Dissertations / Theses on the topic 'Seed size and number'
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1
Goszka, Abigail R. "Seed Production and Seed Quality in Red Maple (Acer rubrum L.)." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1564752025178858.
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Freewalt, Keith. "Creation of a High Density Soybean Linkage Map, QTL Mapping and the Effects of Marker Number, Population Size and Significance Threshold on Characterization of Quantitative Trait Loci." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1402656287.
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Easton, Lyndlee Carol, and lyndlee easton@flinders edu au. "LIFE HISTORY STRATEGIES OF AUSTRALIAN SPECIES OF THE HALOPHYTE AND ARID ZONE GENUS FRANKENIA L. (FRANKENIACEAE)." Flinders University. Biological Sciences, 2008. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20081124.105244.
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This thesis is a comparative study of the life history strategies, and in particular seed germination requirements, in Australian species of the halophyte plant genus Frankenia L. (Frankeniaceae). Frankenia is a cosmopolitan genus that occurs in Mediterranean, semi-arid, and arid regions on distinctive soil types commonly on saline, sodic or gypseous soils in habitats such as coastal cliffs, and on the margins of salt lakes, salt-pans and saltmarshes (Summerhayes 1930; Barnsley 1982). The plants are small shrubs or cushion-bushes with pink, white or pale purple flowers, and salt-encrusted recurved leaves.
This project investigates germination requirements for Frankenia in relation to seed age, light requirements, temperature preferences, salinity tolerance, and soil characteristics. It also explores two divergent reproductive strategies notably seed packaging strategies in relation to environmental variables. Within the 46 currently recognized endemic Australia species, some species have a few ovules per flower and produce only a few larger seeds per fruit, while other species have many ovules per flower and produce many small seeds per fruit. Large-seededness is thought to increase the probability of successful seedling establishment in drought and salt-stressed environments. As both larger- and smaller-seeded species of Frankenia co-occur in close geographical proximity, hypotheses regarding the advantages of large-seededness in stress environments can be tested. By restricting the analysis of seed mass variation to similar habitats and within a single plant genus, it is possible to test ecological correlates that would otherwise be masked by the strong effects of habitat differences and phylogenetic constraints.
Overall, larger-seeded Frankenia species were demonstrated to be advantageous for rapid germination after transitory water availability, and for providing resources to seedlings if resources became limiting before their successful establishment. Smaller-seeded species delayed germination until both soil-water availability and cooler temperatures persisted over a longer time period, improving chances of successful establishment for the more slowly growing seedlings that are more reliant on their surroundings for resources.
This study produces information on the seed and seedling biology of many Australian species of Frankenia including several that are of conservation significance, e.g. F. crispa with its isolated populations, and the rare and endangered F. plicata. This information is important for the development of conservation management plans for these and other arid zone, halophyte species. In addition, the results of this study are of practical significance in determining the suitability of Frankenia for inclusion in salinity remediation and mine-site rehabilitation projects, and for promoting Frankenia as a drought and salt tolerant garden plant.
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Ndirangu, Christopher Mwangi. "Soybean seed yield and size as influenced by row spacing and seeding rate and seed-size heritability." Diss., This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-10052007-143343/.
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Bandekar, Neha Keshav. "Correlation of Neuron Size and Number with Brain Size in Bumblebees." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/612851.
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Over the past several decades, cell size and its resulting effects on tissue and organ function, as well as on its overall ability of the animal to perform complex tasks, has been studied extensively. Neuronal size (diameter of individual neurons) could have an influence on intelligence, brain capacity, and ability to perform complex behavioral tasks. Furthermore, there appears to be an increase in number of neurons with an increase in brain size in vertebrates. In insects, increased neuron number has also been correlated with more complex behavior. In this thesis, I test the hypothesis that the neuronal number and/or neuronal size correlate with the brain size using an insect model. This may help elucidate the apparent positive correlation between brain size and intelligence. To achieve this goal, I used a species of bumblebee, Bombus impatiens. Bumblebee workers vary extensively in brain and body size and weight, therefore allowing comparison between individuals of the same species. Workers within a colony differ in size and the amount of work a worker does depends on their body size. Larger sized workers have more foraging capability than smaller sized workers and foraging requires a more demanding sensory integration and memory capacity. In my study, it was found that brain volume was positively correlated with bee body size. Three cell body regions of the brain were further analyzed: inside of the mushroom body calyces, a cell body region next to the lobula, and cell bodies associated with the antennal lobe. No significant correlations between neuron number per unit of volume (neuron density) and brain volume were found. Assuming similar neuronal density in large and small brains, increased brain size is thus correlated with an overall increased neuron number.
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Hobson, Jennifer M. "Spring seeding, seed size and seed pathology of North American ginseng (Panax quinquefolius L.)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40417.pdf.
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Norem, Margaret A. "Box Number Two Arrives at the Svalbard Global Seed Vault." University of Arizona (Tucson, AZ), 2012. http://hdl.handle.net/10150/556792.
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Larios, Cárdenas Eugenio. "Seed size selection in the wild in Dithyrea californica." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321321.
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Seed size is regarded as a functional trait with very important consequences for the fitness of plant species. Seedlings emerging from larger seeds are more competitive but are more costly to produce than seedlings from smaller seeds. Seed size is also a trait with transgenerational effects, affecting both the fitness of the parent as well as that of the offspring. Theory on the evolution of offspring size predicts an optimum balance between size and number, seen from the parent's perspective; while empirical studies often show selection for larger seeds, seen from the offspring's perspective. Seed size selection arising from post germination traits is, however, often not unidirectional, nor operating with the same strength in all life history stages of the plant. Seed size selection is also environmentally dependent. Even environmental influence might not operate with the same consistency and strength uniformly through the plant's life cycle. This dissertation is intended to study these questions concerning the dynamics of seed size selection in the wild. This work is to my knowledge, the first to document how seed size selection operates through the whole life cycle, with naturally germinated annual plants from the Sonoran Desert. In my first chapter I explored the offspring fitness consequences of seed size in a multiyear observational study using plant demography and relating vital rates (germination, survival, and fecundity) to the size of the seeds that originate individual plants and the environmental variables of precipitation and competition. I detected positive directional selection operating both through survival and fecundity. Water availability increased both survival and fecundity but also strengthened survival selection and had no effect on fecundity selection. Competition detrimental effects were only observed in fecundity but not in plant survival. In my second chapter I ask whether seed size-specific germination could influence seed size selection later in the life cycle. We found that because germination is differential in relation to seed size, the time of optimal conditions for germination in the field would determine the variance of seed size in the germinated fraction and thus influencing the strength of seed size selection operating through survival. In my third chapter I explored the dispersal consequences of phenotypic plasticity in seed provisioning. We found that mother plants that experienced more competition made smaller seeds and affected the seed dispersal process. Smaller seeds were better able to disperse farther away from their mothers and therefore increased their probability of escaping competition in the next growing season. These studies demonstrated that seed size selection varies through the life cycle and in intensity depending on interactions with the environment.
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Ramirez, Herbert 1959. "Flower and seed size in barley (Hordeum vulgare L.)." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291929.
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This study was designed to explore correlations between flower and seed characters and the relationship of flower and seed characters to yield. Thirty six lines selected from Composite Cross XXXII material were planted in a randomized block design with four replications. At anthesis, spikes from each plot were collected and fixed in 70% alcohol. At the same time, an equivalent spike was tagged to be harvested at maturity. Measurements of flower characters were made on the preserved spikes and seed. Length, width and weight were obtained on the mature spikes. Flower volume was calculated by multiplying the area of lemma and palea by flower thickness. Correlations indicated that selection for flower characters at anthesis would be an effective selection technique for seed characters.
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Hughes, Rhiannon. "Determinants of seed size and yield in Arabidopsis thaliana." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519024.
