The glycaemic responses to various carbohydrate-rich foods are partly dependent on the rate at which the carbohydrate is digested and absorbed. The glycaemic index (GI) is a way of ranking foods according to their glycaemic response and is recommended as a useful tool in identifying starch-rich foods that give the most favourable glycaemic response. This investigation was undertaken to determine whether carbohydrate-rich foods with a low GI and a high content of dietary fibre (DF) could have beneficial metabolic effects in the insulin resistance syndrome. This question was addressed both in single-meal studies and in randomised controlled clinical trials. Starch-rich foods with low GI values incorporated into composite meals resulted in lower postprandial responses of both glucose and insulin than foods with a high GI in meals with an identical macronutrient and DF composition, in subjects with type 2 diabetes. After three weeks on a diet including low GI starchy foods metabolic profile was improved in subjects with type 2 diabetes, compared with a corresponding high GI diet. The glucose and insulin responses throughout the day were lower, the total and low density lipoprotein cholesterol was decreased, and the fibrinolytic activity was normalised. In subjects with impaired insulin sensitivity and diabetes low GI foods rich in soluble DF for breakfast gave a more favourable metabolic profile, with smaller glucose fluctuations from baseline during the day, than a breakfast with high GI foods low in DF. A low GI breakfast high in DF also resulted in lower responses of insulin and C-peptide after breakfast and a lower triacylglycerol response after a standardised lunch. However, none of the tested breakfasts improved the glucose and insulin responses after lunch. Similar results were obtained in obese subjects after including a breakfast with a low GI high in soluble DF for a period of four weeks in comparison with a breakfast with a high GI and low content of DF. These results support the therapeutic potential of a diet with a low GI in the treatment of diabetes and also in the treatment of several of the metabolic disturbances related to the insulin resistance syndrome.

Lichens are fascinating symbiotic systems, where a fungus and a unicellular alga, most often green (bipartite green algal lichens; 90% of all lichens), or a fi lamentous cyanobacterium (bipartite cyanobacterial lichens; 10% of all lichens) form a new entity (a thallus) appearing as a new and integrated organism: in about 500 lichens the fungus is associated with both a cyanobacterium and an alga (tripartite lichens). In the thallus, the lichen bionts function both as individual organisms, and as a symbiont partner. Hence, in lichens, the participating partners must both be able to receive and acquire resources from the other partner(s) in a controlled way. Lichens are particularly successful in harsh terrestrial environments. In part this is related to their poikilohydric nature and subsequent ability to repeatedly become desiccated and hydrated. Metabolic activity, i.e. photosynthesis, respiration, and for cyanobacterial lichens N2-fixation, is limited to periods when the thallus is suffi ciently hydrated. Mineral nutrients are mainly acquired from dry or wet deposition directly on the thallus. Taken together it then appears that lichens are to a large extent passively controlled by their environment, making their control over resource allocation and acquisition particularly challenging. The aim of this thesis was to investigate resource acquisition and allocation processes in different lichens, and to see how these respond to changes in resource availability. This was done by following lichen growth in the fi eld during manipulation of water, light, and nutrient supply, and by assessing the responses of both the integrated thallus as well as the individual bionts. As a fi rst step, resource allocation and acquisition was investigated for a broad range of lichens aiming to determine the magnitude of metabolic variation across lichens. Seventy-fi ve lichen species were selected to cover as broad a spectrum as possible regarding taxonomy, morphology, habitat, and nitrogen requirements. The lichens had invested their nitrogen resources so that photosynthetic capacity matched respiratory carbon demand around a similar equilibrium across the contrasting species. Regulation of lichen growth was investigated in another study, using the two tripartite species Nephroma arcticum and Peltigera aphthosa, emphasizing the contribution of both internal and external factors. The empirical growth models for the two lichens were similar, showing that weight gain is to a higher extent dependent on those external factors that regulate their photosynthesis, whilst area gain is more controlled by internal factors, such as their nitrogen metabolism. This might be inferred from another study of the same species, where nitrogen manipulations resulted in an undisturbed weight gain, a similar resource allocation pattern between the bionts, but a distorted area gain. Aiming to investigate lichen nitrogen relations even further, lichens’ capacities to assimilate combined nitrogen in the form of ammonium, nitrate and amino acids were assessed using 14 contrasting boreal species. All these had the capacity to assimilate all the three nitrogen forms, with ammonium absorption being more passive, and nitrate uptake being low in bipartite cyanobacterial lichens. Differences in uptake capacities between species were more correlated to photobiont than to morphology or substrate preferences. Finally, to investigate intra-specifi c plasticity in relation to altered nutrient supply, resource investments between photo- and mycobiont were investigated in the two bipartite green algal lichens Hypogymnia physodes and and Platismatia glauca in a low and a high nutrient environ- in a low and a high nutrient environ- ment. In both species, more of the resources had been directed to the photobiont in the high nutrient environment also increasing their overall carbon status. Taken together, my studies indicate that in spite of the apparent passive environmental control on lichen metabolism, these symbiotic organisms are able to both optimize and control their resource acquisition and allocation processes.

