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The importance of nutrition on reproductive performance is well recognised. However,the mechanisms and specific factors regulating their interaction are still poorly understood. Interest has recently intensified, as fertility in dairy cows has declined. There is a body of evidence on the negative effects of reduced body condition, the high levels of energy and protein intake, however, the results are inconsistent between studies and the role of specific factors, such as insulin and leptin, in the regulation of ovarian function in cattle remains unclear. The main objective of this thesis, therefore, was to test the effects of animal body composition, planes of nutrition and diet composition with emphasis on endocrine and metabolic factors, including progesterone, oestradiol, insulin, IGF-I and leptin, on oocyte quality and early embryo development in cattle. This thesis has demonstrated that alterations in planes of nutrition (Maintenance (M) vs twice maintenance (2M)) affected oocyte quality, and that the effects were dependent on animal body condition score (BCS) (Low vs Moderate). Whilst high (2M) levels of feeding were beneficial for oocytes from animals in Low BCS, they were detrimental to oocyte quality for animals in Moderate BCS. Furthermore, the combination of feeding level and animal BCS created low (10 ull.J/ml), moderate (20 ).lIU/ml) and high (40).lIU/ml) plasma insulin concentrations. Inevitably, however, it also led to the creation of three corresponding levels of plasma leptin concentrations (low: 2 ng/ ml, moderate: 4 ng/ml, and high: 7 ng/ml), indicating that the effects of these metabolic hormones on ovarian function cannot be separated in vivo. However, there was no correlation between changes in metabolic hormones and oocyte quality, suggesting that other endocrine or metabolic factors, not recorded in this study, may be involved in determining the post-fertilisation developmental competence of oocytes. Animal body composition also played an important role in the dietary-induced modifications to oocyte developmental competence both in vivo and in vitro. Indicated by post-fertilisation development in vitro, oocyte quality was enhanced in Low BCS heifers offered the Fibre than the Starch based diets (43.6 vs 24.6% blastocysts for Fibre vs Starch diet), whereas inclusion of protected lipid reduced oocyte developmental competence (27.7 vs 42.9% blastocysts for presence vs absence of Megalac). However, in Moderate BCS heifers, diet composition had litde effect on oocyte quality. Although dietary treatments had little effect on endocrine profile, elevated plasma leptin concentrations were consistently correlated (P<0.001) with increased animal body fatness. The effects of dietary treatments on oocyte maturation in vivo, however, varied from those observed when sera from these animals were used during the final stages of oocyte maturation in vitro, and during early embryo development. These findings suggest that while some diets may be beneficial to oocyte development, they could have a negative effect on embryo quality and subsequent survival. Interestingly, serum harvested from Low BCS heifers enhanced blastocyst formation in vitro compared to serum from heifers in Moderate BCS (24.2 vs 19.0%). This indicates that animal BCS is an important factor involved in the regulation of not only oocyte quality, but also early embryo development. The reasons for these discrepancies between BCS groups, however, remain unknown. Finally, this thesis produced an interesting and novel insight into the nutritional regulation of the lipid content and fatty acid composition of bovine plasma, granulose cells (GCs) and cumulus-oocyte complexes (COCs), and also the effects of serum from contrasting nutritional backgrounds on the lipid content and fatty acid composition of embryos. In general, the inclusion of supplemental fatty acids in the diet significantly increased the lipid content of all tissues tested. The fatty acid composition of COCs and embryos, however, was not correlated with their quality. Nevertheless, differences in the fatty acid composition of plasma, GCs and COCs indicated that there is a selective mechanism of fatty acid uptake by the follicle compartment, which has a preference for saturated fatty acids. The importance and function of specific fatty acids in determining oocyte and embryo quality remain to be elucidated. This thesis has therefore demonstrated that animal body composition is an important factor determining the effects of feeding level and diet composition on oocyte and early embryo development. In summary, high levels of feeding and the Fibre based diets can enhance oocyte quality in thin, but not in moderately fat animals. Alterations in plasma insulin and leptin concentrations did not appear to be correlated with oocyte quality in the present studies, indicating that other factors, not monitored in this project, are possibly involved in the regulation of oocyte developmental competence.

