No description available.

No description available.

No description available.

Senecio aquaticus is a problematic pest species due to its toxic nature. It can cause economic and habitat loss. Senecio aquaticus occurs on the rare and very species rich MG8 plant community. This community relies on management practices including grazing and hay cutting to persist. Where S.aquaticus is prevalent agricultural abandonment could lead to habitat loss. At present there are no adequate control methods for S.aquaticus as current ones are costly or may damage habitat. This thesis aimed to take an ecological approach to this problem to find a new control method that was both cost effective and would not damage the habitat. Four potential control methods were trialled. Farmyard manure application, Lime, Drainage gutters and Early hay cut, aiming to take advantage of S.aquaticus s poor competitive ability, by promoting the surrounding vegetation and out-competing the Senecio. Early hay cut aimed to prevent seed set. Hay cut and manure decreased the Senecio population after two years, hay cut having the biggest effect. Lime and drainage did not reduce abundance although S.aquaticus abundance was demonstrated to correlate with high water table. Pot experiments revealed that cutting time should be around the is" June to prevent plants reflowering and before seedset. Seed bank analysis indicated a short lived seed bank. Competition experiments revealed root competition to be most influential and adult plants most sensitive. Productivity decreased with competition intensity. Early hay cut had no negative impact on the plant community, however manure decreased diversity and likeness to MG8 with an increase in grass and loss of forbes. Due to this negative impact on plant community it should not be used. This study recommends the use of early hay cut around the is" of June for two consecutive years as a S.aquaticus control method. Page 11

The aim of this study was to research the ecology and genetics of Cirsium dissectum and to discuss the implications of the results for its conservation. The ecology of C. dissectum was described through a review of the literature. Site characteristics, plant communities and reproductive biology were investigated by examining 22 populations throughout the British Isles. Microsatellite genetic markers were used to investigate levels of genetic diversity within and between these populations. Within populations, relationships between genetic diversity, population size, fitness and habitat quality (concentrating on soil nutrients and vegetation structure) were explored using multiple regression and structural equation modelling. Differentiation between populations was examined by comparing rnicrosatellite markers with morphological traits and this was supplemented by a crossing experiment that investigated the effects of inbreeding and outbreeding. This study showed that C. dissectum was a clonal species with a mixed mating system. Previous research had suggested that clonal propagation was the dominant form of reproduction but this study showed that sexual reproduction was important in this species, as levels of genotypic diversity were high. There were interactions between population size, genetic diversity, plant fitness and habitat quality. Smaller populations of C. dissectum had lower genetic diversity and this subsequently reduced plant fitness. Higher levels of bare soil and phosphorus were related to higher levels of genetic diversity; bare soil may provide establishment gaps for seedlings and clonal offspring, while phosphorus may encourage flowering and/or seedling survival. Populations of C. dissectum showed high levels of genetic differentiation and strong isolation by distance using microsatellite genetic markers. Both microsatellite genetic markers and morphological traits revealed geographical structuring between populations, but this was less pronounced using the morphological traits. Plants in Ireland showed higher levels of morphological differentiation compared to Britain. C. dissectum showed strong, early acting inbreeding depression when plants were selfed and a trend towards outbreeding depression when genetically distant populations were crossed. Populations of C. dissectum should be conserved throughout the geographical range of the species in the British Isles. Sites should be managed so that habitat heterogeneity is maintained, enabling C. dissectum rosettes to flower and to maintain bare soil for seedling establishment. Habitat restoration should use seed collected from a number of local populations of the same habitat.