The physiological benefits of flaxseed against pathological disturbances, such as cancers and heart diseases, are mainly attributed to its high lignan content. This study (Experiment 1) examined the application of pressurized low polarity water (PLPW) for extraction of lignans, proteins and carbohydrates from defatted flaxseed meal. Key processing conditions included temperature (130, 160, 190°C), solvent pH (4, 6.5 and 9), solvent to solid ratio (S/S) (90, 150 and 210 mL/g) and introduction of co-packing material (0 and 3 g glass beads). The addition of 3 g glass beads as co-packing material facilitated extraction by enhancing surface contact between the liquid and solid thus shortening extraction time. Elevated temperature accelerated the extraction rate by increasing the solid diffusion coefficient thereby reducing the extraction time. The maximum yield of lignans (99 %) was obtained at temperatures ranging from 160°C to 190°C, with solvent volume of 180 mL (90 mL/g meal) at pH 9. Optimal conditions for protein extraction (70 %) were pH 9, extraction volume of 420 mL (210 mL/g meal) and 160°C. Total carbohydrates yield was maximized at 50% recovery at pH 4 and 160°C with 420 mL solvent (210 mL/g meal). Increased temperature accelerated extraction, thus reducing solvent volume and time to reach equilibrium. For the extraction of proteins, however, a temperature of 130-160°C is recommended, as proteins are vulnerable to thermal degradation due to heat decomposition. The effects of flow rate and geometric dimensions for extraction of lignans and other flaxseed meal bioactives were further investigated in Experiment 2, based on the variables optimized in the previous experiment. Defatted flaxseed meal was extracted with pH 9 buffered water with meal to co-packing glass beads ratio of 1:1.5 at 5.2 MPa (750 psi) and 180°C. The aqueous extracts were analyzed for lignan, protein and carbohydrate using HPLC and colorimetric methods. The optimal extraction yields for lignan, protein and carbohydrate were found at flow rates of 1 to 2 mL/min with bed depth between 20 and 26 cm and a S/S ratio of 40 to 100 mL/g. The combination of low flow rate and high bed depth allowed the use of lower S/S ratio with reduced total solvent volume consumption. This study also evaluated the mass transfer kinetics governing the process of lignan extraction from flaxseed meal in a fixed bed extraction cell. Diffusion of solute into the continuously flowing solvent was mainly responsible for the mass transfer mechanism as flow rate did not increase proportionally with the yield and rate of extraction. The extraction kinetics were studied on the basis of two approaches: Fick’s diffusion equation and a two-site exponential kinetic model. The proposed two-site exponential kinetic model corresponding to the two-stage extraction (rapid and slow phases) successfully described the experimental data. Diffusivities attained from Fick’s diffusion model ranged from 2 x 10-13 to 9 x 10-13 m2s-1 while mass transfer coefficients were between 4.5 x 10-8 and 2.3 x 10-7 ms-1 for extraction of lignans at 180°C, pH 9 with 1:1.5 meal to co-packing material ratio. / February 2007

Carbohydrates are a family of polyfunctional natural products and can be chemically modified in numerous ways. The primary significance of carbohydrates rests in their importance in biological functions. A particular class of sugars, namely, 2-deoxy or C-2 modified sugars has received a special attention, due to their importance in biological functions. These sugars are defined as carbohydrates carrying a hetero-atom, other than the hydroxyl group, and their derivatives. There is an ever-leading requirement to synthesize various carbohydrates-containing natural and un-natural products, such as, oligonucleotides, glycopeptides, antitumor drugs and cardiac glycosides, having C-2 modified sugars. Chapter 1 describes various synthetic modifications, particularly at the C-2 of a monosaccharide, as relevant to the work presented in this Thesis. 