood, indulging in one of the key tenets of Lee Edelman’s theory of reproductive futurism: that of the future being realised through an investment in the child. This thesis examines a number of Hollywood films produced between 1989 and 2001, with the aim of demonstrating how fatherhood is persistently constructed as the key to masculine survival during a period of considerable anxiety over the future.
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Kim, Julian. "EFFECT OF RADIATION THERAPY ON SURVIVAL IN PATIENTS WITH RESECTED MERKEL CELL CARCINOMA: A POPULATION-BASED ANALYSIS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1278471897.
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Tinsley, Heather. "Rhabdomyosarcoma Incidence and Survival in Whites, Blacks, and Hispanics from 1973-2013: Analysis from the Surveillance, Epidemiology, and End Results Program." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6594.
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Purpose
Our objectives were to 1) determine the difference in Rhabdomyosarcoma (RMS) incidence and survival between different race/ethnicity groups, and 2) evaluate the difference in survival of RMS between children and adults of these race/ethnicity groups, using the Surveillance, Epidemiology, and End Results Program (SEER) database between 1973-2013.
Patients and Methods
We analyzed racial characteristic and incidence data from 4,280 patients diagnosed with RMS, between 1973-2013, that were reported to the SEER database. Survival and hazard analyses were conducted on 4,268 patients with known follow-up data, with end point being death from any cause.
Results
Over the 40-year study period overall RMS incidence rates have experienced a statistically significant decline (APC: -0.78, 95% CI: -1.28 – -0.28). Whites have experienced a significant decline in incidence rates (APC: -1.05, 95% CI: -1.60 – -0.50). Though not statistically significant, incidence rates in Blacks and Hispanics have trended upwards. While adjusted survival was not predicted by race, survival did significantly differ among racial/ethnic groups in children, with Hispanics and “Others” having the lowest 5- and 10-year survival rates (65% and 58% verses 58% and 56%, respectively). Black race/ethnicity was also shown to be a predictor for mortality for the time period 1990-2013.
Conclusion
Racial/ethnic minorities have worse RMS clinical presentation and incidence rates than Whites. While overall survival is not predicted by race, being an ethnic minority child diagnosed with RMS is predictive of survival. These disparities point towards a genetic component in RMS that has not yet been described.
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Wang, Hongwei. "Effect of Risk and Prognosis Factors on Breast Cancer Survival: Study of a Large Dataset with a Long Term Follow-up." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/math_theses/116.
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The main goal of this study is to seek the effects of some risk and prognostic factors contributing to survival of female invasive breast cancer in United States. The study presents the survival analysis for the adult female invasive breast cancer based on the datasets chosen from the Surveillance Epidemiology and End Results (SEER) program of National Cancer Institute (NCI). In this study, the Cox proportional hazard regression model and logistic regression model were employed for statistical analysis. The odds ratios (OR), hazard ratios (HR) and confidence interval (C.I.) were obtained for the risk and prognosis factors. The study results showed that some risk and prognosis factors, such as the demographic factors (race and age), social and family factor (marital status), biomedical factors (tumor size, disease stage, tumor markers and tumor cell differentiation level etc.) and type of treatment patients received had significant effects on survival of the female invasive breast cancer patients.
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Bowman, Lauren Stewart. "Impacts of inoculation strategy on survival of Salmonella enterica and Enterococcus faecium at low water activity on dry peppercorn and cumin seeds." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/63926.
