Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

A review of the literature revealed that there is a lack of depth in our knowledge of gymnospermous seeds with regard to the development and germination processes. The phytohormones, particularly the cytokinins have been implicated in these processes. The seeds of Podocarpus henkelii were thus selected as experimental material for studying the biochemical and cytokinin-like changes associated with development and germination. The development of these seeds was also followed at the ultrastructural level. These studies revealed that cellular detail within the female gametophyte only began .to form in December (early summer), approximately six weeks after fertilization had taken place. At this time some reserve protein was evident and the embryo sporophyte consisted of only a few pro-suspensor and pro-embryo cells. Concurrently, the cytokinin levels were fairly high in the female gametophyte but low in the epimatium. In both seed components two cytokinin- like compounds predominated which co-chromatographed with the free base cytokinin zeatin and its ribonucleoside. The second sample was taken in late January (mid-summer) by which time the embryo sporophyte had developed rapidly into a readily distinguishable seed component. The cellular detail indicated that much cell division had recently taken place and that the cells were currently increasing in size and accumulating starch and lipid. In the female gametophyte the soluble sugars were at the maximum level recorded during these experiments and the level of starch was increasing. The extractable cytokinin content of the seed was high at this time, particularly in the embryo sporophyte. In all three seed components cytokinin-like compounds which co-chromatographed with zeatin and ribosylzeatin were present. These high levels of cytokinin coincided with the rapid increase in both fresh and dry mass of the embryo sporophyte and female gametophyte. Ultrastructural studies of the third sample collected in mid-March (early autumn) showed that cellular changes were associated mainly with increases in cell size and the accumulation of food reserves, particularly starch. The cytokinin levels had decreased in all three seed components at this time. There was an increase in the cytokinin which co-chromatographed with glucosylzeatin in the female gametophyte. The seeds matured in late April (autumn) and had the unusual features of not drying out during maturation. Fresh seeds collected from the ground had a moisture content of ca. 62 per cent. The main food reserve was starch with relatively small amounts of protein and lipid also present. The seeds of Podocarpus henkelii germinated readily after scarification in the absence of water provided that their moisture content remained ca. 60 per cent. Seeds in which the moisture content had fallen below ca. 54 per cent required additional water for germination. The moisture content of the seeds fell rapidly under natural conditions and viability was lost below a moisture content of ca. 34 per cent. Unscarified seeds of 52 per cent moisture content placed under moist conditions at a constant 25°C took 23 weeks to achieve 68 per cent germination. These experiments showed that although the epimatium limited water uptake by the seeds it did not prevent moisture loss to the atmosphere. This appears to be the main factor contributing to the seed's inefficiency as a propagule. A small degree of after-ripening was recorded with the embryo sporophyte increasing in size with storage. This appeared to contribute to the increased rate of germination of the scarified seeds. An interesting feature of the seeds of Podocarpus henkelii is that they have the ability to fix atmospheric carbon, which is subsequently translocated from the epimatium to the female gametophyte and embryo sporophyte. The mature seeds were stored at 4°C for six weeks during which time little change had occurred at the ultrastructural level. Protein vacuoles in the embryo sporophyte had disappeared and in all three seed components cytokinin levels were low. Three days after scarification and the start of incubation, little change in cellular detail was apparent as limited rehydration was necessary due to the high moisture content. The cytokinin levels in the embryo sporophyte and epimatium had increased, whilst the levels in the female gametophyte had decreased at this time. In the embryo sporophyte lipid mobilization had commenced with these reserves apparently being metabolized within vacuoles. The rate of respiration measured in terms of increases in CO[2] evolution, increased 60 hours after the start of the incubation period, just 12 hours before ten per cent germination was recorded. Germination was accompanied by a large increase in the levels of cytokinins in the female gametophyte and embryo sporophyte. The cytokinins detected co-chromatographed with the free base cytokinin zeatin and its riboside, ribosylzeatin. Concurrently, marked ultrastructural changes were recorded with increases in the amounts of dictyosomes, endoplasmic reticulum and the formation of polyribosomes, all of which are indicative of increased metabolic activity. Similar increases in the female gametophyte were ofa lower order and occurred only after nine days of incubation. By this time the levels of cytokinins had decreased considerably. After 12 days of incubation 65 per cent of the seeds had germinated. As much of the food reserves in the female gametophyte and embryo sporophyte remained, it is suggested that these reserves are utilized for subsequent seedling establishment rather than for germination. The actual role that cytokinins play in the development and germination of these seeds is not clear. High levels of this phytohormone coincide with periods of food deposition and mobilization suggesting that they play an important part in these processes. The results of the biochemical, cytokinin and ultrastructural studies are discussed in relation to the developmental and germination processes and are compared to the data of other seeds. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1981.

Pinus radiata is the most planted tree in the southern hemisphere. The planted trees are especially susceptible to pathogens, but even the native population, nowadays limited tomerely five locations, are threatened by diseases caused by arthropods, fungi and dehydration. Endophytes are bacteria or fungi that reside inside healthy plant tissue, and often have a beneficial effect on their hosts. Endophytes can help plants adapt to abiotic stress such as drought and protect them against pathogens and insect pests. Given the roles that endophytes play in host stress responses, it is possible that without studying endophytes we may not fully understand a plant’s response to increased temperatures and climate-induced disease.Using Illumina-sequencing of the 16S rRNA-gene the bacterial endophyte community in 15 trees from three of the remaining native populations were studied. By investigating trees from several sites geographical community differences were discovered. The three overall most dominating bacterial taxa can all be connected with genera known to contain members withanti-fungal properties.

