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Self-incompatibility (SI), a type of intraspecific reproductive barrier occurs widely in flowering plants and helps to avoid inbreeding and protects the genetic diversity of a population. When the pollen lands on a self-pistil, SI will prevent fertilization; when the pollen lands on the pistil of an unrelated plant, fertilization will not be affected. SI consists of two types: Sporophytic SI (SSI) and gametophytic SI (GSI). In GSI it is the haploid genotype of the pollen itself that controls the pollen phenotype. Transgenic studies in Petunia have shown that the pistil phenotype is determined by a stylar ribonuclease (S-RNase). In the fertilization process, Slinked F-box genes/SLFs that are expressed in pollen work together with S-RNases to determine the outcome of a pollination. Recently up to 20 SLF genes have been reported at the S-locus in Petunia, but the exact role of individual SLFs in controlling the phenotype is still not clear. Part of this project aims to investigate SLF expression between two closely linked varieties of Petunia hybrida, which have different phenotypes. A combination of RT-PCR and qRT-PCR using specific primers were used to determine the expression patterns of individual SLF genes in these two varieties. The results of RT-PCR and qRT-PCR indicate that all SLFs express in these two varieties, and most SLFs share significant differences in the expression levels comparison between these two closely linked varieties of Petunia hybrida. The partial DNA sequences of SLFs in these two varieties are proved that is identical. Therefore, the different expression level of SLFs might is the cause of the different SI between these two closely linked varieties of Petunia hybrida. The finding of this part of this project might be able to provide some evidence in the evolution theory of SI plants. On the other hand, there are only two SLFs expression analysis papers been published to date from Kao et al. (2004) and Hua et al. (2007), which indicated SLFs express in pollen tube, pollen and anther of Petunia by RNA gel blot analysis and RT-PCR, but there is no paper to show the expression pattern of SLFs using GUS or GFP analysis. This project also aims to explore the promoter analysis of SLF genes that have recently been identified as part of a genome sequencing effort of Petunia inflata. The genomic sequence data were used to characterize the promoter regions to identify shared pollen promoter elements such as those identified for the gene LAT52 (a tomato pollen gene). Promoter fragments of three selected SLFs were cloned and used to prepare SLF promoter:GUS fusion constructs. Agrobacterium-based transformation was performed to transfer these constructs into Petunia hybrida. The GUS assay was used to test the SLF expression pattern in Petunia. The result of GUS analysis indicates SLF3 is expressed in pollen of stamens, which is consistent with the findings from Kao et al. (2004) and Hua et al. (2007). This part also provides a good attempt in other transformation experiments to use the SLF promoter of Petunia inflata. In addition, the results of both these two parts of this project support each other: the expression of SLFs in Petunia shows an exponential growth during the maturation of pollen.

Lianas play integral roles in structuring community composition, forest regeneration, the maintenance of species diversity and whole-forest level ecosystem processes in tropical forests. With increasing disturbances to forests worldwide, the relative importance of lianas as players in many areas of forest dynamics is expected to increase, with important ramifications for the global carbon cycle. However, our knowledge of lianas is incomplete and biased: (i) towards the Neotropics; and (ii) against the canopy, yet the canopy is where lianas proliferate most. Research in these areas is hampered by the logistical difficulties of studying lianas; the fact that they are time-consuming to survey, and that it is difficult to quantify what is going on in the canopy. This thesis enhances ecological understanding of lianas in tropical forest tree crowns, focusing on the lesser studied Palaeotropics. The development of a novel method to enable faster, cheaper and more canopy-centred assessment of liana than possible with traditional assessment methods is vital for this. A lightweight unmanned aerial vehicle (UAV) was used to assess liana infestation of tropical forest tree canopies in Sabah, Malaysia. By visually interpreting the images, the UAV-derived liana infestation estimates were compared with those derived from traditional ground methods of liana infestation assessment to determine the validity, strengths and weaknesses of using UAVs as a new method for assessing liana infestation of tree canopies. These data were then used to map and monitor liana load in tree crowns: (i) spatially, to elucidate liana-environmental relationships; and (ii) temporally, to monitor the canopy response, including changes in liana infestation, to El Niño drought. UAV-derived estimates of liana infestation correlated strongly with ground-derived data at individual tree and plot level, and across multiple forest types and spatial resolutions. Furthermore, the UAV surveys improved liana infestation assessment for upper canopy layers and were considerably faster and more cost-efficient than ground-based surveys. Liana infestation was significantly spatially aggregated, with tree canopy height and presence of canopy gaps being the most important variables influencing this. Taller trees were less often and less heavily infested by lianas while liana infestation occurred more often and to greater extents in close proximity to canopy gaps. Temporally, tree-level liana infestation and crown area showed significant increases in the aftermath of the 2015/16 El Niño whereas crown greenness and tree leaf cover showed a significant decrease. Furthermore, liana cover was significantly higher for trees that experienced mortality in the aftermath of the El Niño than for those that did not. This thesis presents a novel UAV-based method of capturing data that can be used to assess liana infestation of tropical forest tree crowns at least as accurately as traditional ground data. This novel method promotes reproducibility of results and quality control, and enables additional variables to be derived from the image data. It is more cost-effective, time-efficient and covers larger geographical extents than traditional ground surveys, enabling more comprehensive monitoring of changes in liana infestation over space and time. By utilising the new UAV method, this thesis presents: (i) the largest and most comprehensive continuous assessment of Palaeotropical tree crown liana infestation, and analysis of environmental variables that may influence this, to date; and (ii) the first study assessing short-term temporal change in liana canopy cover and associated alterations in the forest canopy using UAV image data. Examining how and why lianas are distributed in the forest canopy and how this changes through time may help us to determine what variables could determine increases in lianas with environmental change in the future, with important implications for tropical forest carbon storage and sequestration, and provide a step towards more comprehensive testing of ecological theory in tropical forests.

