Flowering plants possess striking variation in reproductive traits and mating patterns, even among closely related species. In this thesis, I investigate morphological variation, mating and genetic diversity of five taxa of bird-pollinated Babiana (Iridaceae), including two species with specialized bird perches. Field observations in 12 populations demonstrated that sunbirds were the primary pollinators. Babiana ringens exhibited correlated geographic variation in flower and perch size. Controlled field pollinations revealed self-compatibility and low pollen limitation in B. ringens subspecies, and self-incompatibility and chronic pollen limitation in B. hirsuta. Allozyme markers demonstrated moderate to high selfing rates among populations and considerable variation in levels of genetic diversity. In B. ringens there was a positive relation between the geographic and genetic distance of populations. The results of a manipulative field experiment indicated position-dependent herbivory on inflorescences of B. hirsuta and this could play a role in the evolution of specialized bird perches in Babiana.

Flowering plants possess striking variation in reproductive traits and mating patterns, even among closely related species. In this thesis, I investigate morphological variation, mating and genetic diversity of five taxa of bird-pollinated Babiana (Iridaceae), including two species with specialized bird perches. Field observations in 12 populations demonstrated that sunbirds were the primary pollinators. Babiana ringens exhibited correlated geographic variation in flower and perch size. Controlled field pollinations revealed self-compatibility and low pollen limitation in B. ringens subspecies, and self-incompatibility and chronic pollen limitation in B. hirsuta. Allozyme markers demonstrated moderate to high selfing rates among populations and considerable variation in levels of genetic diversity. In B. ringens there was a positive relation between the geographic and genetic distance of populations. The results of a manipulative field experiment indicated position-dependent herbivory on inflorescences of B. hirsuta and this could play a role in the evolution of specialized bird perches in Babiana.

<p>Flowering is a critical step in the plant life cycle. If flowering occurs too early or too late, seed production suffers. Flowering is regulated through numerous flowering repressors. As long as these repressors persist, the plant will remain in a vegetative growth stage. Some plants possess two separate genetic pathways, the autonomous pathway and the vernalization pathway, that promote the transition to flowering through stable downregulation of flowering repressors. Once the plant achieves floral competence, it will flower under inductive environmental conditions.</p> <p>In <i>Arabidopsis</i>, <i>FCA</i> is a key autonomous pathway gene, acting with <i>FY</i> to promote the floral transition. Recently, gene sequences resembling <i>FCA</i> were cloned from hexaploid wheat (<i>Triticum aestivum</i>) and designated as <i>WFCA</i>. WFCA shows numerous similarities to the FCA peptide, especially regarding three key regions: two RNA Recognition Motifs and the WW domain. This study seeks to determine if <i>WFCA</i> genes function similar to <i>FCA</i> by determining if they are able to complement the <i>fca-1</i> mutant of <i>Arabidopsis thaliana</i>.</p> <p>T1 progeny from an <i>Arabidopsis fca-1</i> plant transformed with <i>WFCA</i> were grown without vernalization and assayed for the final leaf number (FLN). The late flowering <i>fca-1</i> control plants bolted with an average FLN of 14.8 while the T1 population had an average FLN of 14.3. Although the numerical difference is slight, the results are statistically significant, and suggest that <i>WFCA</i> genes may have some degree of flowering promotion activity in <i>Arabidopsis</i>. The lack of strong complementation may be due to divergence of the <i>WFCA</i> genes from their <i>Arabidopsis</i> counterparts. With increasing evidence for divergence in flowering promotion between monocot and dicot species, the development of a robust monocot model system appears to be critical to provide a good framework to assist studies of the particular nuances of the monocot flowering process.</p>