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Salmonella contamination of spices and other low water activity foods is a growing concern for the food industry due to increased frequency of salmonellosis outbreaks and detection-based product recalls. The impact of inoculation preparation on the survival of a Salmonella enterica and its proposed surrogate, Enterococcus faecium NRRL B-2385, on the whole black peppercorns and cumin seeds was examined. Three liquid inoculation methods (biofilm-inclusion, agar-grown, broth-grown) for Salmonella enterica and surrogate Enterococcus faecium and one dry transfer method for Salmonella enterica were developed then applied to whole peppercorn and cumin seeds. Spices were returned to original water activity (aw 0.3) and stored for 28 days with periodic sampling (0, 1, 7, 14, 21, 28 days) and surviving bacteria enumerated. Average log reductions (LR) over time were statistically analyzed to determine differences in stability during storage. Inoculation preparation was associated with significant differences in recovered Salmonella and Enterococcus from both peppercorn and cumin over the storage period. At 28 days, the most stable inoculations of Salmonella resulted from the biofilm-inclusion (-0.04 CFU/g LR) and agar grown (-0.75 CFU/g LR) methods on peppercorn and the biofilm inclusion method (-0.28 CFU/g LR) on cumin. Log reductions of Enterococcus faecium (-0.02 CFU/g LR biofilm-inclusion-peppercorn, -0.19 CFU/g LR agar-grown-peppercorn, -0.61 CFU/g LR biofilm-inclusion-cumin) were comparable to Salmonella after 28d desiccated storage. These results will guide the inoculation strategies for validating inactivation processes for reducing Salmonella on whole spices, and for comparisons of inactivation of Salmonella and its proposed surrogate Enterococcus faecium.Master of Science in Life Sciences
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Thomas, Sarah Nichole. "Decisions to Seek and Share: A Mixed Methods Approach to Understanding Caregivers Surrogate Information Acquisition Behaviors." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595545894518707.
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Nicholas, Garth. "Survival analysis of patients seen at the Ottawa Hospital Regional Cancer Centre with early breast cancer, 1985--2001: Effect of changes in stage and adjuvant chemotherapy over time." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27542.
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Breast cancer is the commonest cancer affecting Canadian women. Recent decades have seen a trend of decreasing breast cancer mortality. This has been attributed to several causes, including greater use of screening mammography and increased efficacy of adjuvant chemotherapy. We studied the effect of these two factors on the overall survival of breast cancer patients at the Ottawa Hospital Regional Cancer Centre. Data were collected from 2985 charts from the years 1985, 1988, 1992, 1995, 1998, and 2001. Adjuvant chemotherapy was associated with a decreased hazard of death from any cause (HR=0.783 p=0.0208). A decrease in mean tumour size seen over the time period of the study is potentially attributable to mammography screening. Decreased tumour size was associated with a decreased hazard for death (HR 0.986 p<0.0001). No difference in overall survival between earlier and later cohorts could be demonstrated, perhaps due to shorter follow up in later cohorts.
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Jones, Cassandra L. "FutureBodies: Octavia Butler as a Post-Colonial Cyborg Theorist." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1368927282.
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Graffeo, Nathalie. "Méthodes d'analyse de la survie nette : utilisation des tables de mortalité, test de comparaison et détection d'agrégats spatiaux." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5067/document.
