In much of the English-speaking world, the lawn is the most common of all garden features. For arguably a millennium, it has played a significant role in the anthropogenic landscape and during that period, it has been inextricably linked with grasses. Nevertheless other plant species have accompanied the grasses and also been used in creating lawns. From medieval wildflowers to Victorian weeds, the plants that challenge the formal concept of the perfect lawn have journeyed with it but have until recently remained only small players within the dominion of grass. By the beginning of the 21st century, with a new environmental ethos permeating the garden, the long journey of the grassy lawn and its plant companions has led to the grass mono culture being heretically rethought: by removing both the mono culture and the grass.

The popularity of mixed flowers bouquets has increased in the cut flower industry. The longevity of mixed flowers bouquets is limited by the individual life of each flower in the bunch. Various factors have been studied for their effect on the individual life of each flower in mixed flowers bouquets. The results indicate that the differences in vase life of each flower in mixed bouquets may come from the influence of their phenotype. In cut rose flowers, there were various contents of fructose, glucose, sucrose and myo-inositol in all cultivars. However, levels of sugars contents were not related to the long-lived cultivars. For cut lily flowers, the contents of fructose, glucose and sucrose were measured in the primary and the secondary bud of ‘Tiber’ lilies. Differences in the contents of fructose, glucose and sucrose between the primary and secondary bud, did not relate to the longevity of individual bud life. However, this experiment found increases in sucrose contents in both positions before the time of opening. This increase in sucrose may relate to the role of the carbohydrate energy source for bud opening. Bacteria found in this study seemed to be largely specific to different flower types. Also, species of bacteria found in the vase water of mixed flowers were less than in that of single varieties. Difference in species of bacteria may be due to differences between plants, and the conditions they exert in the vase water. In general bacterial numbers were high at the beginning of all the experiments, indicating a strong inoculum effect from stems, although there was no straightforward relationship between stem numbers and inoculum size, in all cases. Experiments of single varieties were studied using ‘Tiber’ lily, ‘Akito’ rose and ‘Valentino’ rose. The results indicated that the addition of stems did not result in higher numbers of bacteria, but vase life was reduced, especially for the roses. The effect of number of stems in mixed flowers was investigated in distilled water and liquid flower food. The result of the addition of stems was to reduce the vase life of both ‘Tiber’ lily and ‘Akito’ rose. However, the effect of more stems of ‘Akito’ roses had a greater effect on vase life, fresh weight and water uptake than in ‘Tiber’ lilies. This indicated that ‘Akito’ roses had a greater response to high bacteria populations than lilies. The role of chemical exudates on flowers was not clear in the present study as they only had an effect during the early part of the vase life. The vase lives of ‘Tiber’ lilies and ‘Akito’ roses in all treatments were not significantly different. Perhaps treatment effects caused by the presence of chemical exudates may have been ‘masked’ by the presence of micro-organisms. The screening of 12 essential oils (West Indian bay, cinnamon leaf, clove bud, clove leaf, Chinese ginger, lemongrass, mandarin, rosemary, sage, spearmint, sweet fennel, and thyme) showed that thyme oil and lemongrass oil are effective against more bacterial species over other essential oils. The comparison of the minimal bactericide concentration (MBC) of thyme oil and lemongrass oil showed that the average MBC for thyme oil was lower than that of lemongrass. However, the thyme oil failed to extend the vase life of ‘Tiber’ lily and ‘Akito’ rose. Thyme oil was effective against bacteria for a very short time and could not extend vase life, especially that of the ‘Akito’ rose. Overall, thyme oil treatment appeared to reduce vase life. The efficacy of nine weak organic acids was studied in vivo for their effect on six bacterial species. Bacterial samples were inoculated on trypticase soya agar (TSA) pH 4 and 7. At pH 7, the TSA was prepared by using distilled water. All six bacteria species grew well under these conditions. The results of weak organic acids studied at pH 7 showed that Trans-cinnamic acid was the only weak organic acid that could act against some bacteria. At pH 4, only L8 (Bacillus spp.) could grow, and Trans- cinnamic acid was effective against this bacteria. The initial result of testing Trans- cinnamic acid against bacteria offered some promise for it to be applied successfully to the vase water of cut flowers, in combination with buffer systems.