Chaque étape marquante de l’évolution de la lignée verte, notamment la conquête du milieu terrestre, a été marquée par l’émergence de nouvelles voies métaboliques notamment au sein du métabolisme spécialisé via des évènements de duplication et de néo-fonctionnalisation de gènes. Ces mécanismes cruciaux constituent l’un des moteurs de l’évolution en permettant l’apparition de nouvelles molécules. Celles-ci, apparues de manière aléatoire, peuvent conférer un avantage évolutif pour l’organisme dans un environnement donné et leur métabolisme peut donc être maintenu sous la pression de sélection. Au-delà de l’intérêt pour la plante, de nombreux métabolites spécialisés présentent des propriétés nutritionnelles et thérapeutiques exceptionnelles. Le décryptage minutieux des voies de biosynthèse est un élément essentiel à la valorisation de ces composés. Une approche de génétique inverse a été conduite afin de caractériser le métabolisme des acides hydroxycinnamiques majoritaires accumulés chez la chicorée. La recherche de gènes candidats a permis l’identification de 7 séquences appartenant au sous-clade Vb de la superfamille des acyltransférases de type BAHD. Les caractérisations biochimiques et fonctionnelles de ces gènes ont démontré l’implication pressentie de 5 d’entre eux dans la synthèse d’acide cholorogénique et composés apparentés soulevant ainsi la question de la redondance fonctionnelle de ces gènes. Les 2 gènes suivants sont, quant à eux, à l’origine de l’émergence d’un nouveau type de phénolamide spécifique du manteau pollinique des Astéracées. La possible contribution de cette diversification métabolique dans le succès évolutif de cette famille est alors envisagée. / Each milestone in the evolution of the green lineage, notably terrestrialization, was supported by the emergence of new metabolic pathways, particularly within the specialized metabolism via gene duplication and neo-functionalization events. These crucial mechanisms, leading to the emergence of new molecules, are one of the driving forces of evolution. These randomly appeared molecules can confer an evolutionary advantage for the host organism in a given environment, and their metabolism can hence be maintained under selection pressure. Beyond the interest for the plant, many specialized metabolites have exceptional nutritional and therapeutic properties. However, careful decryption of their biosynthetic pathways is an essential element for the valorization of these compounds. A reverse genetic approach was conducted to characterize the metabolism of the major hydroxycinnamic acids accumulated in chicory. The search for candidate genes allowed the identification of 7 sequences belonging to the subclade Vb of the BAHD acyltransferases superfamily. The biochemical and functional characterizations of these genes demonstrated the expected involvement of 5 of them in the synthesis of cholorogenic acid and related compounds, raising the question of the functional redundancy of these genes. The two remaining genes were characterized as well, demonstrating their responsibility in the emergence of a new type of pollen coat phenolamide specific to the Asteraceae family. The contribution of this metabolic diversification in the successful evolutionary path of this plant family is then considered.

Oritrophium peruvianum (Lam.) Cuatr. is a perennial species, endemic to the Páramos of the Cordillera of Los Andes. In Venezuela, where it is known as Frailejón morado, it is harvested for its widely acclaimed medicinal properties in treating asthma, bronchitis, and influenza. This study aimed to investigate the biology and ecology of O. peruvianum and the impacts of harvesting on its populations. Undisturbed populations of O. peruvianum were dominated by adult vegetative individuals, with middle-sized plants prevailing and with low densities of large adults, whilst densities of small plants were variable. The population structure changed slightly after one year and annual plant growth was shown to be extremely slow. Flowering started at the beginning of the rainfall period and overlapped with fruiting throughout the wet season (April to November), with only a few scattered individuals reproducing during the dry season. Seed production was very variable and germination under experimental conditions was successful (51 to 88%). The population dynamics of two populations were analyzed using a five stages time-invariant linear matrix model with field data collected over two years. The growth rate of the first population was higher (?1 =1.32) than that of the second population (?1 = 1.13). Sensitivity analysis showed that their growth rates were more sensitive to a change in the survival of individuals than to reproduction, due to the low survival rate of newly emerged seedlings. Plants were contributing more to the growth rate if they remained in the same stage class than if they grew to the following stage class. The most significant transition was the survival of stage class 3 (small adults) whilst stage class 5 (large adults) contributed little to the population growth rate. A uniform harvesting of the adult stages each year up to 21% and 43% respectively in each of the two populations could be applied without threatening their survivals. The harvesting of small adults would affect the growth rates of the populations most, whilst the complete removal of stage class 5 would have the least impact. The most sustainable practical policy, considering larger plants with higher economic value, allows harvesting of all plants from stage class 5 in both populations, each year. In the population with the higher proportion of plants in stage class 3, more than one half (63%) of this stage class could be also harvested, whilst in the second population 83% of the plants from stage class 4 (middle-sized plants) could be harvested instead.

