Dissertations / Theses on the topic 'Seedling stages'

Euclea natalensis A.DC. belongs to the Ebenaceae family, and is extensively distributed along the eastern coast of southern Africa. Many Euclea species are widely gathered by indigenous people because of their medicinal properties. Roots of these plant species are frequently used to treat respiratory complications such as chest pains, bronchitis, pleurisy and asthma. Ground root powder is topically applied in cases of leprosy and is used by some ethnic groups to treat toothache and headache. The bioactivity encountered is attributable to naphthoquinones, which are common phenolic compounds in the Ebenaceae family. Naphthoquinones isolated from E. natalensis (shinanolone, 7-methyljuglone, diospyrin, isodiospyrin and neodiospyrin) have exhibited a broad spectrum of antimicrobial activity. The demand for these products will escalate due the amount of plant material required to further research. We need to explore techniques that can maximize their productivity. The present study was conducted on E. natalensis, in an attempt to establish if there exists any correlation between the accumulation of naphthoquinones and stages of seedling growth, seasonal fluctuations and application of fertilizers. A possible correlation between seedling growth stages and the accumulation of naphthoquinones (shinanolone, 7-methyljuglone and diospyrin) was investigated in seeds and seedlings of Euclea natalensis. In this study, the seeds represented the first stage, whereas the second seedling stage was defined as the stage when the radicles were about 6 cm long. The lengths of the seedlings at the third, fourth and fifth seedling stages were 9 cm, 12 cm and 16 cm respectively. Plant materials collected from the five seedling stages were separately extracted using chloroform and the naphthoquinones were then quantified by means of High Performance Liquid Chromatography (HPLC). Mobile phase of MeCN: H2O: AcOH (62.5: 32.5: 5) was used as an eluent in an isocratic mode and at a flow rate of 0.8 ml/min. Standard curves of each of the four compounds were obtained by making a series of dilutions in the concentration range of 22.5 µg/ml to 2.25 µg/ml. Ten microlitres of each dilution was injected three times into the HPLC, and the run time for each injection was 20 minutes. Calibration curves were then generated and used for the quantification of each compound. Shinanolone, which was the only naphthoquinone detectible in seeds, accumulated at variable rates (P<0.01) and no trend could be established between its synthesis and seedling growth. The content of shinanolone ranged from 87.5 mg/kg dry weight (dw) in seeds to a high mean value of 1047 mg/kg (dw) during the fourth seedling stage. A significant correlation (P<0.01) was found between the mean concentrations of 7-methyljuglone and seedling growth. 7-Methyljuglone was quantified at a high mean level of 5003 mg/kg during the third seedling stage and was not detected in the seed samples. A positive correlation (P<0.01) was established between the concentration of diospyrin and seedling stages. Diospyrin was detected at an elevated mean concentration of 6182 mg/kg during the fifth seedling stage, which was higher than the other quantified naphthoquinones. Seasonal variation of naphthoquinones (shinanolone, 7-methyljuglone, diospyrin, isodiospyrin and neodiospyrin) was investigated from eleven plants of E. natalensis subsp. natalensis growing in natural populations, over a period of four seasons. The roots were harvested, dried, extracted and analysed as in the previous study. The mean levels of shinanolone and 7-methyljuglone were found to be uniform in all the seasons and no statistically significant variation could be found between seasonal changes and their mean concentrations. Accumulation of isodiospyrin and neodiospyrin varied significantly with seasonal changes (P<0.05). These two bioactive naphthoquinones were detected only in summer and autumn respectively, and not in winter. A statistically significant variation (P<0.05) was established between the levels of diospyrin and seasonal fluctuations. Diospyrin was detected at a mean concentration of 3190 mg/kg (dw) during spring, which was higher than the other naphthoquinones quantified in all four seasons. The effect of NPK fertilizers on growth performance and accumulation of naphthoquinones (shinanolone, 7-methyljuglone, diospyrin, isodiospyrin and neodiospyrin) in seedlings of E. natalensis grown in shade and under field conditions was investigated. Each group was subdivided into four subgroups, which were then subjected to four respective treatments of water-soluble foliar feed (2:1:2 (44) NPK) at three different concentrations. Treatments tested were as follows: Treatment 1 at 40 g/l, Treatment 2 and Treatment 3 at 20 g/l and 10 g/l respectively. The control group received only supplemental water. The first harvest was conducted after 6 months of application of fertilizers and the second one was done after 12 months of treatment. Roots and shoots were harvested and analysed separately. The naphthoquinones were quantified as previously described. The bioactivity of root extracts from seedlings was tested against Mycobacterium smegmatis and extracts with lower MIC were further tested on M. tuberculosis. Growth parameters differed between the two groups, with seedlings from the shadehouse showing more plant vigour than the field grown plants. No significant interaction could be established between the measured growth factors and treatment. A significant interaction (P<0.001) was found between Treatment 2 and shadehouse seedlings. Treatment 2 enhanced vegetative performance with the mean values of fresh weight of shoots and roots being twice as much as their respective control mean values. A significantly positive correlation was established between the concentration of shinanolone (P<0.01), isodiospyrin (P<0.05) and neodiospyrin (P<0.05) with fertilization from field-grown seedlings. Application of NPK fertilizers significantly (P<0.05) increased the accumulation of neodiospyrin in seedlings subjected to shadehouse conditions. The most potent naphthoquinone, 7-methyljuglone, was found to be abundant in all the extracts and was quantified at a high mean concentration of 10200 mg/kg from shadehouse seedlings. Root extracts of E. natalensis seedlings grown under field conditions were generally more active against the bacterial strain of M. smegmatis as compared to extracts acquired from roots of seedlings maintained under a shadehouse setting. A lowest minimum inhibitory concentration (MIC) of 0.78mg/ml against M. smegmatis was observed from the second harvest of field-cultivated seedlings of the control and Treatment 1 subgroups. The MIC values for shadehouse seedlings ranged from 1.6 to 6.3 mg/ml. Minimum bactericidal concentration (MBC) values from all the extracts tested were relatively higher than their respective MIC’s. Root extracts of E. natalensis were more active against M. tuberculosis and their MIC values were lower than the tested concentrations. Extracts acquired from field-grown seedlings were more active against M. smegmatis with a lowest MIC value of 0.78 mg/ml. Extracts from the control group and Treatment 1, which had less application of fertilizers were more active against strains of M. tuberculosis with MIC value of 10 µg/ml. This shows the selectivity of E. natalensis against the mycobacterial strain of M. tuberculosis. Based on the findings, synthesis and accumulation of naphthoquinones in E. natalensis is highly variable within individuals of the species investigated. Naphthoquinones accumulate in relatively higher amounts in roots of E. natalensis than in the aboveground structures, which validate their harvest by indigenous people. The concentration of shinanolone varied slightly and its production increased with seedling growth. The synthesis of 7-methyljuglone is independent of fertilisation as its accumulation was enhanced in seedlings subjected to control treatment. Neodiospyrin and isodiospyrin were always present in every sample obtained from the seedlings but they were not detectible in every profile of samples from mature plants. Diospyrin is the only naphthoquinone that was detected in every sample analysed and also quantified in high concentrations from mature plants harvested in spring. The study showed that depending on the requirement of a particular naphthoquinone for research, one could target the seasons and seedling stages recommended from this study. This study also showed that field-cultivated seedlings produced more potent naphthoquinones than the ones subjected to controlled environments.<br>Dissertation (MSc (Plant Science))--University of Pretoria, 2008.<br>Plant Production and Soil Science<br>unrestricted

In wheat, stem rust is known to rapidly evolve new virulence to resistance genes. While more than 50 stem rust resistance (Sr) loci have been identified in wheat, only a few remain effective, particularly against the highly virulent race Ug99 (TTKSK race) and a mixture of durum-specific races. An association mapping (AM) study based on 183 durum wheat accessions was utilized to identify resistance loci for stem rust response in Ethiopia over four seasons and artificial inoculation with Ug99 (TTKSK race) and a mixture of durum-specific races under field conditions as well as in greenhouse test at seedling stage under controlled conditions for resistance to four highly virulent stem rust races: TRTTF, TTTTF, (TTKSK (Ug99) and JRCQC. The panel was profiled with 1,253 SSR and DArT markers. Twelve QTL-tagging markers were significant (P < 0.05) across three to four seasons. The role of Sr13, Sr9, Sr14, Sr17, and Sr28 was confirmed. Thirteen significant markers were in regions with no Sr genes/QTLs. The results under controlled conditions showed that 15, 20, 19 and 19 chromosome regions harbored markers that showed significant effects for races TRTTF, TTTTF, TTKSK and JRCQC, respectively. These genomic regions showed marker R2 values ranging from 1.13 to 8.34, 1.92 to 17.64, 1.75 to 23.12 and 1.51 to 15.33% for races TRTTF, TTTTF, TTKSK and JRCQC, respectively. The study demonstrates that stem rust resistance in durum wheat is governed in part by shared loci and in part by race-specific ones. The QTLs identified in this study through AM will be useful in the marker-assisted development of durum wheat cultivars with durable stem rust resistance.