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It is becoming increasingly important to improve the yield of seed crops to feed an expanding population and, more recently, to cope with additional strains on food-oriented agriculture posed by biofuel production and global climate change. One strategy to increase yield is to increase seed size. However in nature, due to the limited resources of the mother plant, an enlarged seed size is often associated with a concomitant reduction in seed number. Using the model plant Arabidopsis thaliana, a biotechnological approach to increase seed size through the modification of the triploid endosperm or the ovule integuments was shown to be a viable strategy to improve seed yield. Targeted over-expression of the ANT transcription factor specifically within the endosperm significantly increased seed size without negative effects on fertility. Overcoming compromised fertility in arf2 mutants established that ARF2 and the integuments are important factors in determining seed size and yield. To ensure agronomic relevance, both the gross yield and the harvest index (HI, ratio of seed yield to biological yield) were used to assess the impact of traits, such as increased integument size, introduced into Arabidopsis. To uncover novel regulators of seed size and further develop the current understanding of seed development, second-site mutations were induced in the auxin response factor 2 (arf2) mutant, which produces large seeds due to extra cell division in the ovule integuments. The ARABIDOPSIS CRINKLY 4 (ACR4) gene was identified as a suppressor of the arf2 seed phenotype. In arf2-8 acr4 double mutants, an additive effect on cell proliferation was observed, indicating that ACR4 affects the seed coat through a developmental pathway independent of ARF2. Natural variation present in Arabidopsis was used to study seed yield and its components. Considerable variation in seed size, yield and HI was revealed. Significantly, high seed weight was not associated with high yield or high HI. In contrast, high seed number and reduced plant stature were revealed as important components of high yield and yield efficiency. Additionally, ERECTA was identified as a potential ‘Green Revolution’ gene. Seed size in Arabidopsis was shown to be an extremely plastic trait in response to alterations in the post-flowering source-sink ratio, increasing by 35.0 – 66.2% in the ecotypes tested. Furthermore, a difference in seed weight between restricted (high source-sink ratio) and unrestricted (low source-sink ratio) pollinations was first observed remarkably early in seed development. However, reducing seed number by restricting pollination did not substantially alter integument or endosperm development in order to facilitate increased nutrient uptake.
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Dickson, Ross L. "Seed production in Pinus radiata D. Don : Impact of climate and site on numbers of emergent female strobili." Thesis, University of Canterbury. Forestry, 1995. http://hdl.handle.net/10092/7190.
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This thesis describes a study undertaken to improve the capacity of seed orchard managers to select productive sites for the production of Pinus radiata seed. It is applied in its approach, with the major intent being to explore the relationship between environmental variables, and numbers of emergent female strobili at anthesis.
Following the development of a sampling methodology for counting strobili, data were collected from 52 open grown stands of Pinus radiata ranging in age from 10 to 12 years located over a range of latitudes and altitudes east of the main dividing range of the South Island. Stands were selected to be reasonably close to a meteorological station.
Based on existing knowledge of when environmental variables impact on the numbers of strobili carried at the time of anthesis, monthly temperature and water stress data for the spring months of the year prior to anthesis, and also for subsequent summer months, were correlated with numbers of strobili across sites. Winter temperatures prior to anthesis were also correlated with the strobilus data.
The variables that were significantly correlated with strobilus number were then included in a stepwise multiple regression analysis with the intent of developing a statistical model for strobilus production. The multiple regression analysis selected the following variables into the model equation (with the percentage of the variance accounted for by each variable shown in brackets):
(i) Mean minimum temperature for February (around the time of seed-cone bud
differentiation) (54%).
(ii) Integrated soil water stress for February and March (6%).
(iii) Accumulated growing degree days weighted against rainfall for the spring prior to seed-cone bud differentiation (4%).
(iv) Mean minimum temperature for May (between differentiation and anthesis) (1%).
Overall the model was able to account for around 65% of between-site variability in strobilus number. The model variables suggested that predominantly temperature and to some extent rainfall govern the number of seed-cone buds that begin differentiating; and the number that finally reach antl1esis in the spring. Two years later in 1994 the statistical model was validated across 12 new South Island sites. It was found that the model estimates were in close agreement with actual counts, with 75% of the residual values falling within the 95% confidence limit bounds.
Considering that mean February temperature was so highly correlated with strobilus number it was considered appropriate, whilst validating the model in the South Island, to extend sampling into the North Island. 11 stands were sampled, situated along both east and west coasts, where warmer summer temperatures prevail. However, the model estimates were less accurate in the North Island than the South. Both the data for 1992 and 1994 (total 74 sites) were combined and strobilus data were remodelled. Again the multiple regression analysis selected the mean minimum temperature of February as the variable that explained most of the between-site variance. The mean number of strobili at sites in the North Island was 1.4 times greater than that for the sites in the South Island, with trees at the best North Island site carrying 38% more strobili than those at the best site in the South Island.
Considering that long-term data for the February temperature variable were readily available and that the relationship between temperature and strobilus production is likely to have an upper-limit, the Schumacher sigmoid growth function was fitted to the strobilus data for the 74 sites in the both the 1992 and 1994 studies. This function was found to satisfactorily describe the relationship between strobilus number and February temperature, although due to the lack of data points at the high end of the temperature range, the response curve was not typically sigmoid with a flattening off at higher temperatures.
Using both a GIS mapping system and a climate surface model, mean minimum February temperatures for New Zealand were mapped to assist with the selection of potential seed orchard sites.
It was apparent from the maps that prime sites for strobilus production are likely to be those that have a mean minimum February temperature >15°C, and that those sites tend to be on northern coastal headlands and capes with insular climates. The majority of the sites meeting the temperature criteria are in the North Auckland region. It is likely that a reproductive environment for Pinus radiata is one where the temperature does not vary greatly, either diurnally or seasonally. Assessments of conelet abortion and cone seed yield and weight, made at the time of counting strobili, showed that the levels of conelet abortion were independent of the numbers of strobili carried by trees. Seed weight was also unrelated to strobilus production, but seed number was correlated. The high strobilus-producing sites tended to yield more full seeds per cone.
To verify the significance of the variables in the statistical model experimental studies were undertaken using clonal graft material at Amberley seed orchard, Canterbury.
Firstly, an experimental study confirmed the importance in the model of February as a time to influence strobilus numbers. Grafts put into a low-intensity-light building for 2 week periods during February and early March produced no strobili the following spring, while strobilus production was unaffected on grafts moved at other times between January and the 26th of March.
In a further experiment, cooling grafts during the summer months reduced the number of strobili per whorl by 44% and the number of grafts carrying strobili by up to 80%. Siting grafts at cool inland sites during the winter on the Canterbury plain caused a loss of up to 61% in seed-cone buds. However, neither warming grafts in a polyethylene house during long shoot primordial initiation/differentiation; or in a heated glasshouse during the winter months leading up to anthesis, increased strobilus production. The reasons for this are discussed. In hindsight it would appear that the maximum temperatures in the polyethylene house were too high for strobilus production, whilst in the heated glasshouse there was insufficient diurnal temperature variation, along with an interruption to the normal seasonal cooling pattern. Nonetheless, considering both the site predictions of the strobilus model and findings of these experiments it is proposed that an optimal reproductive environment for radiata pine is probably one where warm temperatures are relatively constant and do not vary greatly diurnally or seasonally.
Summer soil water stress was implicated with strobilus production, although to a lesser extent compared to mean minimum February temperature. That is, the sites more water stressed during February and March tended to produce more strobili than those that were less water stressed. This effect was borne out by an irrigation pot trial in 1993 which showed that irrigation reduced the numbers of strobili carried by grafts by up to 45%. However, due to persistent summer rain this effect was not satisfactorily demonstrated in an irrigation field trial conducted at Amberley seed orchard.
The temperature and moisture conditions during the spring of the year prior to anthesis were found to indirectly impact on strobilus production by modifying the number of branches produced by grafts. When graft shoot growth was increased by modifying spring growing conditions, more branches developed per whorl.
Finally, the effect of nitrogen fertiliser applications on strobilus production was tested across a range of sites and climates. There was no significant direct effect of N-fertiliser on strobilus production, regardless of N-form applied. It is unlikely that the use of nitrogen fertilisers in a well managed radiata pine seed orchard will enhance strobilus production; or that the inclusion of a soil-N variable in the model would improve its predictability.
The statistical model developed in this thesis has added to knowledge regarding the identification and the importance of site environmental variables associated with female strobilus production in Pinus radiata. Further the model identified mean minimum February temperature as a key variable, for which long term data is readily available across New Zealand. These data were used to construct 2 mean minimum February temperature maps for New Zealand which can now be used to assist with seed orchard site screening. Experimentally it was demonstrated that temperature and moisture conditions govern the number of seed-cone buds that are differentiated and reach anthesis. It is recognised that environmental variables can impact on strobilus formation in both direct and indirect ways.
