In two pot experiments using two different crop ryegrass (Lolium perenne) and two flax (Linum usitatissimum) varieties Viola and Elise, ryegrass decreased in the pool of heavy metals compared with bare soil using EDTA as extractant. NH4+ decreased the soil pH, increased EDTA-extractable Zn and increased the Zn uptake. Lime addition increased the pH and depressed Zn uptake. The pool of extractable EDTA was not changed by growing both of the flax varieties. Lime increased EDTA-extractable Cu and Pb significantly, but decreased the Zn, and pH increased in this order NH4+<NO3-<NH4++lime<NO3-+lime. The EDTA –extractable Cu decreased in the order NO3-+lime>NH4++lime>NH4+>NO3-. Ammonium decreased the pH more than other treatments. In agar using Bromocresol purple indicator NH4+ increased the pH in the rhizosphere of different plants. With two different initial pH treatments (7 and 3.2) the NH4_ decreased the pH in the rhizosphere at high initial pH 7 and maintained the low pH at initial pH 3.2 to 4 against the buffer capacity. At different initial pH 4, 5, 6, 7 and 8 the ammonium decreased the high pH and maintained the low pH, but NO3- had no effect on the pH. Ammonium increased the toxicity of Zn due to pH decreases. There was no effect of both nitrogen sources NH4+ or NO3- on rhizosphere pH when applied as a foliar application. These indicated that the NH4+ can decrease the pH in the rhizosphere of plants and could play an important role in manipulation of the rhizosphere bioavailability of heavy metals. Toxicity of the three metals is Cu>Pb>Zn in this order and the crops tolerance is following this order pea>flax>barley. An agar-Hoagland nutrient solution contaminated with two soils, sewage treated soil (SBS) and galena soil (G), was used with flax as a test crop. The ammonium treatment lowered the pH in both soils, but with galena treated greater than SBS soil, this is attributed to the buffering capacity of the SBS soil. Averaged over all the concentrations the NF4+ treatments resulted in higher Zn shoot content that NO3- treatment, while in Cu shoot content nitrate was more than ammonium. The transfer factor of lead with ammonium treatment was greater than nitrate treatments at the 0.1 and 0.25% galena and the transfer factor of the Zn and Pb more than Cu in all treatments. At high initial pH 8 and high concentration of Zn and Cu barley grew well and this is attributed to immobilisation of Zn and Cu compared with low pH 5 and 6.5 where the barley plant did not survive. Ammonium lowered the high pH 8 and caused lower biomass production of barley than nitrate.

This thesis describes the observations of field trials and analytical investigations of the residues of maleic hydrazide (1,2-dihydro-3,6-pyridazinedione) known as MH. MH is marketed in a formulation called `Fazor' and was introduced to the United Kingdom under PSPS (Pesticide Safety Precaution Scheme) in 1985. It is targeted at sprout suppression of ware tubers in store with the added benefits of increased marketable yield and reduced groundkeepers. Two field trials were conducted to investigate the sprout inhibition of MH and its effect on yield. Both field trials used a popular ware seed (c.v. Maris Piper) grown under typical growth conditions and treated with Fazor(5 kg/500 litres/hectare) under optimum conditions. Treated potatoes were observed to have typical characteristics of a break in apical dominance. Every eye on the tubers was active and formed spikelets that developed into growths similar in appearance to a small cauliflower head. It was also noticed that sprout suppression was not complete. A proportion of potatoes had inadequate suppression. Some showed no characteristics of MH, typical of an untreated potato. The inadequate sprout suppression was investigated by analysing the MH distribution and the comparison of sprout suppression. MH treated plots were found to have slightly lower yields than untreated plots. This reduction in yield was not shown to be statistically significant. Two methods to calculate the residues of MH were adapted. The first used the action of zinc in concentrated sodium hydroxide to produce hydrogen, which reduced and hydrolysed MH to hydrazine. The hydrazine was distilled and caught in an acid scrubber containing a colour reagent. The colour reagent and hydrazine combined to produce a coloured chromophore. The colour intensity was proportional to the amount of MH. This method was used to calculate the total MH. The second method calculated the amount of free MH (not metabolised or conjugated) by a methanol extraction, cleanup of the concentrate and analysis by high pressure liquid chromatography (HPLC). The total MH was roughly made up of three factions:- (1) Non-extractable MH (2) Methanol extractable MH (a) free MH (b) metabolised MH The uptake of MH over a four week period, after spraying Fazor, was assessed by harvesting at weekly intervals for four weeks and analysing the tubers by the above methods. The distribution of MH between individual tubers was investigated by calculating the MH in whole tubers. The distribution within individual tubers was calculated by analysing the skin, the outer flesh and the inner