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The molecular composition of organic matter in peatlands reflects local conditions and stores information about botanical composition (plant source) as well as the degree of and conditions during decomposition. A reliable hydrological (and hence palaeoclimatological) interpretation of source and decomposition proxies in peatlands requires the understanding of the interactions between decomposition and botanical composition and the reaction of both to changes in the water table. Only few studies combined vegetation and decomposition characteristics to investigate peat OM dynamics and reconstruct environmental changes, and these included only a limited number of samples. In order to study the three-way relationship between botanical composition, decomposition and environmental conditions, pyrolysis-GC/MS of high-resolution sampled peat cores was used on two contrasting ombrotrophic peatlands. The two sites comprise a Sphagnum-dominated peatland in Tierra del Fuego (Argentina) and a graminoid-dominated peatland in Galicia (Spain). The purpose of this study was to examine the use of analytical pyrolysis in the environmental interpretation of peat profiles and to gain an improved understanding of peat OM dynamics and thereby develop parameters that reliably reflect past environmental conditions.The molecular composition of the Sphagnum-dominated Harberton peatland was first explored for a selection of samples. Several peat fractions have been analysed, including NaOH-extract, NaOH-insoluble residue and bulk sample. A large number of pyrolysis products was identified and quantified for all peat samples; additionally total C, N and ash content were measured. Molecular parameters were identified by a systematic methodological approach. Peatland plants have been analysed in search for specific markers. Factor analysis was used to reduce the number of pyrolysis products for quantification and to assess differences in peat chemistry and relate these to environmental factors. This resulted in a number of molecular parameters that reflect botanical changes, (an)aerobic decomposition and fire incidence.The results of the different peat fractions and plant analysis were applied to a large number of bulk samples (67), and used to reconstruct the 12,000 years of vegetation history of the Harberton core, which was then interpreted in terms of past hydrological conditions. The C:N ratio showed a perfect agreement with the botanical composition according to pyrolytic plant markers. It appeared that the n-alkane distribution showed remarkable changes with respect to shifts in the abundance of Sphagnum. Consequently, the detailed vegetation reconstruction was used to discuss the application of the n-alkane distribution in ombrotrophic peat. The simultaneous effects of botanical shifts (source material) and decomposition may cause conflicting hydrological interpretations for non-specific plant markers such as n-alkanes. The results indicated a considerable effect of aerobic decomposition on the distribution of n-alkanes. Although pyrolysis is not the regular method to establish the n-alkane distribution, comparison of n-alkanes in the NaOH-extract and residue peat samples supported the findings. The results emphasise the importance of combining vegetation and decomposition characteristics.For the graminoid-dominated Penido Vello peatland, all 101 bulk peat samples of the 3 m thick peat deposit have been analysed. In addition to the search for specific compounds of peatland plants, the same pyrolysis products were quantified for plant pyrolysates and peat. Depth records of plant markers agreed well with their preferential habitat, with the degree of decomposition and with the transition from minerotrophic to ombrotrophic peat. Factor analysis was used to reconstruct past hydrology. The results showed the importance of high-resolution sampling through the higher correlations between molecular parameters in the part sampled each 2 cm compared to 5 cm. Furthermore, good correlations of pyrolysis results were found with mineral content, solid-state 13C CPMAS NMR data and total N.The hydrological reconstruction based on depth records of plant markers and factor scores obtained by factor analysis of all quantified pyrolysis products, and the low contribution of Sphagnumto the graminoid-dominated Penido Vello peat allowed studying the effects of source and decay on the lignin composition. A large number of lignin pyrolysis products were quantified for peatland plants and for the three different peat fractions for a selection of 15 samples. Lignin composition of woody and graminoid plant species were compared as well as the lignin composition in different peat fractions, and their relation to source or decay was established.To determine whether the lignin parameters, derived from analysis of plants and peat fractions, can be used to reconstruct peat environment, they were applied to all 51 bulk peat samples of the upper meter of the Penido Vello core. The results show a strong effect of vegetation type and anaerobicity on generally-used lignin decomposition proxies, which indicates that such proxies