Made available in DSpace on 2014-08-20T13:44:34Z (GMT). No. of bitstreams: 1 tese_caroline_borges_bevilacqua.pdf: 1981019 bytes, checksum: 797e667e01edbc569a7b08d3268c701b (MD5) Previous issue date: 2013-10-30<br>Cold stress adversely modifies their physiology, metabolism plant growth and development, as well as, it limits crop productivity. The responses of rice (Oryza sativa L.) subjected to low temperatures are still poorly understood. A better understanding of stress tolerance mechanism in rice plants will help to develop rice germplasm with improved field level tolerance under variable temperature and sowing depth conditions. To characterize rice genotypes with variation in sensitivity to cold, these are the following objectives: to evaluate the applicability of different Stress Indices using seedling lengthas parameter; classify accessions cultivated rice and red rice as Indica or Japonica; compare response to rice cultivars cold-tolerant and cold-sensitive to cold stress according to the dry matter accumulation and possible changes in chlorophyll content; categorize different genotypes with regard to sensitivity to cold and to sowing depth stresses and, analyze the expression of cold-responsive genes, and also genes submergence-responsive. The seeds after seven days at 25°C were exposed at 4°C for 24h and after that, photosynthesis was measured later, the plants were 72h at 25°C (recovery period) to assess the dry mass and chlorophyll. For the other experiments, the seedlings were collected 7 and/or 14 days maintained at 25°C or 18/13°C day/night and different sowing depths (1.5cm, 5cm, 10cm and 15cm), differential gene expression were performed with those seedlings using different genes induced by cold. To evaluated gene expression using different genes induced by cold and anoxia, samples were collected after exposure to 10 ° C for 6, 24 and 96 h at 1.5 cm and 10 cm deep sowing. The results showed that is possible to identify superior genotypes for tolerance to these abiotic stresses based on the Tolerance Index (STI) and Media Geometric (GM) to select genotypes tolerant to cold or sowing depth, using as a parameter the seedling shoot length measurement. Japonica and Indica subspecies respond differently to abiotic stresses, however for some of these stress-responsive genes, these subspecies responded similarly. Furthermore, the analysis at the molecular level of cold tolerance and sowing depth indicated the importance of ABA- dependent and ABA-independent signal transduction pathways in plants under abiotic stress.<br>O estresse causado pelo frio interfere negativamente na fisiologia, metabolismo, crescimento e desenvolvimento das plantas e, portanto, limita a produtividade em lavouras de arroz. As respostas em nível de crescimento em arroz (Oryza sativa L.) submetido a baixas temperaturas ainda são pouco compreendidas. Um melhor entendimento do mecanismo de tolerância ao estresse em plantas de arroz pode ajudar na identificação, no germoplasma de arroz, de plantas com tolerância submetidas à temperatura variável, além de ser útil para outros estresses abióticos, como diferentes profundidades de semeadura. Para caracterizar genótipos de arroz, com variação na sensibilidade ao frio, tiveram-se como objetivos:avaliar a aplicabilidade de diferentes índices de estresse utilizando-se como parâmetro o comprimento de plântula; classificar acessos de arroz cultivado e vermelho como Japonica ou Indica; comparar a resposta ao frio de cultivares de arroz tolerante e sensível a esse estresse, com relação ao acúmulo de massa seca e possíveis alterações no teor de clorofila;categorizá-los com relação à sensibilidade ao frio e à profundidade de semeadura; e analisar a expressão de genes que respondem a frio, assim como genes responsivos a submersão, sob condições de frio e/ou tratamento constituídos por diferentes profundidades de semeadura. Para avaliar o acúmulo de massa seca e o teor de clorofila, as sementes, após sete dias a 25°C, foram expostas a 4°C durante 24 h e logo após, foi medida a fotossíntese e,posteriormente, as plantas ficaram 72 h a 25°C para sua recuperação. Já para os demais experimentos,as plântulas foram coletadas 7 e/ou 14 dias mantidas a 25°C ou 18/13°C dia/noite e diferentes profundidades de semeadura (1.5cm, 5cm, 10cm e 15cm); as avaliações da expressão gênica diferencial foram realizadas com essas amostras coletadas, para 4 diferentes genes induzidos pelo frio e também em amostras coletadas após exposição a 10°C durante 6, 24 e 96 h a 1.5 cm e 10 cm de profundidade de semeadura.Os resultados indicaram que é possível a identificação de genótipos superiores para a tolerância a esses estresses abióticos com base em seus índices de estresse, utilizando como parâmetro o comprimento da parte aérea, devido a habilidade das plantas tolerar estresses abióticos afetar a morfologia assim como a fisiologia da planta de arroz. Assim como é possível a utilização do Índice de Tolerância (STI) e da Média Geométrica (GM) para selecionar genótipos tolerantes ao frio ou profundidade de semeadura, baseado no comprimento de parte aérea de plântula. As subespécies Japonica e Indica respondem diferentemente aos estresses abióticos, no entanto, para alguns genes responsivos a esses estresses, essas subespécies apresentam o mesmo respondem semelhantemente. Além disso, as análises a nível molecular da tolerância ao frio e a profundidade de semeadura indicaram a importância das vias ABA-dependente e ABA-independente como vias de transdução do sinal em plantas sob estresse abiótico.

From the Proceedings of the 1988 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 16, 1988, University of Arizona, Tucson, Arizona

From the Proceedings of the 1990 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 21, 1990, Arizona State University, Tempe, Arizona<br>Effects of applications of cytokinin-like and gibberellic growth regulators, nitrogen fertilizer, and irrigation on the development of containerized eldarica pine (Pinus brutia var. eldarica) seedlings was studied in a greenhouse for 13 weeks. All concentrations of growth regulators reduced nitrogen content of needles and dry weight of shoots; importantly, medium and high concentrations also adversely affected root collar diameter growth and shoot elongation. Nitrogen fertilization alone was not significant in its effect on seedling development, due probably to the nitrogen-rich nature of the potting medium. It is suggested that contentration is a critical factor when applying growth regulators, as phytotoxicity of seedlings can result at high rates.