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La survie nette, indicateur clé de l'efficacité des systèmes de soin dans la lutte contre le cancer, est un concept théorique représentant la survie que l'on observerait dans un monde hypothétique où le cancer étudié serait la seule cause de décès. En s'affranchissant de la mortalité due aux causes autres que ce cancer, elle permet des comparaisons entre populations. Dans cette thèse, après présentation du concept et des méthodes d'estimation de la survie nette quand la cause de décès est inconnue, nous étudions trois problématiques. La première porte sur les tables de mortalité utilisées pour estimer la survie nette. En France, ces tables sont stratifiées sur âge, sexe, année et département. Il serait intéressant d'utiliser des tables stratifiées sur d'autres facteurs impactant la mortalité. Nous étudions l'impact du manque de stratification sur les estimations des effets des facteurs pronostiques sur la mortalité en excès (celle due au cancer en l'absence des autres causes de décès) par des études de simulations et sur données réelles. La deuxième problématique porte sur la construction d'un test de type log-rank pour comparer des distributions de survie nette estimées par l'estimateur Pohar-Perme, estimateur non paramétrique consistant de la survie nette. Notre troisième problématique est de déterminer dans une aire géographique des zones différentes en termes de survie nette. Nous adaptons une méthode de détection de clusters à la survie nette en utilisant le test précédemment développé comme critère de découpage. Ce travail propose ainsi des développements et outils nouveaux pour étudier et améliorer la qualité de la prise en charge des patients atteints d'un cancerIn cancer research, net survival is a key indicator of health care efficiency. This theoretical concept is the survival that would be observed in an hypothetical world where the disease under study would be the only possible cause of death. In population-based studies, where cause of death is unknown, net survival allows to compare net cancer survival between different groups by removing the effect of death from causes other than cancer. In this work, after presenting the concept and the estimation methods of net survival, we focus on three complementary issues. The first one is about the life tables used in the estimates of net survival. In France, these tables are stratified by age, sex, year and département. Other prognostic factors impact on mortality. So it would be interesting to use life tables stratified by some of these factors. We study the impact of the lack of stratification in life tables on the estimates of the effects of prognostic factors on excess mortality by simulations and real data studies. In 2012, the Pohar-Perme estimator was proposed. It is a consistent non parametric estimator of net survival. The second issue involves the building of a log-rank type test to compare distributions of net survival (estimated by the Pohar-Perme estimator) between several groups. Our third issue is to propose a method providing potential spatial clusters which could contain patients with similar net cancer survival rates. We adapt a clustering method using the test we have built as a splitting criterion. This work proposes new developments and new tools to study and improve the quality of care for cancer patients. These methods are suitable to other chronic diseases
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Tavares, Lucas Alves. "O envolvimento da proteína adaptadora 1 (AP-1) no mecanismo de regulação negativa do receptor CD4 por Nef de HIV-1." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/17/17136/tde-06012017-113215/.
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O Vírus da Imunodeficiência Humana (HIV) é o agente etiológico da Síndrome da Imunodeficiência Adquirida (AIDS). A AIDS é uma doença de distribuição mundial, e estima-se que existam atualmente pelo menos 36,9 milhões de pessoas infectadas com o vírus. Durante o seu ciclo replicativo, o HIV promove diversas alterações na fisiologia da célula hospedeira a fim de promover sua sobrevivência e potencializar a replicação. A rápida progressão da infecção pelo HIV-1 em humanos e em modelos animais está intimamente ligada à função da proteína acessória Nef. Dentre as diversas ações de Nef está a regulação negativa de proteínas importantes na resposta imunológica, como o receptor CD4. Sabe-se que esta ação resulta da indução da degradação de CD4 em lisossomos, mas os mecanismos moleculares envolvidos ainda são totalmente elucidados. Nef forma um complexo tripartite com a cauda citosólica de CD4 e a proteína adaptadora 2 (AP-2), em vesículas revestidas por clatrina nascentes, induzindo a internalização e degradação lisossomal de CD4. Pesquisas anteriores demonstraram que o direcionamento de CD4 aos lisossomos por Nef envolve a entrada do receptor na via dos corpos multivesiculares (MVBs), por um mecanismo atípico, pois, embora não necessite da ubiquitinação de