Land leasing, land degradation and agricultural productivity in Finland

This study analysed whether the land tenure insecurity problem has led to a decline in long-term land improvements (liming and phosphorus fertilization) under the Common Agricultural Policy (CAP) and Nordic production conditions in European Union (EU) countries such as Finland. The results suggests that under traditional cash lease contracts, which are encouraged by the existing land leasing regulations and agricultural subsidy programs, the land tenure insecurity problem on leased land reduces land improvements that have a long pay-back period. In particular, soil pH was found to be significantly lower on land cultivated under a lease contract compared to land owned by the farmers themselves. The results also indicate that land improvements could not be reversed by land markets, because land owners would otherwise have carried out land improvements even if not farming by themselves. To reveal the causality between land tenure and land improvements, the dynamic optimisation problem was solved by a stochastic dynamic programming routine with known parameters for one-period returns and transition equations. The model parameters represented Finnish soil quality and production conditions. The decision rules were solved for alternative likelihood scenarios over the continuation of the fixed-term lease contract. The results suggest that as the probability of non-renewal of the lease contract increases, farmers quickly reduce investments in irreversible land improvements and, thereafter, yields gradually decline. The simulations highlighted the observed trends of a decline in land improvements on land parcels that are cultivated under lease contracts. Land tenure has resulted in the neglect of land improvement in Finland. This study aimed to analyze whether these challenges could be resolved by a tax policy that encourages land sales. Using Finnish data, real estate tax and a temporal relaxation on the taxation of capital gains showed some potential for the restructuring of land ownership. Potential sellers who could not be revealed by traditional logit models were identified with the latent class approach. Those landowners with an intention to sell even without a policy change were sensitive to temporal relaxation in the taxation of capital gains. In the long term, productivity and especially productivity growth are necessary conditions for the survival of farms and the food industry in Finland. Technical progress was found to drive the increase in productivity. The scale had only a moderate effect and for the whole study period (1976–2006) the effect was close to zero. Total factor productivity (TFP) increased, depending on the model, by 0.6–1.7% per year. The results demonstrated that the increase in productivity was hindered by the policy changes introduced in 1995. It is also evidenced that the increase in land leasing is connected to these policy changes. Land institutions and land tenure questions are essential in agricultural and rural policies on all levels, from local to international. Land ownership and land titles are commonly tied to fundamental political, economic and social questions. A fair resolution calls for innovative and new solutions both on national and international levels. However, this seems to be a problem when considering the application of EU regulations to member states inheriting divergent landownership structures and farming cultures. The contribution of this study is in describing the consequences of fitting EU agricultural policy to Finnish agricultural land tenure conditions and heritage.

Radical Enhanced Atomic Layer Deposition of Metals and Oxides

Atomic Layer Deposition (ALD) is a chemical, gas-phase thin film deposition method. It is known for its ability for accurate and precise thickness control, and uniform and conformal film growth. One area where ALD has not yet excelled is film deposition at low temperatures. Also deposition of metals, besides the noble metals, has proven to be quite challenging. To alleviate these limitations, more aggressive reactants are required. One such group of reactants are radicals, which may be formed by dissociating gases. Dissociation is most conveniently done with a plasma source. For example, dissociating molecular oxygen or hydrogen, oxygen or hydrogen radicals are generated. The use of radicals in ALD may surmount some of the above limitations: oxide film deposition at low temperatures may become feasible if oxygen radicals are used as they are highly reactive. Also, as hydrogen radicals are very effective reducing agents, they may be used to deposit metals. In this work, a plasma source was incorporated in an existing ALD reactor for radical generation, and the reactor was used to study five different Radical Enhanced ALD processes. The modifications to the existing reactor and the different possibilities during the modification process are discussed. The studied materials include two metals, copper and silver, and three oxides, aluminium oxide, titanium dioxide and tantalum oxide. The materials were characterized and their properties were compared to other variations of the same process, utilizing the same metal precursor, to understand what kind of effect the non-metal precursor has on the film properties and growth characteristics. Both metals were deposited successfully, and silver for the first time by ALD. The films had low resistivity and grew conformally in the ALD mode, demonstrating that the REALD of metals is true ALD. The oxide films had exceptionally high growth rates, and aluminium oxide grew at room temperature with low cycle times and resulted in good quality films. Both aluminium oxide and titanium dioxide were deposited on natural fibres without damaging the fibre. Tantalum oxide was also deposited successfully, with good electrical properties, but at slightly higher temperature than the other two oxides, due to the evaporation temperature required by the metal precursor. Overall, the ability of REALD to deposit metallic and oxide films with high quality at low temperatures was demonstrated.