Conidia of A. linicola germinated over a wide range of temperatures (5 - 25°C) on both agar and leaves. Germination started within 2 h after inoculation at temperatures between 10°C and 25°C, either on agar or on leaves. At 5°C, there were lag periods of 2 and 4 h before the initiation of germination on agar and on leaves, respectively. Germinating A. linicola conidia were very sensitive to drying between 2 and 6 h after inoculation. In the presence of leaf wetness, light applied before the initiation of germination delayed the germination process and decreased the length of the germ tubes. Light applied after the onset of germination decreased both the percentage of conidia which germinated and the length of the germ tubes. In the absence of leaf wetness, light applied before or after the initiation of germination stopped the germination process or decreased the percentage of conidia which germinated, respectively. Conidia of A. Linicola germinated by producing germ tubes and occasionally by producing secondary conidia. Formation of appressoria was inhibited at 5°C. Penetration of the leaf tissues started 12 h after inoculation at 15°C and occurred mainly directly through the epidermal cells and occasionally through stomata. A. linicola is a "diurnal sporulator". In vitro most isolates sporulated only after exposure to diurnal NUV-light. However, for some isolates exposure to diurnal NUV-light did not seem to induce sporulation unless the mycelium was wounded and grown on a medium rich in CaCO3 (S-medium) at high relative humidity. In vivo sporulation of A. linicola was increased after induction by light. The greatest numbers of conidia were produced under continuous leaf wetness and alternating dark/light periods (12 h each). Under these conditions the number of conidia produced increased with increasing temperature from 10°C to 20°C. Alternating 15°C/10°C or 20°C/15°C day/night temperatures decreased the number of conidia produced compared with the constant temperatures 15°C and 20°C, respectively. In controlled environment studies, infection of linseed plants by A. Linicola and development of symptoms was affected by the leaf wetness period, its interaction with temperature and by the light conditions. Eight hours of leaf wetness were sufficient to initiate the disease at 25°C but not at 15°C when a longer period of 10 h was needed. Infection of linseed plants by A. Linicola occurred under interrupted leaf wetness periods at 15°C, but the incidence and severity of the disease was lower than that under continuous leaf wetness. The disease incidence on stems and the disease severity on leaves was negatively correlated with the length of the light period applied immediately after inoculation. Disease incidence and severity increased with increasing inoculum concentration from 1 x 10³ to 1 x 105 conidia ml-¹. The cotyledons appeared to be more susceptible to A. linicola infection than the leaves when the same inoculums density was used. A. linicola was detected on 12 of the 20 seed samples tested and on six of them at a high incidence (> 50%). Seed seems to be the main source of primary inoculum as the pathogen was effectively transmitted from infected seeds to the emerging seedlings. Infected linseed stem debris, volunteer linseed plants and the weed Veronica agrestis were also sources of primary inoculum for the infection of linseed crops by A. linicola. Structures resembling chlamydospores formed in the mycelium and conidia of A. linicola seem to be involved in the survival of the pathogen in stem debris. Conidia of A. linicola were mainly dispersed by the wind (air-borne conidia) and their dispersal followed seasonal and diurnal periodicities, which were influenced by the weather conditions and the incidence of the disease in the crop. The greatest numbers of A. linicola conidia were collected by the Burkard spore sampler on the first dry day following periods of rain, between 12:00 h and 13:00 h and during the period between flowering and harvest of the crop (July - September). Bait plants were more efficient than the Burkard spore sampler in detecting A. linicola conidia present in the crop early in the growing season. The number of A. linicola conidia dispersed within a linseed crop decreased with increasing height above ground, but some conidia were collected 80 cm above the crop canopy. The number of A. linicola conidia dispersed downwind from a line inoculum source decreased with increasing distance from the source and by the end of the growing season conidia were collected by up to 40 m from the source. When the A. linicola disease gradients were studied from point or line inoculum sources, the disease incidence decreased with increasing distance from the inoculum source. By the end of the growing season, the disease was detected 20 or 60 m from the point or line inoculum sources, respectively. Multiple applications of iprodione or prochloraz sprays to control A. Linicola infection in the crop, especially the seed-borne phase of the pathogen, and to increase crop yield gave variable results depending on the weather conditions and the incidence of the disease in the crop. Multiple applications of benomyl or chlorothalonil sprays had either no effect or increased the incidence of the disease in the crop.

