Browsing by Subject "kasvibiologia"

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  • Aalto, Angela (Helsingin yliopisto, 2019)
    Today it is desirable to utilise and reproductive sidestream materials from the industry. The food industry generates lot of sidestream waste which could be utilised in various products. Grain hulls are one example. The aim of this work was to study the structure and chemical features of sidestream oat and barley hulls from the industry. Furthermore, the potential to use hull fractions with pulp to produce kraft paper was examined. The grain structure and chemical features of oat and barley have been studied extensively in the food industry but hulls barely at all. The intention was to study lipids, hemicellulose sugars and lignins. From the perspective of paper production, it was important to examine hulls fibres (anatomy), fibre separation and fibre wall fibrillation. Kraft paper must possess specific mechanical properties. Sufficient fibrillation and fibre network of the plant fibres renders paper durable. The hull fibres were examined with a light microscope. The hulls were macerated before microscopy. Compounds, lipids, organic acids and sugars were extracted with hexane and acetone in the Accelerated Solvent Extraction. The samples were analysed with gas chromatography-mass spectrometry. The hemicellulose sugars of the hulls were isolated with methanolysis and analysed with a gas chromatography-flame ionization detector. The hull lignins were defined with pyrolysis-gas chromatography-mass spectrometry. The other compounds of the samples were extracted with acetone by Accelerated Solvent Extraction before pyrolysis determination. The oat and barley hulls were milled with a disc refiner and added to the softwood (pine) pulp in a Valley hollander beater. The pulp was milled for 90 min and the pulp filtration was measured with a Schopper-Riegler freenes tester. Also, water retention value was calculated. Sheets of paper were made with a conventional sheet mould. The aim grammage of the paper sheets was 60 g/m². The mechanical, physical and optical properties of the paper sheets were measured. The properties measured were thickness, density, surface smoothness/roughness, air permeability, opacity, light scattering, light absorption, brightness, tensile strength, breaking strength, elongation, bursting strength and tearing strength. Half of the paper sheets were calandered. The chemical properties of oat and barley hulls did not differ significantly from each other. The same hemicellulose sugars were found in the hulls of both grains, however more mannose and arabinose were found in oat hulls. The hulls of both grains had almost the same total hemicellulose quantity. The quantity and quality of lignins were also similar in both grain hulls. Guaiacyl lignin was dominant in both hulls. Minor differences in hemicellulose sugars does not have an impact on paper production. The hull fibres were very similar in microscopic examination, but oat hulls were somewhat longer than barley hulls. These differences did not impact the separation of fibres, the fibrillation of fibre wall or paper making. Oat hulls were harder, which became most apparent in the calandering and appearance of the sheets. Barley hulls were darker but the mechanical and physical properties of the grain hull paper sheets were quite similar. The hull fractions amount in the pulp (10% or 20%) did not significantly impact the results. The milled hull fractions were not distributed evenly in the sheets, the fibres did not separate properly and no internal or external fibrillation occurred. As mentioned before, the sheets were not homogeneous and the standard deviation of the sheet properties were partly significant. Adding the hull fractions to the pulp was successful and the milled hull fractions did not fall off the sheets. Calandered sheets were smooth and glossy. Moreover, the sheets were visually pleasing. This study indicated that it is possible to use hull fractions for paper and kraft paper production. The paper mostly met the same quality requirements as commercial paper. More research is needed for further optimisation. More research into the chemical properties of oat and barley hulls is also needed, because of the hulls of both grains contain antioxidant components and could provide more information about advanced fibre separation and fibre wall fibrillation.
  • Nymark, Johanna (Helsingin yliopisto, 2019)
    Elevernas intresse för naturvetenskaper har minskat och en del elever anser att naturvetenskapliga läroämnen är onödiga och att undervisningen i dem är gammaldags. Ungdomar spenderar dessutom mycket mindre tid i naturen än tidigare vilket har lett till att deras kunskap och engagemang för miljön minskat. I dagens värld, med avancerad teknik och komplexa miljöproblem, är det dock viktigt att ungdomarna utvecklar en vetenskaplig och ekologisk läskunnighet för att kunna göra välinformerade och hållbara val. Syftet med den här avhandlingen var att bidra till en förnyelse av undervisningen i biologi genom att skapa aktiverande uteundervisningsuppgifter om växter. Utomhuspedagogik fungerade som didaktisk grund till uppgifterna eftersom undervisningen utförs utomhus och inkluderar aktiverande, undersökande, upplevelsebaserade, samt helhetsskapande och ämnesöverskridande element. Den här typen av undervisning föreskrivs i den nya läroplanen och forskningen påvisar dessutom att den höjer elevernas intresse och lärande i biologi samt främjar deras miljöengagemang. Det antogs finnas ett behov av färdiga undervisningsuppgifter eftersom uteundervisning är tidskrävande att planera och lärarna rapporterat om tidsbrist på arbetet. Uppgifterna fokuserade på växter eftersom kännedomen om dem generellt är sämre än kännedomen om djur och eftersom det befintliga utbudet av växtrelaterade undervisningsuppgifter är bristfälligt. Kvalitativa intervjuer och en webbenkät genomfördes med biologilärare i årskurs sju och åtta i grundskolan med avsikt ta reda på skolornas praktiska förutsättningar för uteundervisning, lärarnas åsikter om uteundervisning, samt deras önskemål jämte behov av uteundervisningsuppgifter. Fyra lärare