core. The distribution of MH between grades was calculated. The carryover of MH into processed foods was calculated by analysis of crisps and boiled potatoes from field treated plots. It was found that the MH accumulated in the potato tubers before one week and remained static up to four weeks. However, there was a fraction, a possible metabolite, that increased in concentration, whereas the free MH concentration decreased. Sprout suppression was found to be dependent on the total MH. Small tubers had lower concentrations than larger tubers. MH was found throughout the whole tuber with a slightly lower concentration in the core. MH was also found in fried and boiled potatoes and was identified as free MH. The metabolites of MH were investigated by applying radiolabelled MH to greenhouse grown potato plants. The potatoes were extracted by methanol and the concentrated extracts separated by thin layer chromatography (tlc). A metabolite was detected after exposing the plates to X-ray photographic plates. However, this metabolite was not successfully identified. This was due to the combination of low specific activity of the radiolabelled material, and the low quantity of metabolite produced. Hydrolytic enzymes were used to cleave possible conjugated metabolites in the potato juice concentrates. The action of a beta-D-glucosidase was found to increase the free MH. This would appear to suggest that a metabolite of MH is a conjugated product between MH and a glucose molecule. However, a conjugate could not be synthesized between uridine diphospho glucose (UDPG) and MH with soluble potato protein. There was no evidence to suggest that a metabolite is produced between MH and glutathione. It was suspected that MH would inhibit wound healing because it inhibits cell division. Cut potatoes treated with various concentrations of MH were examined histologically to assess cell division and suberin production. The rate of water loss from potato discs treated with MH was calculated. If the rate of water loss does not slow down because of chemical inhibition of the process, potatoes will lose weight and condition in store. No difference between control potatoes and MH treated potatoes was found at the beginning of a storage season. At the end of storage (four months), MH treated tubers had better wound healing than controls.

Work described in this thesis was designed to address a number of environmental issues relating to the use of chlorpropham (CIPC) as a sprout suppressant in potato stores. Studies considered the behaviour of CIPC during the application process and storage and also the potential for it to be released into the environment. All commercial studies were carried out in box stores, rather than bulk stores. A survey of potato growers was carried out to provide up-to-date industry information on store management practice and to determine the extent of chlorpropham use in the UK. Results confirmed that the vast majority of crop held in the UK for both pre-packing and processing is treated with chlorpropham. In most cases, several applications are necessary to maintain sprout control throughout the season, which highlights the inefficiency of the application process. Thermal fog application (the industry standard) is known to be inefficient, and to result in uneven distribution of chlorpropham around the store. This can lead to unacceptably high chemical residues in crop at certain locations, and poor sprout control in places that do not receive the correct dose. The imminent introduction of a Maximum Residue Level (MRL) for chlorpropham means that store managers must be able to predict with confidence the amount of chemical reaching each tuber. Analysis of crop from commercial stores found chemical levels ranging from 0-50 mg kg-1 following conventional application. Washing significantly reduced these very high levels in most cases. Improvements in chemical distribution (and a lowering of the highest chemical levels) were seen when the movement of air and fog around the store were manipulated using fans or by restricting air flow using polythene sheeting. A method for the collection and analysis of air samples was developed and used to quantify CIPC in samples of air from treated stores. Vapour concentrations were found to be of the order of mg l-1 (parts per billion), and to increase linearly with air temperature. 3-chloroaniline (a metabolite of CIPC) was also identified in the air samples, suggesting significant breakdown of the CIPC molecule may occur during chemical application or storage. The mechanism of breakdown was not identified. Contaminated fabrics within the store are believed to provide a reservoir of chemical that can readily volatilise and be found in the vapour phase. The presence of chlorpropham in the air has implications for crop contamination and the extent of chemical loss from the store. Samples of effluent from potato washing plants were collected and analysed on several occasions. The CIPC concentration to liquid effluent (after removal of all suspended material) was found to range from several mg/l (parts per million) in untreated samples to <0.01 mg l-1 following filtration and digestion.

