M.Sc. / Wheat is one of the most extensively grown small grain crops in Southern Africa. It is a staple food source used by humans, animals and other living organisms around the globe (Feldman, 2001). One of the major threats of wheat production in South Africa is the Russian wheat aphid (RWA), (Kurdjumov), (Diuraphis noxia, Homoptera: Aphididae) (Brooks et al., 1994; Du Toit & Walters, 1984). The RWA was first described as a pest in South Africa in 1978 and in the US in 1986. Thereafter it was rapidly reported as becoming a major pest of cereals in these countries (Brooks et al., 1994; Du Toit & Walters 1984). A short life span, asexual reproduction, the development of resistance towards insecticides and rapid colonisation of the host plant are all factors that have made the management of the RWA a difficult task (Dogimont et al., 2010; Hein et al., 1998). As a result of complications such as these, host plant resistance is the most viable option to counter the RWA (Dogimont et al., 2010). The method of feeding of the RWA is detrimental to the plant as they insert their stylets into, and feed primarily from, the phloem sieve elements. This damages the plants through nutrient drainage (Dixon, 1985; Klingler et al., 2009) and results in a variety of symptoms, the most common being chlorosis, necrosis, wilting, stunting, curling of the leaves (which provides the pest with a sheltered environment protected from predators and pesticides), misshapen or nonappearance of new growth, and localised cell death at the site of aphid feeding. The RWA elicits an increase in essential amino acids in the phloem sap, by triggering the breakdown of proteins in infested wheat leaves (Burd & Burton, 1992; Du Toit, 1986; Haley et al., 2004; Ma et al., 1998; Miller et al., 2001; Walters et al., 1980). It also reduces transport of labelled tracers (amino acids) from the feeding site to the roots and other sinks in the plant. This increases the nutrient concentration at the site of aphid feeding by increasing the import of resources from other sites in the plant, mobilising local resources and blocking their export to other organs. The damage of the foliar tissue that occurs as a result of the RWA feeding is thought to play a role in the pest’s ability to increase the nutritional quality of the host plant (Botha et al., 2006; Goggin, 2007; Shea et al., 2000).

M.Sc. (Botany) / Wheat is the second most important grain crop produced in South Africa. It is mostly used for human consumption (e.g. biscuits, rusks, breakfast cereals, and bread) with the remainder being used as seed and animal feed. Wheat is also used for production of alcohol for ethanol, absorbing agents for adhesives, disposable diapers and industrial uses as starch on coatings (Department of Agriculture, Forestry and Fisheries, 2011). The leading wheat producing areas in South Africa since 1994 are the Western Cape (38 %), Free State (26 %) and Northern Cape (17 %) (Department of Agriculture, Forestry and Fisheries, 2011). There are two main classes of cultivated wheat, these are durum wheat (Triticum durum) that contributes 5 % and common or bread wheat (Triticum aestivum L.), which contribute 95 % of the world wheat production (Kiplagat, 2005). One of the major threats to wheat production in South Africa and other countries is the Russian wheat aphid (RWA), (Kurdjumov), (Diuraphis noxia, Hemiptera: Aphididae) (Brooks et al., 1994). In South Africa, the Russian wheat aphid was reported as a pest of wheat in 1978 in the Eastern Free State (Walters, 1980). In the beginning of the 1979 season, it was detected only in the Eastern Free State, but quickly spread to the Western Free State and parts of Lesotho. Infestations were also isolated in some areas of KwaZulu-Natal, North West and Gauteng Province (Walters et al., 1980). Aphids are soft bodied insects and are the most economically important phloem feeders impacting on plants (Dixon, 1985; Klingler et al., 2009). Aphids damage plants in four ways. Firstly, they ingest vital plant metabolites including large volumes of translocated sugars from the phloem sap, diverting energy from the plant and reducing yield. Secondly, they secrete saliva into the plant tissues while probing the layers of leaf to find the phloem, in some instances the secreted saliva is thought to be phytotoxic (Dedryver et al., 2010). The physical damage done to the leaf along with the toxic attributes of the saliva leads to localized necrosis in some aphid plant interactions (Klingler et al., 2009). Thirdly, aphids act as virus vectors and they can be transmitted in a non-circulative or circulative manner (Chen et al., 2012).