carga, depende da ação de proteínas que compõem os ESCRTs (Endosomal Sorting Complexes Required for Transport) e da ação de Alix, uma proteína acessória da maquinaria ESCRT. Já foi reportado que Nef interage com subunidades dos complexos AP-1, AP-2, AP-3 e Nef não parece interagir com subunidades de AP-4 e AP-5. Entretanto, o papel da interação de Nef com AP-1 e AP-3 na regulação negativa de CD4 ainda não está totalmente elucidado. Ademais, AP-1, AP-2 e AP-3 são potencialmente heterogêneos devido à existência de isoformas múltiplas das subunidades codificadas por diferentes genes. Todavia, existem poucos estudos para demonstrar se as diferentes combinações de isoformas dos APs são formadas e se possuem propriedades funcionais distintas. O presente trabalho procurou identificar e caracterizar fatores celulares envolvidos na regulação do tráfego intracelular de proteínas no processo de regulação negativa de CD4 induzido por Nef. Mais especificamente, este estudo buscou caracterizar a participação do complexo AP-1 na modulação negativa de CD4 por Nef de HIV-1, através do estudo funcional das duas isoformas de ?-adaptina, subunidades de AP-1. Utilizando a técnica de Pull-down demonstramos que Nef é capaz de interagir com ?2. Além disso, nossos dados de Imunoblot indicaram que a proteína ?2-adaptina, e não ?1-adaptina, é necessária no processo de degradação lisossomal de CD4 por Nef e que esta participação é conservada para degradação de CD4 por Nef de diferentes cepas virais. Ademais, por citometria de fluxo, o silenciamento de ?2, e não de ?1, compromete a diminuição dos níveis de CD4 por Nef da membrana plasmática. A análise por imunofluorêsncia indireta também revelou que a diminuição dos níveis de ?2 impede a redistribuição de CD4 por Nef para regiões perinucleares, acarretando no acúmulo de CD4, retirados por Nef da membrana plasmática, em endossomos primários. A depleção de ?1A, outra subunidade de AP-1, acarretou na diminuição dos níveis celulares de ?2 e ?1, bem como, no comprometimento da eficiente degradação de CD4 por Nef. Além disso, foi possível observar que, ao perturbar a maquinaria ESCRT via super-expressão de HRS (uma subunidade do complexo ESCRT-0), ocorreu um acumulo de ?2 em endossomos dilatados contendo HRS-GFP, nos quais também detectou-se CD4 que foi internalizado por Nef. Em conjunto, os resultados indicam que ?2-adaptina é uma importante molécula para o direcionamento de CD4 por Nef para a via ESCRT/MVB, mostrando ser uma proteína relevante no sistema endo-lisossomal. Ademais, os resultados indicaram que as isoformas ?-adaptinas não só possuem funções distintas, mas também parecem compor complexos AP-1 com diferentes funções celulares, já que apenas a variante AP-1 contendo ?2, mas não ?1, participa da regulação negativa de CD4 por Nef. Estes estudos contribuem para o melhor entendimento dos mecanismos moleculares envolvidos na atividade de Nef, que poderão também ajudar na melhor compreensão da patogênese do HIV e da síndrome relacionada. Em adição, este trabalho contribui para o entendimento de processos fundamentais da regulação do tráfego de proteínas transmembrana no sistema endo-lisossomal.The Human Immunodeficiency Virus (HIV) is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS). AIDS is a disease which has a global distribution, and it is estimated that there are currently at least 36.9 million people infected with the virus. During the replication cycle, HIV promotes several changes in the physiology of the host cell to promote their survival and enhance replication. The fast progression of HIV-1 in humans and animal models is closely linked to the function of an accessory protein Nef. Among several actions of Nef, one is the most important is the down-regulation of proteins from the immune response, such as the CD4 receptor. It is known that this action causes CD4 degradation in lysosome, but the molecular mechanisms are still incompletely understood. Nef forms a tripartite complex with the cytosolic tail of the CD4 and adapter protein 2 (AP-2) in clathrin-coated vesicles, inducing CD4 internalization and lysosome degradation. Previous research has demonstrated that CD4 target to lysosomes by Nef involves targeting of this receptor to multivesicular bodies (MVBs) pathway by an atypical mechanism because, although not need charging ubiquitination, depends on the proteins from ESCRTs (Endosomal Sorting Complexes Required for Transport) machinery and the action of Alix, an accessory protein ESCRT machinery. It has been reported that Nef interacts with subunits of AP- 1, AP-2, AP-3 complexes and Nef does not appear to interact with AP-4 and AP-5 subunits. However, the role of Nef interaction with AP-1 or AP-3 in CD4 down-regulation is poorly understood. Furthermore, AP-1, AP-2 and AP-3 are potentially heterogeneous due to the existence of multiple subunits isoforms encoded by different genes. However, there are few studies to demonstrate if the different combinations of APs isoforms are form and if they have distinct functional properties. This study aim to identify and characterize cellular factors involved on CD4 down-modulation induced by Nef from HIV-1. More specifically, this study aimed to characterize the involvement of AP-1 complex in the down-regulation of CD4 by Nef HIV-1 through the functional study of the two isoforms of ?