- Ziele der Arbeit - Das primäre Ziel der vorliegenden Arbeit bestand in einer möglichst umfassenden Be-schreibung einzelner Entwicklungsstadien im Verjüngungszyklus von Betula pendula Roth. Dabei waren die lokalen Bestandes- und Standortsbedingungen im Untersuchungsgebiet in besonderer Weise zu berücksichtigen. Des Weiteren sollten Optionen zur waldbaulichen Integration der Sand-Birkenverjüngung in bestehende Behandlungskonzepte für in Auflösung befindliche Fichtenaltbestände aufgezeigt werden. - Untersuchungsgebiet - Der Tharandter Wald liegt im Freistaat Sachsen (50° 55’-50° 00’n. Br., 13° 25’-13° 35’ ö. L.) und umfasst eine Fläche von etwa 6.000 ha. Das von der Baumart Fichte dominierte Gebiet kolliner bis submontaner Höhenstufe (350 - 420 m ü. NN) wird der „Unteren Nordostab-dachung des Erzgebirges“ zugeordnet. Als Untersuchungsflächen wurden wechselfeuchte (wechselfrische) Standorte mittlerer Trophie gewählt, die von einschichtigen Fichtenbe-ständen in einem Alter von ≥ 80 Jahren bestockt waren. Einzeln bis truppweise eingemischte Samenbäume der Sand-Birke (B. pendula) bildeten eine Grundvoraussetzung für die Flächen-auswahl. - Methodisches Vorgehen - Das methodische Vorgehen konzentrierte sich auf die verjüngungsökologisch relevanten Entwicklungsstadien (fruktifizierender Samenbaum, Diaspore, Keimling, Sämling und eta-blierte Verjüngungspflanze) der Sand-Birke. Die Wachstumsparameter der vorhandenen Samenbäume wurden durch Untersuchungen zum Fruchtbehang unterlegt. Der mehrstufige Versuchsansatz zur Erfassung einzelner Verjüngungsstadien stützte sich auf Bestandesauf-nahmen, Gefäß- und Laborversuche. Erhebungen auf Bestandesebene erfassten die Diaspo-renausbreitung mithilfe von Samenfallen und dokumentierten die Keimlings- und Ver-jüngungsstadien von B. pendula auf entsprechend etablierten Aufnahmeplots (1 m x 1 m). Darüber hinaus umfassten die Aufnahmen Strahlungs- und Feuchtemessungen und die Charakterisierung der Bodenvegetation. Für die Einschätzung des mikrostandörtlichen Um-feldes wurden exemplarisch Bodendeckungsvarianten (Mineralboden, Nadelstreuauflage, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.)) ausgewählt, die als besonders repräsentativ für reine Fichtenbestände des Erzgebirges gelten. Für die räumliche Modellierung der Diasporen und Keimlinge auf Bestandesebene stand das Pro-gramm WALDSTAT (NÄTHER &amp; WÄLDER 2003) zur Verfügung. Im Rahmen des Mitscherlich-Gefäßversuchs wurden gleichermaßen quantitative und qualitative Entwicklungen von Sand-Birkenkeimlingen und -sämlingen erhoben. Der Einfluss ausgewählter Bodendeckungs-varianten wurde in diesen Betrachtungen berücksichtigt. Neben zahlreichen Pflanzenpara-metern (Spross-, Blatt- und Wurzelentwicklung, Allokationen, Allometrien) war die kleinstandörtliche räumliche Verteilung dieser Verjüngungspflanzen von vorrangiger Be-deutung. Als Verteilungs- und Konkurrenzmaße auf Ebene des Mikrostandortes dienten Tessellationsmodelle, der Aggregationsindex nach CLARK &amp; EVANS, der Gini-Koeffizient und das “Constant Yield Law“. - Ergebnisse - - Die Erfassung der Samenbaumparameter von B. pendula führte zu flächenspezifischen und signifikanten Unterschieden in der Dimension, Höhe und soziologischen Stellung. Für die Darstellung der Durchmesser-Höhenverteilungen erwiesen sich logarithmische und quadra-tische Funktionen gleichermaßen geeignet. Das Kronenprozent ereichte im Mittel Werte zwi-schen 37 % und 49 %. Die einzelnen Kronenparameter (Kronendurchmesser, Kronenlänge und Kronenmantelfläche) zeigten straffe lineare Zusammenhänge. Innerhalb der Kronen-strukturen (z. B. Blatt- und Zweigtrockenmasse) ließen sich zum Teil allometrische Be-ziehungen nachweisen. Im Rahmen der Vollbaumbeerntung war ein durchmesserabhängiger Fruchtbehang nachweisbar, der für den Einzelbaum eine Anzahl zwischen 2,3 und 4,2 Millionen Diasporen erreichte. - Mit den Erhebungen zur zeitlichen Ausbreitungsdynamik der Diasporen waren durch mehrjährige Untersuchungszeiträume, auch für eine Pionierbaumart wie B. pendula, stärkere Samenjahre nachzuweisen. Die räumliche Modellierung der anemochoren Diasporenaus-breitung belegte erwartungsgemäß bessere Modellanpassungen für den anisotropen (richtungsgebundenen) Modellansatz. Dennoch zeichneten sich sowohl jahres- als auch flächenspezifisch deutliche Unterschiede in der Modellgüte ab. Als maximale Diasporen-dichte pro m² wurde ein Wert von 20.700 Diasporen ermittelt. Die mittleren Ausbreitungs-distanzen (MDD - “Mean Dispersal Distances“) lagen nach Modellschätzung für die ge-samten Beprobungszeiträume und unter Berücksichtigung aller Versuchsflächen zwischen 37 m und 90 m. Die durchschnittliche Diasporenproduktion eines Einzelbaumes lag nach Anga-ben des Modells in einem Bereich von 180.000 bis 7.400.000. Die Qualitätsansprache an den Diasporen ergab einen Anteil von etwa 5 % bis 8 % äußerlich Schadhaften. Der unmittelbare Windeinfluss auf Hauptausbreitungsrichtung und -entfernung konnte ebenfalls nachgewiesen werden. - Untersuchungen zum Keimlingsstadium zeigten deutliche Abhängigkeiten zwischen den ausgewählten Bodendeckungsvarianten, der Keimlingsdichte und dem Keimlingswachstum. Sand-Birkenkeimlinge waren sowohl unter Bestandesbedingungen als auch unter den freif-lächenähnlichen Bedingungen des Mitscherlich-Gefäßversuchs auf der Variante mit Mine-ralboden besonders dicht aufgelaufen, blieben jedoch stark in ihrer weiteren Entwicklung zurück. Als besonders wüchsig erwiesen sich Keimlinge auf den Bodendeckungsvarianten mit Nadelstreuauflage und in D. flexuosa. Sand-Birkenkeimlinge der Bodendeckungsvarianten ohne Konkurrenz durch Bodenvegetation (Mb, Nd) besaßen eine längere Hauptwurzel und eine höhere Wurzelmasse (56 % - 60 % der Gesamtmasse). Die oberirdische Allokation (Blatt- und Sprossmasse) fiel hingegen für Sand-Birkenkeimlinge in den Bodendeckungs-varianten mit C. villosa und D. flexuosa höher aus. Verteilungs- und Konkurrenzerhebungen in den Gefäßversuchen erbrachten signifikante Zusammenhänge zwischen Keimlingsdichte, Standraum und Wachstum der Einzelpflanze. - Das Sämlingsstadium und die älteren Verjüngungspflanzen wiesen einen deutlichen Rückgang in der Mortalität auf. Die Erhebungen im Bestand ergaben ein unterschiedliches Durchschnittsalter für Sand-Birken auf den einzelnen Bodendeckungsvarianten (C. villosa 7,6 Jahre, D. flexuosa 6,2 Jahre und Nadelstreu 4,7 Jahre). Die wachstumsrelevanten Umweltbe-dingungen wie Strahlungsverfügbarkeit, Feuchteregime und Entfernung zum nächsten Alt-baum unterschieden sich außerdem in Abhängigkeit von den als repräsentativ eingestuften Bodendeckungsvarianten unter Bestandesbedingungen. Das bestandesbezogene Wachstum der Sand-Birken in einem Alter von 2 bis 6 Jahren ließ sich durch eine exponentielle Funktion mit hoher Anpassungsgüte (p ≤ 0,000) abbilden. Innerhalb des Mitscherlich-Gefäßversuchs haben sich ebenfalls Unterschiede in der Individuendichte, den Mortalitäts- und Wachstums-raten in Abhängigkeit von den Bodendeckungsvarianten ausgebildet. Höchste Verjüngungs-dichten wurden nach einem 2,5jährigen Entwicklungszeitraum auf der Bodendeckungs-variante Nadelstreuauflage erreicht. Die Allokationen in der Trockenmasse näherten sich hingegen in den unterschiedlichen Varianten stärker an. Ein dichteabhängiges Wachstum konnte in der letzten Aufnahme nicht mehr nachgewiesen werden. Abschließend bleibt festzuhalten, dass die ermittelten Untersuchungsergebnisse in Abhängig-keit vom jeweiligen Verjüngungsstadium die zeitliche und räumliche Präsenz, Konkurrenz- und Entwicklungsfähigkeit der Sand-Birke in Fichtenaltbeständen des Tharandter Waldes charakterisieren. Sie belegen eine kleinstandörtliche Heterogenität in den untersuchten Beständen, die sich nachhaltig auf die Etablierung der hier untersuchten Pionierbaumart auswirkt. Anhand der räumlichen Modellierung lässt sich die zu erwartende Verteilung von Diasporen und Keimlingen in Abhängigkeit von den Positionen der Samenbäume prognostizieren. Insgesamt ergibt sich aus den vorliegenden Ergebnissen ein vergleichsweise hohes Verjüngungspotenzial für B. pendula, das sich durch waldbauliche Maßnahmen effizient nutzen ließe. Ein detailliertes Wissen über die einzelnen Verjüngungsstadien bietet zudem die Möglichkeit einer gezielten waldbaulichen Steuerung der Baumart und zur Risikoabschätzung des Verjüngungserfolgs unter den gegebenen Rahmenbedingungen. Bei einer wachsenden waldbaulichen Unsicherheit im Umgang mit unterschiedlichsten Klima-prognosen, die sich in ihrer Wirkung regionalspezifisch erheblich unterscheiden können, sollte die Sand-Birke als Misch- und Vorwaldbaumart unbedingt berücksichtigt werden. Um dem viel zitierten Anspruch an die Nachhaltigkeit waldbaulichen Handelns gerecht zu werden, muss die Option zur Integration von B. pendula gewährleistet bleiben, auch für künftige Generationen und bei sich wandelnden Ansprüchen an den Wald<br>- Objectives - The main goal of this study was to describe comprehensively the particular stages of the regeneration cycle of Betula pendula Roth. Investigations were carried out in local stand and site conditions of a research area in South-East Germany (Tharandter Forest) are considered. In this context options for integrating Silver birch regeneration into silvicultural management concepts of old Spruce stands (Picea abies L.) with lacking vitality are pointed out. - Research area - The Tharandter Forest is located (50°00’N, 13°35’E.) in Saxony (South-East Germany) with an area of around 6.000 ha. It is dominated by Norway spruce stands, and ranges from colline to submontane altitudinal belt (350 to 420 m a.s.l.). These sites are part of the northern declivity of the Ore Mountains. Mono-layered Norway spruce stands with soils of medium trophy and well drained, but featured highly variable soil moisture levels during the growing season were selected for this study. The stand age was ≥ 80 years. Seed trees of Silver birch were mixed as single trees or small groups. - Methodical aspects - The methodical work was concentrated on relevant regeneration aspects like fructification of seed trees, seeds, seedlings, saplings and established regeneration of Silver birch. Growth parameters of seed trees and the amount of fructification were used to quantify allometric relationships. The multi-level research design was based on measurements under stand conditions, pot and laboratory experiments. Seed traps and plots (1m x 1m) were located in spruce stands with regard to different stages of Silver birch development. Therefore micro-environmental growth conditions like soil humidity and photosynthetic active radiation were measured, and plants of ground cover characterized. As examples of ground cover variants with highest presence in homogeneous spruce stands mineral soil, needle litter, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.) were chosen. Using the program WALDSTAT (NÄTHER &amp; WÄLDER 2003) spatial distribution of dispersed seeds (diaspores) and seedlings could be modelled. Additionally pot experiments were done to compare quantitative and qualitative development of birch seedlings between stand and open site conditions. Regeneration density, number of leaves, shoot and root growth and allocations were measured as important growth parameters to evaluate single plant development under different environmental conditions. Finally, spatial distribution of seedlings in microsites and intraspecific competition were calculated by tessellation models, aggregation indices after CLARK &amp; EVANS, Gini-coefficient and ‘constant yield law’. - Main results - - Measurements on seed trees of B. pendula indicate stand specific differences significantly in dimension, height and biosocial position of trees within the birch population (crown classes). For specific height-dbh curves logarithmic and quadratic equations were adapted. The relative crown length for seed trees was located between 37 % and 49 %. Allometric relationships between crown parameters (e.g. crown diameter, crown length and crown surface) were strongly correlated. In specific cases crown structures (e.g. dry mass of leaves and twigs) were also correlated, certainly with different grades. Direct seed counting of felled seed trees provided the relationships between dbh and number of seeds. Counted seeds for single Silver birch trees ranged between 2.300.000 - 4.200.000. - As one result of seed trapping huge varieties in seed production of Silver birch were detectable between years with different seed potential. Spatial modeling of seed dispersal supported strong influences caused by wind (direction and speed). Hence, best fitted model estimations were found for anisotropic scenarios. The maximum in seed density was recorded with 20.700 seeds per m². As data for ‘Mean Dispersal Distances’ (MDD) the program WALDSTAT calculated between 37 m and 90 m. Furthermore the amount of seeds produced by a single tree was estimated with 180.000 - 7.400.000 depending on dbh. Physical quality evaluations for seeds have shown a mean proportion of damaged and not germinable seeds between 5 % and 8 %. - Direct effects of ground cover variants have been identified for seedling density and growth. Seedling density was highest on mineral soil for both, stand conditions and pot experiment, but these birch seedlings developed slowly compared with individuals in the other ground cover variants. The best growth was realized by birch seedlings in needle litter and D. flexuosa. Regarding to root length and mass, birches in ground cover variants without grass competition (mineral soil and needle litter) have shown a significant better development of underground parts. Root dry mass of these birch seedlings reached proportions between 56 % and 60 % of whole plant dry mass. By contrast the aboveground dry mass (leaves and shoot) was higher for birches competing with grasses. Overall results of birch seedling distribution and competition were significant correlations between densities, space, and growth per single plant. - For saplings and established birch regeneration a notable decrease in mortality rates were found. According to regeneration analyses under stand conditions age distributions in Silver birch regeneration have been controlled by ground cover variants and their environment conditions. The average age of Silver birch seedlings was high in areas with C. villosa (7.6 years) and low in needle litter (4.7 years). Furthermore growth influencing environmental conditions like light, humidity, and distance of old spruce trees have shown differences between variants in ground cover. The growth of regenerated Silver birches at the age of 2 to 6 years under those stand conditions can be described by an exponential function with high degree of adaptation (p ≤ 0,000). There were also differences in sapling densities, mortality and growth rates caused by ground cover variants in the pot experiments. After 2.5 years maximum regeneration densities in pots were registered on ground covers with needle litter. Allocations in regeneration dry mass were less influenced by ground cover variants than in previous stages. Density dependent growth rates could not be proved during last measurements. Finally, the presented results provide the opportunity to characterize temporal and spatial presence of different regeneration stages of Silver birch, its potential of competition and further development in old Norway spruce stands of the Tharandter Forest. They document heterogeneous structures of micro-environmental conditions in these spruce stands, which have sustainable effects on regeneration establishment of this studied pioneer tree species. On the basis of spatial modeling it is possible to estimate spatial distribution of seeds and seedlings depending on seed tree positions. Overall the results involve a high potential of successful regeneration in Silver birch, which opens up promising vistas for silvicultural management. More detailed knowledge in particular regeneration stages induces possibilities for selective control in silviculture with Silver birch. Additionally, estimating the regeneration risks and the success under given surrounding conditions will be more precisely. Considering uncertainty in giving prognoses for climate change Silver birch should be integrated in silvicultural strategies because of its role as admixed tree species and pioneer crop combined with comparably high resilience against warming