The possibilities for extending the databases developed in this thesis to develop further
understanding of seed production processes is advocated.
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Crumpton-Taylor, Matilda. "Starch granule number and size in Arabidopsis thaliana leaves." Thesis, University of East Anglia, 2010. https://ueaeprints.uea.ac.uk/25637/.
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Yi, Minyoung Janet. "Variation in Egg Size and Number in Drosophila subobscura." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539626847.
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Squella, Fernando. "Ecological significance of seed size in mediterranean annual pasture legumes." Adelaide Thesis (Ph.D.) -- University of Adelaide, Waite Agricultural Research Institute, Department of Plant Science, 1992. http://hdl.handle.net/2440/21647.
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Title page, contents and abstract only. The complete thesis in print form is available from the University Library.Thesis (Ph.D.)--University of Adelaide, Faculty of Agricultural and Natural Resource Sciences, 1992
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Metcalf, Daniel James. "Seed size, litter and regeneration in tropical rain forest trees." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336743.
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Kemp, Ronelle. "Seed size and light requirements in southern Cape forest species." Thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/26128.
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Goselle, Obed Nanjul. "Genome size, cell nuclei number and endopolyploidy in human demodex." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/genome-size-cell-nuclei-number-and-endopolyploidy-in-human-demodex(2bbaad63-376d-4123-b812-83f8c860acbc).html.
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Saha, Nilanjan. "Gap Size Effect on Low Reynolds Number Wind Tunnel Experiments." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35938.
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A system was designed to measure the effect of gap size on semi-span low Reynolds number wind tunnel experiments. The lift forces on NACA 1412, NACA 2412 and NACA 4412 half wings were measured using a strain gauge balance at chord Reynolds numbers of 100,000 and 200,000 and three different gap sizes including sealed gap. Pressure distributions on both airfoil top and bottom surfaces in the chord-wise direction near the gap were recorded for these airfoils. Also recorded was the span wise pressure distribution on both the airfoil surfaces at the quarter chord section. The results revealed that the presence of the gap, however small, affects the measurements. These effects were mainly observed in drop of lift and change in zero lift angle of attack and change in stall angle for the airfoil. The size of the gap is not linearly related to these changes, which also depend on the camber of the airfoil. These changes occur due to the flow through the gap from the lower surface to the upper surface of the model. The wing/end plate gap effect reduces along the span but is not fully restricted to the base of the model and the model behaves more like a full three-dimensional wing than a semi-span model. This study was made possible with the support of Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University under the supervision of Dr. James MarchmanMaster of Science
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Loehrlein, Marietta Margaret 1957. "Priming techniques and size characteristics of triploid and tetraploid watermelon seed." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276845.
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Triploid and tetraploid watermelon seed are visually indistinguishable, increasing costs to growers, who cannot market the low-quality 4N melons. Efforts were made to separate 3N and 4N seeds by thickness and weight. Means in both cases were not separable. Successful seed 'priming' would be beneficial to seedless watermelon growers. Seeds from the open-pollinated 4N x 2N cross were primed in solutions of distilled water, polyethylene glycol '8000' (PEG), and potassium nitrate (KNO₃), or left untreated; treated seeds were subsequently dried for either 1 or 7 days. Seeds were scored for germination or emergence in the lab and for emergence under field conditions. Water was better than KNO₃ or PEG, but not always better than the control. One day in treatment was superior to 3 or 6 days; length of drying time was insignificant. In the field trial, treatments did not differ in emergence.
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Boman, Jesper. "Genome size and phenotypic plasticity in the seed beetle, Callosobruchus maculatus." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-337280.
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It has long been evident that genome size is not an accurate measure of organismal complexity. This paradox was “solved” with the discovery of nonfunctional and selfish DNA in the 1970s. However, emerging from this explanation was an enigma of complexity. Neither neutral nor adaptive models can account for all genome size variation across the tree of life. An organism with intraspecific variation is needed to investigate the functional role of genome size differences. Here I use different populations of the seed beetle, Callosobruchus maculatus, with a known intraspecific genome size variation of ~4%. It has previously been shown that a larger genome is associated with higher scores in fitness-related traits for this species. In this study, genome size is regressed with phenotypic plasticity along three different environmental gradients. Genome size did not correlate with plasticity in mass and development time along environmental gradients of temperature and host types. However, the results show that larger genomes are consistent with higher canalization of fitness under different food regimes. This further supports the idea that natural selection acts on genome size variation in this species.
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Herat, Lakshman Gamini. "Effects of maturity and seed size on seed vigor and plant growth in snap bean (Phaseolus vulgaris L.)." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/39885.
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Stage of maturity at harvest and relative seed size can affect seed vigor. Greenhouse and field studies were conducted to determine the effect of seed maturity on seed vigor, storability, and subsequent plant growth of four cultivars of snap bean (Topcrop, Provider Black, Provider White, and Cherokee Wax). Seeds harvested between physiological maturity (PM) and harvest maturity (HM) showed the highest seed vigor and storability. At PM, seed moisture content was about 55%. A drop in seed fresh weight and a pod color change from green to yellow appear to signal the stage of PM. Delaying harvest past HM reduced seed vigor. The three cultivars with colored seed coats showed higher seed vigor than Provider White.
Climatic and weathering effects on maturity, vigor, and yield of Topcrop and Cherokee Wax seed were evaluated at three locations (L-I, L-2, and L-3) in Sri Lanka having different agro-climatic conditions. Seeds that developed and matured under cooler conditions (L-l) produced higher yields and had larger size, better color, and higher vigor. Seeds developed and matured faster under warmer conditions (L-3); however, seed vigor and yields were lower and seed vigor dropped prior to HM. Cherokee Wax was the most tolerant to field weathering.
Seeds of Topcrop and Cherokee Wax were separated by weight into three seed sizes (small, medium, and large) and evaluated for crop performance in two plantings (12/90 and 3/91). Field emergence was higher from larger seeds in the second planting, where the soil conditions were more stressful. Seedlings and plants at the flowering stage were larger and pod yields higher from larger seeds.
The cultivar x seed size interaction was significant for pod yield per plant. Topcrop showed no differences, while with Cherokee Wax, pod yield per plant increased with increase in seed size during both plantings. Seeds produced from small seeds were similar or higher in vigor, indicating that small seeds could be used for seed production purposes. The data from these experiments indicate that vigor in snap bean seeds can be optimized by harvesting at an early stage after PM and by grading to remove small seeds.Ph. D.
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Gnan, Sebastian Christopher. "Genetic and environmental effects on natural variation in Arabidopsis thaliana seed size." Thesis, University of Bath, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619284.
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Maintaining global food security in the presence of a growing food demand and climate change will require an improved understanding of the genetic basis of crop yield components, and their response to environmental stress conditions, such as drought. The reproductive output of plants is further limited by partitioning of finite resources, resulting in trade-offs between traits. Here, I address these issues using Multiparent Advanced Generation Inter-Cross (MAGIC) lines of Arabidopsis thaliana for quantitative trait locus (QTL) analysis, and find that (i) there is no evidence for a genetic basis of the seed size/number trade-off, and (ii) A. thaliana responds to drought predominantly via phenotypic plasticity. I also show that seed size affects the probability of seeds germinating in the field. Moreover, I demonstrate that the inflorescence contributes resources to fitness, which suggests that flowering time and vegetative size do not necessarily impose an upper limit on reproductive output. Lastly, I address the evolution of genomic imprinting, as several imprinted genes have been shown to be vital for seed development. Several hypotheses for the evolution of genomic imprinting are tested simultaneously, and I find evidence to support a link between transposable elements and imprinted genes.
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Fatihi, Abdelhak [Verfasser]. "Alterations in the Expression of Seed Development Genes Affect Seed Size and Storage Compound Allocation in Arabidopsis thaliana / Abdelhak Fatihi." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1044190582/34.
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Schutte, Brian J. "Biology and ecology of Ambrosia Trifida L. seedling emergence." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1181937971.
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Hathaway, John Ellis. "Determining the Optimum Number of Increments in Composite Sampling." BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/425.