It is thought that climate change will have a major impact on species distributions by changing the habitat suitability for species. Species distribution modelling is a modern approach to assess the potential effect of climate change on biodiversity. We used 11 environmental variables with the MaxEnt algorithm to model the distributions of 114 Egyptian medicinal plant species under current conditions, then projecting them into three different future times (2020, 2050, and 2080) under two different climate-change emission scenarios (A2a and B2a), under two hypotheses about the capability of the species for dispersal (unlimited and no dispersal). Species richness maps for current and future times were produced. We tested the value of Egypt’s Protected Areas under climate change by estimating the species richness inside and outside under each scenario. We assessed Egyptian medicinal plants based on IUCN Red List categories and criteria, and then used the SDMs for conservation planning with and without consideration of socioeconomic factors using Zonation software. The A2 emission scenario was more harmful than B2 under all assumptions. Species richness inside Protected Areas was significantly higher than outside for all models. Based just on the records, between 75% and 90% of species could be classified as Least Concern, according to the assumptions made. Similarly, based on SDMs all species could be classified as LC at the current time, whilst in the future under climate change, up to 18% of species face the risk of extinction, depending on assumptions and based on the absolute time gap between the two future times. Based on 10 years, most species were assigned as Least Concern. Areas within PAs were no better in conservation prioritization value than area outside when socioeconomic costs (especially the Human Influence Index) were taken into account. Species distribution models appear to be extremely useful for conservation planning under climate change, particularly when only sparse data are available. Socioeconomic information adds a new dimension to conservation planning, which is actually misleading and incomplete without it.

Flooding events are becoming more common throughout the world as a result of climate change, resulting in reduced crop yields. It was recently discovered that plants sense low oxygen (O2) (associated with flooding) through regulated proteolysis of the group VII Ethylene Response Factor transcription factors (ERFVIIs), via the Cys-Arg/N-end rule pathway of ubiquitin mediated proteolysis, which also senses another gas, nitric oxide (NO). The N-terminal (Nt) Cys of physiological (e.g. ERFVIIs) and artificial substrates was shown to be key for N-end rule function, and work in mammalian systems suggested that oxidation of Nt-Cys by O2 and NO was a required prerequisite for subsequent Nt arginylation by arginyl tRNA transferases (ATEs). However the exact mechanism of Nt-Cys oxidation has not been discovered. The primary aim of this thesis was to define the mechanism of in vivo Nt-Cys oxidation essential in determining the stability of Arg/N-end rule protein substrates, including ERFVIIs. In this study a novel approach was developed to investigate the oxidation of Nt-Cys in vivo using transgenic Arabidopsis expressing Cys-2 reporter proteins (derived from the transgenes 35S::MC-polyG-HA-GUS and Ubi1::MCGGAIL-GUS). Cys-2 of the reporter proteins is made Nt constitutively by co-translational Methionine Aminopeptidase (MAP) activity. Biochemical techniques were combined with analytical chemistry to investigate the in vivo oxidation of Nt-Cys using liquid chromatography mass spectrometry (LC-MS). In addition, synthetic peptides representing the Nt-sequence of the in vivoreporter protein were used to define the oxidative and nitrosylative modifications occurring at Nt-Cys in vitro. Findings of this study include the successful development of two new in vivo O2 sensor artificial N-end rule substrates, in the plant genetic model Arabidopsis thaliana. A further outcome revealed that the ERFVII RELATED TO APETALA 2.12 (RAP2.12) is stabilised in the shoot and root apical meristem to a greater extent than in other regions of seedlings in response to hypoxia, indicating that meristematic cells could be important oxygen sensory zones. Cys-2 reporter proteins were used in in vivo studies to attempt to identify the nature of the Nt residues following N-end rule action. Although Nt-peptides derived from affinity purified Cys-2 reporter protein were not identified by LC-MS, it was possible to demonstrate that ubiquitination is required on Cys-2 reporter proteins before 26S proteasome degradation. Combined results from Nt-Cys in vitro synthetic peptides and Cys-2 reporter proteins substrates of the Arg/N-end rule pathway, provide indirect evidence that post translational modifications (PTMs)not defined before occur in vivo. Using synthetic peptides it was possible to show evidence for Nt-Cys-sulfenamide formation after oxidation of Nt-Cys. This finding suggests that Cys-sulfenamide formation, a previously recognised reversible modification preventing irreversible oxidation to Cys-sulfonic acid, could occur at Nt-Cys of in vivoprotein substrates. An important finding of this study was the observednonreactionbetween the nitrosylated Nt-Cys and H2O or conversely oxidised Nt-Cys and NO. As Plant Cysteine Oxidases (PCOs) do not require NO to oxidise Nt-Cys, this result raises further uncertainty as to how NO is involved in the oxidation of Nt-Cys, suggesting that NO may be involved in the enzymatic activation of PCOs or the arginylation of Nt-Cys by ATEs. The findings of this study did not identify the Nt-peptide of the Cys-2 reporter protein, and hence the Nt-Cys oxidation state of an in vivo substrate of the Arg/N-end rule pathway remains unidentified. Despite this the result that Nt-Cys can be oxidised to Cys-sulfenamide is novel and an important discovery to the field of reactive Cys biology and chemistry.