-adaptins, AP-1 subunits. By pull-down technique, we showed that Nef is able to interact with ?2. In addition, our data from immunoblots indicated that ?2- adaptin, not ?1-adaptin, is required in Nef-mediated targeting of CD4 to lysosomes and the ?2 participation in this process is conserved by Nef from different viral strains. Furthermore, by flow cytometry assay, ?2 depletion, but not ?1 depletion, compromises the reduction of surface CD4 levels induced by Nef. Immunofluorescence microscopy analysis also revealed that ?2 depletion impairs the redistribution of CD4 by Nef to juxtanuclear region, resulting in CD4 accumulation in primary endosomes. Knockdown of ?1A, another subunit of AP-1, resulted in decreased cellular levels of ?1 and ?2 and, compromising the efficient CD4 degradation by Nef. Moreover, upon artificially stabilizing ESCRT-I in early endosomes, via overexpression of HRS, internalized CD4 accumulates in enlarged HRS-GFP positive endosomes, where co-localize with ?2. Together, the results indicate that ?2-adaptin is a molecule that is essential for CD4 targeting by Nef to ESCRT/MVB pathway, being an important protein in the endo-lysosomal system. Furthermore, the results indicate that ?-adaptins isoforms not only have different functions, but also seem to compose AP-1 complex with distinct cell functions, and only the AP-1 variant comprising ?2, but not ?1, acts in the CD4 down-regulation induced by Nef. These studies contribute to a better understanding on the molecular mechanisms involved in Nef activities, which may also help to improve the understanding of the HIV pathogenesis and the related syndrome. In addition, this work contributes with the understanding of primordial process regulation on intracellular trafficking of transmembrane proteins.
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Chang, Hsiu-Ming, and 張修銘. "Early Survival Ratio of Mistletoe Seeds (Taxillus tsaii): Effects of Seed Disperser, Host Trees, and Branch Size." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/46181106494082523052.
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碩士國立臺灣大學
森林環境暨資源學研究所
100
Mistletoes have played an important role in studying the evolution of parasitical plants in recent years. Mistletoes are almost hemiparasite and parasitize in clusters on one or many species of hosts. Mistletoes produce abundant fruits and both of their pollination and seed dispersal are mostly relied on birds. Many recent studies suggest these traits of mistletoes are resulted from the long-term co-evolution among the mistletoe, dispersers, and hosts. The clumped distribution of mistletoes is affected by two phases during the early stage of life cycle. One phase is that the seeds are affected by birds’ digestion and spreading range. The other phase is that the seeds have different host compatibility with different species or branches of hosts where they are dispersed. The mechanisms of these two parasitic phases are under-studied and the parasitic mechanisms of the mistletoes of Taiwan have been rarely reported. As a result, this research focuses on the early survival rates of seeds of Taxillus tsaii, an endemic species of Taiwan, and the effects of seed dispersers, host trees, and branch diameter. This study was conducted in the Lianhuachih Research Center of Taiwan Forestry Research Institute (Yuchih Township, Nantou County, Taiwan), where has high density of Taxillus tsaii. I inoculated three types of seeds (coated seeds, uncoated seeds, and defecated seeds) on two classes of branch size (5-23 mm and 26-50 mm in diameter) of three host species, including Cinnamomum micranthum, Cinnamomum osmophloeum, and Camellia oleifera. I monitored the effects of different types of seeds, host species, and branch size on seeds adhesion, seeds germination, holdfast establishment, total active seed ratio, and seed survival ratio from June, 2007 to January, 2008. Results revealed that seed germination was significantly affected by seed types. In addition, seed adhesion, holdfast establishment, total active seed ratio, and survival ratio were significantly affected by both seed types and host species. The adhered ratio greatly decreased in the coated seeds and on the branches with smooth bark. Host species did not have significant influence on germinated ratio. Defecated seeds had significantly lower germinated ratio than uncoated seeds, while coated seeds could not germinate at all. Host species was critical for holdfast established ratio, as the compatibility of Taxillus tsaii seeds differed with tree species. Haustoria of mistletoe could not establish on antagonistic species. The holdfast established ratio of digested seeds was significantly lower than uncoated seeds.