Structural characteristics affecting functions of two actin regulating proteins

Structural biology is a branch of science that concentrates on the relationship between the structure and function of biological macromolecules. The prevalence of a large number of three dimensional structures offers effective tools for bio-scientists to understand the living world. Actin is the most abundant cellular protein and one of its main functions is to produce movement in living cells. Actin forms filaments that are dynamic and which are regulated by a number of different proteins. A class of these regulatory proteins contains actin depolymerizing factor homology (ADF-H) domains. These directly interact with actin through their ADF-H domains. Although ADF-H domains possess very similar three dimensional structures to one another, they vary in their functional properties. One example of this is the ability to bind to actin monomers or filaments. During the work for this thesis two structures of ADF-H domains were solved by nuclear magnetic resonance spectroscopy (NMR). The elucidated structures help us understand the binding specificities of the ADF-H family members.

Tailoring polyolefin properties by metallocene catalysis

This doctoral thesis deals with the syntheses of olefin homo- and copolymers using different kind of metallocene catalyst. Ethene, propene, 1-hexene, 1-hexadecene, vinylcyclohexane and phenylnorbornene were homo- or copolymerized with the catalysts. The unbridged benzyl substituted zirconium dichloride catalysts (1-4), ansa- bridged acenaphtyl substituted zirconium dichloride catalysts, ( 5, 6), rac- and meso-ethylene-bis(1-indenyl)zirconium dichlorides, (rac- and meso-8), rac-ethylene-bis(1-indenyl)hafnium dichloride, ( 12), bis(9-fluorenyl)hafnium dichloride (14 ) enantiomerically pure (R)- phenylethyl[(9-fluorenyl-1-indenyl)]ZrCl2, (11), 14 and asymmetric dimethylsilyl[(3-benzylindenyl-(2-methylbenzen[e]indenyl)] zirconium dichloride, (13), were prepared in our laboratory. Dimethylsilyl-bis(1-indenyl)zirconium dichloride, (9), isopropylidene(9-fluorenyl-cyclopentadienyl)zirconium dichloride, (10), and were obtained commercially. The solid-state structures of the catalysts rac- and meso-1 were determined by X-ray crystallography. Computational methods were used for the structure optimization of the catalyst rac- and meso-1 in order to compare the theoretical calculations with the experimental results. Polymerization experiments were conducted in a highly purified autoclave system using low pressures (< 5 bar) of gaseous monomers. The experiments were designed to attain the optimal catalytic activity and a uniform copolymer composition. The prepared homo- and copolymers were characterized by the gel permeation chromatography, GPC, differential scanning calorimetry, DSC, nuclear magnetic resonance, NMR, and Fourier transform infrared spectrometry, FTIR . Molar mass (Mw, Mn), molar mass distribution (Mw/Mn), tacticity, comonomer content, melting temperature, glass transition temperature, and end group structures and content were determined. A special attention was paid on the correlation of the polymer properties with the catalyst structures and polymerization conditions. An intramolecular phenyl coordination was found in phenyl substituted benzyl zirconocenes 1-3 explaining the decreased activity of the catalysts. Novel copolymers poly(propene-co-phenylnorbornene) and poly(propene co-vinylcyclohexane), were synthesized and high molar mass poly(ethene-co-1-hexene) and poly(ethene-co-1-hexadecene) copolymers with elastic properties were prepared. Activation of a hafnocene catalyst was studied with UV-Vis spectrometry and activation process for the synthesis of ultra high molar mass poly(1-hexene) was found out.