Radioisotopes of caesium (Cs) and strontium (Sr) have been distributed in the environment due to weapons testing, nuclear power production and accidents at nuclear facilities. Radiocaesium and radiostrontium are of major concern in the medium to long term following accidental releases as they have high energies, long half lives (137Cs≈30 years; 90Sr≈29 years) and their easy assimilation into biological systems due to their similarity to the biologically important elements potassium (K) and calcium (Ca), respectively. Radio-caesium and -strontium are transferred to humans primarily via plant root uptake, and therefore minimising this uptake has been the focus of a number of remediation strategies, such as ploughing and fertiliser application. Species or cultivar substitution, where a species/cultivar that has higher uptake is replaced by a species/cultivar that has lower uptake, has been proposed as an effective and socially acceptable remediation strategy for contaminated agricultural land, but not enough is known about its efficacy for it to be recommended internationally. The aim of this thesis is to evaluate the potential of species or cultivar substitution as a remediation strategy for contaminated agricultural areas. Chapter 2 consists of meta-analysis of the available data (115 experiments) on the inter-cultivar variation in Cs and Sr accumulation by 27 plant species. Chapter 3 includes experiments conducted in the laboratory (UK) and two experiments in the field (Ukraine) investigating inter-cultivar variation in radiocaesium and radiostrontium accumulation in Brassica oleracea, and whether consistently lower-accumulating cultivars could be identified. Chapter 4 details analysis of samples from grass breeding experiments in Aberystwyth and Edinburgh (UK) from four forage grass species; hybrid ryegrass (Lolium perenne L. x Lolium multiflorum Lam.), L. perenne, L.multiflorum and Festuca arundinacea Shreb., and investigates inter-species and inter-cultivar variation in uptake of stable Cs and Sr. Hybrid ryegrass cultivars that were lower-accumulating in Cs and/or Sr were also identified. Chapter 5 compares the stable Cs and Sr uptake in six L. perenne and two F. arundinacea cultivars grown in Aberystwyth and Narodychi (Ukraine). Chapter 6 compares the performance in terms of yield and forage quality (elemental concentrations, digestibility and water soluble carbohydrate content) of six hybrid ryegrass cultivars and ten F. arundinacea cultivars identified as consistently lower-accumulating in Cs and/or Sr against the performance of two commercial hybrid ryegrass cultivars. The mean inter-cultivar variation in Cs and Sr was 1.8-fold and 2.0-fold,respectively when 27 plant species were studied. Thirty-five-fold variation in radiocaesium and 23-fold variation in radiostrontium was found between c.70 Brassica oleracea cultivars. In two field experiments in Ukraine, five cultivars had consistently lower radiocaesium concentration ratios and two cultivars consistently lower radiostrontium concentration ratios. One cultivar had lower radiocaesium and radiostrontium concentration ratios. Festuca arundinacea cultivars had lower Cs and Sr concentration ratios than cultivars of hybrid ryegrass, L. perenne and L. multiflorum. Three out of 17 hybrid ryegrass cultivars had consistently lower Cs concentration ratios, two cultivars consistently lower Sr and one consistently lower Cs and Sr. Despite differences in soil properties and environmental conditions, F. arundinacea cultivars grown in Aberystwyth and Narodychi accumulated less stable and radioactive Cs and Sr than L. perenne cultivars. One L. perenne cultivar also accumulated less Cs and Sr at both sites. F. arundinacea cultivars accumulated less Cs and Sr than commercial hybrid ryegrass cultivars, but alsohad up to 59% lower yield and a reduction of up to 19% in K accumulation, up to 46% in Ca accumulation, up to 7% in dry matter digestibility and up to 17% in water soluble carbohydrate content. Selecting lower accumulating cultivars was found to reduce Cs and Sr accumulation less, but with a smaller yield penalty and a smaller reduction in digestibility and water soluble carbohydrate content. It is concluded that species and cultivar substitution could be an effective remediation strategy in contaminated agricultural land provided implications for yield and quality are considered.

