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by Hung-mee Poon. / Includes bibliographical references / Thesis (M.Ph.)--Chinese University of Hong Kong, 1986

by Bi Yu Rong. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 188-220). / Acknowledgment --- p.i / Abstract --- p.ii / Table and contents --- p.v / List of abbreviation --- p.x / List of Tables --- p.xi / List of Figures --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Literature review --- p.5 / Chapter 2.1 --- General information of plant growth regulators --- p.5 / Chapter 2.2 --- Natural plant growth inhibitors --- p.14 / Chapter 2.3 --- Alkaloids and narciclasine --- p.15 / Chapter 2.4 --- Studies on expansion and greening of cotyledons --- p.22 / Chapter 2.5 --- Investigation on chlorophyll synthesis --- p.28 / Chapter Chapter 3 --- Materials and methods --- p.31 / Chapter 3.1 --- Plant materials --- p.31 / Chapter 3.2 --- Isolation and purification of inhibitory substance from Narcissus bulbs --- p.31 / Chapter I. --- Isolation of inhibitory substance from fresh Narcissus bulbs --- p.31 / Chapter II. --- Partial purification of the inhibitory substance with different organic solvents --- p.32 / Chapter III. --- Purification and identification --- p.32 / Chapter A. --- Thin layer chromatography (TLC) --- p.32 / Chapter B. --- Column chromatography --- p.33 / Chapter C. --- Spectrometric analyses --- p.33 / Chapter IV. --- Bioassays --- p.34 / Chapter 3.3 --- Effect of narciclasine (NCS) on the seeds germination and seedling growth --- p.34 / Chapter I. --- Germination experiments --- p.35 / Chapter II. --- Seedlings growth --- p.35 / Chapter 3.4 --- Interaction of NCS and phytohormones --- p.35 / Chapter I. --- Interaction with abscisic acid (ABA) --- p.36 / Chapter A. --- Seed germination --- p.36 / Chapter B. --- Seedling growth --- p.36 / Chapter II. --- Interaction with auxin --- p.36 / Chapter III. --- Interaction with gibberellin --- p.37 / Chapter VI. --- Interaction with cytokinin --- p.38 / Chapter 3.5 --- Interaction of NCS and phytohormones to growth and greening of excised radish cotyledons exposing to light --- p.39 / Chapter I. --- Growth of excised radish cotyledons exposing to light --- p.39 / Chapter II. --- Chlorophyll content determination --- p.40 / Chapter III. --- Effects of a pretreatment with BA or NCS on the growth and greening of excised radish cotyledons --- p.40 / Chapter 3.6 --- Effect of NCS on the growth and greening of excised radish cotyledons and etiolated wheat leaves --- p.41 / Chapter I. --- Effect of NCS on the growth and greening of excised radish cotyledons --- p.41 / Chapter II. --- Effect of NCS on the greening of etiolated wheat leaves --- p.41 / Chapter 3.7 --- Effect of NCS on chlorophyll synthesis and δ-aminolevulinic acid (ALA) accumulation of etiolated wheat leaves in presence of levulinic acid (LA) --- p.42 / Chapter 3.8 --- Enzymes studies in the excised radish cotyledons --- p.43 / Chapter I. --- Assay of isocitrate lyase activity --- p.44 / Chapter II. --- Assay of hydroxypyruvate reductase activity --- p.44 / Chapter 3.9 --- Ultrastructural studies --- p.45 / Chapter Chapter 4. --- Results --- p.47 / Chapter 4.1 --- Chemical studies of NCS --- p.47 / Chapter I. --- Isolation and partial purification of inhibitory substance from Narcissus bulbs --- p.47 / Chapter A. --- "Effect of lyophilized slimy secretion (LSS) on the germination seeds, the growth of radicle and hypocotyl of seedlings of Brassica" --- p.47 / Chapter B. --- Effect of different solvent extracts on the germination and the elongation of radicle and hypocotyl of Brassica seedlings --- p.47 / Chapter C. --- Effect of fraction isolated with n-butanol from dried bulbs or LSS on the germination of Brassica seeds and radicle growth --- p.49 / Chapter D. --- Purification of inhibitory substance from Narcissus bulbs by chromatography --- p.54 / Chapter II. --- Identification of the inhibitory substance from Narcissus bulbs .