The identification of roses with resistance to black spot disease and doubling the genome of diploid roses to facilitate hybridization with tetraploid cultivars are both important in rose breeding and were investigated in this thesis. Thirty five rose species and cultivars were challenged with four pathotypes of Diplocarpon rosae, the causal agent of black spot disease in roses. Patterns of resistance and susceptibility in leaf disc assays identified novel sources of genetic resistance and indicated crosses that might give insight into the inheritance of black spot disease resistance. Only roses from the section Cinnamomeae, or with Cinnamomeae ancestry, were susceptible to pathotype DA2, suggesting a relationship between resistance to black spot disease and the phylogeny of the sub-genus Eurosa. The possibility that the pathosystem involving pathotype DA2 differs from that of the other three pathotypes, DAl, ZM1 and CW1, is discussed. Hybrids between a resistant and a susceptible variety of Rosa rugosa proved susceptible, indicating that the resistance was not inherited as a single dominant gene in this case. Chromosome doubling was induced in vitro in a R. rugosa hybrid using oryzalin as the spindle inhibitor. Nodal sections, 2 mm long, were exposed to 2.5 μM or 5 μM oryzalin and 10 mm nodal sections were exposed to 5 uM oryzalin for 0 (controls), 6, 12, 24 and 48 h. The ploidy of the emergent shoots was determined by flow cytometry. The frequency of tetraploid leaves that developed from 2 mm nodal sections exposed to 5 uM oryzalin peaked at 12 h exposure (35 % tetraploidy) but fell after longer exposures. Fewer tetraploid leaves were found when 2 mm nodes were exposed to 2.5 μM oryzalin for 6 and 12 h, indicating that it took longer for a spindle inhibiting concentration of oryzalin to build up in the meristem. However, the frequencies of tetraploid leaves rose with exposure time and at 48 h, 44 % were tetraploid. In treatments with 5 jiM oryzalin, the frequencies of tetraploid leaves were lower, at equivalent exposure times, in 10 mm nodes than 2 mm nodes. This suggests that oryzalin diffused to the meristem via the cut surfaces and that access via the epidermis and cuticle was impeded.

The anatomical and histological development of the abscission zone is related to the growth of the leaf blade. It is shown that the initiation of the abscission zone coincides with a profound change in growth type of the leaf blade and a drop in the level of auxin in the leaf blade. Changes in volume and shape of the cells of the abscission zone and adjacent tissue are observed during the development of the leaf and at separation. The response of explants taken from leaves at all stages in development to a wide range of concentrations of IAA is determined. Phases in the abscission process are demonstrated and it is shown that the process is partly reversible, and independent of tissue outside the abscission zone. The fate of IAA applied to explants is investigated by various techniques using radioactive IAA. Microautoradiographs were made of the abscission zone and adjacent tissue. The concentration of IAA in the abscission zone relative to adjacent tissue is determined and turnover of IAA in the abscission zone demonstrated. It is shown that some of the IAA is decomposed in the abscission zone and its methyl group involved in the synthesis of a new molecule.

No description available.

No description available.