The N-end rule pathway of targeted proteolysis is regulated by Group VII ethylene response factors (ERFVII’s). The aim of this research work was to analyse the relationship between substrates (ERFVII’s) of the N-end rule pathway and genes, which have promoters containing a double ‘GCCGCC’ Ethylene-Responsive Element Binding Protein (EBP) cis-element. Several genes were identified containing double EBP elements. Cloning and transformation of the promoters from five of these genes (PYL, ERD4, AT1G14810, AT3G13440 and AT5G44420) carrying two copies of the GCC-boxes present in the 5' UTR (5’ untranslated region) or promoter region was conducted into Arabidopsis wild-type (Col-0) and prt6-1 mutant plants. Expression driven by these promoters in the leaves and flowers of transgenic plants was analysed through GUS staining to reveal promoter activities. Enhanced promoter activity was seen in prt6-1 lines (mutated in the E3-ligase of the N-end rule pathway) in comparison to Col-0. Further, cDNA of leaves and flowers of Col-0 and prt6-1 were analysed by q-RT-PCR (quantitative real-time PCR) for expression of PYL7, ERD4, AT1G14810, AT3G13440; t-test analysis showed a significant difference (p-value<0.05) only in leaves of Col-0 and prt6-1 for PYL7. Analysis of the genetic relationship between N-end rule pathway and genes containing GCC-boxes was also performed by analysing double mutant combinations of prt6-1 and mutants of genes containing the EBP elements (pyl7prt6-1, erd4prt6-1 and abi5prt6-1) and Col-0 under different concentration of salt to determine the effect of stress due to salinity on the regulation of genes. At 125mM salt concentration significant difference was identified in highest number of mutant lines in comparison to Col-0. An analysis of the in-vivo binding of the ERFVII RAP2.3 to the promoter of GCC-boxes containing genes was performed through Chromatin Immuno-precipitation assay (ChIP). The t-test analysis on qChIP-PCR data indicated significant difference between IgG and HA-IPs for both ABI5 and PYL7 performed on normoxic 35S:MA-RAP2.3-HA in Col-0 line. Further, in-vivo localization of ERFVII’s HRE1 and RAP2.2 conditional stability was analysed using promERFVII’s:MC/MA-ERFVII’s-YFP constructs in Col-0 and prt6-1. This thesis suggests that genes PYL7, ERD4, AT1G14810, AT3G13440 that have double ‘GCCGCC’ EBP elements are downstream targets of the N-end rule pathway. Further analysis via ChIP suggests that RAP2.3 interacts with the ‘GCCGCC’ binding site of promoters in the ABI5 and PYL7 genes, however further work is needed to confirm this. Additionally, sub-cellular localization of promERFVII’s:MC/MA-ERFVII’s-YFP studies suggest the location of HRE1 and RAP2.2 in nuclei of early stage root tips studied on 4-days old etiolated seedlings.

Root architecture governs the uptake of water and nutrients from the soil and thus is essential for plant growth and survival. The control of lateral root branching is a crucial aspect of determining root architecture, and is a process largely controlled by the phytohormone auxin, which promotes lateral root organogenesis from founder cells within the vasculature and also subsequent lateral root elongation. A small posttranslationally modified peptide, CTERMINALLY ENCODED PEPTIDE1 (CEP1) is a bioactive 15-amino acid peptide cleaved from a larger precursor protein previously shown to negatively affect primary root elongation and lateral root branching in Arabidopsis thaliana. Within this thesis, genetic, biochemical and pharmacological approaches are used to demonstrate that another member of the CEP family, CEP5, reduces primary root length and negatively regulates lateral root branching in Arabidopsis thaliana with minor effects on aboveground architecture. CEP5 is also demonstrated to have an antagonistic relationship with auxin, with increased abundance of CEP5 leading to downstream stabilisation of the auxin signalling repressor AUXIN/INDOLE ACETIC ACID (AUX/IAA) proteins. Correspondingly, reduced abundance of CEP5 increases auxin responses, including enhanced lateral root progression. These studies suggest CEP5 regulates lateral root branching through attenuation of auxin responses.

Despite widespread conservation efforts, global heathland area has substantially decreased in recent decades. Heathland habitats require low nitrogen availability in order to persist. Over the past 150 years, however, nitrogen deposition has increased markedly. Early observational studies and research using artificial N applications have identified N deposition as the primary driver of heathland succession into grassland or woodland, and N enrichment is considered a threat to heathland sustainability. This study investigated soil fertility and vegetation composition at 25 lowland heathland sites in low rainfall regions of mainland Britain within a modelled wet N deposition range of 1.85 to 10.90 kg N ha-1 y-1. A bioassay approach was used to quantify relationships between soil fertility and N deposition, heathland patch size and the management regimes. This study discovered significant positive relationships between N enrichment and C. vulgaris shoot mass, N and P concentrations. No relationship between N enrichment and N : P mass ratio was found suggesting no N induced shift to P limitation. It was determined that soil phosphomonoesterase activity was not up-regulated in response to N enrichment. This suggests that the soil P reserves are sufficient to satisfy demand under current N deposition loads. Heathland patch size was negatively related to C .vulgaris shoot dry-mass which was used as a proxy for soil fertility. Measured atmospheric ammonia concentrations were not related to C. vulgaris growth and shoot chemistry. No relationships were found between any variable tested and heathland vegetation composition suggesting that local factors, such as management intervention, may be substantial determinants of vegetation composition. This study presents relationships between temperature at origin and C. vulgaris growth from populations located along a latitudinal gradient in Western Europe. The findings of this thesis have implications for current heathland management, and for future management under a climate change scenario.

