Many flowering plants are hermaphrodite, which poses the problem of self-fertilisation and the subsequent loss of genetic fitness in the offspring. To prevent this, plants have developed a genetically controlled mechanism called self-incompatibility (SI) which allows self (incompatible) pollen to be recognised and rejected before fertilisation can occur. The SI response of Papaver rhoeas (field poppy) has been extensively studied at the molecular and cellular level. Rejection of incompatible pollen occurs on the stigma surface when the pollen S-determinant PrpS, a transmembrane protein, interacts with the stigmatic S-determinant, secreted S-proteins. This triggers a calcium-mediated signalling cascade that targets the cytoskeleton and results in programmed cell death (PCD) of incompatible pollen. Work presented in this thesis investigated the localisation of PrpS and S-proteins. Other studies investigated the role of the cytoskeleton in SI. These demonstrated the involvement of the microtubule cytoskeleton for the first time. Microtubules were rapidly depolymerised and this was implicated in signalling to PCD. The actin cytoskeleton has previously been shown to exhibit biphasic alterations during SI involving depolymerisation, followed by formation of F-actin foci. Studies described here represent the first steps toward characterisation of the F-actin foci. Their potential involvement in PCD and signalling is discussed.

Africa is a major centre of diversity in the large cosmopolitan genus Solanum. The genus is an important component of the African flora, and, with a variety of uses, many of the species have a significant interaction with man. The objective of the present study was an elucidation of some of the many taxonomic problems found among the African species of the genus. The systematic history of the African species of Solanum is reviewed to provide an insight into the origins of the nomenclatural problems that pervade the genus. Taxonomic characters are described and assessed, and the phytogeography of the genus is discussed. The results of cross-pollinations and protein comparisons using polyacrylamide gel electrophoresis and serological techniques are discussed. No new insights into the taxonomy of the African species were revealed by these experimental studies and the potential for further work is reviewed. An adaptation of earlier methods of analysis of serological data is described. In conclusion a taxonomic review is presented: species of Solanum occurring in Africa and the neighbouring islands are described accompanied by keys and comments on typification, distribution and synonymy. Around 80 species are believed to be autochthonous; three new species are proposed. An index to the species names in the review lists 392 epithets.

Modern crop varieties contain limited genetic diversity. Demand from an expanding human population requires crop yields to increase substantially, however, a low capacity for adaptation may leave crops susceptible to environmental change, threatening future food security. Crop wild relatives (CWR) are a valuable, but threatened, genetic resource containing more genetic diversity than their cultivated relatives that can be utilised by plant breeders to improve the resilience of new crop varieties. This thesis researches methodologies to facilitate systematic, active conservation of CWR and their genetic diversity within a national context using the UK and its devolved administrations as an exemplar. Methods involve the development of CWR inventori es, gap analyses, assessment of CWR habitat preferences , a case study seeking to justify the establishment of the first UK CWR genetic reserve on The Lizard Peninsula, Cornwall and finally, exploration of the use of next generation sequencing as a tool for targeting collection of accessions to fill genetic gaps in genebanks. A key success of this research was the involvement of stakeholders, bridging the gap between research and practice. The methods used can now be applied to other countries and can be integrated into European and global conservation planning, contributing to improved future food security.

Mosses evolved approximately 500 million years ago and were among the earliest plants to make the transition from water to land. Mosses are therefore placed at an ideal evolutionary position in which to understand how plant physiology and development has evolved from simple unicellular aquatic organisms to generate the huge diversity of complex modern day flowering plants. The moss Physcomitrella has the unique ability among known land plants to carry out homologous recombination at a similar efficiency to the yeast Saccharyomyces cerevisiae. Armadillo-related proteins play important roles in cellular processes both in animals and plants. In Arabidopsis, ARABIDILLO1 and ARABIDILLO2 control root system architecture. ARABIDILLO-like proteins have been identified extensively throughout the plant kingdom, including early-evolving moss and agriculturally important crops such as rice and maize. Three Physcomitrella ARABIDILLO homologues have been identified; PHYSCODILLO1A, PHYSCODILLO1B and PHYSCODILLO2. Cloning, sequencing and Southern blotting approaches confirmed that PHYSCODILLO2 was a single copy gene, whereas full-length PHYSCODILLO1A and PHYSCODILLO1B genes were 100% identical and exist in a tail-to-tail orientation with 8kb separating their stop codons. A number of physcodillo deletion mutants have been generated. Phenotypic analyses revealed that PHYSCODILLO proteins appear to play important roles during early developmental processes, including growth of filaments from protoplasts and spore germination.

