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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Pollination processes - maternal and offspring performance

Holmén Bränn, Kristina January 2007 (has links)
<p>Pollination is one of the most important factors determining the reproductive success of plants. This thesis examines processes associated to varying pollination, with focus on plant responses. The first aim was to examine the possibility and constraints for short-term evolution of flower size in <i>Raphanus raphanistrum</i>. The results showed that there exists a possibility for pollinator-mediated short-term evolution of flower size in the study species. Flower size was strongly correlated to plant size. Since flower size cannot evolve separately from plant size, this correlation may constitute a constraint to the evolution of flower size. The second aim was to determine how varying pollen load affects later flowering, reproduction and growth of maternal plants. High pollen load treatment resulted in larger or more flowers on late flowers, which may enhance pollen dispersal and reproductive success, while the total seed mass was the same between treatments. The results indicate that the study species <i>R. raphanistrum</i>, <i>Sinapis arvensis</i> and <i>Brassica napus</i> have plastic responses in floral traits according to the present pollination level. The third aim was to determine how varying pollen load affects seed quality and offspring vigor. The results suggest that high pollen load had no positive effects on seed quality or offspring vigor due to pollen competition. Instead, seed mass determined seed quality and offspring vigor in the three study species and low pollen load treatment resulted in highquality offspring due to heavier seeds. The fourth aim was to examine causes and consequences of variation in reproductive success of <i>Succisa pratensis</i> on a regional scale. The results suggest that the most important variables, on a regional scale, for reproductive success were population size and habitat quality. The results showed that seed weight variation might be important when assessing reproductive success. In this study, seed weight variation did not seem to be adaptive.</p>
12

Pollination processes - maternal and offspring performance

Holmén Bränn, Kristina January 2007 (has links)
Pollination is one of the most important factors determining the reproductive success of plants. This thesis examines processes associated to varying pollination, with focus on plant responses. The first aim was to examine the possibility and constraints for short-term evolution of flower size in Raphanus raphanistrum. The results showed that there exists a possibility for pollinator-mediated short-term evolution of flower size in the study species. Flower size was strongly correlated to plant size. Since flower size cannot evolve separately from plant size, this correlation may constitute a constraint to the evolution of flower size. The second aim was to determine how varying pollen load affects later flowering, reproduction and growth of maternal plants. High pollen load treatment resulted in larger or more flowers on late flowers, which may enhance pollen dispersal and reproductive success, while the total seed mass was the same between treatments. The results indicate that the study species R. raphanistrum, Sinapis arvensis and Brassica napus have plastic responses in floral traits according to the present pollination level. The third aim was to determine how varying pollen load affects seed quality and offspring vigor. The results suggest that high pollen load had no positive effects on seed quality or offspring vigor due to pollen competition. Instead, seed mass determined seed quality and offspring vigor in the three study species and low pollen load treatment resulted in highquality offspring due to heavier seeds. The fourth aim was to examine causes and consequences of variation in reproductive success of Succisa pratensis on a regional scale. The results suggest that the most important variables, on a regional scale, for reproductive success were population size and habitat quality. The results showed that seed weight variation might be important when assessing reproductive success. In this study, seed weight variation did not seem to be adaptive.
13

Plant-herbivore-predator communities and grassland management intensity - Implications for biodiversity conservation practices on local and landscape scales

Rothenwöhrer, Christoph 19 March 2012 (has links)
No description available.
14

Fitohemijski skrining i biološka aktivnost ekstrakata i tradicionalnih proizvoda od plodova divljih ruža (Rosa L.;Rosaceae) / Phytochemical screening and biological activity ofextracts and traditional preserves of rose hips (Rosa L., Rosaceae)