Influence of absicisic acid on flowering in Phalaenopsis hybrida Abscisic acid (ABA) in the buds (or flowering shoots) , leaves and roots of Phalaenopsis hybrida (cv. TS 340) was identified and quantified by gas chromatography-mass spectrometry- selected ion monitoring using hexadeuterated ABA as an internal standard. Leaves contained much lower levels of both free and bound ABA than did roots. Dormant buds contained a relatively higher level of free ABA, whereas no detectable free or bound ABA was found in flowering shoots either at a length of 2 to 3 cm or 7 to 10 cm. Dormant stage P. hybrida ( grown at 28¢J ), levels of free ABA in the roots were higher than those in plants with flowering shoots, the levels of bound ABA in roots exhibited opposite tendency. Free and bound ABA in leaves was slightly increased in plants with flowering shoots as compared to those in the dormant stage. In addition, exogenous ABA application at 0.1 or 1 &#x00B5;g per plant inhibited initiation of flowering shoots, especially at 1&#x00B5;g per plant. These results suggest the decrease in the free ABA contents in the roots and buds, but not in the leaves, is correlated with bud activation and development of flowering shoots. Protein synthesis and flowering in Doritis pulcherrima in relation to daylength Mature doritis plants (Doritis pulcherrima Lindley cv. S84 -3345) were cultured in plastic pots with 9-h (short-day, SD) and 16-h (long-day, LD) photoperiods, respectively. The main 9-h light period was under field conditions (30 ¢J day/20 ¢J night on average). The supplemental 7-h light conditions for the LD was in chambers with 14 £gmol. m-2 s-1 photosynthetic photon flux. When transferred to SD for 30 or 40 days the plants initiated flower spikes (90 % of the total plants) between 2.0 to 3.0 cm and 7.0 to 10.0 cm in length, respectively. In contrast, only 10 % of the plants producing flowering shoots were observed under LD conditions. Unique 21 and 103 kDa proteins were evident in one-dimensional electrophoresis of proteins from mature leaves under SD conditions. Two-dimensional gel electrophoresis confirmed that clear polypeptide spots with a molecular mass of 21 kDa at isoelectric point of 5.2 and 103 kDa at isoelectric point of 5.6 accumulated in leaves when flowering shoot reached 7.0 to 10.0 cm (4 to 5 flowe4 primordia apparent). Possibly, the 21 and 103 kDa proteins play the important role during initiation of flowering shoot in doritis. Polypeptide sequencing of P21 suggested a possible relationship to the product of cell division-like protein in Arabidopsis thaliana. It is clear that doritis is a facultative SD plant, and photoperiodic induction of its flowering is closely associated with changes of protein synthesis in its leaves.

The main objective of this research project was to study the growth and development of the floral nectar spur of Centranthus ruber (L.) DC. Nectar spurs are tubular floral outgrowths, generally derived from the perianth organs, which typically contain secreted floral nectar. The morphological characteristics of the spur, particularly the length, determine which floral visitors will be able to access the nectar reward pooled at the spur tip. Therefore, nectar spurs are ecologically important for the development of specialised pollinator interactions and have been demonstrated to act as key innovations in the evolution of some taxa. Morphological and anatomical characteristics of the spur and floral nectary were investigated using light and scanning electron microscopy. Ultrastructural features of the nectar spur, particularly the floral nectary within, were assessed using transmission electron microscopy. Nectar in C. ruber is produced by a trichomatous nectary which runs along the entire, inner abaxial surface of the spur. The nectary is aligned with the single vascular bundle which runs along the abaxial side of the spur, through the sub-nectary parenchyma, and back up the adaxial side. The secretory trichomes are unicellular and, in late development, they develop a thick layer of secondary wall ingrowths which vastly increases the surface area of the plasma membrane for nectar secretion. Elongate, non-secretory trichomes occupy the entire remaining circumference of the spur’s inner epidermis, but their density is reduced compared to the secretory trichomes. The cellular basis for spur growth is poorly characterized in the literature. Until recently, it was assumed that all nectar spurs grow by the constant production of new cells via up to three potential meristematic regions (the meristem hypothesis, Tepfer 1953). The cellular basis for spur growth in C. ruber was investigated by cell file counts and cell length and width measurements along the lateral side of nectar spurs in each of the developmental stages. DAPI stained spurs were also examined with Confocal/Apotome microscopy to determine the timing and position of cell division activity throughout spur development. It was determined that elongation of the spur epidermal cells contributes much more to spur growth than cell division. In early development, division is the primary driver of spur growth and the cells are isotropic. However, as development progresses, cell division activity slows down and the spur cells become increasingly anisotropic until anthesis. The patterns of nectar secretion were determined by assessing the volume, solute concentration and carbohydrate composition of the nectar throughout flowering phenology in two C. ruber plants. Nectar volumes and solute amounts rose initially, followed by an eventual decline in both as phenology progressed towards senescence. Because this study was conducted on greenhouse grown plants, it can be assumed that nectar was not removed by insects, suggesting that it is likely reabsorbed following secretion. High performance liquid chromatography (HPLC) analysis determined that C. ruber's nectar is sucrose dominant and that nectar composition remains stable following anthesis throughout floral phenology.

No description available.

