Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 19 (1958) no. 4, p. 648-649. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 37-40).

Thesis (PhD) -- Macquarie University, School of Biological Sciences, 1990. / Thesis by publication. Bibliography: leaves 269-324.

Megagametophyte development in situ and in vitro was investigated in Douglas fir to address the following questions: (1) Do endogenous levels of plant hormones change during megagametophyte development and are they associated with morphological changes? (2) Can megagametophytes be cultured prior to fertilization? (3) Can embryos be rescued from megagametophytes cultured soon after fertilization? A histochemical study of storage reserve deposition during megagametophyte development was performed with material isolated weekly for 11 weeks. Prior to fertilization, starch was detected in the neck cells of megagametophytes analyzed 9 weeks after pollination (WAP). During embryogenesis, starch was deposited in the central region of megagametophytes. Proteins and lipids were first detected in the prothallial cells in the periphery of megagametophytes isolated 14 and 15 WAP, respectively. With further development, starch was deposited in prothallial cells around the corrosion cavity, while proteins and lipids were spatially localized to prothallial cells in the periphery. In the embryo, starch accumulation was preferentially localized in the root cap and the embryonal suspensor cells at 17 WAP. A parallel study quantifying the endogenous levels of plant hormones: IAA, IAAsp, Z, ZR, iP, IPA, ABA and ABA-GE, in megagametophytes was performed. Hormones were extracted, purified and fractionated using HPLC. To correct for losses due to procedures, radiolabelled standards were added prior to extraction. The hormones were quantified using an ELISA method. On a dry weight basis, Z levels were highest in megagametophytes at the late central cell stage (8 WAP). During embryogenesis, Z levels peaked during week 13. ZR peaked twice at 13 and 17 WAP. The iP content of megagametophytes increased at 10, 13 and 17 WAP while iP.A concentration increased at 13 and 17 WAP. Prior to fertilization, the free LAA was highest in megagametophytes at 9 WAP. During embryogenesis, the major lA A accumulations occurred at I I ,13 and 15 WAP. lAAsp concentrations reached their highest levels at 10, 14 and 18 WAP. ABA content increased at 11, 13 and 17 WAP. In contrast, ABA-GE levels were relatively constant over the 11 weeks analyzed. Megagametophytes were isolated weekly from 7–10 WAP and cultured on a modified half-strength Litvay's medium supplemented with one of three auxins (NAA, IBA or 2,4-D) and a cytokinin (2 mg/L BAP). Each auxin was tested at three levels: 0.1, 1.0 or 10 mg/L. The objective was to determine whether the megagametophytes would continue to grow in culture. Megagametophytes increased in length after 9 and 18 days of culture. Auxin and cytokinin supplements had a significant effect on growth for material isolated 7 or 10 WAP. However, the viability of the archegonia rapidly declined on all the media tested. The most optimal treatment for each auxin type (BAP in combination with 0.1 mg/L NAA. 1.0 mg/L IBA or 1.0 mg/L 2.4-D) was used to initially culture pollinated megagametophytes in the embryo rescue experiment. After 21 days, megagametophytes were transferred to media containing ABA concentrations of 0.5, 20 or 40 μM. A majority of the rescued embryos were developmentally arrested at the globular stage. Only three embryos, containing over 30 cotyledons each, matured on ABA concentrations of 5, 20 or 40 μM. In conclusion, the prothallial cells of the pre-fertilization megagametophytes could be cultured for long periods and their growth was not dependent on the presence of viable archegonia. The endogenous levels of plant hormones varied with megagametophyte development and were associated with morphological changes. This information has implications for growing megagametophytes for in vitro fertilization and embryo rescue experiments. The endogenous levels of plant hormones could be used to design culture media for rescuing embryos resulting from in vitro fertilization in Douglas fir. / Graduate