Lodging, the permanent displacement of plant stems from the vertical, occurs on average once every four years in UK wheat crops, when it reduces the yield and bread making quality of grain. Lodging usually occurs in the summer and control is most commonly sought by applying growth retarding chemicals in the spring. This thesis develops a method of predicting which crops are prone to lodging so that spring lodging controls can be targeted most effectively. A model was developed in association with this study which calculates stem and root lodging risk from summer-time plant, weather and soil factors. The spread of the plant's root plate, the stem diameter and the number of shoots per plant were shown to have very strong influences on lodging. Structural rooting depth, stem failure yield stress, height at centre of gravity and the rate at which stems oscillate in wind (natural frequency) were also important, but less influential. Methods of predicting the most important lodging-associated plant characters from crop observations in spring were developed from the literature. These were then tested through experiments in 1995 and 1996 with factorial combinations of crops sown in late September and late October, at 500 seeds m-2 and 250 seeds m-2 and with large and small levels of residual soil nitrogen. Early sowing, dense seed rates and fertile soils all increased stem and root lodging, with sowing date having the greatest influence. Plants sown at high densities had small root plates and were poorly anchored; they also had fewer shoots causing a smaller leverage. Early sown plants had shoots with a high centre of gravity and slow natural frequency, causing a greater leverage. Plants sown early on fertile soils had narrow, weak stems. Final shoot number per plant was predicted with good precision (R2=094) from spring plant number m-2 and maximum shoot number m-2 using a model of tiller survival. Stem diameter was predicted with moderate precision (R2=057) from spring canopy size and shoot number m-2, via a calculation of the amount of dry matter partitioned to each stem base. Root plate spread showed a linear and inverse relationship to spring plant density (R2=0.48), mainly as a result of variation in the length of the rigid roots and in the width of the plant base. It is concluded that early season crop observations have the potential to predict the values of the most influential lodging-associated plant characters, from which a model of lodging can calculate the proneness of crops to stem or root lodging in time for remedial action. The next steps would be to develop prediction schemes for other plant characters which influence lodging and test all the predictions in a wider range of crops, sites and seasons.

International interest in fluidised bed combustion (F.B.C.) derives from the fact that it involves new technology and it is the only combustion system that can use low grade fuels (including those of high or variable ash content) efficiently. This thesis presents a study of the combustion of straw in a fully fluidised and systematically interrupted flow test rig. In the interrupted flow mode, it was found that during the period in the cycle when the bed was slumped, due to the reduction in primary air, a gasification process took place. This resulted in a higher percentage of volatiles being burned in the bed and preliminary results indicated that interruption gave an increase in overall efficiency of approximately 4%. It also led to lower losses being incurred in the flue gases and, to a lesser extent, to a reduction in the losses expected due to incomplete combustion of the fuel. Elutriation and carbon losses were also reduced to 88% and 86% respectively of those recorded during uninterrupted fluidisation. By increasing the area of the zone directly above the fluidised bed, the products of combustion were decelerated sufficiently to ensure that ash was not found on the walls or roof to the same extent as that previously noticed on commercial straight-sided combustion chambers. Small quantities of ash were found in the ducting leading to the cyclone but they were approximately the same for operation in both the uninterrupted and interrupted fluidisation mode.