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jen, Kuo yen, and 郭彥仁. "The impact of wildlife on seed and seedling survival of Cyclobalanopsis glauca in Dafen, Yushan National Park, Taiwan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/33587614268364439593.
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碩士國立屏東科技大學
野生動物保育研究所
100
Acorns are important food for wildlife. Consumption of acorns by animals can lead to the failure of oak forest regeneration through seed predation and seedling browsing. The study aimed to understand the effect of various wildlife predation on the acorns and seedlings of ring-cupped oak (Cyclobalanopsis glauca) in Dafen, Yushan National Park, Taiwan. Our specific objectives were to (1) identify the predators on ground of fallen acorns and their relative consumption, (2) compare the acorn removal pressure among different body-sized predators, and (3) the oak seedling survival rate and survival time within and without fences. Six species of ground acorns predators were identified. Small rodent (mainly Niviventer coxingi)and Formosan sambar ate or used ring-cupped oak acorns. Rodent (79%) and Formosan samber (Rusa unicolor swinhoii) had high removal rate, 79% and 20%, respectively. However, the Formosan sambar consumed most of the acorns (73%), followed by rodents (20%). Other predators included Formosan black bears (Ursus thibetanus formosanus), wild boars (Sus scrofa taivanus), Formosan macacas (Macaca cyclopis), jays (Garrulus glandarius taiwanus). There was significant difference between 4 types of enclosure treatments for acorns removal (Kruskal-waillis n=192, H=82.1, P<0.001). The acorn removal rate of plot for exclusion of all mammals was significantly lower than the other 3 mammal-presence treatments. The acorns removal rates for sambar and rodents were negatively related to the fallen acorn density (P<0.001), but positively related to the species occurrence indexes through camera trapping. During the monitoring period (April-Oct 2011), the seedling survival rate within fences (50%) was higher than those without fences (10%). Sambar and rodents were the main acorn seed predators in the study area. However, the pressure of acorn predation and predator occurrence both were related to acorn density, which varied spatially and temporally. The activities and abundance of larger mammals would also affect the oak seed fate though acorn consumption and seedling browsing.
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Marais, Jaco. "Migration patterns and survival of Busseola fusca larvae in maize plantings with different ratios of Bt and non-Bt seed / Jaco Marais." Thesis, 2014. http://hdl.handle.net/10394/10757.