Deep phylogenetic relationships in the angiosperms had long been uncertain. However, by the end of the 1990s, large-scale studies contributed to the current well resolved picture of the tree of flowering plants, in which eudicots, monocots, and magnoliids are the three largest clades. Whereas monocots and eudicots have been recognized since the very first phylogenetic analyses, the monophyly of magnoliids (Canellales, Laurales, Magnoliales, and Piperales) is a more recent result. Magnoliidae, as now circumscribed, consist of 20 families and ca. 10,000 species mostly distributed in the tropics. Before the present thesis, several parts of the magnoliid tree had been well studied, but little was known about the evolutionary history of Magnoliidae as a whole. The first chapter of this thesis is a phylogenetic study conducted to clarify the relationships among families and orders of Magnoliidae. To do so, I sampled 199 species of Magnoliidae and 12 molecular markers from the three genomes and conducted phylogenetic analyses using parsimony, maximum likelihood, and Bayesian methods. The results confirm, with a greater level of support, two clades in Magnoliidae: Canellale + Piperales, and Laurales + Magnoliales. In addition, the relationships among the 20 families are generally well supported, and Lactoridaceae and Hydnoraceae are nested within Aristolochiaceae (Piperales). In the second chapter, the ages and phylogenetic positions of 10 fossils attributed to Magnoliidae were reviewed in detail. The goal of this study was to provide new reliable calibration points in order to conduct molecular dating analyses. These fossils were selected from the rich fossil record of the group because of their previous inclusion in phylogenetic analyses with extant taxa. The resulting calibration scheme provides six solid, internal minimum age constraints. The third chapter includes molecular dating analyses using the present calibration scheme and the same molecular dataset of Chapter 1. This study tends to push back in time the ages of the crown nodes of Magnoliidae (127.1-198.9 Ma), and of the four orders, Canellales (126.3-141.0 Ma), Piperales (88.2-157.7 Ma), Laurales (111.8-165.6 Ma), and Magnoliales (115.0-164.2 Ma). In the same chapter, I investigated the mode of diversification in the group. The strongly imbalanced distribution of species appears to be best explained by models of diversification with 6 to 14 diversification rate shifts. Finally, in the last chapter, I traced the evolution of 26 floral characters to reconstruct the ancestral flowers in key nodes of Magnoliidae. I used the phylogeny of Chapter 1 and an exemplar approach. Our results show that the most recent common ancestor of all Magnoliidae was a tree bearing actinomorphic, bisexual flowers with a differentiated perianth of two alternate, trimerous whorls of free perianth parts (outer and inner tepals) and probably three free stamens. This work provides key results on the evolution of Magnoliidae and raises several new questions such as the impact of geological crises on diversification of the group or the influence of pollinators and the environment on the evolution of floral morphology.

Terpenes are important specialised metabolites produced by all organisms. Plants produce the greatest diversity of terpenoid compounds, which function in a variety of crucial processes including regulation of growth and development, energy production and plant-insect communication, including pollinator attraction and prevention of herbivore damage. Isopentenyl diphosphate (IPP), the building block for all terpenoid compounds, is synthesised in plants via two unique terpene synthesis pathways located in the plastids and the cytosol, and the regulation of these pathways is still not well understood. The aim of this research was to (1) modify and study the regulation of floral volatile production in Nicotiana tabacum (tobacco) by altering the expression of various enzymes in the terpene biosynthesis pathway and (2) determine the role of specific volatile compounds in floral odour blends in feeding and oviposition behaviours of Helicoverpa armigera, a polyphagous moth of widespread agricultural importance. Expression levels of several enzymes in the terpene biosynthetic pathway were altered by genetic modification in order to modify terpene volatile emissions produced by flowers of N. tabacum. Genes chosen for overexpression were cloned from several species and RNAi hairpins were constructed from gene fragments amplified from tobacco flower cDNA. Transgenic plants were produced by Agrobacterium-mediated transformation, and lines with high levels of transgene expression selected for analysis. The flower-specific Antirrhinum majus chalcone synthase promoter was chosen to control gene expression in transgenic lines in order to avoid the potentially deleterious effects of widespread disruption to terpene biosynthesis. Floral volatiles were sampled using two methods; solid phase microextraction, a highly sensitive technique able to detect even trace levels of volatile compounds in headspace samples, and Tenax sampling, a robust and replicable method to quantify volatile emissions. All floral headspace samples were analysed by gas chromatography-mass spectrometry. Floral volatile analysis determined that wild type Ti68 tobacco flowers emit a simple blend of floral volatiles, with only linalool, a monoterpene, and β-caryophyllene, a sesquiterpene, detected by both sampling methods. Volatile emissions were not subject to temporal regulation, but changes in the floral odour blend were detected during flower development. Overexpression of the plastidic terpene biosynthesis genes 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) and geranyl diphosphate synthase did not affect volatile production, however increased farnesyl diphosphate synthase expression in the cytosol surprisingly caused an increase in linalool emissions, synthesised in the plastids. Downregulation of DXR resulted in an albino phenotype affecting all young leaves, the upper stem and the sepals in the most severely affected lines. A significant three-fold decrease in floral linalool emissions, and a nine-fold reduction of both linalool and β-caryophyllene retained within floral tissues was observed in the transgenic lines. In feeding behaviour tests, male and virgin female H. armigera moths did not discriminate between wild type and DXR knockdown flowers at close-range, despite the significant difference in linalool emissions. Expression of an (E)-β-ocimene synthase gene controlled by the CHS promoter did not result in any transgenic plants emitting the novel monoterpene, (E)-β-ocimene. Significant problems with seed germination suggested that (E)-β-ocimene may cause embryo lethality in these lines. However, overexpression of a heterologous (S)-linalool synthase under control of the constitutive cauliflower mosaic virus 35S promoter resulted in a significant two-fold increase in volatile linalool, and β-glycosidase assays confirmed sequestration of a glycosylated linalool derivative in floral tissues. Oviposition preference tests with mated female H. armigera moths indicated a significant preference for egg-laying on wild type flowers compared to flowers with increased linalool production. The results of this research, and previous studies of volatile production in transgenic tobacco, indicate that IPP precursor exchange occurs predominantly in one direction from the cytosol to the plastids, at least under the stress caused by alterations in pathway flux. Regulation of the cytosolic terpene biosynthetic pathway upstream of IPP synthesis appears to be less strictly controlled than the plastidic pathway. Insect behavioural assays support the findings of recent studies in other moth species, and suggest that close-range feeding attraction of H. armigera may be more strongly influenced by visual cues, whereas odour cues, including contact chemoreception, play a more important role in oviposition preferences. The increase in knowledge of the olfactory contribution toward insect-plant communication demonstrated here, and from future work, will lead to improved management of pest species in agricultural and ecological settings.

