Very long chain fatty acids (VLCFAs) are essential to Arabidopsis growth and development. VLCFAs are found in sphingolipids, glycerophospholipids, triacylglycerols, suberin and cuticular waxes. VLCFAs are synthesized by the addition of 2 carbons from malonyl-CoA to pre-existing acyl-CoAs to produce chain lengths of greater than 18 carbon atoms. VLCFA synthesis involves four consecutive reactions that are catalysed by the microsomal Fatty Acid Elongase. In Arabidopsis the first reaction is catalysed by one of 21 different Keto-CoA Synthases (KCS) with diverse levels of expression and overlapping tissue specificities. The other three enzymes are ubiquitously expressed throughout the plant, and form the core components of the elongase. Lipidomic profiling has been performed on roots and shoots of plants with reduced levels of VLCFAs. Mutants of the core components of the elongase were analysed along with herbicides that inhibit a number of KCS enzymes, this allowed the whole elongase complex to be analysed. Differences were seen in the lipidomic profiles of the different elongase mutants and between the roots and shoots of the same mutants. This has revealed correlations between phenotypic differences and lipidomic changes giving insight into which lipid classes might be responsible for the various phenotypes. A forward genetic screen has been conducted in the Arabidopsis cer10-1 mutant to identify novel genes involved in VLCFA metabolism. CER10 encodes for the fourth component of the elongase complex. One suppressor mutant that has been identified has flower buds and fertility comparable to wild type plants but still displays the reduced size of the cer10-1 mutant. The second suppressor mutant identified showed restored size of aerial organs but the flower buds remained fused. Whole genome sequencing allowed localisation of these suppressor mutations on Chromosome 3. Partial biochemical characterisation of these mutants revealed interesting changes in their acyl-CoA and cuticular lipid profiles.

Geographically peripheral populations are believed to be particularly important in a species' response to environmental change and for the conservation of intraspecific genetic diversity. It is expected that as a species' range limits are approached, productivity and reproduction will decline and populations will become less abundant and more isolated. Decreased genetic variability and increased genetic divergence of peripheral populations is predicted based on these patterns. Cirsium heterophyllum reaches a southern geographical limit in the UK, C. acaule and C. eriophorum reach a northern limit and C. arvense occurs throughout the UK. These species have been used to determine whether contemporary patterns of distribution, productivity and reproductive potential across a species' UK latitudinal range are reflected in the predicted patterns of population genetic structure (assessed using microsatellite markers). Population frequency declines approaching the periphery of Cirsium acaule and C. heterophyllum. A decline in abundance was found in C. heterophyllum only. Community surveys suggest that peripheral populations do not occur in atypical habitat. There is no latitudinal variation in morphological characters across the species range, whereas reproductive potential declines approaching the periphery of the species that reach a latitudinal limit in the UK. Population genetic analysis revealed a decline in genetic variation toward the latitudinal limit of C. acaule. This pattern is absent in C. heterophyllum despite a marked decline in seed production and increase in population - . isolation approaching its periphery. C. heterophyllum exhibits almost randomised geographical structure of genetic variation. The lack of agreement between patterns of reproductive potential and population frequency and population genetic structure suggests that contemporary patterns of population distribution and reproduction may be inadequate for indicating patterns of population genetic structure within a species. Interspecific differences in post-glacial history may be important in explaining this disparity.