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Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a model is developed which accounts for different sources of variation in compositing and data analysis. This model is used to define and understand the process of determining the optimum number of increments that should be used in forming a composite. The blending variance is shown to have a smaller range of possible values than previously reported when estimating the number of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated number of increments.
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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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Swarner, Joyce Carroll. "Ordinal size scaling in preschool children." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184584.
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Young children are limited in their usage of comparative adjectives and ordinal numbers, typical ways of describing ordinal relationships. However, research in a number of areas suggests the possibility of a precursor level of ordinal concept. To facilitate the search for precursor ordinal skills, ordinal ability was defined in ordinal measurement terms. Only "greater than - less than," asymmetric judgements were required. Additionally, linguistic demands were reduced by using family-role terms as size designators. Experimental manipulations included variations in scale size and in the complexity level of ordinal conceptualization. Solution strategies based on "good form" and on "pairwise comparison" were precluded by using pictures of randomly placed objects which could not be manipulated by the child. Ninety-six 3-6 year old children pointed to "Daddy," "Mommy," "Big boy/girl," "Little boy/girl," and "Baby" when shown sets of 3 to 5 circles or squares which differed only in size. Tasks were of three types: Identification, mapping labels onto a single set of objects; Coordination, mapping labels onto two identical sets of objects in which corresponding "family members" are the same size; and Transposition, mapping labels onto two separate sets in which corresponding family members are of different sizes. Data were analyzed in an Age (3), by Scale Size (3), by Complexity Level (3), by Shape (2) mixed design ANOVA, and significant main effects were obtained for all variables. Tasks became more difficult with increases in scale size, and in complexity level. Square objects were slightly more difficult than circular, and older children were more proficient than younger ones. Post hoc tests generally supported the obtained main effects. Finer grained analysis using Latent Trait procedures supported the global ANOVA results, and supported the hypothesis that the end points of a scale are easier than the central positions. Response patterns indicated that errors were size-related, and suggested transitional levels of performance. The present study demonstrates that children as young as three can demonstrate a precursor ordinal concept when the task is framed in familiar terms and is placed in a context which is meaningful for them.
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Alqurashi, Faris. "Extension of spray flow modelling using the drop number size distribution moments approach." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/extension-of-spray-flow-modelling-using-the-drop-number-size-distribution-moments-approach(9c11e7da-f583-492d-b6a9-29b6fee71438).html.
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This work is an extension to the spray model of Watkins and Jones (2010). In their model, the spray is characterized by evaluating the three moments Q_2, Q_3 and Q_4 of general gamma number size distribution from their transport equations. The sub-models of drop drag, drop break-up and drop collisions were simulated in terms of gamma distributions. The model is considered as non-vaporising and compared with cases which have low ambient gas temperature and also is strict to a particular set of sub-models for drop drag and break up which they are applicable to produce integrable functions. In this work the model is adjusted to allow a variety of sub-models to be implemented. Three models (TAB, ETAB, DDB) are considered for drop breakup which have been basically introduced to be used with the Droplet Discrete Method (DDM) approach. So in order to implement these models with the model of Watkins and Jones the source terms of the breakup are calculated by grouping the droplets in each cell into parcels which contain a certain number of droplets with similar physical properties (size, velocity, temperature ...). The source terms of each parcel are calculated and multiplied by the number of droplets in these parcels and a numerical integration is then used to obtain the resultant effect of the drop breakup in each cell. The number of drops in each cell is determined from the gamma size distribution. Also three hybrid breakup models (KH-RT, Turb-KH-RT, Turb-TAB) which include two distinct steps: primary and secondary break up model are implemented. The Kelvin- Helmholtz (KH) and the turbulence induced breakup (Turb) models were used to predict the primary break up of the intact liquid core of a liquid jet while the secondary break up is modelled using the TAB model and competition between the KH and the RT models. Both models are allowed to work simultaneously. However it is assumed that if the disintegration occurs due to the RT the KH break up does not occur. In case of drag sub-model, a dynamic drag model is introduced which accounts for the effects of drop distortion and oscillation due to the effects of high relative velocity between the liquid and the surrounding gas. In this model the drag coefficient is empirically related to the magnitude of the drop deformation. The magnitude of drop deformation was calculated by using the TAB model. In this work, the effects of mass and heat transfer on the spray are modelled. An additional equation for the energy of the liquid is solved. The mass transfer rate is evaluated using the model of Godsave (1953) and Spalding (1953) while the Faeth correlation (1983) is used to model heat transfer between the two phases. For all equations of heat and mass transfer between phases, the drop Nusselt and Sherwood number are calculated by using the correlation of Ranz and Marshall. In this model also the liquid surface-average temperature T_l2 which is calculated by Watkins (2007) is used to determine the heat and mass transfer between phases instead of liquid volume-average temperature. It was derived by assuming a parabolic temperature profile within individual drops. All the equations are treated in Eulerian framework using the finite volume method. The model has been applied to a wide range of sprays and compared to a number of experiments with different operating conditions including high liquid injection pressure and high ambient gas density and temperature. A reasonable agreement is found by the ETAB model with most of the data while the TAB and the DDB models continually underestimate the penetration and drop sizes of the spray. The hybrid breakup models perform well and show better agreement with the available experimental data than the single breakup models. In term of high temperature cases, the model correctly captures the effect of evaporation on the different spray properties especially with hybrid break up model.
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Standley, William George. "THE EFFECT OF SEED SIZE ON RESEEDING IN THE PRESENCE OF HETEROMYIDS (RODENTS, PREFERENCE)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275316.
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Bickers, Richard. "Effects of population size and density on seed production and recruitment in Scabiosa columbaria." Thesis, University of Sussex, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436827.
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Yehnjong, Petra Seka. "Paleozoic Seed Bank and Their Ecological Significance." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etd/2316.
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Soil seed banks are a reservoir of viable seeds present in the soil in plant communities. They have been studied and characterized in various ways in different habitats. However, these studies are limited to modern seed banks. This study extends seed bank studies to the Paleozoic Era. It was hypothesized that size distribution and seed density in Paleozoic seed banks exhibit similar patterns as in modern seed banks. Seed sizes and seed density of fossil seed from Wise Virginia were estimated. Modern seed bank information was obtained from published data. Data were analyzed using one-way ANOVA and Kruskal-Wallis test. The Paleozoic size distribution was predominated by larger seeds and the estimated seed density of 19 200 seeds m-3 falls within the range of modern seed banks but at a higher end of modern seed bank densities. During the Paleozoic they were sufficient to insure regeneration of these economically important forests.
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Chanyenga, Tembo Faera. "Effect of population size on viable seed output, seed rand and natural regeneration pattern of a tropical conifer Widdringtonia whytei-Rendle in Malawi." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85589.
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Thesis (PhD(For))--Stellenbosch University, 2013.ENGLISH ABSTRACT: Widdringtonia whytei is a tropical endemic, fire-adapted pioneer coniferous tree species within natural fire-fragmented Afromontane forest patches in a confined area on Mulanje Mountain in Malawi. Natural and anthropogenic fires within the surrounding fire-prone landscape, insect attacks, and uncontrolled harvesting of mature trees for timber threaten the survival of W. whytei. This study investigated the effects of population fragmentation on the reproductive biology of W. whytei, through four specific studies: effects of population size, tree size and crown position on viable seed output; seed rain variation among population sizes; effects of temperature and light on viability and germination of W. whytei seeds; and the influence of population size on natural regeneration patterns. The study was conducted during 2008 and 2009 on three sites using three W. whytei population sizes: small (≤10 reproductively mature cone-bearing W. whytei trees), medium (11-20 cone-bearing trees) and large (>20 cone-bearing trees). Data were collected using field and laboratory experiments and a review of secondary information. The effect of fragment size and crown position on viable seed output and seed rain pattern was tested with a nested linear mixed model. The influence of stem diameter (dbh) on viable seed output was tested using a separate data set. The variation in seed rain was explored with a generalised linear model (GLM) with a negative binomial link function. Variations in seed germination was analysed with a Weibull regression model. The influence of fragment size on seedling regeneration was tested with a GLM (binary logistic regression). Viable seed output from W. whytei cones was very low (23%) and was not affected by population size, tree diameter or crown position. W. whytei population size influenced seed rain with large fragments having higher seed rain densities. Number of dispersed seeds was generally very low and poorly dispersed. W. whytei cones are semiserotinous and depends on moderate to severe fires for heavy seedfall and wider dispersal. Such fires did not occur during the study period. Temperature is a critical factor for seed germination. Seeds germinate between 15 and 25°C with the optimum at ~ 20°C either under light or dark conditions. Regeneration density followed the seed rain pattern indicating that seed availability is a critical factor for regeneration. Regular cool fires outside the forest patches and along the edges during the hot dry season, and the thick litter layer and shady conditions inside forest patches, caused most of the seedling mortality. This study highlighted the difficulties W. whytei experiences with low output of viable seed, limited seed dispersal and low seedling regeneration in and around forest patches, i.e. factors important for conservation management of this species. It is recommended that gaps with diameter equal to canopy height and occasional spot fires would promote seed dispersal onto exposed mineral soil for rapid seedling establishment and subsequent population growth. Such natural fire disturbance events may show the true seed rain and seedling establishment patterns in this species.
