Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 1991. / Includes mounted photographs. Typescript (photocopy). Includes bibliographical references (leaves 111-122). Also available on the World Wide Web.

Extensive investigations have shown that the genetic systems which prevent self-fertilization in many of the Angiosperms are based upon the incompatibility of pollen and style. Past studies have also shown that many of the Gymnosperms, including Pseudotsuga, produce little or no viable seed after self-pollination. The causes of this seed failure, however, had not been determined. It was considered that a cytological study of development within the ovules after the self-pollination of Pseudotsuga menziesii should show whether seed failure was caused by comparable incompatible systems. Controlled self- and cross-pollinations were accordingly made on two trees at Vancouver in 1952 and on three trees each, at Victoria and Lake Cowichan in 1954. Cone samples from both pollinations were removed at various dates from each tree and the ovules embedded for later sectioning. The remaining cones were collected at maturity and the seed extracted. It was found that the yields of viable seed varied greatly in individual trees and the investigation was accordingly divided into two parts. The cytological study was confined to two of the trees which had produced very little viable seed after selfing. The second part of the investigation was concerned with the effect of self-pollination on the progeny. The cytological study showed that neither germination of the pollen nor its subsequent development until the time of syngamy were in any way inhibited and both compared favourably with development in the ovules from cross-pollinated cones. Proembryo formation and early embryonic development were normal but the embryos in both trees collapsed approximately ninety days after self-pollination. This collapse appeared to be caused by some failure in the vital relationship between the young embryos and their surrounding gametophytes. The latter appeared healthy and comparable in every respect with those in which embryos from cross-pollination were growing vigorously. It is considered that embryo collapse after self-pollination is probably an inbreeding effect caused by the action of lethal and semi-lethal genes when brought together in a homozygous state. This explanation could account for the very variable effects of self-pollination on the trees studied. Some viable seed was also obtained from cones isolated and not pollinated. The seedlings are diploid and the possible causes of agamospermy are discussed. A study of the inbred progeny shows that self-pollination usually results in seedlings which are smaller and less vigorous than those from controlled cross-pollination. The seedlings from wind-pollination were intermediate and the small size of some suggests that self-pollination may have occurred. The practical aspects of self-pollination in relation to both the natural and artificial regeneration of forest land are briefly discussed. / Science, Faculty of / Botany, Department of / Graduate

No description available.

The present investigation can be divided into two main sections: the first dealing with the post-shedding embryogenesis of Encephalartos natalensis and the second concerned with the cell wall properties of immature and mature embryos of this species. Development of the embryo of E. natalensis from a rudimentary meristematic structure approximately 700 μm in length, extends over six months after the seed is shed from the strobilus. Throughout its development the embryo remains attached to a long suspensor. Differentiation of the shoot meristem flanked by two cotyledonary protuberances occurs over the first two months, during which peripheral tannin channels become apparent. Tannins, apparently elaborated by the endoplasmic reticulum, first accumulate in the large central vacuole and ultimately fill the channel. By the fourth month of development the root meristem is apparent and procambial tissue forming discrete vascular bundles can be discerned in the elongating cotyledons. Between four and six months, mucilage ducts differentiate, and, after six months when the seed becomes germinable, the embryo is characterised by cotyledons far longer than the axis. Shoot and root meristem cells remain ultrastructurally similar throughout embryo ontogeny, containing small vacuoles, many welldifferentiated mitochondria and ER profiles, abundant polysomes, plastids containing small starch deposits and Golgi bodies. Unusually however, Golgi bodies are infrequent in other cells including those elaborating mucilage which is accumulated in distended ER and apparently secreted into the duct lumen directly by ER-derived vesicles. The nonmeristematic cells accumulate massive starch deposits to the exclusion of any protein bodies, and only very sparse lipid, features which are considered in terms of the prolonged period of embryo development and the high atmospheric oxygen content of the Carboniferous Period, when cycads are suggested to have originated. With regard to plant cell walls, the present investigation employed immunofluorescence microscopy and immunocytochemistry to characterise the cell walls of immature and mature embryos of the recalcitrant-seeded E. natalensis to determine wall composition and potential changes with development. These techniques, together with cryo-scanning- and transmissionelectron microscopy (TEM) were used to analyse potential changes in the cell walls of mature embryos upon desiccation. Immature cell walls appeared to be composed of low- and high methyl esterified epitopes of pectin, rhamnogalacturonan-associated arabinan, and the hemicellulose xyloglucan, while partially-esterified epitopes of pectin appear to have a punctuate distribution in the wall. Arabinogalactan protein recognised by the LM2 antibody, along with rhamnogalacturonan-associated galactan and the hemicellulose xylan, were not positively localised using immunological probes, suggesting that the embryo of the current species does not possess these epitopes. Interestingly, mature embryos appeared to be identical to immature ones with respect to the cell wall components investigated, implying that these may not change during the protracted post-shedding embryogeny of this species. Analysis of the monosaccharide composition of the walls by gas liquid chromatography complemented the immuno-labelling work. However, there appeared to be abnormally high levels of glucose (Glc), which may indicate the presence of Glc-rich polymers not accounted for by the antibodies used in the current study. Preliminary Glc-normalised data revealed that there may be considerable quantities of arabinose polymers in the wall comparable to that found in desiccation tolerant plants. Drying appeared to induce some degree of cell wall folding in mature embryos, correlating with their possession of wall plasticisers such as arabinose polymers, but this was limited, due to the abundance of amyloplasts, which filled the cytoplasmic space. From the results of this study, it is proposed that the embryo cell walls of E. natalensis are constitutively prepared for the flexibility required during cell growth and expansion, which may facilitate the observed moderate cell wall folding in mature embryos upon drying. This, together with an abundant supply of amyloplasts in the cytomatrix may provide sufficient mechanical stabilisation during desiccation even though the seeds of this species are highly desiccation sensitive. Overall, this study has been a relatively comprehensive coverage of histological and ultrastructural aspects of embryogenesis in E. natalensis. This work will form a pivotal basis for future studies, which may ultimately lead to the successful germplasm cryopreservation and in vitro production on a commercial scale of these, and other, endangered cycad species. Furthermore, the work on cell walls in this investigation has provided improved comprehension of the responses of seed cell walls to dehydration. / Ph.D. University of KwaZulu-Natal, Durban 2013.