The aim of this study has been to prepare a systematic revision of the genera of the family Chrysobalanaceae. At the outset of this research it was apparent that the distinctions between the subgenera and some other groups within the single genus Parinari Aubl. were much greater than the differences between other genera in the family. This is largely because most recent work has been done on a restricted regional basis and generic concepts differ widely in different regions. Most of the earlier workers only had access to incomplete material. for the present study complete material for more than 200 species was assembled. The wood anatomy of species representing all genera except Kostermansia Prance and Hunga Prance was studied. Pollen slides representing all genera were prepared. Seedlings from twenty-six species were also examined. Much useful anatomical information published by other workers has been brought together in this work. Papers on leaf anatomy by Kanduuml;ster (1897); the ovary by Juel (1915), leaf trace anatomy by Morvillez (1918a), and pedicel and floral anatomy by Bonne (1928) have all been of the greatest use. The first author to give the group its present circumscription was Robert Brown (1818) who recognized it as a family. The last author, however, to monograph this group on a world-wide basis was De Candolle, who, in his 'Prodromus' (1825) placed it as the first tribe of his Rosaceae. Subsequent authors hive been approximately equally divided into those who treat it as a family and those who treat it as a tribe or subfamily of the Rosaceae. However, the authors of the most widely used general systems of classification have been unanimous in placing it in the Rosaceae (Bentham andamp; Hooker, 1865; Focke in Engler andamp; Prantl, 1894; Hutchinson 1926, 1959). Focke's is the last work in which all genera are described. Focke recognized the following genera:- Chrysobalanus L., Grangeria Comm. ex Juss., Moquilea Aubl., Lecostemon ["Lecostemion"] Moc. andamp; Sessandeacute; ex DC. and Stylobasium Desf. in the subtribe Chrysobalanineae, and Hirtella L., Couepia Aubl., Parinari Aubl., Acioa Aubl., Angelesia Korth. and Parastemon A. DC. in the subtribe Hirtellineae. Lecostemon and Stylobasium were included with some doubt and Focke suggested that they might be more closely related to Phytolaccaceae. Jubsequent authors have added the genera Afrolicania Mildbr., Geobalanus Small and Magnistipula Engl. At an early stage of this investigation it was found that Stylobasium and Lecostemon differ from all other Chrysobalanaceae in almost all important respects. Focke, and all previous and some subsequent authors, have wrongly identified Lecostemon. In this work it is shown that the true Lecostemon is in fact a Sloanea of the Tiliaceae and that Lecostemon sensu Focke is correctly named Rhabdodendron, a genus which has been variously accommodated in Rutaceae and Phytolaccaceae. The present study has shown that Rhabdodendron is not only distinct from all Chrysobalanaceae in external morphology, wood anatomy and pollen morphology, but also differs from the Rutaceae in these respects. In wood anatomy it was found to be very similar to Phytolaccaceae. Its pollen is somewhat different from that of the Phytolaccaceae but not appreciably different from other members of the Centrospermae. In external morphology Rhabdodendron has many distinctive features most of which occur sporadically in the Centrospermae but not in combination. In view of this it seems preferable to treat it as a unigeneric family related to but distinct from the Phytolaccaceae. A Latin description of this new family is given, but it is realized that further work on its relationship to Phytolaccaceae is necessary before it should be published. Many authors have suggested that Stylobasium does not belong to the Chrysobalanaceae or is an isolated member within it, but only Agardh (1858) described it as a separate family. It ie shown in this study that Stylobasium is utterly different from all Chrysobalanaceae in external morphology, wood anatomy, pollen morphology and floral anatomy. In wood anatomy and pollen particularly there are striking similarities to certain members of the Sapindales, and it is suggested that Agardh's family should be recognized and placed near Sapindaceae and Anacardiaceae. Purged of these two anomalous genera, the Chrysobalanaceae is now a homogeneous entity, whose wood structure and pollen morphology is so uniform that few genera can be discriminated on the basis of these characters. However, wood anatomy and pollen morphology are found to differ constantly and to an appreciable degree from the Rosaceae so much so that, taken in conjunction with the anatomical features described by Kanduuml;ster, Juel, Morvillez and Bonne, they seem to justify the recognition of the group as a family distinct from, although related to, the Rosaceae. Most previous authors have variously subdivided the group. Their views are briefly summarised, and it is shown that anatomical characters provide no basis for a rational subdivision. In this work, for convenience, two tribes are recognized based on the symmetry of the flower. In the Chrysobalaneae the ovary is inserted at or near the base of the receptacle-tube. In the Hirtelleae the ovary is inserted laterally or at the mouth of the receptacle-tube. Parinari is unique within the family in having its carpels partitioned by a false septum. This character has been used to define Parinari since it was originally described by Aublet in 1775, but visual inspection is enough to show that its uncritical use has given rise to an extremely heterogeneous assemblage. Some components of this are more closely related to genera outside Parinari than to the rest of Parinari. Some species have been assigned to Parinari which do not even nave its artificial unifying feature. It was quite clear that currently accepted generic limits were untenable and that there were two alternative taxonomic procedures. Either all species within the family should be united to form a single genus Chrysobalanus or an attempt should be made to discover more natural groupings. After a detailed study of the external morphology of more than 200 species, the author was satisfied that various segregates of Parinari should be recognized as genera, and that most of the other genera in the Chrysobalanaceae could conveniently be kept apart. However, it was decided to use a computer to demonstrate as objectively as possible the exact correlation of those characters believed by the author to be of greatest taxonomic worth and of all other important characters used by previous authors. For the tribe Hirtelleae (which includes Parinari sens. lat.) eleven qualitative and ten quantitative characters were used and scored numerically for 124 species. An association-analysis was made for the qualitative data and a principle-component analysis for the quantitative data using programmes devised by Professor W.T. Williams and his associates for a Feranti 'Pegasus' computer. The entire data was analysed by a principle-component analysis programme by Mr. J.N.R. Jeffers for a Feranti 'Sirius' computer. This is possibly the first application of these techniques to a problem concerning generic identities of higher organisms. Although similar methods have been used in discriminating between closely related species, they do not seem to have been used at a higher level.