The formation of viable pollen relies upon a complex interaction of genes in time and space within the anther. One of the most important maternal tissues involved in the production of functional pollen is the tapetum, which is a highly active tissue that plays a major secretory role during pollen development. This project involved the molecular analysis of genes that are expressed in the anther tapetum and are critical for functional pollen development. A number of these are thought to be regulated by, or interact with MALESTERILITY1 (MS1), a transcriptional regulator of male gametogenesis (Yang et al., 2007) or ABORTED MICROSPORE (Xu et al., 2010). Work involved analysis of an ABC transporter (At3g13220), which has been shown to be critical for viable pollen formation and confirmed as directly regulated by AMS (Xu et al., 2010). Another protein, POB2, which appears to be involved in ubiquitin-based proteolytic breakdown, is thought to interact with the MS1 protein. POB2 was identified from a previous screen of a stamen specific yeast-2-hybrid library using the MS1 protein. This interaction has been subsequently confirmed in this work by further yeast two hybrid analyses and bifunctional fluorescent complementation. Further work involved verification of this interaction in vitro and in planta by pull-downs and transient expression of proteins in E. coli and Nicotiana benthamiana respectively. Other work focused on identifying factors that regulate MS1 expression; this identified novel male sterile mutants derived from screening fast neutron mutagenised seed carrying the MS1Prom:MS1-GFP functional fusion protein. Microscopic observation of the fluorescent reporter showed changes in the stage specific expression of MS1 in some of these mutants. Backcrossing of the male sterile mutants with the parental plants (carrying the MS1Prom:MS1-GFP fusion construct) and the ms1 mutant confirmed one as a new mutant and the other three as being allelic to the ms1 mutation. Gene mapping of this mutant was subsequently conducted and suggest that it may be located on chromosome 3. These results are providing insight into the regulatory network of MS1 and AMS during anther development.

Hawaiian Skirt (HWS) is an F-box gene in Arabidopsis that plays a key role in plant floral organ development. HWS has been identified due to sepal fusion along their basal margins resulting in failure to shed its floral organs (Gonzalez-Carranza et al., 2007). Similar phenotypic characteristics can be seen in the ectopically expressed microRNA miR164 (Mallory et al., 2004; Lauf et al., 2004) and in the double mutants cup-shaped cotyledon 1 cucJ/cuc2 (Aida et at., 1997). Previous studies carried out by Gonzalez-Carranza et al. (unpublished) using genetic crosses between hws-1 and other floral mutants has revealed that HWS may play a crucial role in the microRNA biogenesis. In an effort to identify potential substrates of HWS and to identify the role of HWS in the miRNA pathway, a population of EMS mutagenized hws-1 was used for isolation and characterization of suppressors of hws-l. Screening a number of EMS mutagenized hws-l populations has identified several suppressor lines that are currently under study. From the identified mutants, two lines 43.1 and 80.5 were selected for further characterization analysis. These suppressor lines rescue the distinctive sepal fusion phenotype of hws-l as well as displaying other phenotypic characteristics. Characterization of the suppressor lines has identified that 43.1 is an allele of HST gene, which is involved in miRNA biogenesis, and 80.5 is an allele of AS2 gene, which is an adaxial cell fate determinant. Expression analyses have revealed that loss of HWS gene function leads to the repression of both 43.1 and 80.5. Genetic analyses have also confirmed that loss of HWS gene function results in an upregulation of CUC1 and CUC2 gene expression. The results obtained in this project have shown that HWS is involved in miRNA, adaxial-abaxial and Organ boundary signalling, concluding that HWS may have a wider function in different signalling pathways than previously proposed.

Using targeted expression of a constitutively active repressor of GA signalling Susana Ubeda-Tomas et al., (2007) demonstrated that GA action in endodermal cells is necessary for correct root growth. However, GUS studies have shown the final and penultimate GA-biosynthetic genes are not expressed in the endodermis, indicating movement of GAs may be required. This study used the targeted mis-expression of GA degrading enzymes in Col-0 and the attempted targeted rescue of GA biosynthetic and signalling mutants, using the corresponding GA metabolic or signalling component, to gain an insight into the localisation of important GA biosynthesis and signalling sites. This study has demonstrated that GA12 can be made by epidermal, cortical and endodermal cells. However, the ground tissue of the elongation zone does not contain GA12 due to the early GA biosynthetic enzymes only being expressed within cells with a close proximity to the QC. Subsequently the 20-oxidation converts GA12 to GA15, to GA24 to GA9. These reactions mobilise GA allowing it to move from the meristematic region to the elongation zone. GA20ox and GA3ox activity is required in both the meristematic region and the elongation zone for correct root growth to occur. In addition, GA metabolic components are subject to tissue specific GA feedback regulation as a result of post-transcriptional processing and/or post-translational modifications to their protein stability. GA perception in any tissue of the elongation zone can promote complete cell elongation, suggesting that any one tissue can elongate it neighbours, or that each cell is capable of releasing a signal to ensure they all elongate proportionally. The transcriptional network within the endodermis has a disproportionately important role in GAs regulation of cell division within the root proximal meristem but GA action in other cell types is also required. The cambian and bundle sheath cells in aerial tissue like the endodermis in the root contain an important transcriptional network that promotes GA dependant growth.