1, 2-Unsaturated glycopyranosides, namely, glycals, are versatile synthetic intermediates for the elaboration to a number of functionalized glycosyl derivatives. A major utility of the glycals is their conversion to the 2-deoxy glycosyl derivatives. In a programme, it was desired to identify a synthetic method to prepare 2-deoxy sugar derivatives that are endowed with an anomeric activation. In particular, a thioglycoside activation was desired. In the event, a methodology was identified, which allowed the synthesis of activated 2-deoxy-1-thioglycosides.The method involved reaction of a glycal with EtSH, in the presence of ceric ammonium nitrate (CAN) as the catalyst. The reaction was applicable to different epimeric glycals. Apart from the 2-deoxy-1-thioglycosides, formation of the 2, 3-unsaturated enoses, corresponding to the Ferrier product, also observed. Optimal conditions for the formation of the 2-deoxy-1-thioglycosides were identified (Scheme 1) and the reaction was proposed to proceed through a radical oxocarbenium ion and a thiolate intermediate. (Fig) Scheme1 Upon synthesis of 2-deoxy-1-thioglycosides, few glycosylation reactions with both aglycosyl and glycosyl acceptors were performed and the α-anomeric 2-deoxy glycosides were obtained exclusively. Chapter 2 summarizes synthesis, characterization of 2-deoxy-1-thioglycosides and their glycosyl donor properties towards several glycosyl acceptors. Many naturally-occurring antibiotic and antitumor drugs contain 2-deoxy glycosides as important structural components. For example, 2,6-dideoxy-hexopyranoses are common structural units of chromomycin A3, olivomycin A and mithramycin. The most common structural features of these molecules are: (i) the presence of 2-deoxy sugar residues and (ii) the sugar residues are connected to the aromatic moiety, through a β-glycosidic linkage. The synthesis of these biologically important 2-deoxy glycosides encounters difficulties, due to the absence of stereoelectronic influences at C-2 of the 2-deoxy glycosyl derivatives. Direct glycosylation of phenols and naphthols with activated 2-deoxy-1-thio-glycosides, in the presence of the thiophilic activator N-iodosuccinimide/triflic acid (NIS/TfOH), lead to the formation of the α-anomer, as the major glycosylated product (Scheme 2). (Fig) An effort was under taken to identify methods to prepare the 2-deoxy aryl glycosides, in the β-anomeric configuration. A nucleophilic substitution reaction was anticipated to lead to the formation of β-anomeric glycosides. A halide substitution at C-1 for an effective nucleophilic substitution was adopted. Thus, conversion of the activated 2-deoxy-1-thioglycosides with Br2 in the first step, followed by reaction of the resulting bromide with aryloxy anions, led to the facile conversion to 2-deoxy glycosides in a nearly quantitative f-anomeric configuration at C-1(Scheme 3). Scheme 3 (Fig) Chapter 3 presents details of the methodologies that allow a facile preparation of each of the anomers of aryl 2-deoxy-D-glycosides from a common precursor, namely, 2-deoxy-1-thio-glycosides. An easy access to activated 2-deoxy-1-thioglycosides from the 1, 2-unsaturated sugar and their synthetic utility towards various glycosyl and aglycosyl acceptors led towards synthesis of 2-deoxy disaccharides. Synthesis of six new 2-deoxy-arabino-hexopyranosyl and 2-deoxy-lyxo-hexopyranosyl sugar containing disaccharides were accomplished. These are: (i) 2-deoxy-α-D-arabino-hexopyranosyl-(1→4)-D-glucopyranose (2'-deoxy maltose); (ii) 2-deoxy-α-D-lyxo-hexopyranosyl-(1→4)-D-glucopyranose; (iii) 2-deoxy-α-D-arabino-hexopyranosyl-(1→4)-2-deoxy-D-arabino-hexopyranose (2,2'-dideoxy maltose); (iv) 2-deoxy-α-D-lyxo- hexopyranosyl-(1→4)-2-deoxy-D-arabino-hexopyranose; (v) α-D-glucopyranosyl-(1→4)-2 deoxy-D-arabino-hexopyranose (2-deoxy maltose) and (vi) β-D-galactopyranosyl-(1→4)- deoxy-D-arabino-hexopyranoside (2-deoxy lactose). The 2'-deoxy and 2, 2'-dideoxydisaccharides were synthesized using a 2-deoxy glycosyl donor and a normal glycosyl acceptor (in case of 2'-deoxy disaccharides) and a 2-deoxy glycosyl acceptor (in case of 2, 2'-dideoxy disaccharides) with a free OH group at C-4, while the remaining hydroxyl groups protected suitably (Scheme 4). Scheme 4 (Fig) On the other hand, the syntheses of 2-deoxy disaccharides were initiated from a D-maltose and D-lactose, respectively. The conversion of these disaccharides to a disaccharide glycals was targeted first and conversion of these glycals to a 2-deoxy-1-thioglycosides or a 2-deoxy-1-acetates, followed by a hydrolysis of the thiol moiety or the acetate group, afforded the 2-deoxy disaccharides (Scheme 5). (Fig) Chapter 4 describes synthesis, characterization of 2-deoxy, 2,2'-dideoxy