In this thesis I present a study on floral determination in the short day plant Pharbitis nil. Shoot apical meristems are determined if, following induction, they form floral organs even if isolated in non-inductive conditions. Five day old P. nil is fully induced by a 48 h dark period. P. nil apices are determined with respect to carpels 24 h after the 48 h inductive treatment if cultured in glucose medium but not until 5 d after induction if cultured in sucrose. I found that similar differential effects existed in the determination times of the other floral organs by excising shoot apices periodically through a 48 h dark treatment and the following 24 h of continuous light, culturing them in glucose or sucrose medium and measuring the degree of floral development. I cultured apices with glucose analogues instead of glucose. The analogue 3 oxymethylglucose, which is transported into the cell but not phosphorylated, mimicked the effect of glucose so that glucose entry into the cell probably acts as a signal for floral development. Glucose was as prevalent as sucrose in the sap extracted from seedlings, regardless of induction. Structural homologues of the Arabidopsis thaliana genes LEAFY, AGAMOUS and CRABS CLAW were cloned in P. nil. The homologues PnAG1, PnAG2, PnCRC2 and PnLFY1 were found to be expressed more strongly in induced than in non-induced apices in vivo and more strongly in induced apices cultured in glucose medium than in sucrose medium using semi- quantitative RT-PCR. I conclude that PnAG1, PnAG2, PnCRC2 and PnLFY1 are floral homeotic genes and that glucose is involved in signalling for floral development and signals for the increased expression of these genes. Finally a model of floral determination, based on these conclusions, is proposed.

The LFY gene, which has now been isolated in at least 17 species, is important in the transition from vegetative to reproductive growth. The floral meristems of lfy mutants exhibited increased inflorescence characteristics, and constitutive expression of the gene was sufficient to convert lateral inflorescence meristems to solitary flowers in Arabidopsis, tobacco and Populus. Previous work on the determinate plant, Silene coeli-rosa, which required 7 LD for 100% flowering, concentrated on changes to the cell cycle and peptide composition of the shoot apex during floral evocation. A partial cDNA clone of a Silene LFY homologue (SFL) has been isolated. SFL shows strong homology to other LFY homologue proteins within the two conserved domains, with up to 88% identical amino acids. It contains highly acidic and basic domains, a glutamine rich region and leucine repeats: all putat5ive transcriptional activation domains. Expression studies using quantitative PCR show that SFL was not induced by non-inductive SD conditions, or by a continuous light treatment that inhibited flowering. This is in contrast to the expression patterns observed in vegetative Arabidopsis, pea, petunia, Impatiens, tobacco and tomato, but consistent with the expression of Antirrhinum homologue which is restricted to the floral meristems. During the 7 LD induction period, SFL transcripts were first detected after 5 LD, a treatment which resulted in 81% of plants flowering, under the conditions used. Fewer than 5 LD failed to induce flowering or SFL expression. SFL was also expressed in apices subjected to an inductive 7 LD treatment followed by 48h darkness, which delayed flowering and suppressed the synchronisation of the cell cycle which occurs immediately prior to floral initiation. In situ hybridisation revealed the spatial expression of SFL in Silene. No SFL was detected prior to D7 during floral induction or in non-inductive SD controls. On experimental D7, SFL mRNA was restricted to the flanks of the primary apical dome and in D8 apices expression had spread throughout the dome. Importantly, this pattern of expression differs to that observed in the other two determinate species in which LFY has been studied, namely tobacco and Impatiens.

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.

Light signalling mechanisms are crucial for plant adaptation to environmental changes: it has been found that both light and temperature cues are interpreted by closely interacting signalling pathways. In Arabidopsis thaliana, the seedling hypocotyl has emerged as an ideal model system to study light and temperature control of cell expansion. The light sensitivity is affected by the light intensity (fluence rate), an illustration of which is exemplified in the fluence rate response curve, and also the quality of that light (i.e. the ratio of red: far-red wavelengths of light). Here I have elucidated the phytochrome B (phyB) signalling mechanism in great detail and subsequently created a mathematical model of the red-light signalling pathway. This model is further extended to include changes within the ambient temperature range. Through application of stochastic modelling techniques it was possible to demonstrate the importance of dark reversion within the phyB mechanism in a diurnal cycle. Further, by considering alternative modelling methods and applying a highly integrated mathematical and experimental approach, it has been possible to show how the integration of light and temperature signals drives a molecular switch in transcriptional activity and hence control of cell expansion. This work highlights the importance of a multidisciplinary approach to molecular biology and describes the significance of signal convergence on molecular signalling.