are not reliable without information on the context.To examine the interaction between vegetation type and decomposition processes, the results of Sphagnum-dominated peat and graminoid-dominated peat were combined. In addition to the well-known pyrolytic marker from Sphagnum (4-isopropenylphenol), depth records of pyrolysis products specific for lichens and graminoids functioned well in both peatlands and are considered reliable markers for application in other peatlands. A number of other identified markers only functioned well within one of both peatlands. The different functioning of these markers in the two peatlands emphasises the importance of plant analysis prior to the use of pyrolytic biomarkers with low specificity, but also shows that supposedly non-specific pyrolysis products can be specific within a certain peatland ecosystem. The use of different peat fractions (NaOH-extractable and non-extractable peat) provided information on the degree of decomposition and allowed comparison with studies on peat humic acids and humin, and the generally applied colorimetric method to determine peat humification. Furthermore, the comparison of pyrolysates of extracts and residues for a selection of peat samples, in combination with factor analysis, allowed separation of the effects of source, and several stages of aerobic and anaerobic decay. Degradation of lignin-cellulose (vascular plants) and polyphenol-cellulose (Sphagnum) is discussed using the abundance of their markers (lignin moieties, levoglucosan and 4-isopropenylphenol) in pyrolysates of the different peat fractions, and gives insight into degradation mechanisms. The results indicated that, in Sphagnum litter, polyphenols are more easily degraded than polysaccharides. Comparison of pyrolysis results and C:N ratio showed that differences in litter quality between Sphagnum and vascular plants is a major factor that determines the variance of C:N with depth. Large part of the variation in C:N in Sphagnum-dominated peat is caused by decomposition rather than small increases of vascular plants upon drier conditions, while in graminoid-dominated peat this is not true and several processes may disturb the effect of mass loss on the C:N ratio. The C:N ratio can thus be a consistent decomposition proxy in Sphagnum-dominated peat but not in graminoid-dominated peat. Pyrolysis-GC/MS in combination with the applied research design provided detailed chemical information that gave insight in both vegetation and decomposition characteristics. This methodology thus has a high potential for the reconstruction of past environmental conditions.

The molecular composition of organic matter in peatlands reflects local conditions and stores information about botanical composition (plant source) as well as the degree of and conditions during decomposition. A reliable hydrological (and hence palaeoclimatological) interpretation of source and decomposition proxies in peatlands requires the understanding of the interactions between decomposition and botanical composition and the reaction of both to changes in the water table. Only few studies combined vegetation and decomposition characteristics to investigate peat OM dynamics and reconstruct environmental changes, and these included only a limited number of samples. In order to study the three-way relationship between botanical composition, decomposition and environmental conditions, pyrolysis-GC/MS of high-resolution sampled peat cores was used on two contrasting ombrotrophic peatlands. The two sites comprise a Sphagnum-dominated peatland in Tierra del Fuego (Argentina) and a graminoid-dominated peatland in Galicia (Spain). The purpose of this study was to examine the use of analytical pyrolysis in the environmental interpretation of peat profiles and to gain an improved understanding of peat OM dynamics and thereby develop parameters that reliably reflect past environmental conditions.The molecular composition of the Sphagnum-dominated Harberton peatland was first explored for a selection of samples. Several peat fractions have been analysed, including NaOH-extract, NaOH-insoluble residue and bulk sample. A large number of pyrolysis products was identified and quantified for all peat samples; additionally total C, N and ash content were measured. Molecular parameters were identified by a systematic methodological approach. Peatland plants have been analysed in search for specific markers. Factor analysis was used to reduce the number of pyrolysis products for quantification and to assess differences in peat chemistry and relate these to environmental factors. This resulted in a number of molecular parameters that reflect botanical changes, (an)aerobic decomposition and fire incidence.The results of the different peat fractions and plant analysis were applied to a large number of bulk samples (67), and used to reconstruct the 12,000 years of vegetation history of the Harberton core, which was then interpreted in terms of past hydrological conditions. The C:N ratio showed a perfect agreement with the botanical composition according to pyrolytic plant markers. It appeared that the n-alkane distribution showed remarkable changes with