and 2'-deoxy disaccharides. Continuing the efforts to establish the utility of 2-deoxy-1-thioglycosides as potential glycosyl donor, synthesis of 2-deoxy cyclic and linear oligosaccharides was undertaken. Prominent among cyclic oligosaccharides are the cyclodextrins. Due to their unique structural and physical properties, cyclodextrins find manifold applications. Known methods to synthesize cyclic oligosaccharides are (i) the cyclization of linear oligosaccharides to produce the cyclic oligosaccharides and (ii) the synthesis of designed monomers and subjecting them to cyclooligomerization protocols. The cyclooligomerization was adopted to synthesize new types of 2-deoxy cyclic-and linear oligosaccharides. After a series of trials, a disaccharide monomer, namely, ethyl 4-O-(6-O-benzoyl-2,3-di-O-methyl-α-D-glucopyranosyl)-2-deoxy-3,6-di-O-methyl-arabino-hexopyranoside (1), was identified as a suitable monomer for thecyclooligomerization protocol. For an effective oligomerization, the concentration of the monomer and the choice of the reagents are important. The reaction was conducted at three different monomer concentrations, 2 mM, 10 mM and 25 mM, using two thiophilic activators, namely, (i) NIS/TfOH and (ii) NIS/AgOTf. Better yields of the cyclic oligosaccharides, namely, the cyclic tetrasaccharide (2) (40 %) and cyclic hexasaccharide (3) (25 %), were isolated when the monomer (1) concentration was 25 mM and NIS/TfOH acid was used as the promoter (Scheme 6). The formation of linear disaccharide (4) (10 %) and tetrasaccharide (5) (18 %) was also observed at this concentration. On the other hand, when the reaction of the monomer was performed in the presence of NIS/AgOTf, the oligomerization reaction led to the formation of linear oligosaccharides, consisting of di-to eicosa-saccharides. Synthesis of different monomers, their characterization and oligomerization reaction using these monomers through a polycondensation protocol are discussed in Chapter 5. Scheme 6(fig) In summary, the Thesis establishes the chemistry of 2-deoxy sugars, formation of activated 2-deoxy sugars, formation of alkyl and aryl glycosides, 2-deoxy disaccharides, 2-deoxy cyclic and linear oligosaccharides. Routine physical methods were used to characterize the newly formed 2-deoxy sugars and the oligosaccharides. Single crystal X-ray structural determination was performed for an aryl 2-deoxyglycosides, which provided the solid state configurational features of the 2-deoxy pyranose. (For structural formula pl see the pdf file)

Avec les craintes actuelles sur la péjoration du climat, l'enjeu pour des tourbières<br />abandonnées après exploitation est d'y permettre la réinstallation d'une production végétale<br />susceptible d'y réassurer la pérennité de la séquestration du carbone à long terme. Dans cette<br />perspective, les objectifs de cette étude étaient d'identifier des indicateurs de la reprise des<br />processus d'accumulation de la matière organique (MO) dans des tourbières anciennement<br />exploitées, actuellement à des stades de régénération spontanée différents. Dans le but d'identifier<br />l'origine de la MO et d'appréhender les modalités de sa dégradation, une combinaison d'approches<br />micromorphologiques, géochimiques globales et moléculaires a été appliquée à des échantillons de<br />tourbe brute et de fractions fines (< 200μm), ainsi qu'à des végétaux-sources typiques. La MO<br />accumulée dans les niveaux superficiels montre une composition très contrastée (forts C/N,<br />prédominance des tissus hérités bien préservés, fortes teneurs en sucres...) par rapport à celle,<br />beaucoup plus humifiée, des compartiments sous-jacents. Ceci a permis de délimiter précisément la<br />tourbe régénérée de la tourbe du catotelm. Contrairement aux stades de régénération précoces (5-10<br />ans), la composition de la MO des stades plus avancés (30-40 ans) est comparable à celle de la zone<br />non exploitée (MO homogène, dominance des marqueurs de sphaignes, forts C/N). Une analyse en<br />composante principale (ACP) a permis de proposer des trajectoires de régénération distinctes pour<br />chacun des sites d'étude, en fonction de leur végétation et de leur mode d'exploitation.<br />Globalement, la bonne préservation des polysaccharides dans la tourbe, clairement mise en lumière<br />dans cette étude, en fait de bons indicateurs de régénération.