No description available.

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.

The pollination drop is a conservative pollination mechanism observed in all major gymnosperm taxa. Despite its ubiquity and essentiality to gymnosperm reproductive success, it remains poorly understood. Recent studies identifying conifer ovular secretion proteins have indicated a more complex role for ovular secretions than pollen receipt. We used a proteomics approach to analyze the pollination drops of four gymnosperm species (Juniperus communis (common juniper), Juniperus oxycedrus (prickly juniper), Chamaecyparis lawsoniana (Port Orford cedar), and Welwitschia mirabilis). Pollination drop proteins were separated by SDS-PAGE, and the most abundant proteins were analyzed by mass spectrometry and sequenced. Based on BLAST searching of combined amino acid sequences, several proteins were identified: an 83 kDa subtilisin-like proteinase, a 62 kDa glycosyl hydrolase, a 47.5 kDa glucan 1,3-ß-glucosidase precursor, a 30 kDa chitinase, and a 25 kDa thaumatin-like protein in J. connnunis; a 30 kDa chitinase, a 25 kDa thaumatin-like protein, and a 32.5 kDa glucanase-like protein in J. oxycedrus; an 83 kDa subtilisin-like proteinase, a 62 kDa (ß-D-glucan exohydrolase, a 47.5 kDa glucan 1,3-ß-glucosidase, and two 25 kDa thaumatin-like proteins in C. lawsoniana, and a 25 kDa chitinase in W. mirabilis. Gymnosperm phylogeny is a highly debated topic, particularly following the widespread adoption of molecular phylogenetic analyses which conflict with historical morphological phylogenies. The gymnosperms are a difficult group to classify because of their deep evolutionary history and lack of conservative features. Considering that the pollination drop is a highly conservative feature of gymnosperm reproduction, we propose that analysis of pollination drop protein (PDP) variation could be used as an alternative method to resolve gymnosperm phylogeny. PDP variation was analyzed at three taxonomic levels: genus, family, and gymnosperm clade. Based on variation in SDS-PAGE banding patterns, identified peptides, amino acid sequences, and protein identification, we conclude that PDP variation has a phylogenetic component. Further research is necessary to develop this method into a tool used to predict phylogenetic relationships. Based on protein identifications, there is strong evidence that the pollination drop functions in both pathogen defense and pollen development. The observation of hydrogen peroxide and peroxidase activity in the ovular secretions of J. communis, C. lawsoniana, Pseudotsuga menziesii (Douglas fir), and Larix x marschlinsii (hybrid larch) provided further support for the assumed functions of ovular secretions.