Radiocaesium (134Cs, 137Cs) is of environmental concern because of its incorporation into the food chain and prolonged emission of harmful radiation. Plants take up caesium via cation transporters which cannot discriminate between radioactive and stable caesium (133Cs). Around 80% of angiosperms live in symbiosis with arbuscular mycorrhizal (AM) fungi that deliver mineral nutrients to their hosts. Contrasting effects of AM fungi on caesium accumulation by plants have been reported. The ultimate aim of this thesis was to determine whether AM fungi reduced caesium accumulation in Medicago truncatula by down regulating the expression of plant genes encoding specific potassium transporters through improving potassium nutrition of their hosts. Accumulation of potassium and stable caesium by non mycorrhizal and mycorrhizal Medicago truncatula was studied, and the effects of caesium and AM fungi on plant gene expression were investigated. In these experiments, shoot potassium concentrations of non mycorrhizal and mycorrhizal plants were identical. However, in some experiments AM associations decreased shoot caesium concentrations. These observations were also true for five other plant species studied. Colonisation of Medicago truncatula with Glomus sp. influenced expression of some genes encoding cation transport proteins, but the expression profile did not suggest improved potassium nutrition. The presence of caesium also affected the expression of several putative cation transporters, but the consequences of these changes are unknown. A reduced colonisation rate of Medicago truncatula by Glomus intraradices was observed at caesium concentrations that exist in the rhizosphere. In conclusion, in these experiments, AM fungi did not improve plant potassium nutrition, and there was no evidence that AM fungi reduced caesium accumulation by down regulating expression of plant genes encoding potassium transporters. Although colonisation by AM fungi can reduce shoot caesium concentrations, this was not always observed. Thus, fungal inoculation cannot be relied upon to deliver crops with reduced radiocaesium concentrations.

The structural organisation of species-rich plant-pollinator networks is important to understanding their ecology and evolution and is essential for making informed conservation and restoration decisions. This thesis reports on a study located at different altitudes in nine tributary valleys of the Sacred Valley, Vilcanota Highlands, Peru. The assemblages of flower visitors were described and the plant-flower visitor matrices were analysed and compared to those found from other montane systems. Additionally, the thesis also addressed how the European honeybee (Apis mellifera) fits into these communities. Previous studies have predicted that abundance, diversity, and importance of hymenopterans as pollinators decrease with increasing altitude, where they are replaced by Lepidoptera and Diptera. Contrary to other temperate montane areas, Hymenoptera were more diverse at higher elevations. Diptera was the most abundant functional group overall but did not significantly increase in abundance with altitude as predicted. Species richness of visited plants reached a maximum at the highest altitudes. Using ordination analysis, hummingbirds, honeybees, flies and beetles were identified as major functional groups of flower visitors with significantly different visitation profiles. Nestedness analysis revealed that the plant-flower visitor networks had a similar structure to other published networks, consisting of core groups of generalist plants and animals which interacted with one another and with specialised flower visitors and plants, respectively. The core species varied in identity between valleys, but were usually the species in greatest abundance, implying that the networks were abundance structured. In addition, 85% of the interactions were observed only in single valleys. This context specificity may have implications for the conservation of plant-pollinator interactions in the Sacred Valley. Comparisons of the pollinator efficiencies of honeybees, hummingbirds, native bees and moths to Duranta mandonii (Verbenaceae) demonstrated significant variation among flower visitors in rates of visitation, pollen removal ability and contribution to fruit set. This variation was not correlated: hummingbirds were by far the most frequent visitors but removed virtually no pollen and did not contribute to fruit set. Despite the taxonomic diversity of flower visitors, the main pollinators were large native bumblebees and honeybees. Results highlighted the importance of measuring efficiency components when documenting plant-pollinator interactions, and also demonstrated that visitation rates may give little insight into the relative importance of flower visitors. Overall, the study showed that Apis was the most generalist flower visitor and a dominant core species within networks. However, although Apis visited a relatively large proportion of the flora compared to native taxa, they only intensively utilised a small proportion of available plant species. No evidence was found from the surveys to suggest that honeybees used interference competition and displaced other species. It was suggested that because specialised rare species are frequently dependent on a core of generalist taxa honeybees may play an important role for the possibilities of rare species to persist. However, perhaps the greatest threat to biodiversity and the persistence of plant-flower visitor communities in the Sacred Valley is from the destruction and fragmentation of habitats and from facilitative interactions between native and alien plants, mediated through visitation from honeybees