… --- p.62 / Chapter 4.2 --- Physiological and biochemical studies ofNCS --- p.70 / Chapter I. --- Effects ofNCS on seed germination and seedlings growth of Brassica --- p.70 / Chapter II. --- Time course studies ofNCS on germination and growth of radish seeds --- p.70 / Chapter III. --- Comparative studies ofNCS and ABA on seeds germination and seedlings growth --- p.73 / Chapter IV. --- Interaction between NCS and phytohormones --- p.79 / Chapter A. --- Interaction of NCS with ABA --- p.79 / Chapter B. --- Interaction of NCS with IAA --- p.84 / Chapter C. --- Interaction of NCS with gibberellin --- p.84 / Chapter D. --- Interaction of NCS with cytokinin --- p.89 / Chapter V. --- Effects ofNCS and BA on chlorophyll and carotenoid content of excised cotyledons --- p.89 / Chapter A. --- "Effects ofNCS and BA on expansion, chlorophyll content and carotenoid content of excised radish cotyledons" --- p.89 / Chapter B. --- Effects of a pretreatment with BA or NCS on the growth and greening of excised radish cotyledons --- p.97 / Chapter VI. --- Interaction between NCS and phytohormones in growth and greening of excised radish cotyledons --- p.105 / Chapter A. --- "Effects of BA,GA3 and ABA on the growth and greening of excised radish cotyledons" --- p.105 / Chapter B. --- Interaction of NCS with phytohormones on growth and greening of excised radish cotyledons --- p.108 / Chapter 4.3 --- Investigation of effects of NCS on chlorophyll synthesis --- p.113 / Chapter I. --- Effect of preincubation in water on growth and greening of excised cotyledons under light --- p.113 / Chapter II. --- Effect of NCS on the growth and greening of etiolated radish excised cotyledons --- p.116 / Chapter III. --- Effect of NCS on the greening of etiolated leaves of 7-day-old wheat seedlings under light --- p.116 / Chapter IV. --- Effect of LA on ALA accumulation in the light --- p.120 / Chapter V. --- Time course study of NCS on ALA accumulation in the presence of LA --- p.122 / Chapter 4.4 --- Effect of NCS on the development of enzymes activities in the excised radish cotyledons --- p.122 / Chapter I. --- Effect of NCS on isocitrate lyase activity of excised radish cotyledons --- p.122 / Chapter II --- Effect of NCS on hydroxypyruvate reductase activity of excised radish cotyledons --- p.125 / Chapter 4.5 --- Effect of NCS on ultrastructural changes of excised radish cotyledons --- p.128 / Chapter I. --- Time course studies --- p.128 / Chapter II. --- "Effect ofNCS, BA and ABA on the ultrastructural change of excised radish cotyledons in the light" --- p.142 / Chapter III. --- Effect of a pretreatment with dark on the inhibition ofNCS on ultrastructural change of excised radish cotyledons in light --- p.150 / Chapter Chapter 5. --- Discussion --- p.160 / Chapter Chapter 6. --- Conclusions --- p.180 / References --- p.188

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It was found that narciclasine retarded the growth of human cancer cells and plant suspension cells in dose-dependent manner. The inhibitory mechanism of narciclasine was found to be apoptosis for the DNA histogram showed an apoptotic peak in narciclasine-treated A375 cancer cells. The fluorescent signal dUTP fluorescein was found in the narciclasine-treated A735 cancer cell in TUNEL assay. The Annexin-V-FLUOS stained A375 cancer cell at 24-hour treatment with no PI found. These results suggest that narciclasine triggered early apoptosis in A375 cancer cell. Immunoblot analysis of the apoptotic signalling pathway showed that narciclasine induced apoptosis through the intrinsic pathway. Narciclasine induced the cleavage of caspase-9 but not the caspase-8, which was triggered by cytochrome c release from mitochondrial intermembrane space into cytosol. The activated caspase-9 triggered