Reproduction and population structure in European aspen

The European aspen (Populus tremula) is a keystone species for biodiversity in boreal forests. However, the future of aspen may be threatened, because large aspens have mostly been removed from managed forests, whereas regeneration and the long-term persistence of mature trees are subjects of concern in protected areas. Aspen is a pioneer tree, and it can reproduce both sexually by seed and asexually by root suckers. Through asexual reproduction aspen forms clones, groups of genetically identical trees (ramets). In my thesis, I have studied the structure of aspen populations in terms of number, size, clonal and demographic properties. Additionally, I have investigated the emergence and survival of seedlings as well as the seed quantity and quality in crosses between the European and hybrid aspen. To study the regeneration and population structure, mature aspens were recorded in old-growth and managed forests in eastern Finland based on a large-scale inventory (11 400 ha). In addition, small aspen trees were surveyed on sample plots. Clonal structure was investigated both by morphological characters and by DNA-based markers (microsatellites). Seedling emergence and survival was studied with two sowing experiments. With crosses between European and hybrid aspens we wanted to study whether elevated temperatures due to climate change would benefit the different crosses of European and hybrid aspen unequally and thus affect the gene flow between the two species. The average volumes of mature aspen were 5.3 m3/ha in continuous old-growth, and 0.8 m3/ha in managed forests. Results indicate also that large aspen trees in managed forests are a legacy of the past less intensively managed forest landscapes. Long-term persistence of aspen in protected areas can only be secured by restoration measures creating sufficiently large gaps for regeneration. More emphasis should be given to sparing aspens in thinnings and to retaining of mature aspens in regeneration cutting in managed forests. Aspen was found to be spatially aggregated in the landscape. This could be explained by site type, disturbance history and / or limitations in seed dispersal. Clonal structure does not explain the spatial aggregation, since average size of the clones was only 2.3 ramets, and most clones (70 %) consisted of just one ramet. The small size of the clones suggests that most of them are relatively young. Therefore, sexual reproduction may be more common than has previously been thought. Seedling emergence was most successful in mineral soil especially, when the site had been burned. Only few seedlings occurred on humus. Survival of the seedlings was low, and strongly dependent on moisture, but also on seedbed conditions. The seeds were found to maintain their germinability longer than has earlier been thought to be possible. Interspecific crosses produced more seeds with higher quality than intraspecific crosses. When temperature was elevated, germination of hybrid aspen seeds increased more than seeds from P. tremula x P. tremula crosses. These results suggest that hybrid aspen may have a significant genetic impact on the European aspen, and this effect may become strengthened by climate warming.

Meadow plant growth and competition under elevated ozone and carbon dioxide

The main aim of my thesis project was to assess the impact of elevated ozone (O3) and carbon dioxide (CO2) on the growth, competition and community of meadow plants in northern Europe. The thesis project consisted of three separate O3 and CO2 exposure experiments that were conducted as open-top-chamber (OTC) studies at Jokioinen, SW Finland, and a smaller-scale experiment with different availabilities of resources in greenhouses in Helsinki. The OTC experiments included a competition experiment with two- and three-wise interactions, a mesocosm-scale meadow community with a large number of species, and a pot experiment that assessed intraspecific differences of Centaurea jacea ecotypes. The studied lowland hay meadow proved to be an O3-sensitive biotope, as the O3 concentrations used (40-50 ppb) were moderate, and yet, six out of nine species (Campanula rotundifolia, Centaurea jacea, Fragaria vesca, Ranunculus acris, Trifolium medium, Vicia cracca) showed either significant reductions in biomass or reproductive development, visible O3 injury or any two as a response to elevated O3. The plant species and ecotypes exhibited large intra- and interspecific variation in their response to O3, but O3 and CO2 concentrations did not cause changes in their interspecific competition or in community composition. However, the largest O3-induced growth reductions were seen in the least abundant species (C. rotundifolia and F. vesca), which may indicate O3-induced suppression of weak competitors. The overall effects of CO2 were relatively small and mainly restricted to individual species and several measured variables. Based on the present studies, most of the deleterious effects of tropospheric O3 are not diminished by a moderate increase in CO2 under low N availability, and variation exists between different species and variables. The present study indicates that the growth of several herb species decreases with increasing atmospheric O3 concentrations, and that these changes may pose a threat to the biodiversity of meadows. Ozone-induced reductions in the total community biomass production and N pool are likely to have important consequences for the nutrient cycling of the ecosystem.