Geological factors affecting on after-use of Finnish cut-over peatlands : with implications on the carbon accumulation

In Finland, peat harvesting sites are utilized down almost to the mineral soil. In this situation the properties of mineral subsoil are likely to have considerable influence on the suitability for the various after-use forms. The aims of this study were to recognize the chemical and physical properties of mineral subsoils possibly limiting the after-use of cut-over peatlands, to define a minimum practice for mineral subsoil studies and to describe the role of different geological areas. The future percentages of the different after-use forms were predicted, which made it possible to predict also carbon accumulation in this future situation. Mineral subsoils of 54 different peat production areas were studied. Their general features and grain size distribution was analysed. Other general items studied were pH, electrical conductivity, organic matter, water soluble nutrients (P, NO3-N, NH4-N, S and Fe) and exchangeable nutrients (Ca, Mg and K). In some cases also other elements were analysed. In an additional case study carbon accumulation effectiveness before the intervention was evaluated on three sites in Oulu area (representing sites typically considered for peat production). Areas with relatively sulphur rich mineral subsoil and pool-forming areas with very fine and compact mineral subsoil together covered approximately 1/5 of all areas. These areas were unsuitable for commercial use. They were recommended for example for mire regeneration. Another approximate 1/5 of the areas included very coarse or very fine sediments. Commercial use of these areas would demand special techniques - like using the remaining peat layer for compensating properties missing from the mineral subsoil. One after-use form was seldom suitable for one whole released peat production area. Three typical distribution patterns (models) of different mineral subsoils within individual peatlands were found. 57 % of studied cut-over peatlands were well suited for forestry. In a conservative calculation 26% of the areas were clearly suitable for agriculture, horticulture or energy crop production. If till without large boulders was included, the percentage of areas suitable to field crop production would be 42 %. 9-14 % of all areas were well suitable for mire regeneration or bird sanctuaries, but all areas were considered possible for mire regeneration with correct techniques. Also another 11 % was recommended for mire regeneration to avoid disturbing the mineral subsoil, so total 20-25 % of the areas would be used for rewetting. High sulphur concentrations and acidity were typical to the areas below the highest shoreline of the ancient Litorina sea and Lake Ladoga Bothnian Bay zone. Also differences related to nutrition were detected. In coarse sediments natural nutrient concentration was clearly higher in Lake Ladoga Bothnian Bay zone and in the areas of Svecokarelian schists and gneisses, than in Granitoid area of central Finland and in Archaean gneiss areas. Based on this study the recommended minimum analysis for after-use planning was for pH, sulphur content and fine material (<0.06 mm) percentage. Nutrition capacity could be analysed using the natural concentrations of calcium, magnesium and potassium. Carbon accumulation scenarios were developed based on the land-use predictions. These scenarios were calculated for areas in peat production and the areas released from peat production (59300 ha + 15 671 ha). Carbon accumulation of the scenarios varied between 0.074 and 0.152 million t C a-1. In the three peatlands considered for peat production the long term carbon accumulation rates varied between 13 and 24 g C m-2 a-1. The natural annual carbon accumulation had been decreasing towards the time of possible intervention.

Renormalization methods in KAM theory

It is well known that an integrable (in the sense of Arnold-Jost) Hamiltonian system gives rise to quasi-periodic motion with trajectories running on invariant tori. These tori foliate the whole phase space. If we perturb an integrable system, the Kolmogorow-Arnold-Moser (KAM) theorem states that, provided some non-degeneracy condition and that the perturbation is sufficiently small, most of the invariant tori carrying quasi-periodic motion persist, getting only slightly deformed. The measure of the persisting invariant tori is large together with the inverse of the size of the perturbation. In the first part of the thesis we shall use a Renormalization Group (RG) scheme in order to prove the classical KAM result in the case of a non analytic perturbation (the latter will only be assumed to have continuous derivatives up to a sufficiently large order). We shall proceed by solving a sequence of problems in which theperturbations are analytic approximations of the original one. We will finally show that the approximate solutions will converge to a differentiable solution of our original problem. In the second part we will use an RG scheme using continuous scales, so that instead of solving an iterative equation as in the classical RG KAM, we will end up solving a partial differential equation. This will allow us to reduce the complications of treating a sequence of iterative equations to the use of the Banach fixed point theorem in a suitable Banach space.