AFRIKAANSE OPSOMMING: Widdringtonia whytei is ‘n tropiese endemiese, vuuraangepaste pionier naaldhoutagtige boomsoort binne die natuurlike vuurgefragmenteerde Afromontane woudkolle binne ‘n beperkte area op Mulanje berg in Malawi. Natuurlike en menslike vure binne die omringende vuurgeneigde landskap, insekaanvalle, en onbeheerde kap van volwasse bome vir hout bedreig die voortbestaan van W. whytei. Hierdie studie het die effek van populasiefragmentasie op die voortplantingsbiologie van W. whytei ondersoek, deur vier spesifieke studies: die effek van populasiegrootte, boomgrootte en kroonposisie op produksie van lewenskragtige saad; saadreënvariasie tussen populasiegroottes; die effek van temperatuur en lig op lewenskragtigheid en ontkieming van W. whytei saad; en die invloed van populasiegrootte op natuurlike verjongingspatrone. Die studie is gedurende 2008 en 2009 uitgevoer op drie groeiplekke met drie W. whytei populasiegroottes: klein (≤10 keëldraende (volwasse) W. whytei bome), medium (11-20 keëldraende bome) en groot (>20 keëldraende bome). Data is versamel in veld- en laboratorium eksperimente asook 'n oorsig van sekondêre inligting. Die invloed van populasie fragmentgrootte en kroonposisie van bome op saadproduksie en die saadreënpatroon is getoets met ‘n geneste liniêre gemengde model. Die invloed van boomstamdeursnee op die produksie van kiemkragtige saad is met ‘n aparte datastel getoets. Die variasie in saadreënpatroon is met 'n algemene liniêre model (GLM) met 'n negatiewe binomiese skakelfunksie getoets. Variasies in ontkiemingspersentasie van sade is met 'n Weibull regressiemodel ontleed. Die invloed van fragmentgrootte op saailingverjonging is met 'n algemene linêre model (binêre logistiese regressie) getoets. Produksie van lewenskragtige saad in W. whytei keëls was baie lag (23%) en was nie deur populasiegrootte, boomstamdeursnee of kroonposisie beïnvloed nie. W. whytei populasiegrootte het saadreën beïnvloed en groot fragmente het groter saadreëndigthede gehad. Die aantal verspreide sade was in die algemeen baie laag en swak versprei. W. whytei keëls is semi-saadhoudend (serotinous) en is afhanklik van matige tot intense vure vir massiewe saadvrystelling en wyer saadverspreiding. Sulke vure het nie gedurende die studieperiode voorgekom nie. Temperatuur is ‘n kritiese factor vir saadontkieming. Sade ontkiem goed tussen 15 en 25°C met die optimum rondom ~ 20°C onder beide lig en donker toestande. Fragmentgrootte het nie die saailingverjonging in W. whytei beïnvloed nie. Verjongingsdigtheid het die saadreënpatroon gevolg, wat daarop dui dat saadbeskikbaarheid ‘n kritiese factor is vir saailingverjonging. Gereelde koel vure buite die woudkolle en langs die woudrand gedurende die droë warm seisoen, en die dik lae blaarval (litter) en skadutoestande binne ‘n woud, het meeste van die saailingmortaliteit veroorsaak. Hierdie studie het die probleme beklemtoon wat W. whytei ondervind met die lae produksie van kiemkragtige saad, saadverspreiding en saailingverjonging binne en rondom die woudkolle, m.a.w. faktore wat belangrik is vir bewaringsbestuur van hierdie boomsoort. Die aanbeveling word gemaak dat kroonopeninge met ‘n deursnee gelyk aan minstens die kroonhoogte, en sporadiese kolbrande binne die woudkolle kan saadverspreiding op blootgestelde minerale grond vir vinnige saailingvestiging en gevolglike populasiegroei bevorder. Sodanige vuurversteuringsgeleenthede mag die werklike patrone in saadreën en saailingvestiging in hierdie species toon.
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Babale, Aliyu. "The interplay of habitat and seed size on the shift in species composition in a fragmented Afromontane forest landscape: Implications for the management of forest restoration." Thesis, University of Canterbury. Biological Sciences, 2014. http://hdl.handle.net/10092/10055.
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The Cameroon Highlands that run along the Cameroon-Nigeria border are an important source of biodiversity. Not only are they rich in species and high in endemics, but biota from West Africa have not been studied as extensively relative to other parts of the Afrotropics, or the tropics in general. Threatening these rare and diverse habitats is anthropogenic pressure, which fragments forests and changes local animal communities. This thesis wished to address the impact of humans on seed dispersal and recruitment processes on selected tree species in forests on the Mambilla Plateau - a montane region in Nigeria's north-east. Research was conducted at Ngel Nyaki Forest Reserve, a conservation area established by the Nigerian Montane Forest Project. The reserve comprises a moderately-large forest patch (Ngel Nyaki Forest) and many small riparian fragments embedded in a grassland matrix. Cattle grazing and burning of this grassland are major threats to the survival of forest in this area.Hunting of local wildlife for bushmeat is also of concern, considering many of the region’s large-mammalian fauna are now locally extirpated (e.g. elephants) or at low abundances (many primate species). Loss of large-bodied frugivorous species has the potential to negatively impact the recruitment of large-seeded tree species that solely rely on them as seed dispersers. In this study, the ability for scatterhoarding rodents to act as surrogate dispersers for large-seeded species is tested. While much research has been carried out on secondary rodent dispersal in the Neotropics, work in the Afrotropics is still in its infancy. Because the outcome of plant-rodent interactions (i.e. predated or dispersed) may vary with season, habitat, or traits of the seed species in question, a number of experiments were established to quantify how local rodents at Ngel Nyaki may or may not be acting as effective dispersers. Additionally, the benefits of rodent dispersal were examined by creating an experiment that simulated secondary dispersal on seedling recruitment. The results of this study demonstrated that rodents can act as effective dispersers in Afromontane forests, but this is influenced by habitat, seasonal abundance of resources, and palatability of seed species. Furthermore, it was demonstrated that burial of seeds by rodents can increase the establishment probability of a seed by protecting it from removal by other rodents. However, while rodents play a strong driver of seed survival, it was also demonstrated that seedling mortality factors (such as herbivory) can also be heavy filters to seedling success. It is hoped that the results of this study will help to inform better management decisions and understand how the composition of the forest might change in the future.
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Mazibuko, Dickson Mgangathweni. "Phylogenetic relationships of Prosopis in South Africa : an assessment of the extent of hybridization, and the role of genome size and seed size in the invasion dynamics." Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71966.