Pythium diseases are common in the greenhouse production of tobacco transplants and can cause up to 70% seedling loss in hydroponic (float-bed) greenhouses. However, the symptoms and consequences of Pythium diseases are often variable among these greenhouses. A tobacco transplant greenhouse survey was conducted in 2017 in order to investigate the sources of this variability, especially the composition and distribution of Pythium communities within greenhouses. The survey revealed twelve Pythium species. Approximately 80% of the surveyed greenhouses harbored Pythium in at least one of four sites within the greenhouse, including the center walkway, weeds, but especially bay water and tobacco seedlings. Pythium dissotocum, followed by P. myriotylum, were the most common species. Pythium myriotylum, P. coloratum, and P. dissotocum were aggressive pathogens that suppressed seed germination and caused root rot, stunting, foliar chlorosis, and death of tobacco seedlings. Pythium aristosporum, P. porphyrae, P. torulosum, P. inflatum, P. irregulare, P. catenulatum, and a different isolate of P. dissotocum, were weak pathogens, causing root symptoms without affecting the upper part of tobacco seedlings. Pythium adhaerens, P. attrantheridium, and P. pectinolyticum did not affect tobacco seeds or seedlings. The consequences of Pythium infection were more likely to be severe when they occurred during seed germination than at seedling emergence, or after plant stem elongation when seedling roots had started to grow into underlying nutrient solutions, depending on the species of Pythium. High and low variation was observed among isolates of P. dissotocum and P. myriotylum, respectively. Pythium myriotylum co-existed with multiple other Pythium or oomycete species in the same environments within tobacco greenhouses, and significant in vitro and/or in vivo interactions between P. myriotylum and some naturally co-existing species were revealed. Pythium porphyrae may have the potential to protect tobacco seeds and seedlings from P. myriotylum infection. Greenhouse Pythium control trials identified ethaboxam, mefenoxam, and copper ionization as potentially promising alternatives to etridiazole for Pythium disease management in tobacco transplant production. The outcomes of this project provide useful new information to better understand the composition, distribution, and diversity of Pythium communities in tobacco transplant greenhouses and to improve Pythium disease management for tobacco transplant production.<br>Doctor of Philosophy<br>Pythium diseases are common in tobacco transplant production and can cause up to 70% seedling losses in hydroponic (float-bed) tobacco transplant greenhouses. However, little is known about the composition and distribution of Pythium communities in tobacco transplant greenhouses. This project began with a tobacco transplant greenhouse survey, in which 12 Pythium species were recovered from center walkways, weeds, greenhouse bay water, and tobacco seedlings. Pythium dissotocum and P. myriotylum were the two types (species) of Pythium most commonly found in the survey. Pythium myriotylum, P. coloratum, and P. dissotocum were aggressive pathogens that suppressed seed germination and caused root rot, stunting, foliar chlorosis, and death of tobacco seedlings. Pythium aristosporum, P. porphyrae, P. torulosum, P. inflatum, P. irregulare, P. catenulatum, and an isolate of P. dissotocum, were weak pathogens causing root symptoms without affecting the upper part of tobacco seedlings. Pythium adhaerens, P. attrantheridium, and P. pectinolyticum did not affect tobacco seeds or seedlings. The symptoms caused by infection by Pythium species differed among host (tobacco) growth stages, except for the most aggressive species, P. myriotylum. High levels of variation were observed among isolates of P. dissotocum, in terms of vegetative growth rate (on V8 agar media) and aggressiveness on tobacco seed and seedlings. Pythium myriotylum was found to co-exist with multiple other Pythium or oomycete species (neighbor isolates) in the same environments within tobacco greenhouses. Significant interactions between P. myriotylum and some neighbor isolates were revealed, and these interactions significantly affect the consequences of P. myriotylum infection of tobacco seeds. Greenhouse Pythium control trials identified two chemical water treatments (ethaboxam and mefenoxam), and a non-chemical water treatment (copper ionization) as potentially promising alternatives to the current standard Pythium control (etridiazole) for Pythium disease management in tobacco transplant production. The outcomes of this project provide useful new information to both better understand the composition, distribution, and diversity of Pythium communities in tobacco transplant greenhouses and to improve Pythium disease management for tobacco transplant production.

A significant acreage of poorly drained sites occurs in the Western Gulf region of the United States. These sites experience standing water through much of the winter and spring, resulting in poor seedling survival. In addition, the sites occasionally experience a summer drought that affects tree growth. This study was designed to determine the effects of intensive forest management on seedling growth and physiology, and to enhance seedling performance under these harsh conditions. Fertilization, chemical vegetation control and mechanical site preparation were used in different combinations to test the effects of these intensive forest management tools on seedling above- and below-ground growth, survival, water status, gas exchange attributes, and nutrient concentrations in the foliage and soil solution. Ten sites were established in southern Arkansas in 1998 and 1999 to monitor loblolly pine (Pinus taeda L.) seedling performance in three consecutive growing seasons between 1998 and 2000. Fertilization, chemical vegetation control and mechanical site preparation increased above-ground growth. Growth increment from mechanical site preparation was comparable to that from fertilization. Survival was not affected by any treatment. Fertilization enhanced root growth, more so in the shallow soil layers. Subsoil bulk density greatly restricted root growth, resulting in decreased above-ground growth. Chemical vegetation control made more soil water available to the seedlings during drought, resulting in increased seedling water potential. The effect of chemical vegetation control on seedling water potential was absent in the early growing season when soil moisture was abundant. Seedlings on plots treated with bedding-plus-fertilizer or bedding alone experienced stomatal closure at times of severe water stress while those treated with chemical vegetation control were able to continue net carbon dioxide assimilation. Fertilization did not increase needle nutrient concentrations, but increased needle weight, thereby increasing total nutrient content. Fertilization increased base cation concentrations in the soil solution, but had no effect on nitrogen and phosphorus concentrations. Intensive forest management was found to be a viable tool for optimum loblolly pine seedling growth and survival on poorly drained sites in the Western Gulf region of the United States.

Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-02-16T17:56:15Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) cristiane_coelho_moura.pdf: 2162662 bytes, checksum: b2941635e812ffa2d1ef219667e8df5f (MD5)<br>Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-03-09T19:32:06Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) cristiane_coelho_moura.pdf: 2162662 bytes, checksum: b2941635e812ffa2d1ef219667e8df5f (MD5)<br>Made available in DSpace on 2018-03-09T19:32:06Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) cristiane_coelho_moura.pdf: 2162662 bytes, checksum: b2941635e812ffa2d1ef219667e8df5f (MD5) Previous issue date: 2017<br>Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM)<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES).<br>Anglo American<br>Com o intuito de gerar informa??es para produ??o de mudas direcionadas ? projetos de restaura??o de Matas de Galeria, objetivou-se neste estudo, descrever a morfologia e aspectos biom?tricos do fruto e da semente, as caracter?sticas morfofuncionais e desenvolvimento da pl?ntula, e obter a classifica??o fisiol?gica quanto a capacidade de armazenamento das sementes da Richeria grandis Vahl. Verificou-se tamb?m a influ?ncia de diferentes composi??es de substratos e n?veis de redu??o solar sob a emerg?ncia de pl?ntulas e crescimento de mudas via propaga??o sexuada e a viabilidade da t?cnica de miniestaquia na propaga??o assexuada da R. grandis, submetidas a diferentes concentra??es do regulador de crescimento ?cido indolbut?rico (AIB). A coleta de sementes ocorreu em 18 ?rvores-matrizes estabelecidas em Matas de Galeria inund?veis localizadas no Parque Estadual do Biribiri, Diamantina, MG e, todos os experimentos foram conduzidos em Viveiro Florestal e laborat?rio de Sementes pertencente ao Centro Integrado de Propaga??o de Esp?cies Florestais (CIPEF- UFVJM). A caracteriza??o morfol?gica e biom?trica de frutos e sementes se deu por observa??es a olho nu e mensura??es utilizando um paqu?metro universal. A fim de observar o comportamento fisiol?gico, sementes rec?m beneficiadas desta esp?cie foram armazenadas em sacos de papel ao ar livre, e foram submetidas a testes de germina??o e umidade (%) periodicamente. As caracter?sticas morfofuncionais foram observadas, a olho nu, mediante processo de desenvolvimento (desde a protrus?o radicular, emerg?ncia at? o surgimento do primeiro prot?filo) em laborat?rio e casa de vegeta??o. Utilizou-se tr?s composi??es de substratos e tr?s n?veis de sombreamento para testar o efeito destas combina??es sobre a qualidade de mudas jovens da R. grandis, para tal, foi mensurado ao longo de 210 dias, a altura, di?metro do coleto, n?mero de folhas, clorofila total e biomassas secas. Por fim, a base de estacas apicais provenientes de mudas jovens resgatadas em ambiente natural da R. grandis, foram emergidas em quatro concentra??es de AIB e avaliadas aos 90 dias, mensurando o incremento em altura e di?metro, sobreviv?ncia (%), enraizamento (%), calogenia (%) e brota??es (%). Ressalta-se que, para todos os experimentos, os princ?pios b?sicos da experimenta??o (repeti??o, casualiza??o e controle local) foram atendidos, utilizando diferentes delineamentos experimentais. Diferentes ferramentas para an?lise estat?stica tamb?m foram utilizadas para auxiliar na tomada de decis?o. O fruto da R. grandis ? simples, seco, do tipo c?psula, deiscente, com comprimento m?dio de 16,24 mm e largura m?dia de 8,57mm. A semente ? elipsoide com presen?a de sarcotesta, apresentando comprimento m?dio de 7,40mm e largura m?dia de 4,57 mm. A R. grandis apresenta sementes recalcitrantes, a emerg?ncia ? do tipo Fanero-ep?geo-foli?ceo, e o processo de desenvolvimento para a semente se tornar uma pl?ntula completa delonga por, no m?nimo, 50 dias. Os substratos compostos por diferentes propor??es de vermiculita, casca de arroz e Bioplant?, associado com os sombreamentos 30 e 50% foram respons?veis por promover mudas da R. grandis de melhor qualidade. A t?cnica de propaga??o vegetativa por miniestaquia ? vi?vel, uma vez que houve 100% de sobreviv?ncia e alta porcentagem de enraizamento at? para o tratamento sem adi??o do AIB.<br>Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Ci?ncia Florestal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017.<br>The aim of this study was to describe the morphology and biometric aspects of the fruit and seed, the morphofunctional characteristics and development of the seedling, and to obtain the classification the storage capacity of the seeds of Richeria grandis Vahl. It was also verified the influence of different compositions of substrates and levels of solar reduction under the emergence of seedlings and growth of seedlings via sexual propagation and the viability of the technique of minicache in the asexual propagation of R. grandis, submitted to different concentrations of the regulator of indolebutyric acid (IBA) growth. Seed collection occurred in 18 matrix trees established in flooded Forest Mills located in Biribiri State Park, Diamantina, MG, and all experiments were conducted in Forest Nursery and Seed Laboratory belonging to the Integrated Center for the Propagation of Forest Species ( CIPEF-UFVJM). The morphological and biometric characterization of fruits and seeds was by naked eye observations and measurements using a universal caliper. In order to observe the physiological behavior, freshly harvested seeds of this species were stored in paper bags in the open air and germinated and tested (%) periodically. The morphofunctional characteristics were observed in the laboratory and in the greenhouse by means of a developmental process (from root protrusion, emergence until the first protophyte). Three compositions of substrates and three levels of shading were used to test the effect of these combinations on the quality of R. grandis young seedlings. The height, collection diameter, number of leaves , total chlorophyll and dry biomass. Finally, the base of apical cuttings from young saplings rescued in the natural environment of R. grandis, were emerged in four concentrations of IBA and evaluated at 90 days, measuring the increase in height and diameter, survival (%), rooting (% ), calogenia (%) and sprouts (%). It should be noted that for all experiments, the basic principles of experimentation (repetition, randomization and local control) were met using different experimental designs. Different tools for statistical analysis were also used to aid in decision making. The fruit of R. grandis is simple, dry, capsule type, dehiscent, with an average length of 16.24 mm and an average width of 8.57 mm. The seed is ellipsoid with presence of sarcotesta, presenting an average length of 7.40 mm and an average width of 4.57 mm. R. grandis presents recalcitrant seeds, the emergence is of the Fanero-epigene-foliaceous type, and the development process for the seed becomes a complete seedling delonged for at least 50 days. The substrates composed of different proportions of vermiculite, rice husk and Bioplant ?, associated with shading 30 and 50% were responsible for promoting R. grandis seedlings of better quality. The technique of vegetative propagation by minicutting is feasible, since there was a 100% survival and a high percentage of rooting even for the treatment without addition of AIB.