Single layer graphene film by ethanol chemical vapor deposition: Highly efficient growth and clean transfer method

The choice of ethanol (C2H5OH) as carbon source in the Chemical Vapor Deposition (CVD) of graphene on copper foils can be considered as an attractive alternative among the commonly used hydrocarbons, such as methane (CH4) [1]. Ethanol, a safe, low cost and easy handling liquid precursor, offers fast and efficient growth kinetics with the synthesis of fullyformed graphene films in just few seconds [2]. In previous studies of graphene growth from ethanol, various research groups explored temperature ranges lower than 1000 °C, usually reported for methane-assisted CVD. In particular, the 650–850 °C and 900 °C ranges were investigated, respectively for 5 and 30 min growth time [3, 4]. Recently, our group reported the growth of highly-crystalline, few-layer graphene by ethanol-CVD in hydrogen flow (1– 100 sccm) at high temperatures (1000–1070 °C) using growth times typical of CH4-assisted synthesis (10–30 min) [5]. Furthermore, a synthesis time between 20 and 60 s in the same conditions was explored too. In such fast growth we demonstrated that fully-formed graphene films can be grown by exposing copper foils to a low partial pressure of ethanol (up to 2 Pa) in just 20 s [6] and we proposed that the rapid growth is related to an increase of the Cu catalyst efficiency due weak oxidizing nature of ethanol. Thus, the employment of such liquid precursor, in small concentrations, together with a reduced time of growth and very low pressure leads to highly efficient graphene synthesis. By this way, the complete coverage of a copper catalyst surface with high spatial uniformity can be obtained in a considerably lower time than when using methane.

Precipitate growth with composition-dependent diffusivity: Comparison between theory and phase field simulations

We consider the growth of an isolated precipitate when the matrix diffusivity depends on the composition. We have simulated precipitate growth using the Cahn-Hilliard model, and find good agreement between our results and those from a sharp interface theory for systems with and without a dilatational misfit. With misfit, we report (and rationalize) an interesting difference between systems with a constant diffusivity and those with a variable diffusivity in the matrix.

Spontaneous and reversible self-assembly of a polypeptide fragment of insulin-like growth factor binding protein-2 into fluorescent nanotubular structures

In this communication, we report the spontaneous and reversible in vitro self-assembly of a polypeptide fragment derived from the C-terminal domain of Insulin-like Growth Factor Binding Protein (IGFBP-2) into soluble nanotubular structures several micrometres long via a mechanism involving inter-molecular disulfide bonds and exhibiting enhanced fluorescence.

Observation of Peierls transition in nanowires (diameter similar to 130 nm) of the charge transfer molecule TTF-TCNQ synthesized by electric-field-directed growth

We report the growth of nanowires of the charge transfer complex tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) with diameters as low as 130 nm and show that such nanowires can show Peierls transitions at low temperatures. The wires of sub-micron length were grown between two prefabricated electrodes (with sub-micron gap) by vapor phase growth from a single source by applying an electric field between the electrodes during the growth process. The nanowires so grown show a charge transfer ratio similar to 0.57, which is close to that seen in bulk crystals. Below the transition the transport is strongly nonlinear and can be interpreted as originating from de-pinning of CDW that forms at the Peierls transition.

Transforming growth factor -beta signaling through Smad3 in allergy : Studies in the mechanisms of asthma, atopic dermatitis and allergic contact reactions