Wheat (Triticum aestivum L.) is one of the three most important cereal crop grown globally and there is a gap between yield production and world demand. Previous studies on wheat have generally shown traits influencing the capacity of the grains to store assimilate (sink) to be better correlated with yield than traits influencing potential assimilate production (source). Therefore, strategies to improve ear fertility, defined as the number of grains per ear, are one of the most relevant features in the development of new cultivars and genetic improvement of yield potential. In the present study, novel large-ear phenotype (long rachis) is investigated as a trait to increase the number of grains per year, thus grains m", with the aim of identifying physiological processes limiting genetic improvement of ear fertility in wheat. Two advanced lines (NLI and NL2) developed by the International Centre for Maize and Wheat Improvement (CIMMYT) with novel ear morphology and one CIMMYT cultivar with conventional ear morphology Bacanora referred to as the parental spring wheat genotypes were characterized. In addition, 69 doubled-haploid (DR) lines from a cross between NL2 x Rialto (UK-bred cultivar) were used to investigate the physiological basis of improved ear fertility and yield potential in the novel material. Three field experiments were carried out at the CIMMYT experimental station in Cd. Obregon (Mexico) on the parental genotypes (2003/04, 2004/05 and 2005/06) while two field experiments were carried out for the NL2 x Rialto population (2004/05 and 2005/06). An additional experiment consisting of a subset of 15 lines of the NL2 x Rialto population was carried out in 2005/06. Two controlled-environment experiments were carried out at Sutton Bonington, University of Nottingham in 2004 and 2005 to investigate the developmental basis of the large-ear phenotype on the three parental genotypes. A post-anthesis (GS 61+ 14d) degraining treatment was imposed in field experiments examining the parental genotypes in 2004, 2005 and 2006 while a similar degraining treatment was carried out for the subset of 15 DR lines of the NL2 x Rialto population in 2006. A range of physiological traits related to ear fertility were measured on the parental genotypes and the DR lines including rachis length, spikelets ear"1, developmental stages, green area, radiation interception, radiation use-efficiency (RUE), dry matter production and partitioning, stem water soluble carbohydrate reserves, potential grain weight, grain weight and combine yield. In the growth-room experiments, the rate and duration of spikelet primordial production of the main shoots were measured. Present results showed that in the novel genotypes, longer rachis increased spikelets ear" and also grains ear-i. Thus, the novel genotypes showed greater ear fertility by having more grains ear" than the benchmark cultivar Bacanora. Grains m-2 was not actually increased in novel genotypes; indeed lower grains m-2 was found in NL2 compared to Bacanora. Heavier grains were found in the novel genotypes which had greater potential and final grain weight compared to Bacanora. The NL2 genotype possesses a tiller inhibition gene (tin) on chromosome 1A and this genotype had fewer ears m-2 than the other genotypes, and this trait also contributed to the lower grains m-2 ofNL2. The grains-to-ear DM ratio at GS 61 in NL2 was markedly lower compared to other genotypes. Results of the growth-room experiments showed that there was a developmental basis for the higher spikelets ear" observed in NLl and NL2 than Bacanora. A longer thermal duration from floral initiation to terminal spikelet was associated with a higher spikelet number in NL1 (27) and NL2 (29) compared to Bacanora (23). Since the growth-room experiments were carried out under long photoperiod (16 hrs) results also suggested that the large-ear phenotype may have been associated with the effects of 'earliness per se' genes. Grain weight of the parental genotypes did not respond differently to degraining. Averaging across parental genotypes and years, responses to degraining in the field experiments showed that although assimilate supply per grain was potentially increased by 100%, average grain weight was only increased by 15%. These findings indicated that grain yield was mainly limited by post-anthesis sink size in these experiments. In the subset of 15 DH lines experiment, there were different responses of the lines to degraining and the lines which showed larger responses of individual grain weight to degraining had lower grain weight in control intact ears. Results of the DH experiments showed that rachis length was positively correlated with spikelets ear", grains ear" and grains m-2 among the lines. There was also a positive phenotypic correlation between the grains-to-ear DM ratio at GS 61 and grains m-2 amongst the lines. However, the large-ear phenotype (long rachis, high spikelets ear") was not associated with greater grain yield due to a trade-off between grains m-2 and individual grain weight. The physiological mechanisms potentially explaining this trade off are analyzed. Harvest biomass was positively correlated with grain yield amongst the DH lines. So traits to improve biomass whilst maintaining harvest index may be important for future breeding. Present results showed a positive correlation between pre-anthesis RUE and harvest biomass amongst the subset of 15 lines of the NL2 x Rialto DH population. It is suggested that breeders might select for higher RUE (via high specific leaf weight) to improve grains m-2 and yield potential in future years.

Large numbers of adventitious shoots have been induced to form in vitro on floral stem sections of Tulipa gesneriana L. cultivar Merry Widow. In comparison with explants of scale and axillary bud, floral stem tissues showed the greatest potential for shoot production. A modified Murashige & Skoog medium contained inorganic salts and vitamins at full strength and supplemented with benzylamino-purine and napthalene-acetic acid at 1 mg‾1 induced shoots on 70%-90% of floral stem explants. The stage of development of the bulb was found to be an important factor in determining the ability of explants to regenerate shoots. The shoot producing potential of floral stem tissues was greatest during the 'dormant' phase of the bulbs, but the ability to produce shoots was lost once rapid extension growth and greening of the floral stem had commenced. Morphogenesis in vitro was found to be influenced by the origin of explants from within the floral stem. A study of endogenous plant growth regulators was made within the floral stem in order to elucidate their role in the organogenetic processes occurring in vitro. A study of histological and morphological development in vitro showed that the shoot-like structures arise from the epidermal cell layer and have the potential to form whole plants.