The experiments of this thesis were concerned with the involvement of abscisic acid (ABA) in the control of stomatal closure following water stress. The hypothesis that this control is exerted in a truly hormonal manner was introduced by considering the evidence implicating wilt-induced ABA in certain post-stress stomatal responses in relation to present concepts of phytohormone action. The results are presented in seven sections, each dealing with a specific aspect of the investigation. Section 1 was concerned with the development and characterisation of experimental systems whereby the effects of ABA on stomata of isolated leaf epidermis segments of Commelina communis could be studied. In Section 2, 14C-labelled ABA was presented to epidermis tissue floating on buffer solution. The subsequent uptake of radioactivity was assayed quantitatively and qualitatively using the techniques of scintillation spectrometry, TLC, and soluble-compound microautoradiography. Section 3 involved the use of 86Rb+ as a tracer for K+, the major cation involved in stomatal movements. 86Rb+ was taken up by tissue into the guard cell region, and both the pattern of this uptake and the rate of subsequent efflux was found to be affected by ABA treatment. The fourth section described the development of a whole-leaf incubation system which was then used to examine the effects and movement of 14C-ABA supplied via the transpiration stream. Autoradiographic evidence indicating guard-cell uptake of the honnone corroborated the conclusions of Section 2. In addition, it was possible to obtain 'upper limit estimates' of the sensitivity of Commelina stomata to ABA utilising the ability of this plant to yield epidermal peels. Thus, it was found that significant stomatal closure could be effected by as little as amol ABA per stomatal complex. Complete closure (within 40 min) apparently required over 230 amol per complex. Section 5 provided a measure of the ability of Commelina leaf tissue to synthesise ABA during a short-term (0-5 h) water stress. Levels of the hormone estimated by GLC-ECD rose from 31 to 178 ng per gramme fresh weight after 3 h incubation of tissue which had lost 10% of its fresh weight. Investigation of optimal ABA purification procedures was also carried out. An attempt was made in Section 6 to examine the ultrastructure of Commelina epidermis. Plasmodesmatal junctions between cells were observed in all cell walls except those between guard cells and subsidiary cells. The relevance of this finding in relation to intercellular transport routes and mechanisms was discussed. The seventh and final section described the transport of radioactivity from ABA in the phloem sap of Ricinus communis; Double-label techniques were used to study co-transport of ABA and sucrose. The hormone appeared to be readily translocated. GLG-MS was used to identify free ABA in Ricinus phloem sap. In the General Discussion the results were considered in relation to the concept of the hormonal nature of wilt-induced ABA action, and areas of research deserving of further attention were identified.

Pollen diagrams prepared from the sediments of Loch Lomond and the Dubh Lochan have provided a general overview of the vegetational changes which have occurred in the Loch Lomond area during the Flandrian period. Progressive deforestation since 5000 B.P. and particularly during the last few centuries has been high-lighted with the period of maximum extent of mixed Quercus woodland in the Loch Lomond area having occurred between c.6000 B.P. to c.5000 B.P. The Alnus rise horizon has been demonstrated to have occurred later than expected in the Loch Lomond area. Absolute pollen analysis has enhanced the interpretation of the relative percentage data and has shown that the pollen concentration has varied widely in the Loch Lomond sediment during the Flandrian. Pollen deposition data has been calculated from the Dubh Lochan sediments allowing a comparison to be made with deposition data from other lakes in north west England and Scotland, It has been concluded that concentration of pollen within the Dubh Lochan has occurred. Dinoflagellate analysis has provided the first positive evidence of a marine phase in Loch Lomond's mid Flandrian history. A period of meromixis of ectogenic origin has been hypothesised to account for a laminated band following the marine sediment within which pollen and macrofossil preservation was found to be uniquely good, with pollen counting of the Loch Lomond sediment having been generally taxing. Derived Carboniferous spores were noted throughout the length of the Loch Lomond profile. Analysis of selected terrestrial sites to compliment the picture of the status of Pinus sylvestris gained from the Loch Lomond sediments has been undertaken. The locality of the post Ulmus decline Pinus curve increase demonstrated by the Loch Lomond pollen data has been traced to Glen Falloch. The Glen Falloch peat has recorded a change from Betula woodland to Pinus-Betula woodland at a time generally recognised to be one during which Pinus was in decline in Scotland and Northern Ireland. Fire attributable to man has been considered to account for the initiation of growth of Pinus on the Glen Falloch peat surface. Radiocarbon dating of Pinus wood has demonstrated the continuous presence of Pinus in Glen Falloch until C.1600 B.P., with the present day Pinus trees having been considered to be of natural origin. Data from the Ptarmigan has suggested that in at least one part of the southern Loch Lomond area more Pinus exist today than at any time during the last six thousand years.