As a direct approach to investigate the molecular basis of embryogenesis in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco), a cDNA library made from poly(A)⁺ RNA of developing seeds was differentially screened for clones representing transcripts abundant in the developing seeds but absent in mature seeds. Of a number of clones isolated, two groups were selected for further sequence and gene expression analysis. A group of four cDNA clones (PM2S1, PM2S2, PM2S3 and PM2S4) shared a significant nucleotide and deduced amino acid sequence similarity with each other and with gymnosperm 2S seed storage protein cDNAs. The deduced amino acid sequences had low similarity with angiosperm 2S storage proteins but contained all conserved cysteine residues in an arrangement suggestive of a structural similarity between the 2S seed storage proteins from gymnosperms and angiosperms. Northern blot analysis revealed PM2S mRNAs were present specifically in seeds and temporally during seed development. However, the relatively low abundance of PM2S3 mRNAs and the decline of PM2S2 mRNAs in megagametophyte which occurred before that of the other mRNAs suggested that their expression was regulated differentially. The accumulation of PM2S transcripts in megagametophyte started during the early embryogenesis and reached a peak before that in zygotic embryos. PM2S mRNAs were present in Douglas-fir somatic embryos at the same developmental stages as those in zygotic embryos, and ABA and osmoticum stress were necessary for the expression of PM2S genes in somatic embryos. Southern blot analysis of genomic DNA suggested that the Douglas-fir 2S seed protein genes consisted of at least two sub-families each including several gene members. A gene designated gPm2Sl was isolated and sequenced. A comparison of the upstream sequence of gPm2Sl with the promoters of known 2S storage protein genes did not reveal significant sequence similarity except the presence of RY-repeated element (GCATGC), and the frequent occurrence of ACGT-containing motifs and E-box motifs (CANNTG). The 1.2-kb gPm2Sl promoter was fused to a P-glucuronidase (uidA) reporter gene and transformed into developing Douglas-fir seeds using particle bombardment and into tobacco via Agrobacterium tumefaciens. Histochemical analysis showed that the promoter was active in both systems and the gene expression was confined to endosperm and embryos of transgenic tobacco, indicating a common seed-specific regulatory mechanism between angiosperms and conifers. Another cDNA clone, PM2.1, hybridized to a 0.5 kb transcript and was predicted to encode a metallothionein (MT)-like protein. Alignment of the PM2.1 predicted amino acid sequence with other plant MT-like gene products revealed a general paucity of Cys and Cys-Xaa-Cys sequences and the presence of serine residues within the conserved Cys-Xaa-Cys motifs in the C-terminal domain. Phylogenetic analysis showed that PM2.1 grouped with class I/type 3 MT-like genes. The PM2.1 was expressed in somatic and zygotic embryos, in megagametophyte, as well as in hormone- and metal-treated seeds and seedlings. The PM2.1 transcripts were detected in the needles of 10-week-old seedlings, but not the root tissue or mature pollen. The expression of the PM2.1 gene in embryos was dependent upon ABA and osmoticum and was differentially modulated by metals, suggesting that the PM2.1 gene product may play a role in the control of microelement availability during Douglas-fir seed development and germination. Southern blot analysis of genomic DNA suggested that the PM2.1 was encoded by a multigene family. Three genomic clones were isolated and one of these clones (gPmMTa) was cloned and sequenced. The sequence analysis of its 5'-flanking region identified a number of putative regulatory elements such as ACGT-containing motifs, metal-responsive element (TGCGCC) and ethylene-responsive elements (ATTTCAAA) which may be responsible for gene transcription. DNase I-footprinting experiments with nuclear extracts isolated from Douglas-fir megagametophyte identified two protein-protected sites, a 31-bp sequence locating in the -176/-146 region that contained two ACGT-core motifs, and a 12-bp sequence, 5'-TGCCACGGAAGG-3', of unknown function. To identify promoter regions responsible for the regulation of gPmMTa gene expression, a series of deletions in the 0.9-kb fragment of the gPmMTa promoter was fused to the uidA reporter gene and the chimeric gene constructs were assayed in Douglas-fir and transgenic tobacco. Transient expression assays in megagametophyte and zygotic embryos indicated that the sequence lying between -190 and +88 of gPmMTa was sufficient to drive the expression of the reporter gene and the 225-bp fragment (-677 to -453) contained sequences necessary for high level expression. The gPmMTa promoter was not active in the seeds of transgenic tobacco. / Graduate

Investigations were made of the association among megagametogenesis, pollen morphology, and seed production in two irradiated apple varieties, Golden Delicious and McIntosh, and in two years, 1964 and 1965. In each year eight to ten clones of each variety were selected on the basis of low, medium, and high pollen abortion. Untreated and treated Golden Delicious and McIntosh clones with normal pollen production, approximately 90% and 50% respectively, had the highest proportion of embryo sacs at the differentiated 8-nucleate stage, and the smallest proportion of embryo sacs at the 2- and 4-nucleate stages. Irradiated clones with the least normal pollen had the highest proportion of immature 2- and 4-nucleate embryo sacs. With both varieties and in both years reduced pollen fertility was positively correlated with retarded embryo sac development. Check clones with high pollen fertility had the highest number of developed seeds per fruit and irradiated clones with reduced pollen fertility had the smallest number of developed seeds per fruit. The number of developed seeds per fruit was positively correlated with the proportion of mature 8-nucleate embryo sacs. The reduction in seed numbers in irradiated apple clones with reduced pollen fertility may be explained, in part, by retarded embryo sac development. / Land and Food Systems, Faculty of / Graduate