Early studies of the tomato ethylene signalling network using yeast two-hybrid screen previously identified three novel proteins (IntCR22, 242 and 266) that could interact with a putative ethylene kinase LeCTR2 (Lin et al., 2003). In this study, it has been demonstrated that IntCR22 is a cytoplasmic UDP-glycosyltransferase and IntCR266 is a chloroplast metallo-proteinase homologue to the Arabidopsis FtSH5/VAR1, whereas IntCR242 encodes a novel chloroplast protein with a C-terminal histidine-rich domain. In order to gain more insight into the tomato ethylene signalling mechanism, the sub-cellular localization and protein-protein interactions of the tomato ethylene signalling components have been investigated by fluorescent protein labelling and yeast two-hybrid experiments. Three tomato ethylene receptors (ETR1, NR and ETR4) and a downstream regulator EIN2 have been found in the endoplasmic reticulum (ER). Three putative downstream MAPKK kinases (CTRs) could interact with the C-terminus of the ethylene receptor possibly on the cytoplasmic side of the ER, whereas a novel ethylene signalling component GREEN-RIPE was located in the Golgi. It was therefore concluded from the localization study that IntCR242 and IntCR266 were false positives from the yeast two-hybrid screen and could not interact in vivo with the ethylene signalling components. The results presented in this study, in line with previous ethylene research suggest a possible involvement of the plant endomembrane system in the ethylene signalling network. However, the question as to how the ethylene signal moves from the ER localized receptors to promote activation of genes for the transcription factors within the nucleus remains unsolved.

Nutrient dynamics of two sub-types of peat swamp forest, mixed swamp forest and low pole forest, in the upper catchment of the Sebangau River in Central Kalimantan, Indonesia were studied. Three permanent study plots, 50 x 50 m, were established in each forest sub-type to facilitate collection of throughfall, stemflow, litterfall, decomposition, above ground and below ground biomass, peat and water samples. Graphical presentation, Wilm's method, and analysis of variance were carried out for both sub-types of forest in order to analyse data to detect any significant differences. Rainfall is slightly acid (pH 5.96+0.35) with a predominance of NH4-N, Ca and K. Throughfall and stemflow are enriched in most elements analysed compared to rainfall and the pH values are lower. Throughfall pH is 4.76±0.33 in mixed swamp forest and 4.37±0.33 in low pole forest. Stemflow pH is 4.03±0.19 in mixed swamp forest and 3.57±0.11 in low pole forest. Greater litter production was obtained in mixed swamp forest (8,411 kg ha-1 yr-1) than in low pole forest (6,534 kg ha-1 yr-1). Dry weight of the different fractions of litterfall (leaves, branches, reproductive parts and other debris) for MSF and LPF were 6216,1246, 460 and 489 kg ha-1 and 4864,1251,169 and 251 kg ha-1, respectively. Decomposition rates (k) in the MSF and LPF are 0.396 yr-1and 0.285 yr-1 respectively. Above ground biomass in MSF and LPF are 313,899 and 252,547 kg ha-1 respectively, while below ground (root biomass) is 26,533 and 14,382 kg ha respectively. Nitrogen is the predominant nutrient in peat soil at 50 cm depth in both MSF and LPF, while manganese is the lowest. Calcium is the element in greatest amount in water run off in MSF and LPF at 8,15 and 7.15 kg ha-1 yr-1 respectively, while manganese was the lowest at 0.01 and 0.02 kg ha-1 yr-1, respectively. Nutrient inputs were higher than nutrient losses during the 1-year study period with the greatest nutrient gain for calcium while manganese was the lowest in both sub-types of forest. Moreover, the results of this study highlight that nutrient concentrations in peat soils are low and the substrates are acidic. These factors are likely to be strongly limiting to agricultural development, including plantations of estate crops and trees. Under such conditions the maintenance of intact forest for natural ecosystem services (e. g. carbon storage, watershed, biodiversity maintenance, timber production in certain time period) is likely to be a far wiser land use from a long-term perspective.

This thesis investigates the influence of hedges and roads (linear landscape features) on the patch-to-patch foraging movements of insect pollinators and consequent pollen- mediated gene flow in white clover, Trifolium repens. Experimental arrays were located within the lowland UK agricultural landscape incorporating a range of patch separation distances from 25m to 250m (using both artificial and natural linear features). Mark-re-sight, “residence” (the number of visits per foraging bout) and pollen transport observations were used to observe pollinator movement characteristics between experimental patches and re-parameterise an existing model of patch-to-patch gene flow. Levels and directions of plant gene flow were observed with phenotypic and isozyme markers, allowing validation of model predictions. Harmonic radar technology was used for the first time to track butterfly flight paths; data support the hypothesis of a 150 to 200m perceptual range, and non-random flight direction but limited association to wind direction, hedges, tracks or fence lines. Mark-re-sight observations indicated similar levels of patch visitation regardless of patch location, and trap-lining by Bombus spp. only between patches 50m or less apart. A single track road significantly enhanced gene flow between connected patches and was not a barrier to gene flow across it. In contrast, a hedge did not facilitate enhanced gene flow between connected patches and was a partial barrier where it occurred between patches. Model predictions of gene flow (1.3%, range 0.8 to 2.5%) agreed well with observed levels (ranging from 0.2 to 31.4%). It is proposed that pollinator movement observations alone could not provide an accurate means of estimating low level gene flow unless the variables of residence and pollen carryover were also considered. The possible influence of spatial and temporal variables including the role of hetero-specific forage on pollinator foraging movements and consequent plant gene flow from the local to landscape scale is also discussed