Au cours du travail présenté dans ce mémoire, nous sommes parvenus à obtenir, de façon systématique, la micropropagation in vitro et l'acclimatation ex vitro non seulement des poiriers juvéniles issus de pépins de "passe crassane", mais aussi du cognassier de Provence et de deux cultivars de poirier, "williams" et "passe crassane". Les conditions de culture concernant les différentes phases de la micropropagation et l'acclimatation ont été étudiées. Plusieurs problèmes d'ordre physiologique (dormance des bourgeons in vitro, anomalie des pousses formées, nécrose des apex) ont pu être surmontés ou limités.

碩士<br>國立中興大學<br>生命科學院碩士在職專班<br>95<br>Rice (Oryza sativa L. ), one of the most important cereal crops in the world. There are three major cereal crops in the world, namely rice, wheat, and maize and totally offer 50% of the calorie sources to the world population. Soil salinity is a complex and harmful threat faced by plants. High concertrations of salts will suppress crops growth and interfer physiological metabolisms. Rice is a salt-sensitive crop and the soil salinity decreases the yield. This thesis is aimed at the characterizations of physiological responses to salt stress in rice. Mutants of Tainung 67 ( TNG 67 ) rice variety were screened for salt tolerance at seedling stage. Two mutant strains were successfully identified with ST-099, a salt-tolerant strain, and ST-300, a salt-sensitive strain. Their agricultural characteristics showed no difference in growth. The tolerance to salt of ST-099 (salt-tolerant strain) was the same at germination stage and seedling stage. ST-099 has higher relative water content (RWC) and relative growth rate (RGR) than salt-sensitive strain ST-300 under salt stress. On the other hand, ST-099 is more sensitive to water-deficit stress at seedling stage than at germination stage. The results suggest that the adaptation mechanisms to salt and water-deficit stress are not identical. Elemental Analyses showed salt-sensitive strain ST-300 had a lower potassium content, a higher sodium content, a higher chlorine content, and a higher Na+/K+ ratio. There was no significant difference in the amount of calcium at initial stage of salt stress suggesting that delay of Ca2+-mediated signaling was a factor contributing to its salt sensitivity. As for salt-tolerant ST-099 strain, it had the lowest sodium content and Na+/K+ ratio. A rapid increase in calcium concentration at initial stage of salt stress was very prominent in this salt-tolerant strain. Furthermore, other evidences leaded us to hypothesize that this strain might be able to use excess Na+ for osmoregulation, and as the result, the rate of decrease in relative water content was much slower in ST-099. Under the same NaCl concentration, the salt-sensitive strain had a higher proline concent, and the salt-tolerant strain accumulated much lower level of proline suggesting proline accumulation is a result of injury caused by salt stress.

Master of Science<br>Department of Agronomy<br>S.V. Krishna Jagadish<br>Low temperature is one of the most limiting stresses to crops that are adapted to tropical and subtropical regions, such as maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench], when introduced into temperate regions. However, no studies have compared the chilling tolerance of maize and sorghum grown together. Therefore, the objective of this research was to screen maize hybrids and sorghum genotypes for chilling tolerance at the germination and seedling stages. With the hypothesis that grain composition of maize and sorghum could lead to varying chilling tolerance, the seeds were analyzed for concentrations of protein, starch, and amylose. Five commercial hybrids of maize and 18 genotypes of sorghum were maintained in growth chambers for 31 days at two temperatures: a control temperature (25/20 °C, day/night) and at chilling temperatures (11/8 °C for 14 days; 12.5/9.5 °C for 14 days, and 14/11 °C for 3 days). Emergence and seedling height were measured during the experiment. At the end of the experiment, shoot dry weight, root dry weight, and leaf area were determined. Emergence of sorghum under the chilling temperature regime was low (18%). Average height of the emerged sorghum seedlings in the cold temperatures at the end of the experiment was 1.4 cm compared to 55.5 cm in the control treatment. All maize hybrids emerged, but emergence and growth were slowed by the cold temperatures, and average height at the end of the experiment was 4.6 cm compared to 96.1 cm in the control treatment. Shoot dry weight, root dry weight, and leaf area of the sorghum under the chilling temperatures were too small to measure, and, for maize, they were greatly reduced. The results showed that, for sorghum, temperatures should be above 14 °C for emergence, while maize could emerge at lower temperatures. The analyses of the sorghum seeds showed that Redbine 60 and RTx430 had the highest protein concentrations (15.71% and 15.35%, respectively), and Segaolane had the lowest protein concentration (9.83%). Segaolane had the highest starch concentration (72.71%), and RTx430 had the lowest starch concentration (65.31%). There was an inverse relationship between protein and starch concentrations in the sorghum seeds (R2 = 0.69). Amylose concentrations did not vary significantly among the sorghum seeds. The analyses of the maize seeds showed that Dekalb 51-20 and Pioneer 1151 had the highest protein concentrations (10.98% and 10.95%, respectively), and Pioneer 1105 had the lowest protein concentration (9.26%). Starch and amylose concentrations did not vary significantly among the maize seeds.

碩士<br>國立嘉義大學<br>園藝學系研究所<br>98<br>This study aimed to identify effects of nutrition managements at the seedling stage, seedling age and planting period on the growth and flowering of Eustoma grandiflorum. Eight cultivars of E. grandiflorum, including of ‘New Lination White’, ‘Lination Pink’, ‘Exrosa Pink Flash’, ‘Exrosa Green’, ‘Cute Snow’, ‘Noble Jade’, ‘Tsukushi no Nami’ and ‘Tsukushi no Hagoromo’ were subirrigated with 0.5 or 1.0 gL-1 of Peters 20-20-20 and Peters 30-10-10 every 5 to 7 days, respectively. The results showed the size of the second pair of true leaves and fresh weight of these cultivars showed better in subirrigation with Peters 30-10-10 1.0 gL-1. For these same cultivars, the combination of 1.0 gL-1 Peters 30-10-10 and 1.0 gL-1 Hyponex 20-20-20 by foliar spraying every 3 days can promote the second pair of true leaves larger, the root longer and the upper and lower part fresh weight heavier than 0 and 0.5 gL-1 Hyponex 20-20-20. The eight, nine and ten-week-age seedlings of six E. grandiflorum cultivars ‘New Lination White’, ‘Lination Pink’, ‘Exrosa Pink Flash’, ‘Exrosa Green’, ‘Cute Snow’, and ‘Cute Green ver. 2’ were planted in the field in different times of Jan., May., Sep. and Nov.; and these cultivars didn’t rosette. For eight and nine-week-age seedlings planted in May and Sep., the flowering time was shorter, the plant height was shorter, the stem was slimmer, the number of internodes was fewer, and the node number for the first flower appearance was lower. For the ten-week-age seedlings planted in Jan. and eight and nine-week-age seedlings planted in Nov. have longer flowering time, higher height, thicker stem, more inter-node number, and higher node number for the initial flowering. The number of petals of flowers was more for plants planted in Jan. and Nov. Otherwise the number of flower buds was more when planted in May and Nov. than other seasons. According to our results, we suggest that the growth and quality of seedlings can be promoted by the nutrition management of E. grandiflorum subirrigated with 1.0 gL-1 Peters 30-10-10 and foliar fertilized with 1.0 gL-1 Hyponex 20-20-20 simultaneously at the conditions of 24/18℃ (day/night) for 8weeks. In this study, the eight and nine-week-age seedlings of six cultivars can be planted in Nov. and ten-week-age seedlings in Jan. to achieve higher cut-flower quality.