<p>Fosfaters reaktioner i energiomvandlingsprocesser är kritisk för den generella processen som helhet, för askrelaterade problem, emissioner liksom för en effektiv och hållbar användning av askan.</p><p>Denna avhandling är en sammanställning och diskussion med utgångspunkt i åtta artiklar som behandlar strukturella och termodynamiska studier på faser i CaO-K₂O-P₂O₅-systemet, vilka är av relevans inom förbränning av biomassa. Målsättningen med denna avhandling var: i) att sammanställa och granska tillgängliga strukturella och termodynamiska data i CaO-K₂O-P₂O₅-systemet samt att identifiera avsaknad av data, ii) att fylla i dessa luckor med grundläggande termodynamiska, strukturella och fasstabilitets studier samt iii) att visa på användning samt fördelarna med dessa nya data vid praktisk tillämpning.</p><p>En initial litteraturundersökning i CaO-K₂O-P₂O₅-systemet visade att det saknades både strukturella och termodynamiska data. När det gällde tillgängliga termodynamiska data var situationen särskilt otillfredsställande. Det fanns endast data för några kalcium– och kaliumfosfater med varierande tillförlitlighet. Situationen beträffande pulverröntgen för fasidentifiering var bättre, fast fördunklad av det faktum att strukturellt liknande fasövergångar ofta förekommer i det undersökta systemet. Däremot fattades det tillfredställande enkristallstrukturdata för ternära faser i det undersökta systemet.</p><p>Enkristallröntgendiffraktion användes för att bestämma strukturerna för CaK₂P₂O₇, CaKP₃O₉, Ca₁₀K(PO₄)₇ och CaKPO₄. Faserna CaK₂P₂O₇ and CaKPO₄ tillsammans med Ca₃(PO₄)₂, KPO₃ och K₄P₂O₇ studerades med pulverröntgendiffraktion och termiska analysmetoder för att klargöra fasmodifikationer och övergångstemperaturer. Gibbs bildningsenergi bestämdes för Ca(PO₃)₂, Ca₂P₂O₇, Ca₃(PO₄)₂, Ca₁₀K(PO₄)₇, CaK₂P₂O₇, CaKPO₄ och CaK₄(PO₄)₂ med ems-metodik och yttriastabiliserad zirkonia som fast elektrolyt och Ni/Ni₃P som hjälpsystem. Både de strukturella och termodynamiska data användes sedan vid analyser i ett förbrännningexperiment av olika sädesslag. Framtagna data användes både vid identifiering och även vid kvantifiering av bildade faser i biomassaresterna.</p> / <p>The behaviour of phosphates in thermochemical biomass conversion processes are critical for the general process chemistry, for ash related problems, for emissions as well as for an efficient, sustainable and beneficial use of the ash residues.</p><p>This thesis is a summary and a discussion of eight papers dealing with structural and thermodynamical studies of phases in the CaO-K₂O-P₂O₅ system, with relevance for biomass combustion. The objectives were: i) to compile and review the available structural and thermodynamical data of phases in the CaO-K₂O-P₂O₅ system as well as to identify existing gaps in the field of these data, ii) to fill in as many as possible of the gaps by fundamental thermodynamic, structural and phase stability studies and iii) to demonstrate the uses and the benefits of the new data in practical applications.</p><p>An initial review of the CaO-K₂O-P₂O₅ system showed that both structural information and thermodynamic data were lacking. The situation regarding the available thermodynamic data was especially unsatisfactory, data could only be found for some few calcium phosphates and a few potassium phosphates with varying reliability. Concerning powder X-ray diffraction patterns for phase identification the situation was better, though obscured by the fact that structurally close related phase transitions often occur in the studied system. However, adequate single crystal structural data of ternary phases in the system was completely missing.</p><p>Crystal structures of CaK₂P₂O₇, CaKP₃O₉, Ca₁₀K(PO₄)₇ and CaKPO₄ were determined by single-crystal X-ray diffraction. The phases CaK₂P₂O₇ and CaKPO₄ were together with Ca₃(PO₄)₂, KPO₃ and K₄P₂O₇, investigated by powder X-ray diffraction and thermal analysis to elucidate phase modifications and transitions temperatures. Gibbs standard energy of formation was determined for Ca(PO₃)₂, Ca₂P₂O₇, Ca₃(PO₄)₂, Ca₁₀K(PO₄)₇, CaK₂P₂O₇, CaKPO₄ and CaK₄(PO₄)₂ by solid state emf measurements with yttria stabilised zirconia as solid electrolyte and Ni/Ni₃P as auxiliary solid couple. Both the structural and thermodynamical data were subsequently utilised in analysis of a combustion experiment of cereal grains. The data were also used to both identify and quantify the phases formed in biomass combustion residues.</p>