Tannakian Formalism Applied to the Category of Mixed Hodge Structures

Many problems in analysis have been solved using the theory of Hodge structures. P. Deligne started to treat these structures in a categorical way. Following him, we introduce the categories of mixed real and complex Hodge structures. Category of mixed Hodge structures over the field of real or complex numbers is a rigid abelian tensor category, and in fact, a neutral Tannakian category. Therefore it is equivalent to the category of representations of an affine group scheme. The direct sums of pure Hodge structures of different weights over real or complex numbers can be realized as a representation of the torus group, whose complex points is the Cartesian product of two punctured complex planes. Mixed Hodge structures turn out to consist of information of a direct sum of pure Hodge structures of different weights and a nilpotent automorphism. Therefore mixed Hodge structures correspond to the representations of certain semidirect product of a nilpotent group and the torus group acting on it.

Agreeable Agreement : An Examination into the Quest for a Solid Consensus in Light of Bilateral Doctrinal Dialogues among Anglicans, Lutherans and Roman Catholics

The purpose of this study is to analyse the development and understanding of the idea of consensus in bilateral dialogues among Anglicans, Lutherans and Roman Catholics. The source material consists of representative dialogue documents from the international, regional and national dialogues from the 1960s until 2006. In general, the dialogue documents argue for agreement/consensus based on commonality or compatibility. Each of the three dialogue processes has specific characteristics and formulates its argument in a unique way. The Lutheran-Roman Catholic dialogue has a particular interest in hermeneutical questions. In the early phases, the documents endeavoured to describe the interpretative principles that would allow the churches to together proclaim the Gospel and to identify the foundation on which the agreement in the church is based. This investigation ended up proposing a notion of basic consensus , which later developed into a form of consensus that seeks to embrace, not to dismiss differences (so-called differentiated consensus ). The Lutheran-Roman Catholic agreement is based on a perspectival understanding of doctrine. The Anglican-Roman Catholic dialogue emphasises the correctness of interpretations. The documents consciously look towards a common future , not the separated past. The dialogue s primary interpretative concept is koinonia. The texts develop a hermeneutics of authoritative teaching that has been described as the rule of communion . The Anglican-Lutheran dialogue is characterised by an instrumental understanding of doctrine. Doctrinal agreement is facilitated by the ideas of coherence, continuity and substantial emphasis in doctrine. The Anglican-Lutheran dialogue proposes a form of sufficient consensus that considers a wide set of doctrinal statements and liturgical practices to determine whether an agreement has been reached to the degree that, although not complete , is sufficient for concrete steps towards unity. Chapter V discusses the current challenges of consensus as an ecumenically viable concept. In this part, I argue that the acceptability of consensus as an ecumenical goal is based not only the understanding of the church but more importantly on the understanding of the nature and function of the doctrine. The understanding of doctrine has undergone significant changes during the time of the ecumenical dialogues. The major shift has been from a modern paradigm towards a postmodern paradigm. I conclude with proposals towards a way to construct a form of consensus that would survive philosophical criticism, would be theologically valid and ecumenically acceptable.

Christianity and Christian Identity in the Gospel of Philip (NHC II,3)

Previous scholarship has often maintained that the Gospel of Philip is a collection of Valentinian teachings. In the present study, however, the text is read as a whole and placed into a broader context by searching for parallels from other early Christian texts. Although the Valentinian Christian identity of the Gospel of Philip is not questioned, it is read alongside those texts traditionally labelled as "mainstream Christian". It is obvious from the account of Irenaeus that the boundaries between the Valentinians and other Christians were not as clear or fixed as he probably would have hoped. This study analyzes the Valentinian Christian Gospel of Philip from two points of view: how the text constructs the Christian identity and what kind of Christianity it exemplifies. Firstly, it is observed how the author of the Gospel of Philip places himself and his Christian readers among the early Christianities of the period by emphasizing the common history and Christian features but building especially on particular texts and traditions. Secondly, it is noted how the Christian nature of an individual develops according to the Gospel of Philip. The identity of an individual is built and strengthened through rituals, experiences and teaching. Thirdly, the categorizations, attributes, beliefs and behaviour associated on the one hand with the "insiders", the true Christians, and, on the other, with outsiders in the Gospel of Philip, are analyzed using social identity theory the insiders and outsiders are described through stereotyping in the text. Overall, the study implies that the Gospel of Philip strongly emphasizes spiritual progress and transformation. Rather than depicting the Valentinians as the perfect Christians, it underlines their need for constant change and improvement. Although the author seeks to clearly distinguish the insiders from the outsiders, the boundaries of the categories are in fact fluid in the Gospel of Philip. Outsiders can become insiders and the insiders are also in danger of falling out again.