respect to shifts in the abundance of Sphagnum. Consequently, the detailed vegetation reconstruction was used to discuss the application of the n-alkane distribution in ombrotrophic peat. The simultaneous effects of botanical shifts (source material) and decomposition may cause conflicting hydrological interpretations for non-specific plant markers such as n-alkanes. The results indicated a considerable effect of aerobic decomposition on the distribution of n-alkanes. Although pyrolysis is not the regular method to establish the n-alkane distribution, comparison of n-alkanes in the NaOH-extract and residue peat samples supported the findings. The results emphasise the importance of combining vegetation and decomposition characteristics.For the graminoid-dominated Penido Vello peatland, all 101 bulk peat samples of the 3 m thick peat deposit have been analysed. In addition to the search for specific compounds of peatland plants, the same pyrolysis products were quantified for plant pyrolysates and peat. Depth records of plant markers agreed well with their preferential habitat, with the degree of decomposition and with the transition from minerotrophic to ombrotrophic peat. Factor analysis was used to reconstruct past hydrology. The results showed the importance of high-resolution sampling through the higher correlations between molecular parameters in the part sampled each 2 cm compared to 5 cm. Furthermore, good correlations of pyrolysis results were found with mineral content, solid-state 13C CPMAS NMR data and total N.The hydrological reconstruction based on depth records of plant markers and factor scores obtained by factor analysis of all quantified pyrolysis products, and the low contribution of Sphagnumto the graminoid-dominated Penido Vello peat allowed studying the effects of source and decay on the lignin composition. A large number of lignin pyrolysis products were quantified for peatland plants and for the three different peat fractions for a selection of 15 samples. Lignin composition of woody and graminoid plant species were compared as well as the lignin composition in different peat fractions, and their relation to source or decay was established.To determine whether the lignin parameters, derived from analysis of plants and peat fractions, can be used to reconstruct peat environment, they were applied to all 51 bulk peat samples of the upper meter of the Penido Vello core. The results show a strong effect of vegetation type and anaerobicity on generally-used lignin decomposition proxies, which indicates that such proxies are not reliable without information on the context.To examine the interaction between vegetation type and decomposition processes, the results of Sphagnum-dominated peat and graminoid-dominated peat were combined. In addition to the well-known pyrolytic marker from Sphagnum (4-isopropenylphenol), depth records of pyrolysis products specific for lichens and graminoids functioned well in both peatlands and are considered reliable markers for application in other peatlands. A number of other identified markers only functioned well within one of both peatlands. The different functioning of these markers in the two peatlands emphasises the importance of plant analysis prior to the use of pyrolytic biomarkers with low specificity, but also shows that supposedly non-specific pyrolysis products can be specific within a certain peatland ecosystem. The use of different peat fractions (NaOH-extractable and non-extractable peat) provided information on the degree of decomposition and allowed comparison with studies on peat humic acids and humin, and the generally applied colorimetric method to determine peat humification. Furthermore, the comparison of pyrolysates of extracts and residues for a selection of peat samples, in combination with factor analysis, allowed separation of the effects of source, and several stages of aerobic and anaerobic decay. Degradation of lignin-cellulose (vascular plants) and polyphenol-cellulose (Sphagnum) is discussed using the abundance of their markers (lignin moieties, levoglucosan and 4-isopropenylphenol) in pyrolysates of the different peat fractions, and gives insight into degradation mechanisms. The results indicated that, in Sphagnum litter, polyphenols are more easily degraded than polysaccharides. Comparison of pyrolysis results and C:N ratio showed that differences in litter quality between Sphagnum and vascular plants is a major factor that determines the variance of C:N with depth. Large part of the variation in C:N in Sphagnum-dominated peat is caused by decomposition rather than small increases of vascular plants upon drier conditions, while in graminoid-dominated peat this is not true and several processes may disturb the effect of mass loss on the C:N ratio. The C:N ratio can thus be a consistent decomposition proxy in Sphagnum-dominated peat but not in graminoid-dominated peat. Pyrolysis-GC/MS in combination with the applied research design provided detailed chemical information that gave insight in both vegetation and decomposition characteristics. This methodology thus has a high potential for the reconstruction of past environmental conditions.