caspase cascade (e.g. cleavage of caspase-3, caspase-6 and caspase-7) which induced the cleavage of PARP. / Narciclasine is an isoquinoline alkaloid extracted from the bulb of Narcissus tazetta. It shows a wide range of biological activities such as antitumour, antiviral and plant growth inhibitory activities. However, little information is available regarding such inhibitory activities. The objective of this study is to elucidate the mechanisms of the cytotoxic effects of narciclasine in different cell models. / On the other hand, narciclasine triggered programmed cell death (PCD) in plant cells as proved by the increased intensity of Evans blue in narciclasine-treated suspension cells. Fluorescent microscopy showed that narciclasine induced PCD in tobacco BY2 cell with the dUTP fluorescein stained in narciclasine-treated cell. The induction of PCD was in dose-dependent and time-dependent manner. / Proteomic studies showed that narciclasine may affect A375 cancer cell and rice meristemic cells in similar manner. Narciclasine may affect the metabolism and defence system of both A375 cancer cell and rice meristemic cells through down-regulating the expression of metabolic enzymes (e.g. triosephosphate isomerase in A375 cancer cell and fructose bisphosphate aldolase in rice root tip) and defensive proteins (e.g. peroxiredoxin in A375 cancer cell and catalase in rice root tip). Narciclasine down-regulated the heat-shock proteins (HSP) which is involved in regulating cellular homeostasis and promoting cell survival. Therefore, narciclasine reduced HSP to lower the cell survival ability and induced the caspase cascade or caspase-like activity in A375 cancer cell and rice respectively. / To summarize, narciclasine induced apoptosis in A375 cancer cell and programmed cell death in tobacco BY2 cell. / Wong, Chi Fai. / "October 2007." / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4576. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 230-255). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Made available in DSpace on 2014-06-11T19:30:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-02Bitstream added on 2014-06-13T19:01:07Z : No. of bitstreams: 1 figliolia_mb_dr_rcla.pdf: 2811984 bytes, checksum: b1692752dd1e7065b3f766c9d1ca22a9 (MD5) / O objetivo geral da pesquisa foi estudar aspectos da germinação de sementes de Platymiscium floribundum Vog. em laboratório e viveiro e desenvolvimento das mudas em condições de viveiro e natural sob o dossel, com vistas a estabelecer indicadores biológicos quanto à fisiologia e ecologia da germinação e desenvolvimento das plantas para subsidiar projetos de conservação, de manejo e de revegetação de áreas alteradas ou desprotegidas. Tendo como enfoque o estudo das temperaturas cardeais de germinação das sementes e o estabelecimento de padrões tecnológicos de análise foram testadas, em condições controladas de laboratório, temperaturas no intervalo de 10 a 40ºC, com presença contínua e ausência total de luz branca. Verificou-se que a faixa limite de germinação está entre 10 e 12,5 e 37,5 e 40ºC; a 10ºC iniciou-se somente a protrusão radicular, sem emissão da raiz primária e, a 40ºC, houve morte total das sementes. A faixa ótima de temperatura para a germinação, na presença contínua de luz, está entre 15 a 25ºC, com maiores índices de velocidades de germinação a 20 e 25ºC. Para o estudo ecofisiológico foram testadas as interações entre diferentes regimes de temperatura, quantidades de água e luz. As temperaturas onde a germinação das sementes se mostrou superior foram 25, 20 e 15ºC. Os resultados de germinação com as quantidades de água do ii substrato de 30 e 60mL foram superiores à de 90mL. Os percentuais de germinação foram inferiores à medida que se associaram elevadas quantidades de água e temperatura. As sementes da espécie apresentaram insensibilidade à luz, germinando tanto