No description available.

This thesis describes work focused on the chemical synthesis and herbicidal activity of the natural product phyllostictine A, a molecule of unique structure and unknown mode of action. Chapter 1 serves to introduce the natural product and describe the known activity of the natural product. Furthermore, it discusses literature methods for the construction of a-methylene-b-lactams, a key component of phyllostictine A. Chapter 2 describes work towards the construction of the macrocyclic rings found in phyllostictine A. As a result a-methylene-b-lactams have been shown, for the first time, to participate in RCM reactions. Formation of 11- and 12-membered trisubstituted membered rings was possible, however, the nature of the nitrogen substituent has a large impact. For example, 12-membered rings 124, 130 were formed in 37% yield when a para-methoxyphenyl group was utilised, while simple ethyl substitution could only achieve yields of 20%. Boc protected lactam 169 produced only linear dimer 170. The synthesis of tetrasubstituted alkenes via RCM was attempted with lactam 145, however, resulted in an unexpected rearrangement product. Not only was the RCM sensitive to the nitrogen substituent but also the size of ring being formed. For example, 11-membered rings produced significant amounts of the 22-membered dimers 89 and 87. Throughout the RCM reactions performed in this thesis held a preference for the Z-alkene. The trend was confirmed both by NMR shift analysis and X-ray crystallography. Chapter 3 describes work towards the synthesis of 4,4-disubstituted a-methylene-b-lactam subunit of phyllostictine A. Three methods: epoxide rearrangement, carbonylation of methyleneaziridines and carbonylation of 2-bromo-allyl-propenes were explored. Chapter 4 describes the herbicidal activity of phyllostictine A against the single celled algae C. reinhardtii. ED50 data was obtained for phyllostictine A against C. reinhardtii for the first time. Furthermore, it was shown to be comparable to the commercial herbicide glyphosate. Six novel a-methylene-b-lactams synthesised in Chapter 2 were tested for herbicidal activity against C. reinhardtii which has enabled us to develop preliminary structure-activity relationships.

This thesis aims to characterise the structural, adhesion and release properties of polymeric microcapsules which are used ina griculture for t he controlled delivery of pesticides to crops. An adaptation of atomic force microscopy (AFM) known as chemical force microscopy (CFM) has been used to investigate the adhesion characteristics of functionalised polyurea microcapsules to surfaces. The adhesion properties of microcapsules (attached to AFM cantilevers) to self-assembled monolayers (SAMs) of alkyl thiols on gold have been investigated at the single capsule level, and as a function of polymer wall surface functionality. Measurements have been made to OHterminated, CH3-terminated and mixed CH3: COOH-terminated SAMs. The importance of microcapsule topography and elasticity on adhesion measurements has been discussed. The surface pK1I2 of a capsule with a surface modified with a sulfonateterminated molecule has been estimated using force titration methodology. The adhesion properties of functionalised microcapsules to the leaf cuticle of Prunus laurocerasus have been examined, highlighting areas of hydrophilicity on the surface of the leaf. The release properties of a ctive ingredients from p olyurea microcapsules into solution using confocal laser scanning microscopy (CLSM) have been investigated. Preliminary studies obtained the optimum species to use inside the microcapsule and the solution into which the species should be released. The release characteristics 0 f six varieties of microcapsule, differing in the wall thickness and cross linking density were examined and from the release profiles obtained, the product of the mass transfer coefficient and solubility coefficient could be calculated. The high resolution imaging capabilities of the confocal microscope have been demonstrated, providing detail on the structure of the leaf of the Prunus Laurocerasus plant and t he caterpillars Heliothis virescens and P lutella