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The high-dose/refuge strategy is used globally to manage insect resistance development in genetically modified crops with insecticidal properties (Bt crops). The “refuge in a bag” (RIB) strategy is also being considered for deployment against several pest species. Busseola fusca, the target pest of Bt maize in South Africa, evolved resistance to Cry1Ab proteins. The objective of this study was to determine whether migrating B. fusca larvae are effectively controlled using the RIB strategy. A field study with a single-gene event (Cry1Ab) and a “pyramid” event (Cry1A.105 + Cry2Ab2) was conducted in which the migration patterns of B. fusca larvae in plots with different seed mixture treatments were studied. The experiment consisted of five seed mixture ratios (5%, 10%, 15%, 20% non-Bt seed and 100 % non-Bt seed as control). Natural infestation was augmented by artificial inoculation with neonate larvae into the central non-Bt maize plant of each plot. Rate of larval survival and migration, measured in terms of increase in number of plants per plot that exhibited borer damage was recorded at weekly intervals until flowering. A laboratory study was conducted to determine larval growth and survival when simulating migration between Bt and non-Bt maize plants. A feeding experiment in which larvae were reared on different types of maize (Bt and non-Bt) was conducted and larval survival and mass recorded after a 7-day feeding period. The incidence of damaged ears, stem damage and damaged internodes per stem were recorded and relationships between these variables determined by means of correlation analyses. A review was conducted in order to identify and discuss similarities and differences between the high-dose/refuge and seed mixture strategies. This was done to determine which strategy would be the most appropriate insect resistance management (IRM) strategy against B. fusca. The rate of survival and migration of B. fusca larvae was significantly higher in the plots with maize expressing Cry1Ab and control plots, than in plots with the pyramid Bt event. Older larvae exhibited improved growth and survival in the laboratory experiment when they were transferred from non-Bt to Bt plants. Positive correlations were found between early and late season damage, although some weaker than others. Plants of the “pyramid event” suffered less late-season damage than those of the single-gene event. Since the increase in number of damaged maize plants over time is associated with migration of older and larger larvae, the observed tendencies may indicate that the assumed high-dose does not kill larvae above a certain developmental stage. The high-dose refuge strategy seems to be the better option for delaying resistance development.MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
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Yen-LingLee and 李艷林. "Survival difference between young age and old age of colon cancer, SEER data based." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/35069796826981191292.
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碩士國立成功大學
臨床醫學研究所碩士在職專班
102
Colorectal cancer is the second leading cause of cancer death in the United States and is an important contributor to cancer morbidity. The majority of patients with colorectal cancer (CRC) are older than 65 years, and our population is aging. Aging may increase the susceptibility of various tissues to initiation of carcinogenesis and facilitates promotion and progression of carcinogenesis. However, about 20% of patients of colorectal cancer are associated with familial clustering and first-degree relatives of patients with colorectal adenomas or invasive colorectal cancer are at risk for colorectal cancer. This group of patients are general younger and may have different genomic expression. Whether the prognosis of young age and old age in colon cancer are the same is still debated. We used Surveillance, Epidemiology, and End Results Program (SEER) database to study survival difference between young age and old age of colon cancer. Patients diagnosed with colon cancer from the SEER database (1995-2008) were analyzed. Only adenocarcinoma was included. A total of 261,523 patients with a median follow-up of 32 months were included. The cutoff point of age is 50 years. Median survival and 5-year survival rate of patients with the same stage of young and old group were evaluated. The colon cancer study group included 129,969 men (49.7%) and 131,554 women (50.3%). Of the 261,523 patients with colon cancer, 91.7% are old age and 8.3% are young age. The colon cancer incidence of old age was 9 times greater than the young age incidence. Mean age of the older group patients was 72.5 years and 43.74 years for young group. The gender ratio among colon cancer in young group was similar with old group. The right site tumors are more common in old group. Unlike women with breast cancer that young women generally face more aggressive stages and lower survival rates, patients diagnosed with colon cancer of young group have better survival than old group in all stages possible due to less comorbidities and better tolerance to treatment.
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WANG, CHUN-SHENG, and 王俊升. "Preparation of Corn (Zea mays) Synthetic Seeds and Evaluation of Survival Rate after Low Temperature Preservation." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/c34mvw.