na presença quanto na ausência de luz, não apresentando variação significativa entre os espectros de luz testados. Os resultados indicam que P. floribundum apresenta plasticidade... / The purpose of the present work was the study of germination under laboratory and nursery conditions and seedling development under nursery and field conditions for getting biological indicators of ecophysiology of germination and establishment of Platymiscium floribundum Vog for conservation, management and reforestation projects. Determination of cardinal, and optimum temperatures was done by isothermic incubations in the range of 10 to 40°C, under continuous white light and darkness. The minimum temperature was 12.5°C and the maximum 37.5°C. At 10°C, only radicle protrusion was observed and at 40°C the seeds have died. The optimum temperature range from 15 to 25°C with highest germination rate at 20 to 25°C. For ecophysiological study, different temperatures were tested under different conditions of substrate humidity and light. The germination under low humidity (30mL) and moderate humidity (60mL) of the substrate was higher than high humidity (90mL). Seeds of P. floribundum were light insensitive. The seedling emergence capacity under nursery conditions were high under both natural light (NL) and far red light (FR) in all tested shading percentage (10, 18, 30, 50 and 80 shading), with high seedling survival under 30 and 80% shading NL and 18, 30 and 50% shading FR. Seedling development was high under FR at 18, 30 and 50% and in stem diameter at all WL treatments. Plants accumulated more root and aerial dry matter under NL. By aerial to root dry matter ratio, highest aerial development was observed under 0, 30, 18 and 80% shading WL and 18 and 80% shading FR. Analysis of seedling development was carried out under natural conditions under two shading intensities under canopy at Serra da Cantareira, São Paulo... (Complete abstract, click electronic address below)

The apple rootstock ‘Geneva® 41’ (‘G.41’), is desirable for its resistance to fire blight, Erwinia amylovora, while producing high yields. However, ‘G.41’ and other Geneva® selections tend to form weak graft unions in the nursery that are susceptible to breaking in the wind, at harvest, or during shipment. In order to understand and remedy this graft union weakness, six scions (‘Fuji’, ‘Gala’, ‘Honeycrisp’, ‘McIntosh’, ‘Pink Lady’, and ‘Scilate’) by seven rootstocks (‘G.41’, ‘G.935’, ‘G.214’, ‘G.11’, ‘M.9-NIC 29’, ‘B.9’ and ‘EMLA 26’), by two grafting methods (chip bud and saddle graft) in a factorial design were tested for graft union flexural strength and flexibility. Additionally, plant growth regulators (PGR) were applied to trees with ‘G.41’ as rootstock as a solution to overcome graft union weakness. Transpiration rate and hydraulic resistance were measured for comparison of a weak graft forming rootstock (‘G.41’) to a strong graft forming rootstock (‘M.9-NIC 29’). ‘G.41’ consistently formed a weaker graft union regardless of scion or grafting method. Scions such as ‘McIntosh’ and ‘Pink Lady’ formed stronger graft unions, while ‘Scilate’ and ‘Honeycrisp’ form weaker graft unions. Saddle grafting did not improve graft union strength. Nurseries that graft on ‘G.41’ should choose scions that form stronger graft unions. Benzyl adenine (BA) in a latex paint increased the strength and flexibility of the graft union relative to scion cross sectional area (SCSA), but further research is needs to identify more efficient methods of application. Rootstock effect on transpiration rate was different between years. No detectable differences were found for hydraulic resistance through the graft union of different rootstocks, suggesting weaker graft unions did not limit hydraulic conductance or transpiration rate. Thus graft union weakness is not an indicator of poor vascular connection.