"Ettei tää olis niin kalkkismeininkiä" : Iltaohjelman merkitys rippikoulussa

Tämä on laadullinen tapaustutkimus erään suomalaisen evankelisluterilaisen seurakunnan rippikoululeiriltä. Tutkimusjoukkoon kuuluivat rippikoululeirin kaksi ohjaajaa, kahdeksan isosta sekä kaksitoista rippikoululaista. Tutkimuksen tarkoituksena oli selvittää, mikä on rippikoulun iltaohjelman merkitys rippikoulun kokonaisuudessa. Tätä selvitettiin seuraavien kysymysten avulla: 1. Millaisia tavoitteita rippikoululeirin ohjaajat ja isoset asettavat rippikoulun iltaohjelmalle? 2. Mitä rippikoulun iltaohjelmassa tapahtuu? 3. Miten rippikoululaiset arvioivat toteutuneita iltaohjelmia? Tutkimuksen havainnointi- ja haastatteluaineisto kerättiin viikonmittaisen rippikoululeirin aikana. Aineistonkeruumenetelminä käytettiin osallistuvaa havainnointia, videointia sekä puolistrukturoituja tutkimushaastatteluita. Tutkija oli rippikoululeirillä mukana havainnoimassa koko rippikoululeirin ajan. Rippikoululeirin kaikki iltaohjelmat videoitiin ja koko tutkimusjoukkoa haastateltiin. Haastattelu- ja havainnointiaineistoa analysoitiin laadullisen sisällönanalyysin menetelmällä. Saatiin selville, että rippikoulun isoset ja ohjaajat asettivat iltaohjelmalle ryhmän koheesion edistämiseen liittyviä tavoitteita, iltaohjelman hauskuuteen, monipuolisuuteen ja sujuvuuteen tähtääviä tavoitteita, rippikoulun keventämiseen tähtääviä tavoitteita sekä hengellisiä ja seurakunnallisia tavoitteita. Iltaohjelmat koostuivat mm. isosten esittämistä sketseistä, yhteisleikeistä, hengellisistä yhteislauluista, vapaaehtoisohjelmanumeroista ja luottamusharjoituksista. Sketseihin ja muuhun isosjohtoiseen toimintaan käytettiin eniten aikaa. Rippikoululaiset arvioivat iltaohjelmaa yhteistoiminnallisena ohjelmana, esityksenä sekä suhteessa rippikoululeirin kokonaisuuteen. Kokonaisuutta peilattiin opetuksen tavoitteisuuden ja linjakkuuden ihanteeseen. Johtopäätöksinä todettiin, että iltaohjelmien tavoitteet olivat vain osittain linjassa rippikoulun opetussuunnitelman tavoitteiden kanssa. Osa tavoitteista myös toteutui iltaohjelmissa ja osa jäi toteutumatta. Ryhmän koheesion edistämiseen liittyvät tavoitteet toteutuivat iltaohjelmissa vaihtelevasti. Iltaohjelma vaikutti isosten tavoitteiden ja rippikoululaisten arvioiden valossa olevan opetuksen vastapainoa, mikä ei ole rippikoulun tavoitteiden mukaista. Kaksimielisten sketsien esittämisen todettiin olevan ristiriidassa rippikoulun tavoitteiden kanssa. Hengellisten laulujen laulaminen ja luottamusharjoitukset puolestaan olivat linjassa rippikoulun opetussuunnitelman tavoitteiden kanssa.