Successful cultivation of sunflower in UK as an oil crop requires the production of early maturing, semi-dwarf. high seed yield and high oil content varieties which must be resistant to the attack by the indigenous pathogens. The present study evaluated a large number of F 1 hybrids produced by utilising cytoplasmic male sterile (CMS) lines of diverse foreign origin and fertility restorer lines developed locally. The two sets of inbred lines of different genetic make-up, derived from the Asmer hybrids and a very early flowering variety S47, have been crossed with the available CMS stocks for their assessment in hybrid combinations. The aim was to produce a wide range of divergent hybrids to make the possible selection of the most suitable lines/hybrids with desirable characteristics. Quantitative methods were used to identify and compare the genetic potentials of the inbred lines and their hybrids among themselves, and to compare their performance with commercial hybrids for some characters of economic interest. The results have been very encouraging and several promising inbreds and crosses have been identified which can be developed into possible varieties for the UK. Genetic analysis of the agronomic characters by the analysis of variance approach has revealed substantial heritable variation in the inbred lines for all the agronomically important characters which partitioned into general and specific combining ability effects and related to the possible types of genes action. Both the additive genetic and the non additive genetic portions arising largely from dominance and epistatic deviations were detected significant. It was revealed that GCA and SCA provide adequate information for making selection when parental lines show a wide range of genetic variability. Combining ability analysis further revealed the predominance of SCA effects and heterosis was detected for all the traits studied. Some yield traits have shown positive heterosis and negative heterosis for flowering time and Sclerotinia sclerotiorum meant that incorporation of earliness and high yield into one genotype is a distinct possibility in this crop. Flowering time and oil content were found to be highly heritable. This result was unusual in the case of flowering time because it was subjected to strong directional selection during the production of inbred lines. Further, heterosis in most characters was caused by directional but partial dominance. The estimates of dominance were found to be rather high in the present study, indicating that hybrids will have a considerable advantage over inbreds as varieties of sunflower. Significant epistasis and dominance for most traits confirmed that the genetic control of variation in sunflower is as complicated as in many other species. A part of the thesis was devoted to the assessment of sunflower families under normal and late sowings. This experiment revealed that early sown material has advantage in most seasons because it matures early, before the onset of autumn. The late sown seeds grow into better quality plants but their yield is affected badly and on many occasions total yield loss can occur when there is high humidity during September. The implications of the present study and those conducted before are discussed at the end and it is concluded that sunflower can prove to be a very useful and profitable crop in the UK provided suitable varieties are made available for cultivation.

Climate change and urbanization has increased the risk of pluvial flooding. Sustainable Drainage Systems (SuDS) aim to control a greater proportion of rainwater at source. Green roofs can partly offset the loss of urban terrestrial landscape and provide additional capacity for the retention and detention of rainwater. The objective of this research was to improve the understanding of the physical controls that affect a green roof’s hydrological response. Experimental studies were undertaken to monitor the performance of nine different extensive (80 mm substrate) green roof configurations. A four-year record of rainfall, runoff, climate and moisture content data has been analysed for a field research site in Sheffield. Nine test beds incorporated three substrates with different moisture retention characteristics and three different vegetation treatments (Sedum, Meadow Flower and non-vegetated). Consistent differences were observed. The effects of vegetation and substrate were most evident for rainfall events where the depth exceeded 10 mm: mean per-event retention varied between beds from 14% to 70%. Retention was highest from the configuration with the highest moisture storage capacity (Sedum-vegetated HLS) and lowest from the configuration with the lowest moisture storage capacity (non-vegetated LECA). The difference between rainfall depth and available moisture capacity provided a highly credible indication of runoff. Evapotranspiration (ET) regenerates the moisture retention capacity. Experimental studies in a climate-controlled chamber enabled the monitoring of ET from the nine configurations across continuous dry periods of up to 28 diurnal cycles in spring and summer. ET rates were variably influenced by climate, vegetation treatment, soil and residual moisture content. A conceptual hydrological flux model was developed to allow both long term continuous simulation of runoff and drought risk and per-event responses to design storms. The model includes a function that links ET rates to residual moisture content, and is validated against observed runoff data. Detention was characterised via the calibration of a reservoir-routing model that linked net rainfall to the measured runoff response. The parameter values identified here – when combined with the retention model component – provide a generic mechanism for predicting the runoff response to a time-series or design rainfall for any unmonitored system with comparable components, permitting comparison against regulatory requirements.