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Thesis (MSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Invasive alien plants have had diverse ecological and social impacts on recipient ecosystems and are a major problem for land managers. Successful management demands an understanding of the ecology of invading taxa. The invasive status and impacts are documented for Prosopis populations in South Africa. However, unresolved taxonomic issues, the extent of hybridization, the applicability of morphology as a species identification approach, and the role that some traits plays in the invasion success have not been studied. This creates a gap that hinders implementation of effective management policies. In this thesis I use a phylogenetic approach to determine the taxonomic make-up of invasive Prosopis populations in South Africa (Chapter 2) and compare the results to morphological identification (Chapter 3). I also look at seedling growth rates in the context of variation in genome size and seed size (Chapter 4). Almost all regions invaded by Prosopis are characterized by taxonomic uncertainty exacerbated by the ease of inter-specific hybridization. In Chapter 2 I aim to resolve taxonomic issues of invasive Prosopis populations in South Africa using a phylogenetic approach. In addition, I aim to unravel the extent of hybridization and the species involved in South Africa. Here, I found that Prosopis populations in South Africa comprise both reported and previously unreported species, indicating a need for a reassessment of the identity of invasive taxa. Hybridization is prevalent and all confirmed species are involved. These findings call for a rethink of legislation and management approaches, e.g. the selection of classical biological control agents. Overall the extent of hybridization indicates that Prosopis species in South Africa comprise a freely inter-breeding population typical of a syngameon. Proper morphological identification of invasive species is crucial for ecological studies and management of invasions. In Chapter 3, I use the total evidence approach to assess whether morphological approaches for identification are adequate for identifying Prosopis species in South Africa. I found that Prosopis taxa in South Africa cannot be reliably distinguished using existing morphological keys. This is likely due mainly to the proliferation of hybrids with a diverse morphology. Therefore, molecular tools are crucial for confirming any morphological identities and for determining the presence of any unreported species. Genome size and seed size have been reported to be associated with invasiveness in a number of plant groups, but not often in a system with multiple hybrids like Prosopis. In Chapter 4, I first investigate the relationship between genome size and seed size in invasive populations of Prosopis spp. in South Africa and secondly I investigate how genome and seed sizes influence germination and early growth. Here I found that genome size loses its distinctness, being diluted in hybridizing populations, but can still be used to assess hybridization events themselves. Large seed size seems to be important for invasiveness as it positively influences germination and early growth. This thesis confirms the taxonomic conundrum of Prosopis species in invasive ranges. This coupled with inadequacy of morphological identification calls for a global study involving native and invasive range taxa to clarify the existing confusions. In view of the presence of unreported Prosopis species in South Africa and extensive hybridization, a rethink of the current legislation and control is needed.
AFRIKAANSE OPSOMMING: Uitheemse indringer plante het grootskaalse ekologiese en sosiale impakte op die ekosisteme wat hulle indring en stel 'n groot uitdaging vir bestuurders van natuurlike hulpbronne. Suksesvolle bestuur en bestryding van indringer plante verg deeglike kennis oor hulle ekologie. Die indringer status en impakte van Prosopis populasies in Suid Afrika is reeds voorheen beskryf. Nieteenstaande, die problematiese taksonomie, die omvang van hibridisasie, die waarde van morfologiese identifikasie, en die rol wat sekere eienskappe speel in die sukses van hierdie groep is nog nie bestudeer nie. Daar is dus 'n gaping in kennis wat die effektiewe beheer van die groep in Suid Afrika belemmer. In hierdie tesis pas ek 'n filogenetiese benadering toe om die taksonomiese verwantskappe van Prosopis populasies in Suid Afrika te bepaal (Hoofstuk 2) en vergelyk my resultate met morfologiese identifikasie sleutels (Hoofstuk 3). Ek ondersoek ook saailing groei tempos in die konteks van variasie in genoom en saad groote in die groep (Hoofstuk 4). Bykans alle areas in Suid Afrika waar Prosopis voorkom word gekenmerk deur taksonomiese onsekerheid, verder bemoeilik deur die gemak waarmee spesies vrylik hibridiseer. Ek vind dat beide bekende en voorheen-onbeskryfde Prosopis spesies in Suid Afrika aangetref word en beklemtoon die behoefte om die identiteit van spesies in die land te hersien. Hibridisasie kom algemeen voor tussen alle spesies teenwoordig in Suid Afrika. Hierdie bevindinge beklemtoon dat wetgewing en beheermaatreêls hersiening benodig, byvoorbeeld in die toepassing van biologiese beheer. In samevatting kom dit voor asof hibridisasie gelei het tot 'n vrytelende Prosopis groep in Suid Afrika, tipies van 'n singameon. Ordentlike morfologiese identifikasie van indringer spesies is belangrik in enige ekologiese studie en die implementering van doeltreffende beheermaatreëls. In Hoofstuk 3 gebruik ek ʼn ‘totale bewys’ benadering om vas te stel of morfologiese eienskappe alleenlik genoegsaam is om Prosopis spesies in Suid Afrika korrek te kan identifiseer. Ek vind dat spesies nie geloofwaardig geïdentifiseer kan word nie, heel moontlik as gevolg van wydverspreide hibridisasie tussen alle spesies teenwoordig in die land. Genoom en saad groote is voorheen geassosieer met die indringer aard van verskeie plant groepe. In Hoofstuk 4 ondersoek ek die verwantskap tussen genoom en saad groote. Tweedens bepaal ek die invloed van genoom en saad groote op ontkieming en vroeë groei eienskappe van Prosopis. My bevindinge toon dat, terwyl die kenmerklikheid van genoom groote verloor word as gevolg van hibridisasie, dit steeds hibridisasie gebeurtenisse per se kan identifiseer. Groot sade het ook ʼn positiewe invloed op die ontkieming en vroeë groei eienskappe van Prosopis. Die tesis bevestig die taksonomiese onduidelikheid van indringer Prosopis taksa in Suid Afrika. Tesame met die onakkuraatheid van morfologiese sleutels beklemtoon my bevindinge die behoefte vir ʼn dringende wêreldwye studie op indringer en inheemse populasies van Prosopis om taksonomiese onsekerhede op te klaar. Die identifikasie van nuwe spesies in Suid Afrika beklemtoon ook die behoefte om huidige wetgewing en beheer van die groep in die land te hersien.
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Amarillo-Suárez, Angela Rocío. "INFLUENCES OF HOST SIZE AND HOST QUALITY ON HOST USE IN A SEED-FEEDING BEETLE." UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/352.
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For insects that develop inside discrete hosts both host size and host quality constrain offspring growth, influencing the evolution of body size and life history traits. This dissertation examines the effects of host size, host quality, and intraspecific competition on life history and associated traits of populations of the seed-feeding beetle S. limbatus adapted to different host plants, and quantifies population differences in phenotypic plasticity. Populations of the study correspond to divergent clades of the species phylogeography (Colombia and United States).
Clades compared differ genetically for all traits when beetles were raised in a common garden. Contrary to expectations from the local adaptation hypothesis, beetles from all populations were larger, developed faster and had higher survivorship when reared in Acacia greggii, the larger host. Two host-plant mediated maternal effects were found: offspring matured sooner, regardless of their rearing host, when their mothers were reared on Pseudosamanea guachapele and females laid larger eggs on Ps. guachapele. These results also show that this species in addition to be a smaller is a low quality host. Females also laid more eggs and sooner on A. greggii than in Ps. guachapele and, laid more eggs on P. guachapele when A. greggii seeds were small than when they were large. Eggs were larger when laid on Ps. guachapele and Parkinsonia florida, two hosts that reduce survivorship in all populations. However, Colombia females laid eggs of similar size on Ps. guachapele and Pa. florida, while USA females laid the largest eggs on Pa. florida. Larger beetles were most affected when larval competition was increased and seed size decreased. The responses of different body sized females were asymmetrical showing significant variation in plasticity.
Although differences between populations in growth and life history traits appear to be adaptations to the size and quality of their host plants, host-associated maternal effects, partly mediated by maternal egg size plasticity play an important role in the evolution of S. limbatus’ diet breadth. More generally, phenotypic plasticity mediates the fitness consequences of using novel hosts, likely facilitating colonization of new hosts but also buffering herbivores from selection post-colonization.
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White, Merlin M. "Assessment of copepod development in relation to genome size and 18S rDNA copy number." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24996.pdf.
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Christians, Julian Kenneth. "The physiological basis of intraspecific variation in egg size, quality and number in birds." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0010/NQ61631.pdf.
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Cook, Casey Lee. "Seeding rate and seed size as management techniques for ryegrass (Lolium Multiflorum, Lam) in winter wheat." Texas A&M University, 2002. http://hdl.handle.net/1969.1/2284.
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Higher seeding rates and larger seed sizes could enhance the competitiveness of
wheat with ryegrass. Growth room and field research evaluated the effects of wheat
seeding rates and seed size in competition with Italian ryegrass. Winter wheat seeds
cultivar “Ogallala” were divided into three seed sizes: small seed passed through a sieve
with 2.08mm round holes, large seed which did not pass through a sieve with 3.18mm
round holes, and bulk seed directly from a commercial seed bag.