Nađpal Jelena 13 July 2017 (has links)
<p>&nbsp;&nbsp; Cilj ove doktorske disertacije predstavljalo je ispitivanje fitohemijskog sastava i biolo&scaron;ke aktivnosti vodenih i metanolnih ekstrakata svežih i suvih plodova, kao i voćne ka&scaron;e i džema pripremljenih po tradicionalnoj recepturi od plodova &scaron;est samoniklih vrsta <em>Rosa L.: R. canina, R. dumalis, R. dumetorum, R. tomentosa, R. arvensis, R. sempervirens. </em>Ispitivanje fitohemijskog sastava obuhvatalo je LC -MS/MS analizu 64 odabrana fenolna jedinjenja, hinske kiseline (organske kiseline) kao i tri triterpenoida. Takođe, izvr&scaron;eno je spektrofotometrijsko određivanje sadržaja ukupnih fenolnih i flavonoidnih jedinjenja, kao i vitamina C. Evaluacija biolo&scaron;ke aktivnosti obuhvatala je in vitro ispitivanja&nbsp; antioksidantne i antiinflamatorne aktivnosti, kao i ispitivanje uticaja ekstrakata odabranih vrsta Rosa na aktivnost enzima acetilholinesteraze i rast tumorskih i netumorskih ćelija.</p><p>&nbsp;&nbsp; Sumiranjem dobijenih rezultata može se zaključiti da sveži i suvi plodovi ispitivanih vrsta <em>Rosa</em>, kao i voćne ka&scaron;e i džemovi predstavljaju značajan izvor vitamina C i fenolnih jedinjenja, sa elagnom kiselinom kao najzastupljenijom fenolnom komponentom. Takođe u pojedinim ekstraktima vrsta<em> R. dumetorum</em> i<em> R. tomentosa</em> detektovana je visoka koncentracija ursolne kiseline, dok je hinska kiselina prisutna u značajnoj koncentraciji u svim ispitivanim ekstraktima.</p><p>&nbsp; &nbsp;Ekstrakti ispitivanih vrsta, izuzev vrste<em> Rosa arvensis</em>, pokazali su visok antioksidantni potencijal koji se ogleda u njihovoj sposobnosti neutralizacije nekoliko radikalskih vrsta, redukcionom potencijalu i sposobnosti inhibicije lipidne peroksidacije. Ispitivani ekstrakti ispoljili su umerenu antiinflamatornu aktivnost u pogledu inhibicije produkcije odabranih metabolita ciklooksigenaznog (12-HHT, TXB<sub>2</sub>, PGE<sub> 2</sub>) i 12-lipooksigenaznog (12-HETE) metaboličkog puta arahidonske kiseline,&nbsp; posebno prostaglandina E&nbsp; . Takođe, in vitro ispitivanjem uticaja ekstrakata odabranih vrsta Rosa na aktivnost acetilholinesteraze pokazana je umerena aktivnost. Vodeni ekstrakti i ekstrakti voćnih ka&scaron;a vrsta <em>R. canina, R. tomentosa i R. sempervirens</em> pokazali su umereni inhibitorni potencijal prema rastu HeLa ćelijske linije, dok su ekstrakti vrste <em>R. sempervirens </em>pokazali aktivnost i prema HT-29 ćelijama. Dobijeni rezultati ukazuju na značajni potencijal plodova i tradicionalnih proizvoda ispitivanih vrsta <em>Rosa</em> za upotrebu u proizvodnji nutraceutika i funkcionalne hrane.</p> / <p>&nbsp;&nbsp; The aim of presented doctoral thesis was investigation of phytochemical composition and biological activity of water and methanol extracts of fresh and air-&nbsp; dried rose hips, as well as pur&eacute;e and jam made according to traditional recipe of&nbsp; hips of six wild growing<em> Rosa L. species: R. canina, R. dumalis, R. dumetorum, R</em>.&nbsp; <em>tomentosa, R. arvensis, and R. sempervirens.</em> Examination of phytochemical composition included LC-MS/MS analysis of 64 selected phenolic compounds, quinic&nbsp; acid (organic acid) and three triterpenoids. Also, total phenolic and flavonoid contents, as well as vitamin C contents were determined spectrophotometrically. Biological activity evaluation of extracts of six <em>Rosa</em> species included in vitro investigation of antioxidant, anti- inflammatory, anti-acetylcholinesterase and cytotoxic activity.<br />&nbsp;&nbsp; According to obtained results, fresh and air-dried rose hips, as well as their preserves present valuable source of vitamin C and phenolic compounds, especially&nbsp; ellagic acid, which was the most abundant examined phenolic compound. Furthermore, high concentration of ursolic acid was detected in some<em> Rosa &nbsp;</em> <em>tomentosa and R.&nbsp; rumetorum</em> extracts, while notable concentration of quinic acid&nbsp; was present in all examined extracts.<br />&nbsp;&nbsp; Extracts of all examined species, apart from <em>Rosa arvensis</em>, showed considerable antioxidant activity in terms of radical scavenging ability, reduction potential and inhibition of lipid peroxidation. Moreover, extracts exhibited moderate anti- inflammatory activity by means of inhibition of the main arachidonic acid metabolites &nbsp; formed incyclooxygenase-1 (12-HHT, TXB<sub>2</sub>, PGE <sub>2</sub> ) and 12-lipoxygenase (12-HETE)&nbsp; pathway, especially prostaglandin E<sub>2</sub> . Also, investigation of anti- cetylcholinesterase&nbsp; activity revealed moderate activity of extracts of all examined species. In addition,&nbsp; predominantly water extracts of fresh andair-dried rose hips, as well as pur&eacute;e of<em> R</em>.&nbsp; <em>canina, R. tomentosa </em>and <em>R. sempervirens</em> showed inhibitory activity toward HeLa, while <em>R.sempervirens</em> extracts also inhibited HT-29 cell growth. Presented results indicate significant potential of examined rose hips and their preserves for use as nutraceuticals and functional food.</p>
15