Abstract It appears that "carbohydrate loading" may enhance the performance of resistance training, but studies on CHO supplementation prior to a resistance-training bout are limited and have resulted in conflicting findings. PURPOSE: To investigate the effects of pre-exercise CHO supplementation on high-intensity (>75% 1RM) resistance training performance for resistance-trained women during an acute bout of resistance exercise. METHODS: Thirteen resistance trained female participants (21.9 ± 4.8 yrs; 64.5 ± 3.0 in; 137.0 ± 14.8 lbs) came to the Exercise and Performance Nutrition Laboratory on three separate occasions; the day of the Familiarization Trial (FT) and the two Exercise Testing sessions (ET1 and ET2, respectively) all separated by seven days. Familiarization testing determined each participant's 1RM of the bench press and leg press and then 75% of the bench press 1RM and 85% of the leg press 1RM was determined. The participants were then randomly assigned to either the CHO or P treatment session using a double blind, counterbalanced technique in a cross-over design with each participant consuming 1.0 g CHO/kg body weight or a non-caloric P beverage 60 minutes before beginning the exercise bout for each ET. The total volume of weight lifted during five sets of the bench press, the total volume of the weight lifted during five sets of the leg press, and whole body total lifting volume was analyzed by a two-way repeated measures within subjects ANOVA with significance set at P <.05. RESULTS: There was no statistically significant difference between the CHO and P treatments in the three variables analyzed. Specifically total volume of weight lifted in pounds during five sets of the bench press was 3,200 (± 912) and 3,152 (± 852) (p = 0.655), total volume of weight lifted during five sets of the leg press was 44,004 (± 29,711) and 37,705 (± 19,681) (p = 0.136), and total lifting volume was 47,204 (± 30,399) and 40,857 (± 20,434) for the CHO and P treatment, respectively (p = 0.138). CONCLUSIONS: Pre-exercise CHO supplementation does not improve high-intensity resistance training performance for resistance-trained women during an acute resistance training session. PRACTICAL APPLICATIONS: It is evident that consuming CHO 60 minutes prior to performing resistance training exercises will not increase the number of sets, repetitions, or total work volume completed during acute high-intensity (>75% 1RM) resistance training sessions for women. During lower-intensity resistance training sessions, however, pre-exercise CHO supplementation may provide ergogenic effects and enhance resistance-training performance.

Grünlandfutter mit einem hohen Ertrag und gutem Futterwert ist eine Grundvoraussetzung für die effiziente Produktion von wiederkäuenden Nutztieren. Im Zuge des prognostizierten Klimawandels werden sich die Niederschlagsmuster ändern und das Auftreten von Extremwetterereignissen, wie temporärer Trockenheit, wird sich erhöhen. Besonders produktives Grünland benötigt aber eine ausreichende und regelmäßige Wasserversorgung während der Wachstumsperiode. Deshalb werden die Futterproduktion von Grünland, die Ertragsstabilität und der Futterwert von temporärer Trockenheit beeinflusst werden. Aus diesem Grund sind Anpassungsstrategien nötig, um eine zukünftige und nachhaltige Grünlandfuttererzeugung zu sichern. Erhöhte pflanzliche Biodiversität wird oft als Möglichkeit angesehen, Funktionen von Ökosystemen, wie Produktivität und Futterwert, im Grünland zu verbessern. Es gibt eine fortlaufende Diskussion wie eine erhöhte Artenzahl auf Stress, besonders Trockenstress, reagiert und wie dabei Produktivität, Futterwert und Wassernutzung beeinflusst werden. Andere Untersuchungen zeigten, dass Artidentität und die Zusammensetzung der funktionellen Gruppen wichtige Faktoren für Produktivität und Futterwert sind. Auf Grund dessen haben wir von Juli 2009 bis Juni 2011 ein Trockenstressexperiment in einer Vegetationshalle durchgeführt. Verschiedene temporäre Trockenstressereignisse wurden in drei Aufwüchsen in zwei Vegetationsperioden durchgeführt. Die klimatischen Verhältnisse in der Vegetationshalle folgten normalen saisonalen Verläufen mit Frost im Winter und höheren Temperaturen im Sommer. Trockenstress wurde induziert, indem, nach einer anfänglichen Bewässerung, die Wasserversorgung für einen bestimmten Zeitraum