碩士<br>國立中興大學<br>農藝學研究所<br>85<br>Three cadmium tolerant rice varieties ie., Kang Lung Do, Tpipei No.108, and Nohrin No.37, and three sensitive varieties, ie, Kae Bye,Tainung No.28, and Taipei No.103, were used for diallel crosses analysis. The seeds of F1 and F2 were used to do the genetic analysis of cadmium tolerance on the root length root、number、seedling height、total seedling height、shoot dry weight、root dry weight and total seedling dry weight. The results of the experiments are summarized in the followings: 1.Diallel analysis of cadmium tolerance in rice: (1)The results of diallel analysis indicated that the 7 characters of 6 varieties differed from varieties to varieties and also from different cross combination. (2)The result of regression analysis were invided into two sections: One was observed that the shoot dry weight、root length、root number、seedling height and total seedling height were controlled by partial dominance. The other was observed that root dry weight and total seedling dry weight were controlled by over dominance (3)The results of estimates of genetic components and genetic analysis: It was observed that shoot dry weight, root dry weight, seedling height and total seedling dry weight were controlled by the dominance gene and the addition effect of polygene. Root length, and total seedling height were controlled by dominance gene. Mean degrees of dominance on all characters were over dominance. Ratio of total number of dominance to recessive genes in parent were unequal. 2.Phenotypic correlations of F2 populations: (1)Phenotypic correlations among all pairs of 7 characters were observed. Root length with shoot dry weight and seedling height were significant positive correlation when the population were treated, but untreated population were no significant difference. (2)Heritabilities are different when the characters and populations were different. For the most results, the heritability of cross combination of Tainung No.28 X Nohrin No.37 were maximal, and of Tainung No.28 X Kang Lung Do were next.

碩士<br>國立臺灣大學<br>農藝學研究所<br>100<br>Rice grown in temperate areas is subjected to chilling stress at seedling and booting stages. The purpose of this thesis was to identify quantitative trait loci (QTLs) for chilling tolerance at the seedling stage of rice, using 243 recombinant inbred lines derived from a cross between a chilling-tolerant japonica cultivar, TNG67, and a chilling-sensitive indica cultivar, TN1. The phenotypes of chilling tolreance at seedling stage was scored by the measurements of the survival rate and the artifical chilling-tolerant classes. The results showed that the correlation coefficient between the survival rate and the artifical chilling-tolerant classes was 0.50. Both phenotypic measurements identified two major QTLs on the same chromosomal region: one on chromosome 6, the other on the chromosome 11. The former QTL linked to the SNP marker RC6-1, and the latter QTL linked to the SNP marker RC11-11. The QTLs for the survival rate under chilling stress were named qCTSS6.1 and qCTSS11.1, and the QTLs for the chilling-tolerant classes were named qCTS6.1 and qCTS11.1 The combined effects of the two QTLs were able to explain approximately 30% of phenotypic varions within the genetic mapping population, for either the survival rate or the chilling-tolerant classes.

碩士<br>國立臺灣大學<br>農藝學研究所<br>104<br>Rice basic-Helix-Loop-Helix (OsbHLH) transcription factors (TFs) belong to a multiple gene family and are known to involve in rice growth, development, regulating abiotic stress-responsive gene expression and tolerance of rice. However, because functional redundancy within the super gene family and the pleiotropic effect of individual TF, the specific function for corresponding OsbHLH is not easy to be determined. In this study, we identified an OsbHLH046 TF which is down-regulated by salt and cold treatments from previous microarray result and further confirmed the gene expression by reverse transcription-PCR (RT-PCR). The OsbHLH046-GFP fusion protein showed OsbHLH046 is located in nucleus. Based on the predication of rice eFP browser and the GUS-histochemical staining indicated that OsbHLH046 is expressed in the embryo, seedling root, lateral roots, shoots and anthers. The gene expression was higher at the early germination stage then declined to lower level within 3rd leaf stage. Compared with WT, the Osbhlh046, a Tos17 knocked-down rice mutant, displayed late seed germination, growth retardation, and unable to recover from salt stress at seedling stage. The q-PCR data indicated that salt tolerance related genes in such as OsABI5, OsNHX2 were differential expressed between two plants during recovery stage. The MDA was overaccumulated in Osbhlh046 mutant compared to wild type after recover from salt stress. The ICP-OES elemental analysis also revealed that the Osbhlh046 plant have lower K+ content level, which may not able to maintain the Na+ homeostasis. Meanwhile, the callus of OsbHLH046 overexpression line showed a relative poor regeneration rate. Taken together, these results suggested that OsbHLH046 plays as a positive regulator in seed germination, seedling growth, and contributes to the ability of rice to recover from salt stress.

碩士<br>國立臺灣大學<br>農藝學研究所<br>102<br>Rice is one of the major crops in the world. Because human population grows, increasing rice production is necessary to meet human’s need. Salinity is a common abiotic stress to affect crop production, and rice is one of salt sensitive crops, therefore maintaining rice growth vigor under salt condition is an important issue. Root system is a major physical interaction between plants and soil substrates, it affects nutrients and salt absorption. In this research, we used two populations as study materials, one is recombinant inbred lines population derived from a cross between indica and temperate japonica, and a global diversity panel with 196 accessions. We measured root length under normal and salt condition at seedling stage, and found out degree of root growth vigor inhibited by salinity stress differs by root types. We used high density SNP markers to map QTLs controlling shoot and root growth in response to salt stress, many QTLs in RILs and in global diversity panel were mapped in this study. Although there was positive correlation between root and shoot traits under salinity stress, no identical QTLs were mapped. We selected accessions with good performance under salinity stress, these accessions will be good breeding materials to improve root vigor in elite cultivars, and through molecular assisted selection, QTLs with positive effect can be introduced to elite cultivars efficiently.

In anticipation of widespread planting of putatively blight-resistant hybrid chestnuts (Castanea spp.), it is critical to understand the silvics and competitive ability of the species. This dissertation examines preliminary growth and survival of several species and genetic crosses of chestnut grown as 1-0 high-quality nursery seedlings and planted in two study sites: Southeastern Kentucky (Daniel Boone National Forest; chapter 2), and Northeastern Connecticut (Yale-Myers Forest; chapter 4). The effects of three silvicultural treatments on the Daniel Boone National Forest (DBNF), and four silvicultural treatments on the Yale-Myers Forest (YM) were evaluated. Furthermore, the effect of initial seedling size on seedling performance was tested. In both studies, seedlings grew largest in height and root collar diameter in silvicultural treatments with the most available light. High mortality at the DBNF planting was caused by Phytophthora cinnamomi, ink disease, and high mortality at the YM planting was caused by repeated deer, Odocoileus virginianus, browsing and competition from hay-scented fern, Dennstaedtia punctilobula. Additionally, seedlings at the DBNF study were repeatedly defoliated by Craesus castaneae, chestnut sawfly, during the first growing season (chapter 3). Seedlings with larger root collar diameters at planting demonstrated greater survival and growth in the DBNF study while seedlings larger in height and RCD added less growth and were more likely to die in the YM study, likely due to the high deer population and dense understory competition. These results indicate that silvicultural treatments that create high-light environments are ideal for chestnut, however the species can establish successfully under a variety of light conditions, from low light [10% photosynthetically active radiation (PAR)] to high light (65% PAR). Ink disease will present a formidable obstacle to chestnut reintroduction efforts in the south, while northern efforts will be challenged by deer browsing due to overpopulated deer herds.

碩士<br>國立中興大學<br>園藝學系<br>83<br>The growth activities of ''Royal White'',''King of Blue''and ''Si En'' in the early stage were inhibited by spraying Ethrel.This inhibitory effect increased when higher concentrations were applied. There was no difference in the bolting percentage of the cultivars except ''Si En'' by using Ethrel at more than 200ppm.It increased the node to the first flower but delayed flower.As the concentrations of Ethrel increased, the days to flower increased.The highest stem length of ''Royal White'' was at Ethrel 200 and 400ppm for ''King of Blue''.ABA 300 and 600ppm treatments did not reduce the early activity and bolting percentage.The effects of Sumi-7 20ppm and PP333 200ppm were constant. Sumi-7 20ppm application to ''Royal White''and B-9 5000ppm Sumi-7 20ppm, A-Rest 50ppm and PP333 200ppm to ''Si En'' decreased the bolting percentage. Treated ''Royal White''with Sumi-7 20ppm, PP333 50ppm, and ''Si En'' with B-9 5000ppm, Sumi-7 5 20ppm A-Rest 10 ppm and PP333 50, 200ppm delayed the flowering. The longer the cool night temperature treated during the seedling stage, the later the flowered. It also had the higher number of the first node to flower but shortened the internode.The highest stem lengths of the 2-month-old seedlings of ''Azuma no Nami'' were treated with 4 weeks cool night temperature,and the 3-month-old seedlings were 2 to 4 weeks. The highest stem length of the 2-month-old seedlings of ''Romio'' were treated with 6 weeks cool nigh temperature and the 3-month- old seedlings were 2 to 4 weeks. It could break rosette completely by cool temperature from November to March if the plants sown in the late October and treated with 1-7 weeks high temperature(33/28C). It bolted and flowered uniformly although later than the control. It also had higher number of node to bolting and branches. There was no significant difference in height, nodes to the first flower and the fresh weight.