Fosfaters reaktioner i energiomvandlingsprocesser är kritisk för den generella processen som helhet, för askrelaterade problem, emissioner liksom för en effektiv och hållbar användning av askan. Denna avhandling är en sammanställning och diskussion med utgångspunkt i åtta artiklar som behandlar strukturella och termodynamiska studier på faser i CaO-K2O-P2O5-systemet, vilka är av relevans inom förbränning av biomassa. Målsättningen med denna avhandling var: i) att sammanställa och granska tillgängliga strukturella och termodynamiska data i CaO-K2O-P2O5-systemet samt att identifiera avsaknad av data, ii) att fylla i dessa luckor med grundläggande termodynamiska, strukturella och fasstabilitets studier samt iii) att visa på användning samt fördelarna med dessa nya data vid praktisk tillämpning. En initial litteraturundersökning i CaO-K2O-P2O5-systemet visade att det saknades både strukturella och termodynamiska data. När det gällde tillgängliga termodynamiska data var situationen särskilt otillfredsställande. Det fanns endast data för några kalcium– och kaliumfosfater med varierande tillförlitlighet. Situationen beträffande pulverröntgen för fasidentifiering var bättre, fast fördunklad av det faktum att strukturellt liknande fasövergångar ofta förekommer i det undersökta systemet. Däremot fattades det tillfredställande enkristallstrukturdata för ternära faser i det undersökta systemet. Enkristallröntgendiffraktion användes för att bestämma strukturerna för CaK2P2O7, CaKP3O9, Ca10K(PO4)7 och CaKPO4. Faserna CaK2P2O7 and CaKPO4 tillsammans med Ca3(PO4)2, KPO3 och K4P2O7 studerades med pulverröntgendiffraktion och termiska analysmetoder för att klargöra fasmodifikationer och övergångstemperaturer. Gibbs bildningsenergi bestämdes för Ca(PO3)2, Ca2P2O7, Ca3(PO4)2, Ca10K(PO4)7, CaK2P2O7, CaKPO4 och CaK4(PO4)2 med ems-metodik och yttriastabiliserad zirkonia som fast elektrolyt och Ni/Ni3P som hjälpsystem. Både de strukturella och termodynamiska data användes sedan vid analyser i ett förbrännningexperiment av olika sädesslag. Framtagna data användes både vid identifiering och även vid kvantifiering av bildade faser i biomassaresterna. / The behaviour of phosphates in thermochemical biomass conversion processes are critical for the general process chemistry, for ash related problems, for emissions as well as for an efficient, sustainable and beneficial use of the ash residues. This thesis is a summary and a discussion of eight papers dealing with structural and thermodynamical studies of phases in the CaO-K2O-P2O5 system, with relevance for biomass combustion. The objectives were: i) to compile and review the available structural and thermodynamical data of phases in the CaO-K2O-P2O5 system as well as to identify existing gaps in the field of these data, ii) to fill in as many as possible of the gaps by fundamental thermodynamic, structural and phase stability studies and iii) to demonstrate the uses and the benefits of the new data in practical applications. An initial review of the CaO-K2O-P2O5 system showed that both structural information and thermodynamic data were lacking. The situation regarding the available thermodynamic data was especially unsatisfactory, data could only be found for some few calcium phosphates and a few potassium phosphates with varying reliability. Concerning powder X-ray diffraction patterns for phase identification the situation was better, though obscured by the fact that structurally close related phase transitions often occur in the studied system. However, adequate single crystal structural data of ternary phases in the system was completely missing. Crystal structures of CaK2P2O7, CaKP3O9, Ca10K(PO4)7 and CaKPO4 were determined by single-crystal X-ray diffraction. The phases CaK2P2O7 and CaKPO4 were together with Ca3(PO4)2, KPO3 and K4P2O7, investigated by powder X-ray diffraction and thermal analysis to elucidate phase modifications and transitions temperatures. Gibbs standard energy of formation was determined for Ca(PO3)2, Ca2P2O7, Ca3(PO4)2, Ca10K(PO4)7, CaK2P2O7, CaKPO4 and CaK4(PO4)2 by solid state emf measurements with yttria stabilised zirconia as solid electrolyte and Ni/Ni3P as auxiliary solid couple. Both the structural and thermodynamical data were subsequently utilised in analysis of a combustion experiment of cereal grains. The data were also used to both identify and quantify the phases formed in biomass combustion residues.