Transforming growth factor β signalling through Smad3 in allergy Allergic diseases, such as atopic dermatitis, asthma, and contact dermatitis are complex diseases influenced by both genetic and environmental factors. It is still unclear why allergy and subsequent allergic disease occur in some individuals but not in others. Transforming growth factor (TGF)-β is an important immunomodulatory and fibrogenic factor that regulates cellular processes in injured and inflamed skin. TGF-β has a significant role in the regulation of the allergen-induced immune response participating in the development of allergic and asthmatic inflammation. TGF-β is known to be an immunomodulatory factor in the progression of delayed type hypersensitivity reactions and allergic contact dermatitis. TGF-β is crucial in regulating the cellular responses involved in allergy, such as differentiation, proliferation and migration. TGF-β signals are delivered from the cytoplasm to the nucleus by TGF-β signal transducers called Smads. Smad3 is a major signal transducer in TGF-β -signalling that controls the expression of target genes in the nucleus in a cell-type specific manner. The role of TGF-β-Smad3 -signalling in the immunoregulation and pathophysiology of allergic disorders is still poorly understood. In this thesis, the role of TGF-β-Smad -signalling pathway using Smad3 -deficient knock out mice in the murine models of allergic diseases; atopic dermatitis, asthma and allergic contact reactions, was examined. Smad3-pathway regulates allergen induced skin inflammation and systemic IgE antibody production in a murine model atopic dermatitis. The defect in Smad3 -signalling decreased Th2 cytokine (IL-13 and IL-5) mRNA expression in the lung, modulated allergen induced specific IgG1 response, and affected mucus production in the lung in a murine model of asthma. TGF-β / Smad3 -signalling contributed to inflammatory hypersensitivity reactions and disease progression via modulation of chemokine and cytokine expression and inflammatory cell recruitment, cell proliferation and regulation of the specific antibody response in a murine model of contact hypersensitivity. TGF-β modulates inflammatory responses - at least partly through the Smad3 pathway - but also through other compensatory, non-Smad-dependent pathways. Understanding the effects of the TGF-β signalling pathway in the immune system and in disease models can help in elucidating the multilevel effects of TGF-β. Unravelling the mechanisms of Smad3 may open new possibilities for treating and preventing allergic responses, which may lead to severe illness and loss of work ability. In the future the Smad3 signalling pathway might be a potential target in the therapy of allergic diseases.

Synthetic arabinomannan glycolipids and their effects on growth and motility of the Mycobacterium smegmatis

Arabinomannan-containing glycolipids, relevant to the mycobacterial cell-wall component lipoarabinomannan, were synthesized by chemical methods. The glycolipids were presented with tri- and tetrasaccharide arabinomannans as the sugar portion and a double alkyl chain as the lyophilic portion. Following synthesis, systematic biological and biophysical studies were undertaken in order to identify the effects of the glycolipids during mycobacterium growth. The studies included mycobacterial growth, biofilm formation and motility assays. From the studies, it was observed that the synthetic glycolipid with higher arabinan residues inhibited the mycobacterial growth, lessened the biofilm formation and impaired the motility of mycobacteria. A surface plasmon resonance study involving the immobilized glycan surface and the mycobacterial crude lysates as analytes showed specificities of the interactions. Further, it was found that cell lysates from motile bacteria bound oligosaccharide with higher affinity than non-motile bacteria.

Juvenile rheumatoid knee : Management of knee growth disturbances in children with juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is associated with growth disturbances, especially leg length discrepancy (LLD) and knee valgus deformity (KVD). Studies have demonstrated growth plate stimulation with chronic arthritis. In the context of surgical treatment of LLD or KVD of a growing knee, the less invasive procedures, which allow immediate mobilisation, are preferred. Establishment of the skeletal age and the correction potential in the knees of rheumatic children is difficult due to rheumatic changes. In this present work, an analysis of the efficacy, safety and long-term results of temporary epiphyseal arrests performed in Rheumatism Foundation Hospital (Heinola, Finland). The distribution of diagnoses among children (n=71) with JIA and LLD (68 knees) was consistent with the normal oligoarthritis-predominated population of children with JIA. A higher male:female ratio (1:1.7 vs. 1:2.4 in population-based studies (PBS)) and earlier mean onset age (4 vs. 7 years in PBSs) were, however, distinct features in the study population. In most cases the correction was reliable and temporary arrest produced a mean correction of 1mm per month. The time of arrest required, however, varied significantly, probably due to the effect of underlying diseases and medication, and the age of the child. All complications encountered (10%) were minor. The correction achieved persisted in long-term follow-up. KVD (n=112, 177 knees) was associated with a high proportion of polyarthritic disease subtype (45% vs. 12-31% in PBSs), and the male:female distribution was grossly female-dominated (1:4.9 vs. 1:2.4 in PBSs). The early mean onset age (3 vs. 7 years in PBSs) was also notable in this cohort. Successful correction was achieved in 2/3 cases and the mean angular correction was 0.7 degrees per month. The required time of arrest, however, varied considerably. In 13% of knees the paucity of follow-up visits resulted in over-correction to varus. The complication rate (3%) in the knees operated for KVD was considerably lower compared to ten per cent in the management of LLD. Most of the complications related to epiphyseal stapling were reversible. However, the risk of premature closure of growth plates does exist. The number of over-corrections was notably high, with 13% knees turning to varus. The correction achieved persisted in long-term follow-up.