Orientadores: Fresia Soledad Ricardi-Branco, Mary Elizabeth Cerruti Bernardes-de-Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-08T17:15:06Z (GMT). No. of bitstreams: 1 Fanton_JeanCarloMari_M.pdf: 53708571 bytes, checksum: 10fdd91a8af8b2efda0335d5645afdef (MD5) Previous issue date: 2007 / Resumo: Fitofósseis inéditos excelentemente preservados na forma de impressões/ são descritos e revelam novas espermatófitas da Paleoflora Crato, proveniente dos calcários laminados do Membro Crato, Fonnação Santana, Cretáceo Inferior, Aptiano da Bacia do Araripe, Ceará, Nordeste do Brasil. Importantes lacunas taxonômicas da paleoflora deverão ser preenchidas a partir de três novos táxons, com designações já sugeridas e que futuramente serão erigidos através de publicações: Cratopteris fertilis, uma gimnosperma basal (pteridospenna mesozóica), afim da família Caytoniaceae, ordem Caytoniales, preservada como um galho portador de folhagem composta com padrão reticulado típico e de ramificações férteis (cupuladas e sinangiadas) organicamente conectadas, fato inusitado na literatura do grupo; Araripephedra papiliofoliata, uma gimnosperma derivada, afim da família Ephedraceae, ordem Gnetales, preservada na forma de caules articulados, ramificações caulinares opostas estéreis de folhas amplas, opostas e férteis com estróbilos solitários pedunculados, abundantes raízes, além de excepcionais detalhes anatômicos externos e internos preservados. As partes vegetativas e reprodutivas compõem uma planta completa, fato inédito na literatura do grupo. Alguns desses caracteres revelam profundas semelhanças com o atual gênero Ephedra L., confirmando as afinidades efedráceas da nova espécie; Iara ipaguassu (Incertae sedis), possível gnetaleana ou ainda uma monocotiledônea alismataleana, preservada como um eixo articulado e lenhoso, com sucessivos verticilos de ramificações tubulares a cilíndricas, áfilas, delgadas e flexíveis. Tais espennatófitas distribuíam-se em habitats distintos ao redor do sistema lacustre do Membro Crato: Cratopteris fertilis foi um arbustó/ arvoreta que habitava áreas não inundáveis, compondo estratos intennediários do dossel de florestas dominadas por gimnospennas; Araripephedra papiliofoliata foi um sub-arbusto de porte muito reduzido, rasteiro, caracteristicamente xerófilo, desenvolvendo-se em moitas devido à propagação vegetativa, fortemente ancorado ao substrato poroso de áreas -secas expostas à radiação solar e vivendo sob tufos de outras gimnospennas xerófitas; Iara ipaguassu, de design sugestivamente hidrodinâmico e muito similar às atuais ervas aquáticas alismataleanas, foi possivelmente uma hidrófila que vivia submersa em ambientes aquáticos do amplo sistema lacustre, influenciados por deltas/ estuários que garantiam condições fisico-químicasnão adversas até o período de estiagem. Caracteres morfológicos e anatômicos (por exemplo, os tipicamente xeromórficos) e as implicaçõestafonômicas e paleoecológicas apartadas a partir da análise dos espécimes permitiram sugerir a grande variedade de paleohabitats existentes ao redor do paleoambiente deposicional e corroborar assim condições climáticas predominantementequentes, de altas taxas de evaporação, porém marc~damentesazonais, com ciclos úmidos a secos. / Abstract: Unknown phytofossils well-preserved as impressions-replacements are described and reveal new spermatophytes from the Early Cretaceous Crato Palaeotlora, which is preserved in the Crato Member laminated limestones, Santana Formation, Aptian, Araripe Basin, Ceará State in the northeastern of Brazil. Three new taxa are proposed: Cratopteris fertilis, Araripephedra papiliofoliata and laTa ipaguassu. These taxonomic novelties will be submitted to publication in specific joumals. Cratopteris fertilis is a basal gymnosperm (mesozoic seed fern) related to the Caytoniaceae family, Caytoniales order, preserved as a twig bearing of compound foliage with typical reticulate venation and fertile branches (bearing cupules and synangia), organically connected, that is reported for the first time in the group literature. Araripephedra papiliofoliata is a derived gymnosperm, related to the Ephedraceae family, Gnetales order, preserved as articulated stems with sterile and fertile opposite branches. The sterile ones bear large opposite leaves, and the fertile, with non-compound pedunculate strobili. The roots are dense. Furthermore, exceptional anatomic details (external and internal) are exhibited. All these parts are attached, in a whole plant. This fact is totally new in the literature. Some of these features reveal deep similarities with extant genus Ephedra L. supporting the fossil ephedracean affinity. lara ipaguassu (Incertae sedis), a possible gnetalean or an alismatalean monocot, is preserved as a wood articulated axis with successive whorls of tubular to cylindrical, flexible, thin, leatless branches. Such plants possibly inhabited distinct habitats around Crato lacustrine system. Cratopterisfertilis was probably a shrub or a small tree which inhabited non-flooded areas compounding the intermediate strata in the canopy gymnosperm forests. Araripephedra papiliofoliata was a sub-shrub, with caulinar branches erect or prostrate, typically xerophyllous, and that grew like bush formations due to the vegetative propagation. This underbrush was strongly sticked to the porous substrate in dry areas exposed to sun light, and living under the xeromorphic gymnosperms tufts. lara ipaguassu of hydrodynamic design and very similar to the extant alisma!alean aquatic herbs, might have been a hydrophyll which lived submerged in aquatic environrnents of wide lacustrine system with delta! estuarine intluence. Morphological and anatomical characters from studied specimens and their taphonomic and palaeoecological implications aIlowed to suggest a diversity of palaeohabitats around the depositional palaeoenvironment, and confirmed mostly warm climatic conditions with high evaporation rates, although pronounced seasonal with cyc1es from moisture to dry ones. / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