Eru Ilúvatar : Jumala J.R.R. Tolkienin legendariumissa

The purpose of my research is to inquire into the essence and activity of God in the legendarium of the English philologist and writer J.R.R. Tolkien (1892-1973). The legendarium, composed of Tolkien’s writings related to Middle-earth, was begun when he created two Elvish languages, Quenya based on Finnish, Sindarin based on Welsh. Tolkien developed his mythology inspired by Germanic myths and The Kalevala. It is a fictional ancient history set in our world. The legendarium is monotheistic: God is called Eru ‘The One’ and Ilúvatar ‘Father of All’. Eru is the same as the Christian God, for Tolkien wanted to keep his tales consistent with his faith. He said his works were Christian by nature, with the religious element absorbed into the story and the symbolism. In The Silmarillion, set in the primeval ages of Middle-earth, the theological aspects are more conspicuous, while in The Lord of the Rings, which brings the stories to an end, they are mostly limited to symbolic references. The legendarium is unified by its realistic outlook on creaturely abilities and hope expressing itself as humbly defiant resistance. ”The possibility of complexity or of distinctions in the nature of Eru” is a part of the legendarium. Eru Ilúvatar is Trinitarian, as per Tolkien’s faith. Without contextual qualifiers, Eru seems to refer to God the Father, like God in the Bible. Being the creator who dwells outside the world is attributed to Him. The Holy Spirit is the only Person of the Trinity bestown with names: the Flame Imperishable and the Secret Fire. When Eru creates the material world with His word, He sends the Flame Imperishable to burn at the heart of the world. The Secret Fire signifies the Creative Power that belongs to God alone, and is a part of Him. The Son, the Word, is not directly mentioned, but according to one writing Eru must step inside the world in order to save it from corruption, yet remain outside it at the same time. The inner structure of the legendarium refers to the need for a future salvation. The creative word of Eru, “Eä! Let these things Be!”, probably has a connection with the Logos in Christianity. Thus we can find three “distinctions” in Eru: a Creator who dwells outside the world, a Sustainer who dwells inside it and a Redeemer who shall step inside it. Some studies of Tolkien have claimed that Eru is distant and remote. This seems to hold water only partially. Ilúvatar, the Father of All, has a special relation with the Eruhíni, His Children, the immortal Elves and the mortal Men. He communicates with them directly only through the Valar, who resemble archangels. Nevertheless, only the Children of Eru can fight against evil, because their tragic fortunes turn evil into good. Even though religious activities are scarce among them, the fundamental faith and ultimate hope of the “Free Peoples” is directed towards Eru. He is present in the drama of history as the “Author of the Story”, who at times also interferes with its course through catastrophes and eucatastrophes, ‘good catastrophes’. Eru brings about a catastrophe when evil would otherwise bring good to an end, and He brings about a eucatasrophe when creaturely strength is not sufficent for victory. Victory over corruption is especially connected with mortal Men, of whom the most (or least) insignificant people are the Hobbits. However, because of the “primeval disaster” (that is, fall) of Mankind, ultimate salvation can only remain open, a hope for the far future.

Membrane Insertion of C-tail Anchored Proteins

The correct localization of proteins is essential for cell viability. In order to achieve correct protein localization to cellular membranes, conserved membrane targeting and translocation mechanisms have evolved. The focus of this work was membrane targeting and translocation of a group of proteins that circumvent the known targeting and translocation mechanisms, the C-tail anchored protein family. Members of this protein family carry out a wide range of functions, from protein translocation and recognition events preceding membrane fusion, to the regulation of programmed cell death. In this work, the mechanisms of membrane insertion and targeting of two C-tail anchored proteins were studied utilizing in vivo and in vitro methods, in yeast and mammalian cell systems. The proteins studied were cytochrome b(5), a well characterized C-tail anchored model protein, and N-Bak, a novel member of the Bcl-2 family of regulators of programmed cell death. Membrane insertion of cytochrome b(5) into the endoplasmic reticulum membrane was found to occur independently of the known protein conducting channels, through which signal peptide-containing polypeptides are translocated. In fact, the membrane insertion process was independent of any protein components and did not require energy. Instead membrane insertion was observed to be dependent on the lipid composition of the membrane. The targeting of N-Bak was found to depend on the cellular context. Either the mitochondrial or endoplasmic reticulum membranes were targeted, which resulted in morphological changes of the target membranes. These findings indicate the existence of a novel membrane insertion mechanism for C-tail anchored proteins, in which membrane integration of the transmembrane domain, and the translocation of C-terminal fragments, appears to be spontaneous. This mode of membrane insertion is regulated by the target membrane fluidity, which depends on the lipid composition of the bilayer, and the hydrophobicity of the transmembrane domain of the C-tail anchored protein, as well as by the availability of the C-tail for membrane integration. Together these mechanisms enable the cell to achieve spatial and temporal regulation of sub-cellular localization of C-tail anchored proteins.