To overcome the `post-weaning growth check' commonly seen at weaning, the incorporation of antibiotic growth promoters (AGPs) to the diet has been a useful management tool. Recent legislation within the European Union banning the use of AGPs at sub-therapeutic levels in animal feed means that the quality of dietary ingredients used in weaner diets has assumed a much more fundamental role. In order to improve the availability of starch in the piglet diet, processing of cereals is widely practised. However, descriptions of processing techniques used in many studies are simply referred to by name, with no regard of the precise variables used. In addition, many of the feed materials are simply referred to as `cooked' which gives little indication of nutritional value. Five trials were conducted in order to assess the use of raw and processed cereals on diet component digestion, digesta properties and gut morphology in newly-weaned piglets. The main objective was to examine the use of precisely controlled processing variables, such that starch digestibility was maximised with benefits for the gastrointestinal environment. A second aspect of the programme of work reported was the application of a number of analytical tests commonly used in the field of human food science, to examine the physicochemical properties of starch granules, and the changes they undergo upon processing. Using this approach, a comparison could be made between in-vitro (rheological) results and in-vivo (biological) responses. Trials 1 and 2 examined variability between raw cereals. Wheat, barley, rye and triticale were assessed in Trial 1. Wheat (identical batch), naked oats, whole oats and maize were evaluated in Trial 2. Coefficients of apparent digestibility (CAD) for starch and nitrogen revealed considerable variation between the cereals. In Trial 1, there was a strong trend (P = 0.051) for starch digestion to be highest for the rye diet and lowest for triticale. CAD for starch was not significantly affected by cereal type in Trial 2. Despite having more viscous intestinal digesta than other animals (P = <0.001), pigs fed the rye-based diet did not experience any detrimental effects to animal performance. Trial 3 examined the use of raw wheat, of either hard or soft endosperm texture. From 5 days post-weaning, piglets fed the soft wheat diet had a tendency (P = 0.063) to have higher feed intakes. In addition, pigs fed soft wheat diets had significantly less viscous tract digesta (P = 0.029) than those animals fed the diet based on hard wheat. There was no significant difference in CAD for starch between the two dietary treatments but CAD for nitrogen was found to be significantly higher (P = 0.006) in the distal region of the small intestine for pigs fed the soft wheat diet. The results from Trial 3 suggest that endosperm texture of wheat can have an effect on nutritional value, and that wheat of soft endosperm texture is more beneficial than hard wheat for the young piglet. Trial 4 was a 2x2 factorial study examining wheat endosperm texture (hard vs. soft) and degree of micronisation (high cook vs. low cook). CAD for starch was not affected by endosperm texture, although degree of cook was an important factor with significantly higher starch digestion for the high cook diets, compared to low cook (P = 0.047). The use of micronised wheat lessened the reduction in starch digestibility seen on day 4 post-weaning in the small intestine, compared against the decline seen using raw wheat diets in Trial 3. In summary, Trial 4 demonstrated that micronisation can enhance the nutritional value of wheat for the weaned piglet, with degree of cook, a more significant factor than wheat endosperm texture. Trial 5 assessed wheat endosperm texture (hard vs. soft) and degree of extrusion (high cook vs. low cook). Raw soft wheat was used as a control. Results showed that CAD for starch in the small intestine was noticeably higher than in the other animal trials. Starch digestion was significantly affected by endosperm texture (greater coefficients for soft than hard; P <0.001) and by degree of cook (high SME greater than low SME; P <0.001). The use of extruded wheat diets almost eliminated the drop in starch digestion at the 0.5 intestinal site seen on day 4 post-weaning. Wheat of soft endosperm texture responded better to extrusion processing than hard wheat under the conditions of Trial 5. The use of computer modelling was able to demonstrate a correlation between in-vitro starch parameters and in-vivo starch digestion in the small intestine of the piglet.