- Ziele der Arbeit - Das primäre Ziel der vorliegenden Arbeit bestand in einer möglichst umfassenden Be-schreibung einzelner Entwicklungsstadien im Verjüngungszyklus von Betula pendula Roth. Dabei waren die lokalen Bestandes- und Standortsbedingungen im Untersuchungsgebiet in besonderer Weise zu berücksichtigen. Des Weiteren sollten Optionen zur waldbaulichen Integration der Sand-Birkenverjüngung in bestehende Behandlungskonzepte für in Auflösung befindliche Fichtenaltbestände aufgezeigt werden. - Untersuchungsgebiet - Der Tharandter Wald liegt im Freistaat Sachsen (50° 55’-50° 00’n. Br., 13° 25’-13° 35’ ö. L.) und umfasst eine Fläche von etwa 6.000 ha. Das von der Baumart Fichte dominierte Gebiet kolliner bis submontaner Höhenstufe (350 - 420 m ü. NN) wird der „Unteren Nordostab-dachung des Erzgebirges“ zugeordnet. Als Untersuchungsflächen wurden wechselfeuchte (wechselfrische) Standorte mittlerer Trophie gewählt, die von einschichtigen Fichtenbe-ständen in einem Alter von ≥ 80 Jahren bestockt waren. Einzeln bis truppweise eingemischte Samenbäume der Sand-Birke (B. pendula) bildeten eine Grundvoraussetzung für die Flächen-auswahl. - Methodisches Vorgehen - Das methodische Vorgehen konzentrierte sich auf die verjüngungsökologisch relevanten Entwicklungsstadien (fruktifizierender Samenbaum, Diaspore, Keimling, Sämling und eta-blierte Verjüngungspflanze) der Sand-Birke. Die Wachstumsparameter der vorhandenen Samenbäume wurden durch Untersuchungen zum Fruchtbehang unterlegt. Der mehrstufige Versuchsansatz zur Erfassung einzelner Verjüngungsstadien stützte sich auf Bestandesauf-nahmen, Gefäß- und Laborversuche. Erhebungen auf Bestandesebene erfassten die Diaspo-renausbreitung mithilfe von Samenfallen und dokumentierten die Keimlings- und Ver-jüngungsstadien von B. pendula auf entsprechend etablierten Aufnahmeplots (1 m x 1 m). Darüber hinaus umfassten die Aufnahmen Strahlungs- und Feuchtemessungen und die Charakterisierung der Bodenvegetation. Für die Einschätzung des mikrostandörtlichen Um-feldes wurden exemplarisch Bodendeckungsvarianten (Mineralboden, Nadelstreuauflage, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.)) ausgewählt, die als besonders repräsentativ für reine Fichtenbestände des Erzgebirges gelten. Für die räumliche Modellierung der Diasporen und Keimlinge auf Bestandesebene stand das Pro-gramm WALDSTAT (NÄTHER &amp; WÄLDER 2003) zur Verfügung. Im Rahmen des Mitscherlich-Gefäßversuchs wurden gleichermaßen quantitative und qualitative Entwicklungen von Sand-Birkenkeimlingen und -sämlingen erhoben. Der Einfluss ausgewählter Bodendeckungs-varianten wurde in diesen Betrachtungen berücksichtigt. Neben zahlreichen Pflanzenpara-metern (Spross-, Blatt- und Wurzelentwicklung, Allokationen, Allometrien) war die kleinstandörtliche räumliche Verteilung dieser Verjüngungspflanzen von vorrangiger Be-deutung. Als Verteilungs- und Konkurrenzmaße auf Ebene des Mikrostandortes dienten Tessellationsmodelle, der Aggregationsindex nach CLARK &amp; EVANS, der Gini-Koeffizient und das “Constant Yield Law“. - Ergebnisse - - Die Erfassung der Samenbaumparameter von B. pendula führte zu flächenspezifischen und signifikanten Unterschieden in der Dimension, Höhe und soziologischen Stellung. Für die Darstellung der Durchmesser-Höhenverteilungen erwiesen sich logarithmische und quadra-tische Funktionen gleichermaßen geeignet. Das Kronenprozent ereichte im Mittel Werte zwi-schen 37 % und 49 %. Die einzelnen Kronenparameter (Kronendurchmesser, Kronenlänge und Kronenmantelfläche) zeigten straffe lineare Zusammenhänge. Innerhalb der Kronen-strukturen (z. B. Blatt- und Zweigtrockenmasse) ließen sich zum Teil allometrische Be-ziehungen nachweisen. Im Rahmen der Vollbaumbeerntung war ein durchmesserabhängiger Fruchtbehang nachweisbar, der für den Einzelbaum eine Anzahl zwischen 2,3 und 4,2 Millionen Diasporen erreichte. - Mit den Erhebungen zur zeitlichen Ausbreitungsdynamik der Diasporen waren durch mehrjährige Untersuchungszeiträume, auch für eine Pionierbaumart wie B. pendula, stärkere Samenjahre nachzuweisen. Die räumliche Modellierung der anemochoren Diasporenaus-breitung belegte erwartungsgemäß bessere Modellanpassungen für den anisotropen (richtungsgebundenen) Modellansatz. Dennoch zeichneten sich sowohl jahres- als auch flächenspezifisch deutliche Unterschiede in der Modellgüte ab. Als maximale Diasporen-dichte pro m² wurde ein Wert von 20.700 Diasporen ermittelt. Die mittleren Ausbreitungs-distanzen (MDD - “Mean Dispersal Distances“) lagen nach Modellschätzung für die ge-samten Beprobungszeiträume und unter Berücksichtigung aller Versuchsflächen zwischen 37 m und 90 m. Die durchschnittliche Diasporenproduktion eines Einzelbaumes lag nach Anga-ben des Modells in einem Bereich von 180.000 bis 7.400.000. Die Qualitätsansprache an den Diasporen ergab einen Anteil von etwa 5 % bis 8 % äußerlich Schadhaften. Der unmittelbare Windeinfluss auf Hauptausbreitungsrichtung und -entfernung konnte ebenfalls nachgewiesen werden. - Untersuchungen zum Keimlingsstadium zeigten deutliche Abhängigkeiten zwischen den ausgewählten Bodendeckungsvarianten, der Keimlingsdichte und dem Keimlingswachstum. Sand-Birkenkeimlinge waren sowohl unter Bestandesbedingungen als auch unter den freif-lächenähnlichen Bedingungen des Mitscherlich-Gefäßversuchs auf der Variante mit Mine-ralboden besonders dicht aufgelaufen, blieben jedoch stark in ihrer weiteren Entwicklung zurück. Als besonders wüchsig erwiesen sich Keimlinge auf den Bodendeckungsvarianten mit Nadelstreuauflage und in D. flexuosa. Sand-Birkenkeimlinge der Bodendeckungsvarianten ohne Konkurrenz durch Bodenvegetation (Mb, Nd) besaßen eine längere Hauptwurzel und eine höhere Wurzelmasse (56 % - 60 % der Gesamtmasse). Die oberirdische Allokation (Blatt- und Sprossmasse) fiel hingegen für Sand-Birkenkeimlinge in den Bodendeckungs-varianten mit C. villosa und D. flexuosa höher aus. Verteilungs- und Konkurrenzerhebungen in den Gefäßversuchen erbrachten signifikante Zusammenhänge zwischen Keimlingsdichte, Standraum und Wachstum der Einzelpflanze. - Das Sämlingsstadium und die älteren Verjüngungspflanzen wiesen einen deutlichen Rückgang in der Mortalität auf. Die Erhebungen im Bestand ergaben ein unterschiedliches Durchschnittsalter für Sand-Birken auf den einzelnen Bodendeckungsvarianten (C. villosa 7,6 Jahre, D. flexuosa 6,2 Jahre und Nadelstreu 4,7 Jahre). Die wachstumsrelevanten Umweltbe-dingungen wie Strahlungsverfügbarkeit, Feuchteregime und Entfernung zum nächsten Alt-baum unterschieden sich außerdem in Abhängigkeit von den als repräsentativ eingestuften Bodendeckungsvarianten unter Bestandesbedingungen. Das bestandesbezogene Wachstum der Sand-Birken in einem Alter von 2 bis 6 Jahren ließ sich durch eine exponentielle Funktion mit hoher Anpassungsgüte (p ≤ 0,000) abbilden. Innerhalb des Mitscherlich-Gefäßversuchs haben sich ebenfalls Unterschiede in der Individuendichte, den Mortalitäts- und Wachstums-raten in Abhängigkeit von den Bodendeckungsvarianten ausgebildet. Höchste Verjüngungs-dichten wurden nach einem 2,5jährigen Entwicklungszeitraum auf der Bodendeckungs-variante Nadelstreuauflage erreicht. Die Allokationen in der Trockenmasse näherten sich hingegen in den unterschiedlichen Varianten stärker an. Ein dichteabhängiges Wachstum konnte in der letzten Aufnahme nicht mehr nachgewiesen werden. Abschließend bleibt festzuhalten, dass die ermittelten Untersuchungsergebnisse in Abhängig-keit vom jeweiligen Verjüngungsstadium die zeitliche und räumliche Präsenz, Konkurrenz- und Entwicklungsfähigkeit der Sand-Birke in Fichtenaltbeständen des Tharandter Waldes charakterisieren. Sie belegen eine kleinstandörtliche Heterogenität in den untersuchten Beständen, die sich nachhaltig auf die Etablierung der hier untersuchten Pionierbaumart auswirkt. Anhand der räumlichen Modellierung lässt sich die zu erwartende Verteilung von Diasporen und Keimlingen in Abhängigkeit von den Positionen der Samenbäume prognostizieren. Insgesamt ergibt sich aus den vorliegenden Ergebnissen ein vergleichsweise hohes Verjüngungspotenzial für B. pendula, das sich durch waldbauliche Maßnahmen effizient nutzen ließe. Ein detailliertes Wissen über die einzelnen Verjüngungsstadien bietet zudem die Möglichkeit einer gezielten waldbaulichen Steuerung der Baumart und zur Risikoabschätzung des Verjüngungserfolgs unter den gegebenen Rahmenbedingungen. Bei einer wachsenden waldbaulichen Unsicherheit im Umgang mit unterschiedlichsten Klima-prognosen, die sich in ihrer Wirkung regionalspezifisch erheblich unterscheiden können, sollte die Sand-Birke als Misch- und Vorwaldbaumart unbedingt berücksichtigt werden. Um dem viel zitierten Anspruch an die Nachhaltigkeit waldbaulichen Handelns gerecht zu werden, muss die Option zur Integration von B. pendula gewährleistet bleiben, auch für künftige Generationen und bei sich wandelnden Ansprüchen an den Wald.<br>- Objectives - The main goal of this study was to describe comprehensively the particular stages of the regeneration cycle of Betula pendula Roth. Investigations were carried out in local stand and site conditions of a research area in South-East Germany (Tharandter Forest) are considered. In this context options for integrating Silver birch regeneration into silvicultural management concepts of old Spruce stands (Picea abies L.) with lacking vitality are pointed out. - Research area - The Tharandter Forest is located (50°00’N, 13°35’E.) in Saxony (South-East Germany) with an area of around 6.000 ha. It is dominated by Norway spruce stands, and ranges from colline to submontane altitudinal belt (350 to 420 m a.s.l.). These sites are part of the northern declivity of the Ore Mountains. Mono-layered Norway spruce stands with soils of medium trophy and well drained, but featured highly variable soil moisture levels during the growing season were selected for this study. The stand age was ≥ 80 years. Seed trees of Silver birch were mixed as single trees or small groups. - Methodical aspects - The methodical work was concentrated on relevant regeneration aspects like fructification of seed trees, seeds, seedlings, saplings and established regeneration of Silver birch. Growth parameters of seed trees and the amount of fructification were used to quantify allometric relationships. The multi-level research design was based on measurements under stand conditions, pot and laboratory experiments. Seed traps and plots (1m x 1m) were located in spruce stands with regard to different stages of Silver birch development. Therefore micro-environmental growth conditions like soil humidity and photosynthetic active radiation were measured, and plants of ground cover characterized. As examples of ground cover variants with highest presence in homogeneous spruce stands mineral soil, needle litter, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.) were chosen. Using the program WALDSTAT (NÄTHER &amp; WÄLDER 2003) spatial distribution of dispersed seeds (diaspores) and seedlings could be modelled. Additionally pot experiments were done to compare quantitative and qualitative development of birch seedlings between stand and open site conditions. Regeneration density, number of leaves, shoot and root growth and allocations were measured as important growth parameters to evaluate single plant development under different environmental conditions. Finally, spatial distribution of seedlings in microsites and intraspecific competition were calculated by tessellation models, aggregation indices after CLARK &amp; EVANS, Gini-coefficient and ‘constant yield law’. - Main results - - Measurements on seed trees of B. pendula indicate stand specific differences significantly in dimension, height and biosocial position of trees within the birch population (crown classes). For specific height-dbh curves logarithmic and quadratic equations were adapted. The relative crown length for seed trees was located between 37 % and 49 %. Allometric relationships between crown parameters (e.g. crown diameter, crown length and crown surface) were strongly correlated. In specific cases crown structures (e.g. dry mass of leaves and twigs) were also correlated, certainly with different grades. Direct seed counting of felled seed trees provided the relationships between dbh and number of seeds. Counted seeds for single Silver birch trees ranged between 2.300.000 - 4.200.000. - As one result of seed trapping huge varieties in seed production of Silver birch were detectable between years with different seed potential. Spatial modeling of seed dispersal supported strong influences caused by wind (direction and speed). Hence, best fitted model estimations were found for anisotropic scenarios. The maximum in seed density was recorded with 20.700 seeds per m². As data for ‘Mean Dispersal Distances’ (MDD) the program WALDSTAT calculated between 37 m and 90 m. Furthermore the amount of seeds produced by a single tree was estimated with 180.000 - 7.400.000 depending on dbh. Physical quality evaluations for seeds have shown a mean proportion of damaged and not germinable seeds between 5 % and 8 %. - Direct effects of ground cover variants have been identified for seedling density and growth. Seedling density was highest on mineral soil for both, stand conditions and pot experiment, but these birch seedlings developed slowly compared with individuals in the other ground cover variants. The best growth was realized by birch seedlings in needle litter and D. flexuosa. Regarding to root length and mass, birches in ground cover variants without grass competition (mineral soil and needle litter) have shown a significant better development of underground parts. Root dry mass of these birch seedlings reached proportions between 56 % and 60 % of whole plant dry mass. By contrast the aboveground dry mass (leaves and shoot) was higher for birches competing with grasses. Overall results of birch seedling distribution and competition were significant correlations between densities, space, and growth per single plant. - For saplings and established birch regeneration a notable decrease in mortality rates were found. According to regeneration analyses under stand conditions age distributions in Silver birch regeneration have been controlled by ground cover variants and their environment conditions. The average age of Silver birch seedlings was high in areas with C. villosa (7.6 years) and low in needle litter (4.7 years). Furthermore growth influencing environmental conditions like light, humidity, and distance of old spruce trees have shown differences between variants in ground cover. The growth of regenerated Silver birches at the age of 2 to 6 years under those stand conditions can be described by an exponential function with high degree of adaptation (p ≤ 0,000). There were also differences in sapling densities, mortality and growth rates caused by ground cover variants in the pot experiments. After 2.5 years maximum regeneration densities in pots were registered on ground covers with needle litter. Allocations in regeneration dry mass were less influenced by ground cover variants than in previous stages. Density dependent growth rates could not be proved during last measurements. Finally, the presented results provide the opportunity to characterize temporal and spatial presence of different regeneration stages of Silver birch, its potential of competition and further development in old Norway spruce stands of the Tharandter Forest. They document heterogeneous structures of micro-environmental conditions in these spruce stands, which have sustainable effects on regeneration establishment of this studied pioneer tree species. On the basis of spatial modeling it is possible to estimate spatial distribution of seeds and seedlings depending on seed tree positions. Overall the results involve a high potential of successful regeneration in Silver birch, which opens up promising vistas for silvicultural management. More detailed knowledge in particular regeneration stages induces possibilities for selective control in silviculture with Silver birch. Additionally, estimating the regeneration risks and the success under given surrounding conditions will be more precisely. Considering uncertainty in giving prognoses for climate change Silver birch should be integrated in silvicultural strategies because of its role as admixed tree species and pioneer crop combined with comparably high resilience against warming.