This work centres on Cosmos atrosanguineus, a rare Mexican endemic self-incompatible species of Asteraceae that is now believed to be extinct in the wild. The two known wild C. atrosanguineus collections, made in made in the 19th century, localise the species to the pine-oak mountain forest ecological region in two areas of central Mexico. Its disappearance from the natural environment is attributed to habitat destruction by the copper mining industry and subsequent urbanisation, so that C. atrosanguineus is now known only as a cultivated species. European and American C. atrosanguineus populations are probably the progeny of seed collected in the 1860s by Benedict Roezl and brought to Europe for plant verification. Sir William Jackson Hooker (1785-1865), Director of the Royal Botanic Gardens, Kew initially identified the Roezl specimen as Cosmos diversifolius var. atrosanguineus, but it was classified as the distinct species, Cosmos atrosanguineus by Andreas Voss in 1894. Cosmos atrosanguineus is much prized in horticulture for its deep-red "atrosanguinate" blooms, which are deliciously chocolate scented, giving rise to its common name, "the Hot Chocolate Plant". From 1885 to 1942, C. atrosanguineus was sold as seed in England by Thompson and Morgan Seed Merchants, under the name of C. diversifolius atrosanguineus, but disappeared from the Thompson and Morgan seed catalogue thereafter. Cosmos atrosanguineus exhibits strong sporophytic self-incompatibility (SSI), does not set seed, and must be propagated vegetatively, a factor that has contributed to the proliferation of closely related or identical genotypes. Microsporogenesis within the species appears normal, with no discernible differences between microsporogenesis in C. atrosanguineus and two seed-producing Cosmos species. The C. atrosanguineus karyotype and chromosome associations at meiosis identify the species as an allotetraploid that produces viable gametes with ~30% pollen viability. Self- and cross-pollinations of C. atrosanguineus are strongly incompatible with an average of zero pollen grains germinating per stigma. In contrast, cross and self-pollinations in C. bipinnatus and C. sulphureus produced three compatibility groups; incompatible (-), compatible (+) and semi-compatible (±), and four categories of pollen-stigma interaction that putatively identify a gametophytic-sporophytic (G-S) incompatibility system in Cosmos. Dominance interactions of S-alleles are prevalent in the genus and pseudo-self-compatibility was observed in C. bipinnatus but not C. atrosanguineus. The Cosmos stigma is dry, papillate and becomes receptive only after stigmas become reflexed. Prior to this period, the stigmas do not respond to pollination and selfed bud pollinations and crossed bud pollinations are incompatible. Degenerate S-specific primers identified 41 S-domain-encoding sequences from Cosmos and four other genera of Asteraceae. These 41 Asteraceae sequences encoded S-domains related to Brassica S-domain proteins, but none identified as a putative self-incompatible molecule, indicating the control of SI in Cosmos is probably different to that in Brassica. Genetic fingerprinting studies (AFLP) of various European sources of C. atrosanguineus showed no genetic variation. In conclusion, Cosmos atrosanguineus is a strongly self-incompatible species with a reduced genome. It does not set seed because the gene pool of cultivated individuals has narrowed to a level where S-allele numbers are too few to produce cross compatible genotypes. For this to have occurred, the genetic diversity of plants at the Royal Botanic Gardens Kew and in commercial cultivation must have been reduced to genets that share one, but more probably both S-alleles, thus preventing germination of pollen and formation of seed.