Fertilisers received a lot of attention when growers first started using substrates. Since then the nutritional requirements of the plant have been largely driven by the need to reduce runoff emissions. In addition, more efficient use of fertilisers is playing a role. Until now growers went along with standerd fertiliser strategies. Now they are starting to adjust the nutrients given to suit the plant's needs.

Fertilisers received a lot of attention when growers first started using substrates. Since then the nutritional requirements of the plant have been largely driven by the need to reduce runoff emissions. In addition, more efficient use of fertilisers is playing a role. Until now growers went along with standerd fertiliser strategies. Now they are starting to adjust the nutrients given to suit the plant's needs.

The demand for high quality fruits and other plant material is increasing. New consumer demands involve taste, ripeness, and health-promoting compounds. These criteria are often related to the presence, absence and spatial distribution patterns of specific biochemical compounds in the food. This thesis deals with the role of spectral imaging for visualization and quantification of these biochemicals in plant material. I hope that it will contribute to the application of spectral imaging to sort plant products by their quality. Compared to traditional machine vision applications, with color cameras, or spectroscopic point measurements, without spatial information, spectral imaging is a new challenge in real-time sorting applications. Due to the additional complexity of the recording system, calibration of the system is much more complicated. Also the huge amount of data which comes from this system asks for methods like data reduction, and sophisticated analysis procedures. In this thesis several techniques for calibration, data-analysis, data-reduction, and measurement of the spatial distribution of compounds are described.

Specific food compounds, especially from fruits and vegetables, may protect against development of colon cancer. In this thesis effects and mechanisms of various phytochemicals in relation to colon cancer prevention were studied through application of large-scale gene expression profiling. Expression measurement of thousands of genes can yield a more complete and in-depth insight into the mode of action of the compounds. Effects of quercetin (a flavonoid present in e.g. apples and onions), curcumin (a spice used e.g. in curries) and resveratrol (present e.g. in grapes) were studied in cultured colon cancer cells. These studies confirmed some hypothesized mechanisms of action of these compounds (e.g. effects on cell cycle) and yielded new interesting leads (e.g. effects on proteasome genes, DNA repair genes, tubulin genes). In addition, expression profiles of a panel of 14 human cell lines derived from colonic tissue were compared and related to expression profiles of human colon biopsies from normal and tumor tissue. Changes in expression profiles of a subset of colon cancer-specific genes (as a biomarker set) in cultured colon cancer cells could be useful to translate in vitro results to the in vivo situation. In addition to the in vitro studies, effects of wheat bran, curcumin,rutinand benzyl isothiocyanate on colon carcinogenesis were studied in a rat model. Wheat bran and curcuminshoweda protective effect (lower tumor multiplicity after 8 months compared to the control group). Expression profiles of differentially expressed genes in small intestinal tissue at intermediate time points were predictive of colon tumor development at the end of the study, confirming a correlation between effects in small intestine and colon. In summary, the studies in this thesis demonstrate the potential of large-scale expression profiling in nutrition studies. These studies also demonstrated that although the technological advancements in large-scale gene expression analysis allow for the collection of 'whole genome' results, the challenge for the coming years will be to further exploit these data. Only when advances in the bioinformatics field lead to easier interpretation of large amounts of data from nutrigenomics studies, the large potential of nutrigenomics can become reality.

Fertilisers received a lot of attention when growers first started using substrates. Since then the nutritional requirements of the plant have been largely driven by the need to reduce runoff emissions. In addition, more efficient use of fertilisers is playing a role. Until now growers went along with standerd fertiliser strategies. Now they are starting to adjust the nutrients given to suit the plant's needs.