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碩士元培醫事科技大學
生物科技暨製藥技術系碩士班
106
With the emerging technology, human life is getting convenient, however, environment damages are getting worse as well. There are many valued food crops today that have either been extinct or endanger due to environmental changes and the development of human civilization. In order to preserve important food species, the purpose of this project is to create artificial seeds from corn embryos coated with 3% Sodium Alginate and 25 mM Calcium chloride . The artificial seeds were stored in PVS2 (Plant Vitrification Solution 2) that was composed of 30% glycerol、15% DMSO (dimethyl sulfoxide)、15% ethylene glycol, and various amount of sucrose to final 0 M, 0.2 M, 0.4 M and 1.0 M of sucrose respectively. These artificial seeds stored in PVS2 were then subjected to low temperature treatment at -20 °C. After 3 weeks, the artificial seed survival rate was evaluated by tissue culture. Recovery rate was assessed through tissue culture technique to determine the protective effects of cryoprotectant against chilling injury on artificial corn seeds. Artificial corn seeds can be recovered successfully after 3 weeks under -20 ºC storage. The results of this study can provide information for future artificial corn seed production and serve as a reference for cryo-preservation.
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Lai, Jing-Ting, and 賴勁廷. "Early Survival Rate of Mistletoe Seeds (Taxillus tsaii): Effects of Host Trees, Branch Diameter, and Relative Inoculating Site." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/26700737505722266518.
Full textAbstract:
碩士國立臺灣大學
森林環境暨資源學研究所
100
Compatibility between mistletoes and host trees is a major factor in determining seed dispersal and population distribution of mistletoes. Early establishment of mistletoes on host trees could be divided into (1) seed adhesion, (2) germination, and (3) holdfast stages. I inoculated 2100 seeds of Taxillus tsaii on 14 tree species (Prunus campanulata, Canarium album, Paulownia fortunei, Castanopsis indica, Aleurites montana, Camellia oleifera, Mallotus paniculatus, Mallotus japonicus, Cinnamomum camphora, Cinnamomum osmophloeum, Pasania konishii, Cinnamomum micranthum, Calocedrus formosana, and Araucaria hunsteinii) in Lien-Hwa-Chi Research Center and recorded their adhesion, germination, and survival from July 2008 to April 2009. Each host tree species had five replicate trees and I inoculated 10 seeds sequentially on each branch of three diameter classes (6-15 mm, 16-25 mm, 26-35 mm) of each tree. Main objectives of this study were to examine the effects of host species, branch diameter, and relative inoculation site on the rates of adhesion, germination, and early survival of mistletoe seeds and compare the early survival rate of seeds with actual rate of mistletoe establishment in the study site. Results showed that host species had significant effects on the adhesion rate and germination rate of 69 days after inoculation and the early survival rate of 223 days after inoculation. Relative inoculation position also had significant but less prominent effects on the adhesion rate, germination rate, and early survival rate. By contrast, branch diameter had no significant effect on the adhesion rate, germination rate, and early survival rate of mistletoe seeds. The results suggest that the variations in adhesion rate and germination rate of mistletoe seeds among different host species were mainly affected by different physical structures and chemical compounds on barks of tree species and various microclimates caused different tree shapes of species. Early survival rate was mainly determined by the adhesion rate and germination rate and had no significant correlation with the actual rate of mistletoe establishment in the study site. I observed that some of the tree species had mechanisms of peeling bark and embedding resin to prevent establishment of mistletoes. Therefore, the compatibility between mistletoes and host trees was affected by host bark structure, chemical composition of bark, physiological characteristics, defense mechanisms, and micro-environmental condition caused by tree shapes. The establishment of mistletoes in field should be mainly affected by seed rain distribution, which is determined by habits of seed dispersers, and compatibility between mistletoes and host trees. Mistletoe seeds might fail to parasitize highly-compatible hosts due to lack of seed rains and unfavorable micro-environment.
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Ohaji, Ikechi U. Cardenas Victor M. Douglas Tommy C. Pedroza Claudia. "Gastric cancer survival amongst Hispanics- A Hispanic paradox? : a case series study using the SEER 1973--2005 data registry." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1459862.
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