La chicorée produit et accumule une panoplie originale d’esters d’acide caféique : les acides caftarique (CTA), chicorique (diCTA), isochlorogénique (diCQA) et chlorogénique (CQA). En plus de leurs multiples rôles physiologiques et écologiques pour la plante, ces composés phénoliques sont dotés de nombreuses propriétés nutritionnelles et thérapeutiques. La valorisation de ces composés nécessite, au préalable, une connaissance approfondie de leur métabolisme. Si la biosynthèse du CQA est bien documentée, celles des autres molécules ne sont que partiellement décrites. L’objectif de ce travail de thèse consistait en la caractérisation de la voie de biosynthèse du CQA et du diCQA. L’analyse détaillée des contenus en polyphénols a révélé une distribution tissulaire originale. Le CTA et le diCTA sont les composés majeurs dans les feuilles alors que le diCQA est le composé majeur dans les racines. Les contenus en CQA ne permettent pas de différencier ces organes. En vue d’une analyse transcriptomique, plusieurs systèmes expérimentaux ont été testés de manière à induire la production et l’accumulation des composés ciblés. Par une approche de génétique inverse, deux gènes codant des HCTs et trois des HQTs ont été identifiés et caractérisés. Ces protéines interviennent dans la synthèse du CQA. Une approche de biochimie a permis d’identifier une séquence protéique potentiellement impliquée dans la synthèse de diCQA chez la patate douce. Par homologie de séquence, un gène candidat a été identifié chez la chicorée. Les travaux présentés dans ce mémoire constituent une contribution significative au décryptage des voies de biosynthèse de ces molécules au fort potentiel. / Chicory synthesizes and accumulates an original combination of caffeic acid i.e. caftaric (CTA), chicoric (diCTA), isochlorogenic (diCQA) and chlorogenic (CQA) acids. In addition to their multiple physiological and ecological roles in plants, these compounds have many pharmaceutical and nutritional properties. A complete understanding of their biochemical pathways is required for optimization of their production. If CQA biosynthesis is well documented, the pathways involved in the synthesis of the other molecules are far to be fully understood. The goal of this PhD thesis was to characterize the pathways involved in CQA and diCQA synthesis.Detailed analysis of phenolic contents revealed an original tissue distribution. CTA and diCTA are mainly accumulated in shoots whereas diCQA was the main compound in roots. CQA is uniformly distributed. To anticipate a transcriptomic analysis, several experimental models have been used in order to modulate the synthesis and the accumulation of the compounds of interest. Through a reverse genetic approach we identified and characterized 2 genes encoding HCTs and 3 genes encoding HQTs. These proteins are involved in the synthesis of CQA. By a biochemical approach, we identify a peptide sequence putatively involved in diCQA synthesis in sweet potato. An homologous gene has been identified in chicory. Data reported here contribute to a better understanding of the biosynthesis of these high-value compounds.

Thesis (M.Sc. (Crop science)) --University of Limpopo, 2007 / Vernonia (Vernonia galamensis) is a new potential industrial oilseed crop. The seeds of this crop contain unusual naturally epoxidised fatty acids which are used in the production of various industrial products. The objective of this study was to evaluate the genetic diversity of selected vernonia lines in Limpopo Province through morphological, seed oil content and RAPD DNA markers. Significant differences were observed for days to 50 % flowering (93 - 140 days), plant height (141.80 - 166.33 cm), number of productive primary heads (29 - 60 head/plant), number of productive secondary heads (12 - 30 head/plant), thousand seed weight (1.85 - 3.52 g) and seed yield (454.44 - 786.85 kg/ha) between lines. Further results from oil analysis showed differences in the contents of seed oil (22.4 - 29.05%), vernolic acid (73.09 - 76.83%), linoleic acid (13.02 - 14.05%), oleic acid (3.77 - 5.28%), palmitic acid (2.48 - 2.98%) and stearic acid (2.26 - 2.75%). Among 13 RAPD DNA primers screened, primer OPA10 amplified DNA samples and resulted in four distinct groupings among tested lines. Four promising lines were selected viz. Vge-16, Vge-20, Vge-27 and Vge-32 displaying greater seed yield, increased vernolic acid content and reduced number of days to 50 % flowering. / National Research Foundataion