The ascomycete fungus Microdochium nivale (Fr.) Samuels and Hallett (teleomorph Monographella nivalis (Schafnitt) is one of the most ubiquitous and damaging pathogens of cool-season amenity turfgrasses. Current control measures rely on inputs of chemical fungicides, making alternative means of disease reduction desirable. Phosphite (PO33-), which is derived from the alkali metal salts of phosphorous acid (H3PO3-),has proven efficacy in reducing susceptibility to oomycete pathogens. The aims of this research were to determine if PO33- treatments to amenity turfgrasses can suppress the incidence and severity caused by M. nivale, to determine the processes involved in such suppression and to assess the effect PO33- treatment had on turfgrass growth and quality. The research produced significant and novel data. In vitro inhibition of M. nivale mycelial growth was determined by amending PDA with PO33- and phosphate (PO43-), with concentrations from 0.5 to 1000 μg/ml-1. It was determined that PO33- concentrations of 100 μg/ml-1 and above, fully inhibited mycelial growth, with EC50 values from 38 to 45 μg/ml-1. PO43- caused no inhibition. Microscopic analysis of hyphal morphology showed distinct irregularities in M. nivale growing on PO33- amended PDA, while on PO43- amended PDA, mycelial growth was normal. Further in vitro studies determined PO33- was fungistatic rather than fungicidal, and that the presence of PO33- in growth media significantly inhibited conidial germination. Field trials determined significantly lower percentages of M. nivale incidence on PO33- treated plots of turfgrass, when compared with untreated controls, with the addition of PO33- significantly enhancing fungicide efficacy. Turfgrass quality on all PO33- treated plots was significantly better than either control or PO43- treated plots. Analysis of PO33- treated turfgrass tissues using High Performance Ion Chromatography, determined rapid in planta accumulation, symplastic mobility and no conversion to PO43- The data also indicate that PO33-, applied sequentially at four week intervals, would maintain leaf tissue amounts of approximately 2000 ppm, but would lead to cumulative accumulations in meristematic tissues. Furthermore, PO33- applications applied sequentially in excess of a six month period, can lead to increases in soil P levels. In phosphorus (P) deficient rootzones foliar applied PO33- does not supply a usable form of P and can repress plant P deficiency responses. In P sufficient rootzones foliar-applied PO33- increases plant biomass, with a reduction in root to shoot ratios. Assessment of turfgrass infection incidences determined M. nivale hyphae are the main source of inoculum and that infection was by means of stomatal penetration. Conidia produced via sporodochia following infection, are the means of propagation and dispersal. Analyses of infected turfgrass confirmed that increased synthesis of phenolic compounds and H2O2 are a component of initial defence responses and that PO33- pre-treatment, enhanced these responses. In conclusion, this work has shown that phosphite, when applied sequentially as a component of a balanced nutrient program, will suppress M. nivale incidence, increase the efficacy of turfgrass fungicides and lead to an enhancement of turfgrass quality. The results of this research will lead to changes in golf green management procedures, resulting in reduced requirements for chemical plant protectants, with added benefits of cost savings and a reduced environmental impact.

This study analyses vegetation succession following the clearance of Rhododendron in a sessile oakwood in North Wales. The Rhododendron has been cleared since 1984/5 and prior to clearance dominated the understorey. The succession was analysed in relation to the number of years since clearance; method of clearance; density of the former Rhododendron cover, and vegetation adjoining the site. An experiment was undertaken in the University's nursery to assess the presence and viability of seed within the seedbank, and the ability of the soil to support germination. Over 50% of the samples were dominated by bryophytes (60%), with birch, bramble and Rhododendron seedlings each present at less than 10%. There was a significant difference between the mean percentage crown cover of each TWINSPAN group; those groups with more light demanding species had a lower mean percentage crown cover than groups dominated by more shade tolerant species. Only bramble and birch germinated in soil collected from the two most recent years of clearance. Their presence is probably due to seed dispersed prior to clearance, and there is therefore no viable seed in the seedbank. Colonisation must therefore rely on immigration of seed. There was no significant difference between the ability of soil recently infested by Rhododendron, or the ability of peat, to support germination of Betula pendula or Festuca ovina. There is a significant difference between the frequency and abundance of vegetation and the year of clearance. With the exception of one plot, frequency and abundance increased with the number of years since clearance. Rhododendron seedlings are associated with a bryophyte cover. The site contains substantial Rhododendron coppice and seedlings, and continued eradication and containment programmes will be needed.