Shoot morphogenesis in Eucalyptus occidentalis and Metrosideros excelsa was analysed at the morphological, physiological and molecular levels to understand the regulation of phase change and the floral transition. Study of the regulation of these developmental plant processes is limited in woody species due to their long juvenile phase. Six ecotypes of E. occidentalis were grown to two predetermined architectures (free branching or single stem). Free branching plants of ecotype 13648 displayed adult shoot phenology (lanceolate leaves) earlier than single stem counterparts. In addition, changes in leaf morphology in free branching plants were accompanied with changes in leaf anatomy and gas exchange signifying that in E. occidentalis complexity of shoot architecture had a significant effect on rate of phase change. Flowering was observed in all but one ecotype irrespective of architecture demonstrating that vegetative phase change and floral transition are temporally uncoupled in this species. To understand the floral transition at the molecular level in E. occidentalis, partial homologues of the inflorescence meristem identity gene TERMINAL FLOWER1 and floral meristem identity genes LEAFY and APETALA1 were isolated. The expression patterns of these meristem identity genes during development of free branching and single stem plants were analysed by quantitative real-time PCR. Increased levels of expression of EOLFY and EOAP 1 (relative to α -TUBULIN) were displayed at more proximal nodes in free branching plants than in single stem plants. Elevated floral meristem identity gene expression levels correlated with flower initiation. Further, effects of architecture and environment on gene expression were monitored in E. occidentalis. The overriding effect of shoot architecture on the floral transition was observed under warm long day and ambient environments. Elevated levels of EOLFY and EOAP 1 were correlated with floral bud score and EOAP1 was found to be a reliable marker of floral transition in E. occidentalis. Low levels of EOTFLI expression were detected in buds irrespective of their position on the plant leading to the suggestion that this might have contributed to the precocious flowering observed in this species. In contrast to E. occidentalis, M excelsa attained adult shoot phenology (pubescent leaves) faster when grown as single stem plants than as free branching plants. It appears that growth as height is required for vegetative phase change in this species. However, floral transition occurred only once single stem plants were allowed to branch. Vegetative phase change and the transition to flowering seem to be coordinated in this species with the former being a pre-requisite for the latter.

Memoria para optar al título profesional de Ingeniero Agrónomo / La presente recopilación bibliográfica, sintetiza los principales usos que han tenido las giberelinas de síntesis ( y ) como fitorreguladores en la fruticultura chilena. La mayor cantidad de investigaciones, con este regulador de crecimiento (), han sido desarrolladas en uva de mesa, sobre todo en variedades sin semillas como Sultanina, Flame Seedless, Black Seedless, entre otras, obteniéndose resultados significativos en el raleo de estructuras reproductivas, incremento del tamaño de frutos al igual que otras variables de calidad de la fruta como el color de cubrimiento de frutos. Sin embargo, también se encuentran efectos indeseados con este fitorregulador como son el desgrane, raleos severos al igual que aumentos de la infertilidad de yemas en uva de mesa. Este efecto inhibitorio de la inducción floral con aplicaciones de , también ha sido evaluado en cítricos, paltos, olivos y durazneros, donde los resultados han sido beneficiosos, dado que al inhibir parte de la inducción floral, en los años de alta floración, se disminuye el grado de alternancia productiva.