Cytokinin signalling in the regulation of cambial development

Secondary growth of plants is of pivotal importance in terrestrial ecosystems, providing a significant carbon sink in the form of wood. As plant biomass accumulation results largely from the cambial growth, it is surprising that quite little is known about the hormonal or genetic control of this important process in any plant species. The central aim of my thesis studies was to explore the function of cytokinin in the regulation of cambial development. Since their discovery as regulators of plant cell divisions, cytokinins have been assumed to participate in the control of cambial development. Evidence for this action was deduced from hormone treatment experiments, where exogenously applied cytokinin was shown to enhance cambial cell divisions in diverse plant organs and species. In my thesis work, the conservation of cytokinin signalling and homeostasis genes between a herbaceous plant, Arabidopsis, and a hardwood tree species, Populus trichocarpa. Presumably reflecting the ancient origin of cytokinin signalling system, the Populus genome contains orthologs for all Arabidopsis cytokinin signalling and homeostasis genes. Thus, genes belonging to five main families of isopentenyl transferases (IPTs), cytokinin oxidases (CKXs), two-component receptors, histidine containing phosphotransmitters (HPts) and response regulators (RRs) were identified from the Populus genome. Three subfamilies associated with cytokinin signal transduction, the CKI1-like family of two-component receptors, the AHP4-like HPts, and the ARR22-like atypical RRs, were significantly larger in Populus genome than in Arabidopsis. Potential contribution to the extensive secondary development of Populus by the members of these considerably expanded gene families will be discussed. Representatives of all cytokinin signal transduction elements were expressed in the Populus cambial zone, and most of the expressed genes appeared to be slightly more abundant on the phloem side of the meristem. The abundance of cytokinin related genes in the cambium emphasizes the important role of this hormone in the regulation of the extensive secondary growth characteristic of tree species. The function of the pseudo HPts in primary vascular development was studied in Arabidopsis root vasculature. It was demonstrated that the pseudo HPt AHP6 has a role in locally inhibiting cytokinin signalling in the protoxylem position in the Arabidopsis root, thus enabling differentiation of the protoxylem cell file. The possible role of pseudo HPts in cambial development will be discussed. The expression peak of cytokinin signalling genes in the tree cambial zone strongly indicates that cytokinin has a role in the regulation of this meristem function. To address whether cytokinin signalling is required for cambial activity, transgenic Populus trees with modified cytokinin signalling were produced. These trees were expressing a cytokinin catabolic gene from Arabidopsis, CYTOKININ OXIDASE 2, (AtCKX2) under the promoter of a Betula CYTOKININ RECEPTOR 1 (BpCRE1). The pBpCRE1::CKX2 transgenic Populus trees showed a reduced concentration of a biologically active cytokinin, correlating with their impaired cytokinin response. Furthermore, the radial growth of these trees was compromised, as illustrated by a smaller stem diameter than in wild-type trees of the same height. Moreover, the level of cambial cytokinin signalling was down-regulated in these thin-stemmed trees. The reduced signalling correlated with a decreased number of meristematic cambial cells, implicating cytokinin activity as a direct regulator of cambial cell division activity. Together, the results of my study indicate that cytokinins are major hormonal regulators required for cambial development.

The Emerging Phenotype: Ecological Genetics of Color, Form and Sex in the Common Frog

One of the main aims of evolutionary biology is to explain why organisms vary phenotypically as they do. Proximately, this variation arises from genetic differences and from environmental influences, the latter of which is referred to as phenotypic plasticity. Phenotypic plasticity is thus a central concept in evolutionary biology, and understanding its relative importance in causing the phenotypic variation and differentiation is important, for instance in anticipating the consequences of human induced environmental changes. The aim of this thesis was to study geographic variation and local adaptation, as well as sex ratios and environmental sex reversal, in the common frog (Rana temporaria). These themes cover three different aspects of phenotypic plasticity, which emerges as the central concept for the thesis. The first two chapters address geographic variation and local adaptation in two potentially thermally adaptive traits, namely the degree of melanism and the relative leg length. The results show that although there is an increasing latitudinal trend in the degree of melanism in wild populations across Scandinavian Peninsula, this cline has no direct genetic basis and is thus environmentally induced. The second chapter demonstrates that although there is no linear, latitudinally ordered phenotypic trend in relative leg length that would be expected under Allen s rule an ecogeographical rule linking extremity length to climatic conditions there seems to be such a trend at the genetic level, hidden under environmental effects. The first two chapters thus view phenotypic plasticity through its ecological role and evolution, and demonstrate that it can both give rise to phenotypic variation and hide evolutionary patterns in studies that focus solely on phenotypes. The last three chapters relate to phenotypic plasticity through its ecological and evolutionary role in sex determination, and consequent effects on population sex ratio, genetic recombination and the evolution of sex chromosomes. The results show that while sex ratios are strongly female biased and there is evidence of environmental sex reversals, these reversals are unlikely to have caused the sex ratio skew, at least directly. The results demonstrate that environmental sex reversal can have an effect on the evolution of sex chromosomes, as the recombination patterns between them seem to be controlled by phenotypic, rather than genetic, sex. This potentially allows Y chromosomes to recombine, lending support for the recent hypothesis suggesting that sex-reversal may play an important role on the rejuvenation of Y chromosomes.

