The isotopic fractionation of sulphur in the plant metabolism of sulphate by chlorella was investigated; and for this purpose an apparatus was devised for growing chlorella under sterile conditions. A green alga from the shores of Lake Erie, and mustard plants from the field were also investigated. No isotopic fractionation was found in the plant metabolism of sulphate either in the laboratory or in nature. A new method for the reduction of sulphate to hydrogen sulphide was also developed. / Thesis / Master of Science (MS)

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published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Four methods of analysis for the determination of total and individual glucosinolates in Brassica napus cultivars (ie Gas Chromatography (GC), High Pressure Liquid Chromatography (HPLQ, Glucose Release, and X-ray Fluorescence Spectrometry (XRF)) were developed, refined, validated and applied. These were used to investigate both high and low glucosinolate cultivars of rapeseed (oilseed rape, Brassica napus), and reproducibility (between replicates) and repeatability (between analysis days) of these methods was assessed. From these studies, an indirect method of glucosinolate determination, involving X-Ray Fluorescence analysis, proved to give the least variable results. Furthermore, this was markedly more rapid than the other methods of analysis. Of the methods assessed for the determination of individual glucosinolates, High Pressure Liquid Chromatography (HPLC) gave less variable results than Gas Chromatography (the European Community (EC) recommended method for glucosinolate determination in oilseed rape at the time of study). Thus, BPLC and XRF analysis were selected as methods for subsequent glucosinolate analysis in the remainder of the study. Effects of geographicallo cation in relation to atmospherics ulphur depositiona nd plant sulphur uptake in Brassica napus cv Ariana grown throughout the UK were determinedin two consecutivey ears. An initial study comparedg lucosinolatele vels in rapeseed samples from 211 sites. A second more detailed study involved determinationo f foliar sulphurl evels (by XRF analysis)a t three stagesd uring plant developmenftr om selecteds itest hroughoutt he UK, and comparisono f thesew ith glucosinolate levels in the harvested seed from these sites. The results of these investigations proved comparable between years, with final glucosinolate levels generally corresponding to atmospheric sulphur deposition levels. Furthermore, high glucosinolatele vels in harvesteds eedg enerallyc orrespondewd ith high sulphur levelsi n foliage ast he plantse ntereds eed-podd evelopment.A series of controlled environment and glasshouse experiments were developed to investigate the effects of sulphur nutrition on glucosinolate development in rape plants during growth. These highlighted that glucosinolate levels in plant material could be manipulated with variation in supplied nutrients. Furthermore, plants initially propagated with sulphur-complete nutrient in hydroponic media, then transferred to sulphur-free nutrient mid-development, were found to give good seed yields with substantially lower glucosinolate levels. In conclusion, attention must be given to choosing the appropriate method for analysis of glucosinolates. Secondly, sulphur availability and sulphur status are critical factors in the determination of glucosinolatelevels, and the relationship between these factors merits further study

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