Thesis (M.S.)--Oregon State University, 1993. / Includes mounted photographs. Typescript (photocopy). Includes bibliographical references (leaves 64-86). Also available on the World Wide Web.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1991. / Bibliogr.: f. 58-63. Document électronique également accessible en format PDF. CaQCU

Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 148-159). Also available online.

Thesis (M.S.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 78-83). Also available on the World Wide Web.

The overall objective of this thesis was to improve our understanding of the light environment associated with two of the major deciduous competitors of commercial conifer seedlings in low elevation coastal British Columbia, and the physiological response of young conifers to specific environments and changes in the environment. Studies were conducted to investigate: 1) seasonal and herbicide-induced changes in the light regimes beneath the canopies of two brush species, 2) growth and physiology of seedlings of three conifer species in several different deciduous brush environments throughout the year, and 3) changes in the physiology and growth of suppressed conifer saplings when different methods and schedules were used to reduce shading from an overtopping red alder canopy. Seasonal changes in the light quantity and quality were documented within salmonberry (Rubus spectabilis Pursch) and below red alder (Alnus rubra Bong.) canopies. The prediction of light attenuation within salmonberry canopies using the Beer-Lambert law was good for foliated canopies using leaf area index, and defoliated canopies using stem area index. As salmonberry leaf area increased, the ratio of red to far-red light declined exponentially. Growth of grand fir (Abies qrandis (Dougl.) Forbes), western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Douglas-fir (Pseudetsuga menziesii (Mirbel) Franco) seedlings decreased with increases in the canopy density of overtopping deciduous species. Physiological differences between conifer species and differences between overtopping canopy treatments declined in the autumn and winter. Based on the physiological measurements, suppression of the shade intolerant Douglas-fir seedlings was greatly reduced during the period that overtopping deciduous canopies were leafless. Animal damage reduces growth and probably increases the duration seedlings are under overtopping canopies. Suppressed Douglas-fir saplings released from overtopping by red alder canopies showed the greatest growth response when the alder canopies were removed in the spring; complete removal of the alder canopy during the summer had a predictably deleterious effect on the sapling physiology and growth. Herbicide injections resulted in a slower but predictable increase in conifer growth. / Forestry, Faculty of / Graduate

Please read the abstract in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2005. / Genetics / Unrestricted

O presente trabalho teve como objetivo caracterizar o desenvolvimento da semente de Araucaria angustifolia através da proteômica comparativa, buscando compreender as alterações fisiológicas e metabólicas que ocorrem durante esse processo. Inicialmente, foram avaliados três diferentes metodologias de extração de proteínas. A metodologia composta por solução de extração contendo 7 M de uréia, 2 M de tiouréia, 1% de ditiotreitol, 2% de Triton-100, 1 mM de fluoreto de fenilmetilsulfonil e 5 µM de pepstatina, seguido de precipitação em 20% de ácido tricloroacético apresentou géis de maior resolução e reprodutibilidade, tendo sido escolhida como metodologia de extração protéica para o estudo das alterações no proteoma da semente de A. angustifolia. Uma dificuldade associada ao estudo do proteoma de espécies não sequenciadas é a baixa representatividade nos bancos de dados protéicos, resultando em identificações baseadas em homologia. Estratégias proteômicas baseadas em fracionamento em gel resultam em grandes contaminações por fragmentos de queratina. Sendo assim, foi desenvolvido um programa de remoção de espectros de baixa qualidade para utilização em proteômica baseada em homologia. As análises mostraram que o programa reduz o tempo de busca, melhora a qualidade dos alinhamentos e não resulta em perda de identificações positivas. Finalmente, utilizando as metodologias descritas, foram estudadas as alterações no proteoma durante o desenvolvimento da semente de A. angustifolia. Noventa e seis proteínas foram identificadas e agrupadas de acordo com sua função biológica e padrão de detecção. Os resultados obtidos permitiram o estabelecimento de marcadores protéicos no início e final do desenvolvimento embrionário. A análise das proteínas abundantes no início da embriogênese indica um maior controle no metabolismo oxidativo em relação aos estádios finais. Contrariamente, o final da embriogênese é caracterizado por um alto metabolismo de assimilação de carbono e acúmulo de proteínas de reserva. As implicações dos resultados obtidos no controle e melhoramento de sistemas de embriogênese somática na espécie também foram discutidas. / The aim of the present work was to characterize the seed development of Araucaria angustifolia through proteomics in order to understand the physiological and biochemical changes during this process. For that, initially, three different protein extraction methods were evaluated. The extraction based on protein solubilization in 7 M urea, 2 M thiourea, 1% dithiothreitol, 2% Triton-100, 1 mM phenylmethylsulphonyl fluoride, 5 µM pepstatin, followed by 20% trichloroacetic acid precipitation showed the highest gel resolution and reprodutivity and, thus, was chosen to be used in the analysis of the proteome of A. angustifolia seeds. One aspect that hampers the proteome study of unsequenced species is the low protein representativity in databases. So, protein identification is usually carried out through homology. Strategies based on 2-DE result in high keratin contamination. In the present work a spectra filtering software was developed and evaluated for use in homology driven proteomics. The software reduced the time of search, improved alignment quality and did not result in lost of positive identifications. Finally, using the described strategies, the changes in the proteome of A. angustifolia seeds were studied. Ninety six proteins were identified and classified according to their biological functions and expression profiles during seed development. The identified proteins may be used as protein markers of early and late embryogenesis. Proteins involved in the control of oxidative metabolism were highly expressed during the early stages of seed development; while, carbon metabolism and storage proteins were highly expressed in late stages. Considerations on the improvement and control of somatic embryogenesis through medium manipulation and protein markers screening using data generated are also discussed.