These wheat seed and seed of the Italian ryegrass cultivar AGulf@ were planted in
plastic pots containing fritted clay. A replacement series design with 12 plants per pot
compared the relative growth in pure culture and competitiveness in mixtures of the two
species. The planting proportions of each wheat seed group and ryegrass were 100% and
0%, 50% and 50%, and 0% and 100%, respectively. Wheat seed size did not affect the
growth of the wheat plants in pure culture. Wheat seed size did not affect
competitiveness with ryegrass. There were no differences related to seed size among the
pure or mixed cultures of wheat. The failure of increased wheat seed size to affect
competition with ryegrass may be the result of the relative seed size difference between
the two species. Even the small wheat seed in this study were almost 9-fold greater inweight than the ryegrass seed.
Field experiments conducted for two years from fall 2002 through spring 2004 at
the Texas A&M University Agronomy Farm measured wheat yields at the same three
wheat seed sizes, two wheat densities of 250 plants m-2 and 400 plants m-2, and three
ryegrass densities of 0, 100 and 200 plants m-2. Small, bulk, and large wheat seed
produced similar yields in both years: one season favorable (2003) for growth and the
other (2004) unfavorable. Thus, seed size in the field under favorable or unfavorable
conditions or in the growth room experiment did not affect the competitiveness of wheat
in the presence of ryegrass. Increasing the wheat plant population from 250 to 400 plants
m-2 in the field also failed to enhance the competitiveness of wheat in either year.
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Mendes, Calebe Pereira [UNESP]. "Patch size, shape and edge distance influences seed predation in a keystone palm in tropical rainforests." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/122104.
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000814781.pdf: 508841 bytes, checksum: 114537088394da2fa462089c26ce1a78 (MD5)A predação de sementes é um importante tipo de processo ecológico, que afeta a abundância, diversidade e distribuição de espécies vegetais. Uma vez que esse processo ecológico depende da presença, abundancia e comportamento dos predadores de sementes, o que é afetado pelas características da paisagem, o processo de predação de sementes também acaba sendo afetado pelas características da paisagem. A maioria dos estudos em paisagens antrópicas não levam em conta as diferentes escalas em que esse processo opera. Aqui, nós avaliamos como a estrutura da paisagem afeta a predação de sementes de uma palmeira espécie-chave (Syagrus romanzoffiana) em 13 paisagens que variam em cobertura florestal, número e tamanho de fragmentos na Mata Atlântica brasileira. Nós observamos que a predação total de sementes é explicada pelo tamanho, forma e distância até a borda do fragmento. A predação de sementes pelo principal vertebrado predador de sementes (esquilos) também é relacionada com o tamanho e forma dos fragmentos, e eles interagem com os invertebrados de modo que a predação de sementes por estes é explicada principalmente pela predação por esquilos e pela distância até a borda mais próxima. Por sua vês, roedores não arborícolas são mais correlacionados com a quantidade de habitat na paisagem, predando mais sementes em paisagens com menos de 30% de habitat. Nossos resultados indicam que a predação de sementes de Syagrus romanzoffiana é mais afetada por variáveis do fragmento do que por variáveis da paisagem, e que o tamanho, a forma do fragmento e o efeito de borda são melhores preditores da predação de sementes dessa espécie-chave do que a quantidade de habitat na paisagem. Nossos resultados também ressaltam que a geometria do fragmento, uma variável negligenciada na maioria dos estudos, é importante para sistemas ecológicos
Seed predation is an important kind of ecological process that affect the abundance, diversity and distribution of plant species. Since this ecological process depends on the presence, abundance and behavior of seed predators, what it is affected by the landscape characteristics, the process of seed predation becomes also affected by the landscape characteristics. Most of studies on seed predation in human-modified landscapes do not take into account the different scales in which this process operates. Here we evaluate how landscape structure affects seed predation in a palm (Syagrus romanzoffiana) that provide a keystone resource to the frugivory community in 13 landscapes that vary in forest cover, fragment number and size in the Brazilian Atlantic forest. We found that the overall seed predation is explained by the fragment size, shape and the distance to the edge. Seed predation by the dominant vertebrate seed predator (squirrels) is also related with the fragment size and shape, and they interact with the invertebrates in such way that the invertebrate seed predation is mainly explained by the squirrel predation and by the distance to the edge. In turn, seed predation by terrestrial rodents is correlated with the habitat amount in the landscape, preying upon more seeds in landscapes with less than 30% of habitat. Our results indicate that the Syagrus romanzoffiana seed predation is more affected by the fragment variables than by landscape ones, and that patch size, shape and edge effect are more important predictors of seed predation of this palm than habitat amount in the landscape. Our results also highlights that the fragment geometry, a neglected variable in most of studies, is importance to ecological systems
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Mendes, Calebe Pereira. "Patch size, shape and edge distance influences seed predation in a keystone palm in tropical rainforests /." Rio Claro, 2014. http://hdl.handle.net/11449/122104.
Full textAbstract:
Orientador: Mauro Galetti RodriguesCoorientador: Milton Cezar Ribeiro
Banca: Paulo Roberto Guimarães Junior
Banca: Marco Aurelio Pizo Ferreira
Resumo: A predação de sementes é um importante tipo de processo ecológico, que afeta a abundância, diversidade e distribuição de espécies vegetais. Uma vez que esse processo ecológico depende da presença, abundancia e comportamento dos predadores de sementes, o que é afetado pelas características da paisagem, o processo de predação de sementes também acaba sendo afetado pelas características da paisagem. A maioria dos estudos em paisagens antrópicas não levam em conta as diferentes escalas em que esse processo opera. Aqui, nós avaliamos como a estrutura da paisagem afeta a predação de sementes de uma palmeira espécie-chave (Syagrus romanzoffiana) em 13 paisagens que variam em cobertura florestal, número e tamanho de fragmentos na Mata Atlântica brasileira. Nós observamos que a predação total de sementes é explicada pelo tamanho, forma e distância até a borda do fragmento. A predação de sementes pelo principal vertebrado predador de sementes (esquilos) também é relacionada com o tamanho e forma dos fragmentos, e eles interagem com os invertebrados de modo que a predação de sementes por estes é explicada principalmente pela predação por esquilos e pela distância até a borda mais próxima. Por sua vês, roedores não arborícolas são mais correlacionados com a quantidade de habitat na paisagem, predando mais sementes em paisagens com menos de 30% de habitat. Nossos resultados indicam que a predação de sementes de Syagrus romanzoffiana é mais afetada por variáveis do fragmento do que por variáveis da paisagem, e que o tamanho, a forma do fragmento e o efeito de borda são melhores preditores da predação de sementes dessa espécie-chave do que a quantidade de habitat na paisagem. Nossos resultados também ressaltam que a geometria do fragmento, uma variável negligenciada na maioria dos estudos, é importante para sistemas ecológicos
Abstract: Seed predation is an important kind of ecological process that affect the abundance, diversity and distribution of plant species. Since this ecological process depends on the presence, abundance and behavior of seed predators, what it is affected by the landscape characteristics, the process of seed predation becomes also affected by the landscape characteristics. Most of studies on seed predation in human-modified landscapes do not take into account the different scales in which this process operates. Here we evaluate how landscape structure affects seed predation in a palm (Syagrus romanzoffiana) that provide a keystone resource to the frugivory community in 13 landscapes that vary in forest cover, fragment number and size in the Brazilian Atlantic forest. We found that the overall seed predation is explained by the fragment size, shape and the distance to the edge. Seed predation by the dominant vertebrate seed predator (squirrels) is also related with the fragment size and shape, and they interact with the invertebrates in such way that the invertebrate seed predation is mainly explained by the squirrel predation and by the distance to the edge. In turn, seed predation by terrestrial rodents is correlated with the habitat amount in the landscape, preying upon more seeds in landscapes with less than 30% of habitat. Our results indicate that the Syagrus romanzoffiana seed predation is more affected by the fragment variables than by landscape ones, and that patch size, shape and edge effect are more important predictors of seed predation of this palm than habitat amount in the landscape. Our results also highlights that the fragment geometry, a neglected variable in most of studies, is importance to ecological systems
Mestre
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Worley, Anne Catherine. "Flower size-number trade-offs and the evolution of floral display in animal-pollinated plants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0026/NQ49827.pdf.
