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Påverkar variationer i promotorn till VRN1 frostresistens i vete (Triticum aestivum) från Nordeuropa? / Do variations in the promotor of VRN1 affect frost resistance in wheat from Northern Europe?Rundquist, Olof January 2013 (has links)
Vete, Triticum aestivum är en mycket viktig matgröda. Under historiens gång har arten fått anpassa sig till många vitt skilda miljöer. I Nordeuropa har frost-resistens varit extra viktigt. En viktig gen för frostresistensen är VRN1som kontrollerar vernaliseringen d.v.s. övergången från vegetativt till aktivt tillstånd som sker på våren. Olika varianter av denna gen leder till skillnader frostresistens under våren. I detta arbete undersöktes hur variationer i promotorn till VRN1A i accessioner från norra Europa påverkar frostresistensen. Alla sorter som kunde sekvenseras visade sig ha samma promotor trots varierande frost-resistens. Detta kan bero på att promotorn till VRN1 inte är det enda som påverkar genens utryck. Även variationer i intron1 är betydelsefulla och det är därför rimligt att variationen mellan sorterna ligger där istället. En annan förklaring kan även vara att variationen ligger på ett annat genom då T. aestivum är hexaploid. Att alla sorter har samma promotorsekvens kan också tyda på ett selektivt svep. Detta selektiva svep har i så fall förekommit innan vete kom till Nordeuropa då även de franska och tyska sorterna har samma promotor som de finska och svenska. / Bread wheat, Triticum aestivum is an important crop. As history has progressed the species has been forced to adapt to different environments. In Northern Europe, frost resistance has been especially paramount. An important gene for frost resistance is VRN1 that controls vernalization, i.e. the transition from vegetative state to active state during spring. Different variants of this gene confer differences in frost resistance during spring. In this study I examined how the promotor region of VRN1A affects frost resistance in accessions of landraces of wheat from Northern Europe. All accessions from which the promotor region could be sequenced shared the same promotor sequence even though they had very varied frost resistance. This could be because the expression of VRN1 is not only affected by the promotor. Variations in intron one is also important, and so it is reasonable to assume that the variation between these landraces lies there instead. The variations could also be on one of the other genomes, because bread wheat is hexaploid. The fact that all the accessions shared the same promotor sequence indicates that a selective sweep has taken place. This selective sweep could have occurred before bread wheat arrived in Northern Europe because landraces from Germany and France shares the same promotor as Nordic Landraces.
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Kalkputs : porstrukturens betydelse för beständighetBalksten, Kristin January 2005 (has links)
When restoring historic lime plaster it can be difficult to reach the required durability. Today newly made lime plaster can fall off due to frost damages after only a couple of winters. To understand and solve these problems, the subject has been studied from different perspectives. Several factors in the production step are making an influence on the durability of lime plaster: 1. A binder, suitable for the building, must be chosen along with sandthat gives good material properties in both fresh mortar and in plasters. 2. The lime/sand ratio and the mixing technique should be chosen from the properties in the lime and the sand, in order to get a mortar with good workability. 3. The craftsmanship should be adjusted to the mortar, the weather and the underlying materials. A plaster with good frost resistance has a certain pore structure. The plaster should have some round air pores that contain air even when the material is filled capillary with water. Such air pores give the water a free space to expand when it is freezing. If the air pores are missing, the ice crystals may damage the plaster when expanding. To increase the chance of making a frost resistant lime plaster, the lime/sand ration must be adjusted so the lime can fill up well in the sand. Otherwise a collapsed pore system can easily occur, which means an open pore system without distinct air pores. A collapsed pore system contains many pores well connected with each other. Such a system is easily damaged by frost. To increase the chance of success, it is of great importance to work the surface of the lime plaster at the right time and in the correct way. Before working on a surface the mortar must be aloud to stiffen. Only then a homogeneous material can be created; cracks due to shrinkage can be pressed together and the result is a more compact material with an open surface. The time necessary for mortars to stiffen is related to the water content of the mortar, the suction of the underlying surface and the weather conditions. If the surface is worked on while the mortar is still fresh, the binder can form a hard lime shell on the surface. Inside thematerial a lack of binder can appear. Such plasters have a very low frost resistance. Other durability problems related to plaster are damages in the underlying materials, i.e. rotten wood in covered constructions or leached lime in old joints. Such damages can occur if the covering mortar is made of strong hydraulic lime or cement, since they form plasters with a low permeability in comparison to lime. Due to mentioned findings, it is important to study how a pore structureis influenced by materials, mixture and craftsmanship. Only then it is possible to understand how damages can be decreased.
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