Population dynamics and population genetics of the Critically Endangered Raso lark : implications for conservation

Dierickx, Elisa Gwenda Godelieve January 2018 (has links)
The Raso lark is a Critically Endangered bird endemic to the islet of Raso, Cape Verde. This thesis investigates two phenomena that particularly put the species at risk: its extreme fluctuations in population size, and its potentially very low genetic diversity arising from small population size and severe past population contraction. More specifically, two chapters estimate year-to-year survival and explore the factors - environmental and individual - that influence it, while two other chapters examine the lark’s genetic characteristics compared to its two continental closest relatives, including phylogenetic relationships and levels of genetic diversity. The conclusion of the thesis then uses these results to make recommendations for the conservation of the Raso lark. Each of the data chapters is summarized below: Chapter 3 estimates adult survival in the Raso lark and tests whether it could be linked to two population phenomena observed in the field: a highly variable population size and a male-biased sex ratio in certain years. Using a dataset spanning 10 years, I estimated survival for both sexes to fluctuate between 0.76 and 0.94 over this period. This is much higher than the survival rate of its closest relative, the skylark. I also found strong evidence for survival fluctuating over time and differing between males and females (with males having higher survival until 2011, at which point the trend inverted), which could play a role in the aforementioned population size fluctuations and male-biased sex ratio, respectively. Chapter 4 aims at understanding which factors shape survival in the Raso lark. Two types of variables were considered: year-dependent (rainfall, population size, population mean clutch size) and individual-dependent (age, body size characters, size ratio with mate, Ase18 genotype). Amongst the year-dependent variables, only sameyear rainfall impacted survival, with a 13% decrease in survival in the wettest year compared to the driest year, making it the most likely explanation for the inter-annual fluctuations in survival found in Chapter 3. Results also hint at some of the individual factors - morphological measurements and Ase18 genotype - influencing survival. The picture that emerges is that of a species whose life history strategy is to invest heavily in maintenance and survival, but less into fecundity, which stands in sharp contrast with the mainland-dwelling skylark. This is consistent with the theory that island birds generally have slower life history strategies than their continental counterparts. Chapter 5 determines the precise relationship between members of the Alauda clade, resolving a node on the phylogenetic tree of all larks that the study by Alström et al. (2013) was unable to resolve. My RADseq results indicate that the Raso lark and the skylark are sister species, and that the Oriental lark is likely to be a subpopulation, or maybe a subspecies, of the skylark. Chapter 6 compares the population genetics of the Raso lark with those of the skylark. In particular, it estimates the genetic diversity of the Raso lark and investigates the drivers behind it. I found unexpectedly high nucleotide diversity in the Raso lark, and explain this by showing that the population contraction that the species underwent was recent enough for most of the diversity to still be present. Moreover, 16% of the Raso lark genome has levels of heterozygosity on average 6.6 times higher than elsewhere on the genome, likely due to suppressed recombination and the existence of a neo-sex chromosome in larks. Despite this, I found high levels of relatedness and of linkage disequilibrium in the Raso lark, two clear genetic signs that it underwent a severe population contraction several centuries ago.

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