No description available.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Made available in DSpace on 2014-06-11T19:26:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-15Bitstream added on 2014-06-13T20:54:01Z : No. of bitstreams: 1 pereirajunior_ej_me_sjrp.pdf: 1176824 bytes, checksum: ea26888e0c90e98ae7bc9367c03e1901 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Caracteres embriológicos possuem valor sistemático e sua utilidade foi demonstrada por diversos autores para elucidar o posicionamento filogenético de certas famílias de angiospermas. Este estudo visa analisar a ontogenia das estruturas reprodutivas de Cybistax antisyphilitica, com o propósito de acrescentar dados embriológicos relevantes ao delineamento filogenético da família, ou de categorias taxonômicas infrafamiliares. As características embriológicas observadas demonstraram similaridade com espécies pertencentes à ―Tabebuia alliance‖ cuja embriologia já foi investigada. Observou-se durante a ontogenia do óvulo de C. antisyphilitica que apenas o ginósporo calazal se desenvolve e, durante sua diferenciação em célula-mãe do saco embrionário, a face micropilar de sua parede celular assume uma conformação côncava, na qual há grande deposição de calose. No estádio octonuclear, há acúmulo de uma substância fibrogranular entre o endotélio e a parede do ginófito fazendo com que o saco embrionário apresente um característico afunilamento mediano. Em relação a ontogenia da antera da espécie estudada, verificou-se que as camadas tapetais são dimórficas, embora ao final do estádio pré-meiótico se tornem similares; embora, após a meiose, o dimorfismo se acentua novamente nas camadas tapetais. Os amiloplastos das células-mãe dos andrósporos são herdados pelos andrósporos e grãos de pólen deles resultantes. Os amiloplastos dos grãos de pólen gradualmente aumentam em número e tamanho em um único ciclo de amilogênese/amilólise. Com base nos dados obtidos conclui-se que a configuração da parede distal do ginósporo calazal e o acúmulo de secreção na porção mediana do saco embrionário são características não relatadas para outras espécies da família e podem... / Embryological characters have systematic value and its usefulness has been demonstrated by several authors to elucidate the phylogenetic position of certain angiosperms families. This study aims to analyze the ontogeny of reproductive structures of Cybistax antisyphilitica, with the purpose of adding relevant embryological data to the phylogenetic design of the family or, infra-familiar taxonomic categories. The embryological features observed was similar to species belonging to ―Tabebuia alliance‖ whose embryology has been investigated. During the ontogey of C. antisyphilitica ovule, only the chalazal megaspore develops, and in the course of its differentiation in the embryo sac mother cell, the micropylar side of its cell wall assumes a concave conformation in which there is an expressive deposition of callose. In the octonuclear stage, there is an accumulation of a fibrogranular substance between the endothelium and megagametophyte wall causing a bottleneck in the middle portion of embryo sac. For anther ontogeny of the species studied, the tapetal layers are dimorphic, although becoming similar at the late pre-meiotic stage. After meiosis, the dimorphism is accentuated between the two tapetal layers. The microspore mother cell amyloplasts are inherited by the microspores and the resulting pollen grains. The pollen grain amyloplasts gradually increasing in number and size in a single amylogenesis/amylolyse cycle. Based on the obtained data we concluded that the configuration of the distal wall of the chalazal megaspore and the accumulation of secretion in the median portion of embryo sac are characters not reported for other species of the family, and may possibly be autapomorphic characters. Regarding the ontogeny of the anther, Cybistax antisyphilitic showed a multistratified fibrous endothecium... (Complete abstract click electronic access below)

The purpose of this thesis is to present the results of a morphological investigation of the megagametophytes of two species of Fritillaria. The author has attempted to present the data in sufficient detail to clearly picture the significant features in the histories of this gametophyte generation without unnecessary repetition. The data are presented as their chronological sequence dictates.

There is but a single species of Iris native to Utah. This is Iris missouriensis Nutt. This plant was chosen for investigation because of its possible significance and because material of this species was readily available. The embryo of Iris missouriensis Nutt. shows some resemblance to the Lily type in its development of an irregular dividing suspensor. It also resembles the Orchid type in the usual development of sixteen cells before the dermatogen is cut off. In general development, however, the writer believes it to have an embryo sequence more similar to the Alisma type than to the dexcriptions given of either of the above.