Screening of an En element population of Arabidopsis thaliana resulted in the identification of a mutant known as snakeskin (sks) in which the epidermal cell-cell linkages appear to be significantly perturbed (Marchant and Bennett, unpublished results). As a result of the breakdown of epidermal cell-to-cell linkages there are changes in epidermal cell architecture and distribution. These include alterations in pavement epidermal cell shape, stomatal distribution and trichome morphology. The defect in epidermal cell-to-cell adhesion may be a consequence of reduced cell expansion resulting in increased cell division as a compensation mechanism. This results in altered stomatal index and density and reduced root and hypocotyl elongation. A change in the ability of a cell to expand may be attributed to defects in cell wall composition or to the cytoskeleton that determines where the cell wall components arc localised during expansion. The sks mutant was found to have changes in its cellulose, xyloglucan and pectin fractions of the cell wall resulting in defects in cell wall adhesion, strength and expansion. To gain a greater understanding of the sks mutation the molecular basis of the SKS gene map based cloning was undertaken employing a combination of SSLPs, InDels and SNP markers. The SKS gene was found to be located on the bottom arm of chromosome 1 on BAC clone TIl 111. SALK insert lines have been utilised in a candidate gene approach in addition to fine mapping the mutation with SNP markers.

Hedgerows are increasingly being recognised as important in terms of landscape biodiversity. In Britain, recent hedgerows are not valued as highly as ancient hedgerows due to distinct differences in species-richness and historical significance. However, other potential ecological functions of species-poor hedgerows may have been overlooked, especially their potential role as corridors and habitats that help overcome the effects of habitat fragmentation. This thesis examines the spatial and temporal distributions of plant species in recent hedgerows in close proximity to remnant ancient woodland seed sources, and evaluates immigration, colonization and establishment processes that occur at this interface.;Transects were used to sample plant species distributions across the transition between remnant ancient woodland communities and adjoining Enclosure Act hedgerows in Northamptonshire. An analysis of the distribution of herbaceous plant species within the seed bank across the woodland-hedgerow transition is also presented. A census of colonizing woody plant species within the Experimental Hawthorn Hedgerows at Monks Wood, in Cambridgeshire was used to investigate the: i) influence of seed source availability, ii) immigration potential, iii) colonization and iv) establishment success under three hedgerow management regimes.;Woodland herbaceous plant species were found to have limited spatial and temporal dispersal strategies and species successfully dispersing into adjoining species-poor recent hedgerows were those able to reproduce vegetatively. The seed bank analysis showed that species of disturbed landscapes were dispersing into the woodlands, but were not successfully colonizing. Woody plant species dispersal was found to be operating at a larger spatial scale than herbaceous plant species. The abundance of seed sources and the availability of potential bird dispersers were found to correlate with the colonization success of woody plants within the Experimental Hedgerows, but the survival and establishment was related to hedgerow structure. The implications of these findings in relation to seed source-sink dynamics, corridor theory, habitat function, conservation and landscape planning were considered.

In the present study the use of haploid plants and tissues was considered in relation to plant genetic manipulation. Haploid plants can be exploited directly, in the synthesis of true breeding lines. Alternatively, haploid plants and tissues may provide material for further experimentation involving protoplast fusion. Both approaches were investigated. Cyclamen persicum an attractive flowering plant is grown commercially from seed produced following open cross-pollination. As a result, Cyclamen is highly heterozygous, but the resulting variation is commercially undesirable. Inbreeding depression prevents the recovery of commercial inbred lines. Anther culture as an alternative approach for the recovery of true breeding lines was attempted. In order to test the efficiency of the culture procedure and conditions, anther culture of N. tabacum was also attempted, since this species is known to be highly responsive to anther culture. Despite the recovery of very many allodihaploid N. tabacum, plants from anther culture, no success was achieved with Cyclamen, and the possible reasons for this are discussed. It has recently been proposed that limited gene transfer might be achieved by somatic hybridisation if diploid protoplasts of a crop species were fused with haploid protoplasts of a wild type species, and novel allotriploid somatic hybrid plants recovered. Haploid protoplasts can be isolated from anther culture derived plants, however the range of species responsive to anther culture is limited. Tetrads, formed as a result of meiosis in the pollen mother cells, were investigated as an alternative source of haploid protoplasts for fusion studies. Somatic hybrids were recovered following fusion between N. tabacum leaf mesophyll (2n) and N. glutinosa tetrad (n) protoplasts. The somatic hybrids were fertile, and the progeny of the first backcross to N. tabacum were obtained. These results, and potential limitations to somatic hybridisation are considered in the context of plant breeding.