eingestellt wurde. Die Wasserverfügbarkeit des Bodens konnte dabei immer kontrolliert werden. Für das Experiment wählten wir ertragsstarke und landwirtschaftlich nutzbare Arten des Grünlands der gemäßigten Zonen aus. Die Arten wurden in Monokultur und Drei- sowie Fünfartenmischungen gesät und enthielten die funktionellen Gruppen Leguminose (Trifolium repens L.), Gras (Lolium perenne L., Dactylis glomerata L.) und Kraut (Plantago lanceolata L., Taraxacum officinale F.H. Wigg. agg.). Der von uns gewählt Umfang der Artenzahl zeigte schon in anderen Biodiversitätsexperimenten einen Einfluss auf die Produktion. Untersucht wurden die Effekte von Artenzahl und funktionellen Gruppen auf Ertrag, Ertragsstabilität, Wassernutzung und Futterwert (Rohprotein, wasserlösliche Kohlenhydrate, neutrale und saure Detergenzienfasern). Als Indikatoren für die Ertragsentwicklung und die agronomische Wassernutzungseffizienz (Verhältnis von Ertrag zu Wasserverbrauch) dienten der Stickstoffertrag und die Stickstoffkonzentration der Bestände sowie δ13C Signaturen, sowohl mit unlimitierter Wasserversorgung als auch mit Trockenstress. Überdies führten wir 2009 ein Kurzzeitfeldexperiment auf einem alten Grünlandbestand auf dem Versuchsgut der Universität Göttingen in Reliehausen durch. In diesem Versuch wurde ebenso der Einfluss von Trockenstress und Artenzahl auf den Ertrag und die Wassernutzung untersucht. Unsere Daten zeigten, dass Trockenstress die Produktivität verringert und die Wassernutzung beeinflusst, beides abhängig von der Stärke des Stresses. Bei moderatem Stress war die agronomische Wassernutzungseffizienz unverändert oder stieg leicht an, bei starkem Stress verringerte sie sich jedoch. Der Stickstoffertrag und die Stickstoffkonzentration waren brauchbare Indikatoren für die agronomische Wassernutzungseffizienz, wohingegen δ13C weniger geeignet war. Die agronomische Wassernutzungseffizienz wurde von Stickstoff erhöht. Es gab keinen oder nur einen sehr geringen Einfluss von Trockenstress auf den Futterwert. Saisonale Effekte hatten mehr Einfluss auf den Futterwert. Allgemein scheint der Ertragsrückgang wichtiger als die Veränderungen des Futterwerts zu sein. Die Artenzahl beeinflusste den Futterwert und die Ertragsstabilität über die Vegetationsperiode nicht. Mit Hilfe des “sampling effect“ (Probennahmeeffekt) können der manchmal positive Einfluss der Artenzahl auf den Ertrag und die agronomische Wassernutzungseffizienz und der Rückgang dieses Einflusses unter Trockenheit erklärt werden. Mit erhöhter Artenzahl stieg der Anteil der leistungsfähigen, aber trockenheitssensitiven Leguminose. Weiterhin gab es einen Hinweis, dass die Artenzahl die Geschwindigkeit des Wasserverbrauchs erhöht. Die Ergebnisse des Feldexperiments bekräftigten die Befunde bezüglich der Effekte des Trockenstresses, des Ertrages und der Wassernutzung. Aus diesen Gründen kann die „insurance hypothesis“ (Versicherungshypothese), die besagt, dass eine erhöhte Artenzahl Ökosystemfunktionen gegenüber Umweltveränderungen stabilisieren kann, nicht bestätigt werden. Jedoch waren die funktionellen Gruppen wichtige und bestimmende Faktoren der Leistung unter nicht Wasser limitierten Bedingungen und Trockenstress. Die Leguminose hatte besonders auf Ertrag, agronomische Wassernutzungseffizienz und Rohprotein einen positiven Einfluss, jedoch erhöhte sie auch den Wasserverbrauch und die saisonale Variabilität. Gräser stabilisierten den Ertrag und den Wasserverbrauch und erhöhten die wasserlöslichen Kohlenhydrate sowie die Faserfraktionen, während sie den Ertrag und die agronomische Wassernutzungseffizienz unter den stickstofflimitierten Bedingungen unseres Experiments verringerten. Die funktionelle Gruppe Kräuter zeigte ähnliche Ergebnisse bezüglich Ertrag und Wassernutzung, aber sie erhöhte das Rohprotein. Unsere Ergebnisse demonstrieren, dass die vorhergesagte Zunahme von Trockenstressereignissen die Produktion reduzieren und die Wassernutzung ändern wird. Änderungen im Futterwert werden dabei weniger wichtig als der Ertragsrückgang sein. Für die Produktion, die Wassernutzung und den Futterwert wird die Artenanzahl weniger relevant sein als die funktionelle Zusammensetzung von Grünland. Deshalb wird eine angepasste Grasnarbenzusammensetzung für die Sicherung der Produktion von wiederkäuenden Nutztieren unter den Bedingungen des erwarteten Klimawandels Bedeutung erlangen.