碩士<br>國立中興大學<br>生命科學系所<br>106<br>Soil salinization has caused considerable losses in global agriculture. Understanding the mechanism of salt tolerance is critical for improving the production of crops. Ice plant (Mesembryanthemum crystallinum) has unique responses for tolerating high salinity and is a model halophyte for studying salt tolerance. Ice plant can maintain the ion homeostasis and reduce the oxidative damage under salt stress by accumulating excessive sodium ion in the vacuole and compatible solute in the cytosol. Changes in expression profiling have been identified in ice plant under salt stress by microarray and expressed sequence tag. In this thesis, the ice plant transcriptome was de novo assembled by Trinity after high throughput sequencing and was used to identify the functions and pathways by the Swiss-Prot protein database, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database, and the Gene Ontology database (GO). Total RNA was extracted from 3-day-old ice plant seedlings treated with 0 mM (Control), or 200 mM of NaCl for 6 h (Salt). Totally 53,031,502 and 55,702,462 pair-end reads were obtained from Control and Salt, respectively. Most sequences based on the quality score were capable for assembly. The de novo assembly resulted in 85,667 transcripts, and the average and maximum N50 length of the assembled transcripts were 460 nt and 1,360 nt, respectively. Most of the sequencing reads (88.66%) can be mapped to the assembled transcriptome. The result showed that 6,326 unigenes were differentially expressed, including 3,917 up-regulated genes and 2,409 down-regulated genes (FDR＜0.001), indicating these genes were significantly differentially expressed at an early stage of salt stress. A total of 28,520 (37.93%) unigenes were annotated by Swiss-Prot protein database. A total of 27,843 (37.03%) and 4,754 (6.32%) unigenes were assigned by the GO and KEGG databases, respectively. The GO terms ‘cation binding’, ‘antioxidant activity’, ‘response to stress’ and ‘membrane part’ were enriched in up-regulated genes. The GO terms ‘nucleic acid binding’, ‘cellular metabolic process’ and ‘cytoplasmic part’ were enriched in down-regulated genes. The result indicated the increase of ion transport for maintaining ion homeostasis and the induction of the antioxidant activity for reducing the oxidative damage. Simultaneously, the tolerance to stress was improved by reducing the pathways for energy consumption. The KEGG analysis revealed that the up-regulated genes were involved in the pathway of Ca+ signal transduction, peroxisome and root development. The Swiss-Prot annotation also revealed the genes of peroxidase, sugar transporter and potassium transporter were up-regulated. These results revealed the increase of stress signal transduction by Ca+ and ROS involving in hormone accumulation and antioxidant production under salt stress. Analyses of transcriptome and differential expressed genes will be useful for future studies on salt tolerance mechanism of ice plant.

碩士<br>國立屏東科技大學<br>森林系<br>93<br>Leaf is the most important organ for photosynthesis. There will be a trade-off between the length of a living leaf and the capability of its photosynthetic rate. A short-lived leaf often performs higher physiological activity with shorter active period than a long-lived leaf does. Bischofia javanica, Machilus japonica var. kusanoi, and Gordonia axillaris are 3 common tree species in subtropical broad-leaved forest of Taiwan. This study investigates the patterns of physiological activities in various leaf age of these species. The amount of carbon fixed during a leaf’s life-span was investigated also. The physiological activities and leaf life-span of each species were measured for potted young trees in nursery of the National Pingtung University of Science and Technology. The hypothesis of this study was that, with shorter leaf life-span, B. javanica should perform higher photosynthetic rate than M. japonica and G. axillaris which have longer leaf life-span. In addition, the physiologically active duration of B. javanica should be shorter than those of the other 2 species. Result showed that average leaf life-span in potted B. javanica in the nursery was about 7 months which was shorter than that of M. japonica and G. axillaries. In addition, leaf life-span of mature trees of M. japonica and G. axillaris were determined in terms of annual leaf turnover rate and half-life in Nanjenshan Forest. Their leaf life-spans were about 18 and 15 months, respectively. Physiological activities of all these 3 species increased as their leaves start to mature. Physiological activities of B. javanica peaked when the leaves just became fully expend. On the other hand, physiological activities of M. japonica and G. axillaris peaked 20-40 days after their leaves became fully expend. Maximum rate of photosynthesis of B. javanica, M. japonica, and G. axillaris were between 12.7-13.8 μmol CO2 m-2s-1. There was no significant difference in the length of days when the photosynthetic rates of the 3 species maintained over 90% of their peak rates (photosynthetic peak stage). However, the length of the photosynthetic peak stage for B. javanica composed 23.4% of its leaf life-span, which was longer than those for the other 2 species. In addition, both the slopes of linear regressions between potential photosynthetic rates and the leaf age from the first day to the day of peak photosynthesis as well as from the peak day to the end of the leaf in B. javanica were all much steeper than those for the other 2 species. These findings indicated that initiation and senescence in photosynthetic machinery of B. javanica were all faster than the other 2 species. Bischofia javanica had the same patterns in photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll concentration and chlorophyll fluorescence (Fv/Fm) during their leaf life-span. However, both Chlorophyll concentration and chlorophyll fluorescence of M. japonica and G. axillaris still maintained at high values before senescence of their leaves. These patterns were different form those of photosynthesis, stomatal conductance, and transpiration. During the whole life-span, single leaf of G. axillaris fixed only 1.4 g of carbon but B. javanica and M. japonica fixed much higher amount of carbon, 4.3 and 4.4 g, respectively. In conclusion, there were no significant differences in terms of both the length of physiological peak stage and the potential of photosynthesis among the 3 species. Therefore, the hypothesis of this study was not supported. Key words: fixed carbon, chlorophyll concentration, chlorophyll fluorescence, leaf age, leaf life-span