xylostella, two of t he most common pests, which the microcapsules of interest are aimed at controlling. The release properties to leaf surfaces of two types of polyurea microcapsules, which have different release mechanisms, were investigated using CLSM. Detailed release studies to model surfaces showed that one type of capsule (lambda cyhalothrin) released in the dry state and the other (emamectin benzoate) did not. A release rate was determined in the former case. A technique has been developed which is capable of visualising the release and diffusion of a species (Cd2+) from a hemisphere. Voltammetry has been used in conjunction with CLSM to monitor quantitatively and visually the preconcentration and release of Cd2+ into and away from a mercury hemisphere UME. The fluorescent indicator used was Calcium Green-5N, which is a cadmium-sensitive fluorophore that fluoresces upon binding Cd2+and can thus be detected by CLSM. A delay was observed between the release of C d2+ from t he hemisphere (determined voltammetrically) and binding to the fluorophore (visualised using CLSM).

Targeted delivery of an active ingredient to plant systems required extensive studies in areas of soil mobility, plant root adhesion and encapsulation. To accomplish the aims of mobility and adhesion to roots, specific surface charges and colloidal forces are required. These charges are required to provide sufficient repulsive forces preventing adhesion to soil and attractive forces allowing adhesion to roots. To accomplish the aims of synthesising colloids for mobility, adhesion and also encapsulation we formed a specific strategy. We aimed to increase the anionic surface charge on colloidal nanoparticles as a means to aid mobility studies of colloids through soil by providing increased repulsive forces to prevent adhesion to both air interfaces and soil. We also designed a way to decorate colloidal nanoparticles with microgel particles thus forming a soft adhesive surface layer with which further functionality could be incorporated i.e. surface charges. Finally we designed a simple methodology for the encapsulation of oil with post functionalisation in mind. We synthesised colloidal nanoparticles, less than 200 nm, using soap-free emulsion polymerisation of styrene where up to 50 wt% of protected ethyl styrene sulphonate monomer was incorporated. The nanoparticles were hydrolysed to release the sulphonic charge using thermolysis in an autoclave. Soap-free emulsion polymerisation was used to synthesise raspberry-like and core-shell morphology decorated nanoparticles by the adhesion of crosslinked nanogel particles to a range of hydrophobic and hydrophilic seeds. Poly(acrylic) and poly(styrenic) seeds were synthesised with a range of hydrophobicities whereby more decoration of nanogel particles was achieved for hydrophilic seeds. The nanogel decoration was studied using di-, tri- and multi-functional acrylates and the morphologies changed from raspberry-like to core-shell as the functionality of the crosslinker increased. The presence of Vinyl functional groups was proved using Raman microscopy. Post functionalisation with different thiols was carried out using nucleophilic thiol-Michael addition chemistry and a loss of vinyl groups was shown. Encapsulation of aromatic oil was carried out using an interfacial thiol-Michael addition reaction between a tetra- functional thiol and a penta-/hexa- functional ene using an amine nucleophilic catalyst. A microfluidic device was used to control the capsule sizes and dispersity and light microscopy was used to study capsule sizes and dry-down properties. No rupture was observed for the millimetre and microcapsules produced but unfortunately size scale-down could not be accomplished for the current system using high shear homogenisation. In conclusion we increased the loading of sulphonate charge for colloidal poly(styrene) nanoparticles and we successfully increased the surface area of styrenic and acrylic seed nanoparticles using nanogel particle adhesion. We post functionalised decorated nanoparticles using thiol-Michael addition reactions and synthesised capsules using thiol-Michael addition reactions confined in a microfluidic device.