Begonia L. is one of the ten largest plant genera with >1,830 currently accepted species distributed throughout the tropical Americas, Africa and Asia. This exceptional diversity offers the opportunity to study the processes underlying recent and rapid radiations, including the theory of adaptive radiations, but also poses major challenges. Methods to test adaptive radiation theory require sufficient occurrence data to produce species distribution models for the majority of species in a group. In many groups, including Andean, Central American and Mexican Begonia, this criterion is not met. The availability of specimen data on GBIF for species distribution modelling in vascular plants as a whole was assessed. The potential contribution of databased and freely available but indetermined or non-georeferenced specimens to the field of species distribution modelling was estimated. More than half of vascular plant species are currently unavailable for species distribution modelling. Our results indicate 22% of currently unavailable species could be modelled with already available herbarium data that is not yet georeferenced or determined to species. We argue that a greater focus on georeferencing and identification skills are vital if herbaria are to contribute fully to the growing field of species distribution modelling. We highlight those families and geographic regions that would most benefit from this approach and discuss the historical factors have influenced differences among regions. Another prerequisite for species distribution modelling is a stable species level taxonomy. In preparation for investigation involving SDM’s in Begonia, five taxonomic papers are presented, including revised species concepts, distribution data suitable for use in species distribution models, seven new species and a new section of Begonia. Three plastid markers for 574 species and 809 accessions of Begonia were used to produce the largest, most representative phylogeny of Begonia published to date. An updated sectional classification of the genus is provided. The sections of Begonia are used frequently as analogues to genera in other families but, despite their taxonomic utility, few of the current sections have been examined in the light of molecular phylogenetic analyses. The relationships among some species and sections are poorly resolved, but many sections and deeper nodes receive strong support. We recognise 77 sections of Begonia including four new sections: Astrotricha, Jackia, Kollmannia, and Stellanthera; five sections are reinstated from synonymy: Australes, Exalabegonia, Latistigma, Pereira and Poecilia; and four sections are newly synonymised. The new sectional classification is discussed with reference to identifying characters and previous classifications. Central to the theory of an adaptive radiation is that the majority of speciation events are adaptive, implying speciation driven by adaptation to different environments and resulting in niche shifts. Species in an adaptive radiation should display distinct ecological niches and environmental disparity across the group’s phylogeny should best fit a kappa ‘niche-shift’ or ‘speciational’ model of character evolution. These characteristics were tested in two clades of Neotropical Begonia. Species were compared through the comparison of their distributions in environmental space calculated from species distribution models. The fit of four models of environmental evolution (a kappa ‘niche-shift’ model, a Brownian motion model, an early-burst model, and a white noise model) to the observed niche disparity in the group were assessed using the Akaike Information Criterion Patterns of ecological diversification in the two clades of Begonia examined strongly diverge from those predicted by an adaptive model, and we conclude Begonia is not an adaptive radiation with respects to climatic niche. Ecological disparity within Begonia clades best fits the predictions of a Brownian model of niche evolution. The characteristics of a Brownian model include constant niche evolution over the phylogeny, no increases in niche evolution during speciation, and independent niche evolution in sister lineages. This is incompatible with the predictions of an adaptive radiation. We suggest the remarkable diversity of the genus has developed through geographic speciation, and subsequent adaptation to local environments. This phenomenon may be widespread among plant radiations in topographically- and environmentally-heterogeneous areas, and a re-evaluation of putative adaptive radiations throughout the world’s montane regions may be necessary.