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The plant growth-promoting bacterium (PGPB) Pseudomonas putida UW4, previously isolated from the rhizosphere of common reeds growing on the campus of University of Waterloo, promotes plant growth in the presence of different environmental stresses, such as flooding, high concentration of salt, cold, heavy metals, drought and phytopathogens. The known mechanisms used by P. putida UW4 to promote plant growth include 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA) synthesis and siderophore production. In this work, the genome sequence of UW4 was obtained by pyrosequencing and the gaps between the contigs were closed by directed PCR. The P. putida UW4 genome contains a single circular chromosome that is 6,183,388 bp with a 60.05% G+C content. The bacterial genome contains 5,431 predicted protein-coding sequences that occupy 87.4% of the genome. Nineteen genomic islands were predicted and thirty one complete putative insertion sequences were identified. Genome analyses were conducted in order to better characterize the general features of the UW4 genome. Genes potentially involved in plant growth promotion such as IAA biosynthesis, trehalose production, siderophore production, and acetoin synthesis were identified, which will facilitate a better understanding of the mechanisms of plant-microbe interactions. Moreover, genes that contribute to the environmental fitness of UW4 were also determined including genes responsible for heavy metal resistance such as nickel, copper, cadmium, zinc, molybdate, cobalt, arsenate, and chromate. Central metabolic pathways helped elucidate the physiological roles of diverse metabolites of UW4. Unexpectedly, whole-genome comparison with other completely sequenced Pseudomonas sp. revealed that UW4 is more similar to the fluorescens group rather than to the putida group. More surprisingly, a putative type III secretion system (T3SS) was found in the UW4 genome, and T3SS was thought to be essential for bacterial pathogenesis. Although putative T3SS was observed in other non-pathogenic Pseudomonas spp. previously, this is the first report indicating that a T3SS in a Pseudomonas sp. is highly similar to the one from Salmonella spp.

Although plant growth-promoting rhizobacteria (PGPR) have shown tremendous potential to be used as inoculants for many agricultural crops, they may not survive severe environmental conditions in the field which could limit their large scale applications. Endophytic bacteria, which can be recovered from inside plant tissues such as roots, stems and leaves, might overcome this limitation due to their unique ecological niche inside plant roots where they are sheltered from external environmental disturbances. Some of these bacterial endophytes have beneficial effects on their host plants and stimulate plant growth or reduce disease symptoms, apparently through mechanisms that are similar to those proposed for PGPR. The objective of this study was to assess a collection of endophytic bacteria for PGPR traits and potential use to enhance the rhizobial-legume symbiosis. Forty isolates obtained from the roots of various plants were identified by fatty acid methyl ester (FAME) analysis, and 16S RNA gene sequencing analysis. The majority (i.e., 75%) were identified as Pseudomonas species. Many of these isolates were able to solubilize phosphate, produce indole-3-acetic acid (IAA), produce aminocyclopropane-1-carboxylic acid (ACC) deaminase, synthesize siderophores and show antagonistic activities against several soil-borne plant pathogenic fungi under in vitro conditions. Selected isolates were further evaluated for the ability to enhance plant growth and nodulation of alfalfa when co-inoculated with Sinorhizobium meliloti under growth chamber conditions using growth pouch and potted soil assays. Results revealed that P. putida strain EB EE 4-25, P. syringae strain EB XDE 4-48, and P. fluorescens strain EB EE 2-23 significantly increased shoot length, root length, enhanced nodulation and increased lateral root formation of alfalfa plants in growth pouch and potted soil assays when co-inoculated with S. meliloti strain P102 compared to plants inoculated with S. meliloti strain P102 alone. Results also suggested that expression of one or more of the mechanisms, such as solubilization of phosphate, production of IAA, production of siderophores, and ACC deaminase production might have played a role in the enhancement of the alfalfa- Sinorhizobium symbiosis. These results suggest that some endophytic bacterial strains may be useful as biofertilizers and/or biocontrol agents in sustainable agricultural practices.