Controlled Growth of ZnO Tetrapods: Influence of Temperature and Temperature Gradient

Though it has been established that ZnO tetrapods can be synthesized by heating Zn in air, it is advantageous to grow tetrapods with legs of different morphologies with different lengths. Here, we report the large scale synthesis of ZnO tetrapods by heating Zn in air ambient. The parameters that control the diameter, length, and morphology of tetrapods are identified. It is shown that the morphology and dimensions of the tetrapods depend not only on the vaporization temperature but also on the temperature gradient of the furnace. The controlled synthesis procedure and the key parameters that influence the morphology are discussed.

Cucumber chloroplast trnL(CAA) gene: nucleotide sequence and in vivo expression analysis in etiolated cucumber seedlings treated with benzyladenine and light.

The nucleotide sequence of a 714 bp BamHI-EcoRI fragment of cucumber chloroplast DNA was determined. The fragment contained a gene for tRNA(Leu) together with its flanking regions. The trnL(CAA) gene sequence is about 99% in similarity to broad bean, cauliflower, maize, spinach and tobacco corresponding genes. The relative expression level of the gene was determined by Northern (tRNA) gel blot and Northern (total cellular RNA) slot-blot analyses using the trnL gene probe in 6-day old etiolated cucumber seedlings and the seedlings that had been kept in the dark (dark-grown), treated with benzyladenine (BA) and kept in the dark (BA-treated dark-grown), illuminated (light-grown), and treated with BA and illuminated (BA-treated light-grown), for additional 4, 8 or 12 hr. The trnL transcripts and tRNA(Leu) levels in BA-treated dark-grown seedlings were 5 and 3 times higher, respectively after 4 hr BA treatment, while in the BA treated light-grown seedlings the level of trnL transcripts was only 3 times higher and had no detectable effect on mature tRNA(Leu) when compared to the time-4 hr dark-grown seedlings. However, the level of mature tRNA(Leu) did not show marked changes in the light-grown seedlings, whereas the level of trnL transcripts increases 3 times after 8 hr illumination of dark-grown seedlings. These data indicate that both light and cytokinin can signal changes in plastid tRNA gene expression. The possible regulatory mechanisms for such changes are discussed.

Cucumber chloroplast trnL(CAA) gene: nucleotide sequence and in vivo expression analysis in etiolated cucumber seedlings treated with benzyladenine and light

The nucleotide sequence of a 714 bp BamHI-EcoRI fragment of cucumber chloroplast DNA was determined. The fragment contained a gene for tRNA(Leu) together with its flanking regions. The trnL(CAA) gene sequence is about 99% in similarity to broad bean, cauliflower, maize, spinach and tobacco corresponding genes. The relative expression level of the gene was determined by Northern (tRNA) gel blot and Northern (total cellular RNA) slot-blot analyses using the trnL gene probe in 6-day old etiolated cucumber seedlings and the seedlings that had been kept in the dark (dark-grown), treated with benzyladenine (BA) and kept in the dark (BA-treated dark-grown), illuminated (light-grown), and treated with BA and illuminated (BA- treated light-grown), for additional 4, 8 or 12 hr. The trnL transcripts and tRNA(Leu) levels in BA-treated dark-grown seedlings were 5 and 3 times higher, respectively after 4 hr BA treatment, while in the BA treated light-grown seedlings the level of trnL transcripts was only 3 times higher and had not detectable effect on mature tRNA(Leu) when compared to the time-4 hr dark-grown seedlings. However, the level of mature tRNA(Leu) did not show marked changes in the light-grown seedlings, whereas the level of trnL transcripts increases 3 times after 8 hr illumination of dark-grown seedlings. These date indicate that both light and cytokinin can signal changes in plastid tRNA gene expression. The possible regulatory mechanisms for such changes are discussed.