There is increasing interest in special heptose carbohydrates, their multifunctional roles from a plant physiological view point in fruit growth and development as well as in the whole plant in general due to their potential in mitigating photo-oxidative injury to the whole plant system and the image of avocado as ‘health fruit’. Studies have been carried out to investigate the role of avocado heptoses, rare carbohydrates predominantly produced in avocado. Several authors have documented various research findings and speculated on multifunctional roles of avocado special sugars. However, few reports have made an attempt to elucidate the multifunctional roles of avocado heptose carbohydrates as: ‘sources of energy’, storage and phloem-mobile transport sugars, and precursors for formation of antioxidants. Assessing the avocado carbohydrates over the plant growth and development during ontogeny may, therefore, offer clues to better understand whole plant behaviour. Plant sampling was carried out over different developmental stages. Using plants grown in the light versus etiolated seedlings; sugar determinations were also done to determine what sugar is produced from which storage organs. The sugars were extracted and analysed by isocratic HPLC/RID. The embryo had 47.11 % hexose and 52.96 % heptose sugars. The seed, however, also released significant amounts of D-mannoheptulose (7.09 ± 1.44 mg g-1 d. wt) and perseitol (5.36 ± 0.61 mg g-1 d. wt). Similarly fruit and leaf tissues had significant amounts of heptoses relative to hexoses at specific phenological stages. In postharvest ‘readyto-eat’ fruit the following carbohydrate concentrations were as follows:exocarp heptoses 13 ± 0.8; hexoses 4.37 ± 1.6 mg g-1 d. wt, mesocarp heptoses 8 ± 0.2; hexoses 3.55 ± 0.12 mg g-1 d. wt), seed heptoses (only perseitol) 13 ± 1.1; hexoses 5.79 ± 0.53 mg g-1 d. wt. The results of this experiment was the first to demonstrate that the heptoses D-mannoheptulose, and its polyol form, perseitol, are found in all tissues/organs at various phenological stages of avocado growth and development. Secondly, heptoses, as well as starch are carbohydrate reserves that are found in avocado. The heptoses, beyond being abundantly produced in the avocado plant, are also found in phloem and xylem saps as mobile sugars. The study also presents data on the interconversion of the C7 sugars Dmannoheptulose and perseitol. It is deduced that D-mannoheptulose can be reduced to perseitol, and perseitol can also be oxidized to D-mannoheptulose by enzymes present in a protein extract of the mesocarp. The potential catalyzing enzyme is proposed to be an aldolase, as electrophoretic determinations prove the presence of such an enzyme during various stages of development in various plant organs. Avocado heptoses play an important role in plant growth and development and in fruit in particular. Moreover, they are reported as sources of anti-oxidants, and contribute significantly to fruit physiology if they function in coordination with other anti-oxidants in fruit tissues. To evaluate the presence of anti-oxidant systems throughout avocado fruit development, various tissues were analysed for their total and specific anti-oxidant compositions. Total anti-oxidant levels were found to be higher in the exocarp and in seed tissue than in the mesocarp. While seed tissues contained predominantly ascorbic acid (AsA) and total phenolics (TP), the anti-oxidant composition of the mesocarp was characterised by the C7 sugar, D-mannoheptulose. Among the anti-oxidant enzymes assayed, peroxidase (POX) and catalase (CAT) were present in higher concentrations than superoxide dismutase (SOD) in mesocarp tissue. Different anti-oxidant systems seem to be dominant within the various fruit tissues. Carbohydrates are the universal source of carbon for cell metabolism and provide the precursors for the biosynthesis of secondary metabolites, for example via the shikimic acid pathway for phenols. The preharvest free and membrane-bound phenols, catechin and epicatechin, are distributed differently in the various fruit tissues. Membrane-bound and free phenols also play a role as anti-oxidants, with free ones being more important. KSil (potassium silicate) application to fruit as postharvest treatment was used to facilitate the release of conjugates to free phenols via lysis. This treatment improved fruit shelf life. Western blotting also revealed that postharvest Si treatment affects the expression of enzymatic anti-oxidant-catalase (CAT). Overall the thesis results revealed that C7 sugars have anti-oxidant properties and that D-mannoheptulose is the important anti-oxidant in the edible portion of the avocado fruit. Dmannoheptulose is furthermore of paramount importance as a transport sugar. Perseitol on the other hand acts as the storage product of D-mannoheptulose, which can be easily converted into D-mannoheptulose. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Disturbances, such as herbivory and fire are commonplace in savanna ecosystems. The effects of herbivory and fire on growth and defences of adult trees is a much studied filed in plant ecology. However, there are comparatively few studies that have investigated the effects of herbivory and fire on seedling growth, defences and establishment. African Acacia trees are common and widespread, and are suggested to be keystone species in savanna ecosystems. They have been shown to significantly positively increase soil characteristics, such as soil moisture and infiltration, while also increasing spatial heterogeneity of savannas. These trees are distinguishable by their array of physical and chemical defences. Physical defences are either in the form of spines (physiologically costly to produce, thus considered inducible) or prickles (physiologically cheap to produce, thus considered constitutive), while condensed tannins are the most common form of chemical defences. Adult Acacia trees have been shown on several occasions to be highly resilient to disturbance events, primarily due to their large size. However, the effects of herbivory and fire on Acacia seedlings have been little studied despite their apparent importance for our understanding of African savanna ecosystem functioning. In two separate experiments, this thesis aimed to investigate the individual and combined effects of simulated herbivory and fire on the regrowth, defences, and total non-structural carbohydrates (TNC) of the seedlings of several Acacia species, while also testing the Resource Availability Hypothesis (RAH) (14 Acacia species) and the Expanded