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Rutherford, Stephen Mark. "The genetic and physical analysis of mutants of chloroplast number and size in Arabidopsis thaliana." Thesis, Open University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308129.
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Stuart, Joseph Scott 1971. "Observational constraints on the number, albedos, size, and impact hazards of the near-Earth asteroids." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/49805.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.Includes bibliographical references (p. 132-144).
This work provides a statistical description of the near-Earth asteroids (NEAs) in terms of number, orbital parameters, reflectance spectra, albedos, diameters, and terrestrial and lunar collision rates. I estimate the size and shape of the NEA population using survey data from the Lincoln Near-Earth Asteroid Research project including more than 1300 NEA detections. The NEA population is more highly inclined than previously estimated and the total number of NEAs with absolute magnitudes (H) brighter than 18 is 1227 +170/-90. The absolute magnitude and orbital parameter distributions for the NEAs are combined with reflectance spectra and albedo measurements. I obtain a debiased estimate of the fraction of NEAs in each of 10 taxonomic complexes, and a debiased average albedo for each. The number of NEAs larger than 1 km is 1090 +/- 180. Next, I determine the impact frequency, collision velocity distribution and collision energy distribution for impacts of NEAs into the Earth and Moon. Globally destructive collisions ([approx.] 1021 J) of asteroids 1 km or larger strike the Earth once every 0.60 +/- 0.1 Myr on average. Regionally destructive collisions with impact energy greater than 4x1018 J ([approx.] 200 m diameter) strike the Earth every 47,000 +/- 6,000 years. The rate of formation of craters expected from the NEAs is found to be in close agreement with the observed number of craters on the Earth and Moon.
(cont.) These results combine the largest set of NEA discovery statistics from a single survey, the largest set of physical data on NEAs, and corrections for observational bias. The result is a comprehensive estimate of the total NEA population in terms of orbital parameters, absolute magnitudes, albedos, and sizes. This improved description of the NEAs will help us to plan surveys to find and study the remaining undiscovered NEAs, to connect the NEAs to their origins in the main-belt, to connect the NEAs to meteorite samples, to compare the lunar and terrestrial cratering record to the current population of potential impactors, and to understand the magnitude of the NEA impact hazard to the Earth's biosphere.
by Joseph Scott Stuart.
Ph.D.
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Savage, Matthew John. "Rheological studies of non-aqueous poly methyl methacrylate dispersions stabilised using graft copolymer steric stabilisers." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/13844.
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Steric stabilisers were synthesised via the copolymerisation of styrene with acrylic macromonomers. The macromonomers were prepared by end capping reactions of poly 2-ethyl hexyl acrylate (PEHA) prepolymer with vinyl containing species. Preliminary reaction routes proceeded via the use of oxalyl chloride to create an acyl chloride intermediate followed by end capping with hydroxy ethyl methacrylate. This process was found to be inefficient due to the moisture sensitivity of the acyl chloride. The second route involved the direct end capping of the PEHA pre-polymer with glycidyl methacrylate (GMA). Macromonomer conversion levels were improved for the GMA route via the use of high temperatures and tertiary amine catalysts. An optimum set of conditions was achieved using 1.4 diazabicyclo [2.2.2.] octane as the catalyst and a reaction temperature of 160 QC. Non aqueous dispersion polymerisations of methyl methacrylate were performed. The factors affecting particle size in both single stage and twin stage polymerisation schemes were studied. Increases in the particle sizes of these dispersions were observed with increases in the total monomer concentration and also with decreases in the total stabiliser concentration. Increases in the particle size could also be achieved by increasing the proportion of the total monomer in the seed stage of the twin stage reaction and also by decreasing the proportion of the total stabiliser in the seed stage. The importance of the role of the seed upon the final particle size was firmly established. The rheology of these non aqueous dispersions was studied over a range of concentrations and under increasing shear stresses. At Iow and intennediate volume fractions the dispersions were observed to be predominantly Newtonian. Non-Newtonian behaviour was only observed at the extremes of the shear stress ranges studied. At high volume fractions of the dispersions non-Newtonian behaviour was observed over the range of shear stresses studied. Maximum volume fractions (~m) were calculated for these dispersions using the Kreiger-Dougherty equation. When these dispersions were blended in size ratios of 2:1 it was observed that 4 > m could be increased due to improved particle packing efficiency.
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Hovatter, Stephanie R. "THE EFFECTS OF BIOTIC AND ABIOTIC SOIL CHARACTERISTICS ON POPULATION SIZE VARIATION OF LOBELIA SIPHILICITA." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1228160953.
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Madhavan, Sharmila. "Screening of HvNAM-B1 gene polymorphism, grain nutrient content and seed size in 80 Scandinavian barley cultivars." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69079.
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Micronutrient malnutrition is a leading worldwide health problem that affects billions of people particularly in the developing countries resulting in serious health conditions. The domestication of crops produced high yield and larger seed size but with a reduction in nutritious quality. The locus NAM or Gpc-1 affects both the seed size and nutrient content in wheat and barley. A non-functional allele of the gene increases the seed size but at the expense of protein and micronutrient content. However, this gene was found to be lost in wheat during the early domestication resulting in lower nutrient content. Therefore, the selection for high yield has lead to lower grain nutrients. Our aim of the present study is to investigate when the selection for yield occured in barley and to check the existence of the wild type allele in the 19th century of landrace barley crops. In addition, to analyse the barley grain concentration of protein, iron and zinc among the landrace and cultivars from various time periods of northern Europe. The grain nutrient concentration of Nitrogen, Iron and Zinc did not show significant difference among the investigated 80 Scandinavian barley accessions. The grain nutrient concentration did not correlate with the seed size and chlorophyll content. The polymorphism was not observed among the allelic diversity of HvNAM-1 gene indicating that the NAM-B1 gene still prevails in the 19th century barley cultivars.
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Jones, Trevor A. "The effects of seed size on seedling growth response to elevated CO¦2 in four conifer species." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62346.pdf.
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Koehler, Christopher M. "Visualization of Complex Unsteady 3D Flow: Flowing Seed Points and Dynamically Evolving Seed Curves with Applications to Vortex Visualization in CFD Simulations of Ultra Low Reynolds Number Insect Flight." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1291756507.
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Geierman, Christina. "Barnacle feeding : comparing cirral anatomy, feeding behavior, Reynolds numbers, and cirral fan leakiness across three size classes of three species of common acorn barnacles /." Connect to title online (Scholars' Bank), 2007. http://hdl.handle.net/1794/6003.
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Baloch, Abdul Hameed. "Effects of seed size and a fungal pathogen, Colletotrichum coccodes, on population dynamics of velvetleaf (Abutilon theophrasti Medic.)." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36949.
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Experiments were conducted in controlled and field conditions to determine the effect of seed size, a fungal pathogen (Colletotrichum coccodes), and soybean interspecific competition on the population dynamics of Abutilon theophrasti (velvetleaf). Seed size differences among ten individual A. theophrasti plants significantly (P < 0.001) affected seed germination and dormancy. Higher seed viability (98%) was observed among seeds having a weight above 6.0 mg. The response of A. theophrasti plants that originated from two extreme seed size groups (small <7mg and large >12mg) to the pathogen, C. coccodes, did not change over generations, and the most vigorous plants produced heavier seeds regardless of the initial seed size or infection with C. coccodes. Under field conditions, the application of C. coccodes and the herbicide, bentazon, did not affect the vegetative and reproductive biomass of A. theophrasti plants when grown in monospecific stands. However, a split application of C. coccodes and bentazon significantly reduced the aboveground biomass and reproductive output of A. theophrasti plants when grown in competition with soybean. The frequency distributions of A. theophrasti plant height, aboveground biomass, and stem diameter were positively skewed (L-shaped) when competing with soybean. However, A. theophrasti plant height and stem diameters were negatively skewed (J-shaped) and the aboveground biomass was positively skewed (L-shaped) in monospecific stands. The allometric relationships of A. theophrasti aboveground biomass and stem diameter in comparison with plant height were curvilinear when grown alone and when in the presence of soybean. However, aboveground biomass and stem diameter showed a simple linear relationship on a log-log scale in both monospecific stands and in competition with soybean.