Sostdc1 Plays an Essential Role in Mammalian Tooth Patterning : Insight into the Rodent Dental Evolution

This thesis work focuses on the role of TGF-beta family antagonists during the development of mouse dentition. Tooth develops through an interaction between the dental epithelium and underlying neural crest derived mesenchyme. The reciprocal signaling between these tissues is mediated by soluble signaling molecules and the balance between activatory and inhibitory signals appears to be essential for the pattern formation. We showed the importance of Sostdc1 in the regulation of tooth shape and number. The absence of Sostdc1 altered the molar cusp patterning and led to supernumerary tooth formation both in the molar and incisor region. We showed that initially, Sostdc1 expression is in the mesenchyme, suggesting that dental mesenchyme may limit supernumerary tooth induction. We tested this in wild-type incisors by minimizing the amount of mesenchymal tissue surrounding the incisor tooth germs prior to culture in vitro. The cultured teeth phenocopied the extra incisor phenotype of the Sostdc1-deficient mice. Furthermore, we showed that minimizing the amount of dental mesenchyme in cultured Sostdc1-deficient incisors caused the formation of additional de novo incisors that resembled the successional incisor development resulting from activated Wnt signaling. Sostdc1 seemed to be able to inhibit both mesenchymal BMP4 and epithelial canonical Wnt signaling, which thus allows Sostdc1 to restrict the enamel knot size and regulate the tooth shape and number. Our work emphasizes the dual role for the tooth mesenchyme as a suppressor as well as an activator during tooth development. We found that the placode, forming the thick mouse incisor, is prone to disintegration during initiation of tooth development. The balance between two mesenchymal TGF-beta family signals, BMP4 and Activin is essential in this regulation. The inhibition of BMP4 or increase in Activin signaling led to the splitting of the large incisor placode into two smaller placodes resulting in thin incisors. These two signals appeared to have different effects on tooth epithelium and the analysis of the double null mutant mice lacking Sostdc1 and Follistatin indicated that these TGF-beta inhibitors regulate the mutual balance of BMP and Activin in vivo. In addition, this work provides an alternative explanation for the issue of incisor identity published in Science by Tucker et al. in 1998 and proposes that the molar like morphology that can be obtained by inhibiting BMP signaling is due to partial splitting of the incisor placodes and not due to change in tooth identity from the incisor to the molar. This thesis work presents possible molecular mechanisms that may have modified the mouse dental pattern during evolution leading to the typical rodent dentition of modern mouse. The rodent dentition is specialized for gnawing and consists of two large continuously growing incisors and toothless diastema region separating the molars and incisors. The ancestors of rodents had higher number of more slender incisors together with canines and premolars. Additionally, murine rodents, which include the mouse, have lost their ability for tooth replacement. This work has revealed that the inhibitory molecules appear to play a role in the tooth number suppression by delineating the spatial and temporal action of the inductive signals. The results suggest that Sostdc1 plays an essential role in several stages of tooth development through the regulation of both the BMP and Wnt pathway. The work shows a dormant sequential tooth forming potential present in wild type mouse incisor region and gives a new perspective on tooth suppression by dental mesenchyme. It reveals as well a novel mechanism to create a large mouse incisor through the regulation of mesenchymal balance between inductive and inhibitory signals.