Growth-Differentiation Balance Hypothesis (GDBH) (three Acacia species). The RAH (Coley, Bryant & Chapin 1985) and the GDBH (Loomis 1932) both assume that arid-adapted (resource-poor) species are slow growing, with low tissue turnover rates. Contrastingly, humid-adapted (resource-rich) species have fast growth rates and thus a high tissue turnover rate. Therefore, arid-adapted species are predicted to invest more carbohydrate reserves in defence after a disturbance event, in order to defend new photosynthetic material. Conversely, humid-adapted (resource-rich) species are predicted to invest carbohydrate reserves into increased growth after a disturbance event, in order to compensate for tissue loss. The first greenhouse experiment found that, in accordance with the RAH, humid-adapted species displayed elevated growth rates compared to arid-adapted species. Overall, defences significantly increased after herbivory, but significantly decreased after fire. Herbivory was also shown to significantly reduce TNC stores in roots more than fire. We found that arid-adapted species did indeed invest more carbohydrate stores (TNC) into defence, and displaying an increase in spine and prickle abundance, spine and prickle length, and condensed tannin concentration. Humid-adapted species displayed an increase in growth rather than in defence, with the majority of species only increasing one defensive trait. Humid-adapted species also displayed significant trade-offs (negative correlations) between new stem growth and defence traits, while arid-adapted species overall did not display any significant trade-offs between stem growth and increased defences. The majority of arid-adapted species also displayed an allometric effect for spine abundance and length, with an increase in one trait led to an increase in the other. Prickles were found to be inducible, despite the assumption that due to low physiological cost, they are no inducible. Herbivory and fire were shown to not be substitutable in their effects on Acacia seedlings in a controlled experimental setting. The second greenhouse experiment tested the Expanded Growth-Differentiation Balance Hypothesis (GDBH) in the seedlings of A. erioloba, A. karroo, and A. nilotica using five levels of nutrient availability. Overall, spine abundance and spine length displayed a unimodal trend in all three species, with spine abundance and spine length being greatest at a nutrient availability of 800 mg/ ℓ. Spine abundance, spine length and condensed tannins increased significantly after herbivory, but were shown to significantly decrease after fire. We found that with an increase in nutrient availability, the growth of stems and roots, along with the production of TNC in roots and stems of all species significantly increased. Our data provide mixed support for the assumptions and predictions of the expanded GDBH. The regrowth of stems and physical defences were consistent with the GDBH. Chemical defences (i.e. condensed tannins) were however, inconsistent with the predictions of the GDBH. We have shown that Acacia seedlings are highly resilient to disturbance events, while the growth responses of Acacia seedlings are underpinned by TNC stores in roots. Simulated herbivory and fire are often substituted for one another in controlled experiments. However, we have shown that the effects of herbivory and fire have significantly different effects on regrowth patterns of Acacia seedlings. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Adolescent athletes of this era are more pressurized than adolescents of previous generations to perform at an optimum level (Micheli & Jenkins 2001, p49). The importance of winning can result in adolescent athletes developing inappropriate nutritional practices such as neglecting hydration and consuming insufficient carbohydrate (Micheli & Jenkins 2001, p57). Consuming insufficient fluid leads to dehydration which reduces a soccer player’s ability to continue training. Consuming inadequate carbohydrate reduces performance and blood glucose levels during training. This study aimed to determine the hydration status, fluid and carbohydrate intake of male, adolescent soccer players during training. A cross-sectional study was conducted among 122 amateur male, adolescent soccer players (mean age = 15.8 ± 0.8 years; mean BMI = 20.4 ± 2.0 kg/m2). The players’ hydration status before and after training, was measured using urine specific gravity and percent loss of body weight. Their carbohydrate intake, as well as the type and amount of fluid consumed, were assessed before, during and after training. A questionnaire was administered to determine the players’ knowledge regarding the importance of fluid and carbohydrate for soccer training. The study had an 87.1% response rate. The mean environmental conditions did not predispose players to heat illness. However, the players were at risk of developing heat illness during six of the 14 training sessions. Although the mean urine specific gravity indicated that players were slightly dehydrated before and after training, 43.8% of players were very or extremely dehydrated before training and 53.6% after training. A few (3.3%) were extremely hyperhydrated before training and after training (7.0%). On average players lost less than 1% of body weight during training and less than 3% of players dehydrated more than 2%. Players consumed mainly water before (289.17 ± 206.37 ml), during (183.20 ± 158.35 ml) and after (259.09 ± 192.29 ml) training. More than 90% stated that water was the most important fluid to consume before, during and after training. Very few (4.7%) correctly stated that carbohydrate should be consumed before, during and after training. Players were found to be slightly dehydrated before and after training and therefore were not consuming enough fluids during training. Players consumed inadequate amounts and types of fluid and carbohydrate. This not only compromises their performance but also health. Players were not aware of the importance of fluid and carbohydrate for soccer training. This study is unique in that it focused on the carbohydrate and hydration practices of socioeconomically disadvantaged adolescent soccer players during training. The study sample therefore represents a high risk group about which there is limited published data both locally and internationally. This study generated important baseline information which was lacking before on the hydration status, fluid and carbohydrate intake of adolescent soccer players in South Africa. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.