A Formação Crato, localizada na bacia do Araripe, Nordeste do Brasil, contém um dos registros fossíferos vegetais mais importantes do Cretáceo Inferior. Estes fósseis apresentam excelente estado de preservação, no geral, com pouca fragmentação, órgãos em conexão e estruturas epidérmicas e anatômicas delicadamente substituídas por óxidos de ferro. Como acontecia globalmente, as gimnospermas eram o grupo vegetal dominante na paleoflora eocretácea da Formação Crato, ocorrendo na forma de Bennettitales, Coniferales e Gnetales. As Bennettitales foram um componente aparentemente raro, estando representado pelas espécies Otozamites sp. e Zamites sp. Dentre as Coniferales, encontram-se as famílias Araucariaceae e Cheirolepidiaceae, as Araucariaceae registradas nas espécies Araucarites vulcanoi Duarte e Araucarites kunzmanni sp. nov.; as Cheirolepidiaceae, o grupo mais diverso, estão representadas pelas espécies Brachyphyllum obesum Heer, Brachyphyllum ponsi sp. nov., Brachyphyllum araripense sp. nov., Tomaxellia aff. T. biforme Archangelsky, Toxamellia aff. T. degiustoi e Pseudofrenelopsis sp. As Gnetales ocorrem na forma das espécies Limaephyton cratense gen. et sp. nov., Limaephyton duartei gen. et sp. nov. e Limaephytophyllum mohrium gen. et sp. nov. Características morfológicas, epidérmicas e anatômicas presentes nos macrofitofósseis da Formação Crato, evidenciam adaptações a um ambiente de baixa umidade. Esta flora se desenvolveu dentro da Região Equatorial, numa área intracontinental sob condições climáticas áridas e semi-áridas. / Crato Formation, located in the Araripe Basin, Northeastern Brazil, bears one of the most important Lower Cretaceous fóssil plant Record. The fossils have an excellent preservation, usually low fragmentated, with attached organs and epidermic and anatomic features delicatedly replaced by iron oxides. As it happens worldwide, gymnosperms were the dominant group in the Lower Cretaceous Crato Formation paleoflora, existing as Bennettitales, Coniferales e Gnetales. Bennettitales were an apparently scarce component, represented by the species Otozamites sp. and Zamites sp. Between the Coniferales, are the families Araucariaceae and Cheirolepidiaceae, the Araucariaceae recorded by the species Araucarites vulcanoi Duarte and Araucarites kunzmanni sp. nov.; Cheirolepidiaceae, the most diverse group, is registered by species Brachyphyllum obesum Heer, Brachyphyllum ponsi sp. nov., Brachyphyllum araripense sp. nov., Tomaxellia aff. T. biforme Archangelsky, Toxamellia aff. T. degiustoi e Pseudofrenelopsis sp. As Gnetales are documented by the species Limaephyton duartei gen. et sp. nov. and Limaephytophyllum mohrium gen. et sp. nov. Morphologic, epidermic and anatomic features founded in the plant fossils from Crato Formation, evidence low moisture environment adaptations. That flora was developed in the Equatorial Region, in an intracontinental area with arid to semi-arid climatic conditions.