The aim of this project was to enhance our knowledge of how nitrogen is transported and utilised within Brassica napus through the use of proteomics, phenotyping and genetic mapping. It highlights the importance of looking at all possible plant tissues to determine the mechanisms underlying seven macronutrients (N, P, Mg, Ca, S and Na) and five micronutrients (B, Cu, Fe, Mn and Zn) accumulation, since differences were observed between different tissues. Significant amount of mineral elements were found to remain in both the stem and roots at harvest, which in turn, highlights the inefficient mechanisms applied by some plants in the way they redistribute and utilise minerals such as N, P, K and S. Large genotypic differences in minerals concentration was found between different accessions of B. napus, ranging from 1.48-fold for Ca in the bottom of the stem to 20-fold for Na in top of the stem at maturity. Genotypes were identified that differed significantly from one another in relation to mineral concentration in the stem and root at harvest or in both. Differences were observed in the parents of the TN mapping population allowing a QTL approach to be adopted. Complex network of relationships between minerals were observed within and between tissues, and found to be dependent on the tissue and the growth stage. The strongest significant positive correlations (0.91 > r >0.71) were between Ca/P, S/Ca and N/Ca in taproot, Ca/Mg in stem, and Mg/P and N/S in seed. A significant source of N is that stored within proteins. Several proteins were shown to be accumulated significantly in the top part of the plants especially in the senescing silique walls and the stem adjacent to them. Putative vegetative storage proteins, VSPs, were identified in these tissues and we have suggested that these could be associated with N remobilisation. Development of a screening methodology based on these proteins through which quantitative analysis could be performed on a proteomic based experiment has been successfully developed which will allow the identification of QTLs associated with the N remobilisation and utilisation in plants. These finding could assist plant breeders in developing varieties with enhanced mineral utilisation efficiency. Such developments will eventually lead to significant benefits both economically and socially worldwide as they should lead to increased abilities to enhance crop yields of oilseed rape while lowering the fertiliser requirements.

Activation of plant defence responses requires significant transcriptional reprogramming to mount an effective response to pathogens. This response must be finely balanced with growth and development processes to ensure optimal allocation of cellular resources. A fundamental mechanism of gene expression regulation is covalent modification of histones. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) antagonistically control the acetylation levels of histones at specific genomic loci to ultimately affect gene expression. This thesis focuses on histone acetylation as a mechanism by which plants mount an effective immune response. In Chapter 3, a reverse genetic screen of Arabidopsis HAT mutants is presented where a negative regulator (HAM2) of defence against the plant pathogen Pto DC3000 was identified. Whilst mutants of the negative regulator (ham2 ) demonstrate enhanced resistance to P. syringae, their susceptibility to the necrotrophic pathogen B. cinerea is unchanged. Alongside the immunity phenotype, ham2 plants exhibit increased adult leaf surface area, fresh weight and root length. Since ham2 is the only known Arabidopsis mutant with increased immunity and growth, it represents a promising target in an agricultural context. In Chapter 4, homology models of A. thaliana, B. napus and S. lycopersicum HAM2 proteins were created, supported by a series of cheminformatics and in silico docking methods, to identify chemical inhibitors for future agricultural applications. Finally, the role of Arabidopsis HATs in effector-triggered immunity was investigated in Chapter 5. Here, HAG1 was identified as a key positive regulator of effector-triggered responses. Overall, this thesis contributes to our understanding of the role of HAM2 and HAG1 histone acetyltransferases in plant immunity, and presents HAM2 as a novel target in an agricultural context.

The biochemical principles underlining carbohydrate metabolism of ornamental geophytes such as hyacinth and the lily are poorly understood. The present studies were therefore undertaken to investigate the regulation and partitioning of carbohydrates, as well as growth and development of these flower bulbs. Results indicated that starch was the major storage carbohydrate in these bulbs. Starch degradation occurred through amylolysis rather than phosphorolysis. The flower accumulated the highest amount of the reserves in hyacinth, following the depletion of these substances in the bulb scales, whilst in the case of the lily; it was the stem and roots, which accumulated the highest amount of reserves. The isolation of gene fragments of starch phosphorylase and starch synthase from hyacinth as well as the sequences generated for these enzymes implies that primers which are specific to hyacinth can be designed, and full characterisation of the genes can be made in the future by making and probing genomic libraries and isolating clones from cDNA libraries. In general, peeling of bulbs prior to planting resulted in a delay in emergence and reductions in vegetative growth as well as flower quality. Hyacinth plants subjected to defoliation did not show any compensation for leaf loss because growth was always reduced whilst flowering was unaffected, however, the lily responded positively to complete shoots removal especially when herbivory occurred at the beginning of their growth. Plants produced from large bulbs, just like those from the shallow planting regimes performed better in terms of growth and flower quality as compared to those of small bulbs and deep planting. Also, the application of (NH4)2SO4 enhanced more vigorous growth and bulb yield in both species of flower bulbs than did Na2HPO4, but in hyacinth it was Na2HPO4 that produced better flower quality than the former. Varieties such as Sky Jackets and Purple Voice produced the highest vegetative growth and bulb yield, whilst Fondant and Blue Jacket recorded the highest flower quality.