Since it was first published, many additional species have been ascribed to the genus Boea Comm. ex Lam. As the genus grew in size, it also grew in morphological diversity until it was recircumscribed and became the source of a number of new segregate genera. Today, the Boea group (i.e. Boea, the segregate genera and other close relatives) comprises over 200 species in some 15 genera, found from China to Australia and throughout Malesia from Sumatra to the Solomon Islands. Previous molecular studies suggested a much more complex structure to the clade than previously thought. Here the most up to date phylogeny, covering all the genera known to belong to the Boea group, is presented. Parsimony and Bayesian Inference were the chosen approaches to the phylogenetic analysis of nine matrices generated using DNA data from 277 accessions. The markers used were the nuclear ITS and the chloroplast regions trnL-trnF (intron and spacer) and ndhF-rpl32-trnLUAG. The results show important discrepancies between the current taxonomy of the group and the clades delineated by the phylogeny. In an attempt to establish a natural classification of Boea and its allies, taxonomic and nomenclatural work was carried out on most of the genera found to be non-monophyletic. Boea Comm. ex Lam. is divided into two genera. The recircumscribed Boea is restricted to the group of taxa found in New Guinea, Solomon Islands and Australia. The genus is fully revised and contains 11 species, including the newly described Boea morobensis C.Puglisi. The Southeast Asian group of species formerly attributed to Boea, centred in Thailand, is given the resurrected name Dorcoceras Bunge. To the four species traditionally known to belong to this group, three new ones are added. These are Dorcoceras brunneum C.Puglisi, D. glabrum C.Puglisi and D. petiolatum C.Puglisi. Damrongia is deeply transformed with the synonymisation of D. cyanantha Triboun in D. trisepala (Barnett) D.J.Middleton & A.Weber, and the inclusion of Boea clarkeana Hemsl. and the three Asian species of Streptocarpus Lindl., S. orientalis Craib, S. burmanicus Craib and S. sumatranus B.L.Burtt. As a result of the phylogenetic study, a new genus, Middletonia C.Puglisi, is segregated from Paraboea. Middletonia consists of five species, including the newly described Middletonia glebosa C.Puglisi, and has its centre of distribution in Thailand. Finally, Paraboea (C.B.Clarke) Ridl. is recircumscribed with the inclusion of the genera Trisepalum C.B.Clarke and Phylloboea Benth. In order to limit the number of new combinations needed and maintain clarity, the name Paraboea was conserved against both Phylloboea and Trisepalum. In addition to the 15 new combinations in Paraboea, a new species from the Philippines, P. zamboangana C.Puglisi, is described.

No description available.

High temperature can have a serious impact on plant development; rising temperatures and environmental fluctuations mean that this is becoming an increasing problem for sustainable agriculture. Many studies have indicated that pollen development is very susceptible to high temperature (HT) stress, particularly during early development, and that the anther tapetum cell layer is extremely vulnerable, resulting in reduced fertility or complete male sterility (MS). In this project, Arabidopsis plants were stressed with 32°C HT during flowering and then assessed by microscopy for phenotypic changes to anther and pollen development, and subsequent reproductive development. The results indicate that the HT had a significant negative impact on plant reproduction, particularly during the stress treatment, with some recovery of fertility post HT. Samples of plant buds were divided into different growth stages and collected for analysis of fertility and for gene expression analysis. Several genes, which appear from available microarray data to be associated with HT stress and are also specifically expressed during tapetum development, were chosen to test for expression changes associated with temperature stress, both during and after HT stress. Phenotype analysis of insertional knockout mutants of these genes, both with and without HT stress, was used to assess their potential impact on resilience to temperature stress. Transcriptomic analysis of whole genome was conducted by RNA-seq in young (prior to polarized microspore stage) and old buds (from polarized microspore stage to pollen mitosis) isolated from HT-stressed and non-stressed Arabidopsis Ler plants. This has identified a set of HT specific genes that are differentially expressed in different HT period treated plants. The anther tapetum serves to regulate pollen development and is critical in the production of the pollen wall. It goes through a defined process of programmed cell death (PCD) to facilitate transfer of pollen wall materials onto the developing pollen grains. Disturbance of the timing or progression of this PCD process, for example by heat stress frequently results in male sterility. Four GFP reporter constructs that have been used as markers during ovule PCD analysis were tested for expression during pollen development and particularly focusing upon the stages of tapetal PCD. These reporter genes showed different stage specific expression during anther development. They have now been introgressed into a number of Arabidopsis male sterile mutants that show PCD-related defects, including ms1, ams and myb26 male sterile mutants. The F1 generation of these showed similar GFP expression to the parent plants, however the homozygous male sterile F2 generation plants appeared to show different patterns of GFP expression. Two of them (BFN1 and CEP1) are expressed in the anther tapetum during the stages of tapetum PCD. Expression analysis suggests that HT-stress affects the expression of BFN1 and CEP1, which may be linked to abnormal degeneration of the tapetum under HT-stress.