intervjuades och 18 lärare svarade på webbenkäten. Enkäten analyserades och intervjuerna transkriberades och analyserades. Resultaten påvisade att lärarna saknar tid för att konstruera egna uteundervisningsuppgifter och att lärarna ansåg att färdiga uppgifter skulle underlätta deras arbete. Nio undervisningsuppgifter och en växtartlista skapades för att svara på lärarnas behov och inkluderade de åtta mest önskade arbetssätten. Utomhuspedagogikens fördelar utnyttjades i uppgifterna till exempel genom att mångsidigt begagna sinnesupplevelser och reflektion samt rörelse, samarbete och diskussion. Uppgifterna beaktade de praktiska förutsättningarna för uteundervisningen i skolorna genom att förlägga majoriteten av uppgifterna till hösten och våren och genom att göra uppgifterna anpassningsbara till olika naturtyper. Uppgifterna kan användas för att förverkliga läroplanens mål för utveckling av mångsidig kompetens samt de flesta målen för undervisningen i biologi, och inkluderade dessutom ämnesövergripande och helhetsskapande undervisning. Undervisningsuppgifterna som skapades kan användas för att förnya undervisningen i biologi och för att underlätta lärarnas arbete. Uppgifterna har, tack vare utomhuspedagogikens och det aktiva lärandets unika särdrag, potential att höja elevens intresse och lärande i biologi, kapacitet att utveckla kvalitativ kunskap och högre former av tänkande och dessutom utsikter att skapa ett personligt förhållande mellan eleven och naturen vilket i förlängningen kan leda till att eleven utvecklar en miljömedvetenhet och hållbar livsstil. En utmaning som synliggjordes var att lärarna inte verkar inse uteundervisningens kvalitativa mervärde utan istället antar en mer kvantitativ kunskapssyn vilket varken är förenligt med samtida forskning eller den nya läroplanen. Några av uppgifterna kommer att publiceras som en del av en nätpublikation som produceras inom ramen för ett lärarfortbildningsprojekt finansierat av Utbildningsstyrelsen och kommer således att bli tillgängliga för lärarna.
  • Vaahtera, Lauri (Helsingin yliopisto, 2016)
    The air pollutant ozone (O3) enters plant leaves through stomata and activates apolastic reactive oxygen species (ROS) signaling. Depending on growth conditions and genotype, this results in large transcriptional reprogramming,closure of stomatal pores and activation of cell death programs. These responses are also regulated through plant stress hormones. This thesis sheds light on how stress hormone signaling is connected with apoplastic ROS signaling in the model plant Arabidopsis thaliana, and investigates regulatory mechanisms which generate specificity among sequence-specific transcription factors (TFs), the executers of apoplastic ROS -induced transcriptional reprogramming. The essential methods of the thesis include O3 exposures of Arabidopsis wild type and mutant plants followed by quantification of cell death and characterization of transcriptional responses supplemented with several protein-level analyses of selected WRKY family TFs. The O3-induced cell death was found to be inhibited by plant hormone salicylic acid, and genes RESPIRATORY BURST OXIDASE HOMOLOG F (RBOHF) and WRKY70 were found to be required for O3-induced cell death in jasmonic acid insensitive genetic background. Even though stress hormones were verified to play important roles in the regulation of cell death, the transcriptional response to apoplastic ROS in a hormone deficient/insensitive mutant was highly similar to wild type, suggesting that much of the signaling involved is independent of the studied hormones jasmonic acid, salicylic acid, and ethylene. The potential major executers of transcriptional response to apoplastic ROS, WRKY family TFs, were studied for their transcriptional regulation, DNA-binding preferences, protein-protein interactions, subcellular localization, and effects on transcriptome. The results showed that the DNA-binding preferences of WRKYs vary substantially between phylogenetic groups, implying that the specificity in signaling between different WRKYs can be partly achieved through DNA binding preferences. Transcriptomic analyses of mutants with altered expression levels of the strongly ROS-inducible WRKY75 implicate this TF as a positive regulator of well-known pathogen-responsive genes, such as PATHOGENESIS-RELATED GENE 1 (PR1) and PATHOGENESIS-RELATED GENE 2 (PR2), and as a negative regulator of several hormone signaling pathways and TFs.
  • Kolari, Pasi (2010)
    The forest vegetation takes up atmospheric carbon dioxide (CO2) in photosynthesis. Part of the fixed carbon is released back into the atmosphere during plant respiration but a substantial part is stored as plant biomass, especially in the stems of trees. Carbon also accumulates in the soil as litter and via the roots. CO2 is released into the atmosphere from these carbon stocks in the decomposition of dead biomass. Carbon balance of a forest stand is the difference between the CO2 uptake and CO2 efflux. This study quantifies and analyses the dynamics of carbon balance and component CO2 fluxes in four Southern Finnish Scots pine stands that covered the typical economic rotation time of 80 years. The study was based on direct flux measurements with chambers and eddy covariance (EC), and modelling of component CO2 fluxes. The net CO2 exchange of the stand was partitioned into component fluxes: photosynthesis of trees and ground vegetation, respiration of tree foliage and stems, and CO2 efflux from the soil. The relationships between the component fluxes and the environmental factors (light, temperature, atmospheric CO2, air humidity and soil moisture) were studied with mathematical modelling. The annual CO2 balance varied from a source of about 400 g C/m2 at a recently clearcut site to net CO2 uptake of 200 300 g C/m2 in a middle-aged (40-year-old) and a mature (75-year-old) stand. A 12-year-old sapling site was at the turning point from source to a sink of CO2. In the middle-aged stand, photosynthetic production was dominated by trees. Under closed pine canopies, ground vegetation accounted for 10 20% of stand photosynthesis whereas at the open sites the proportion and also the absolute photosynthesis of ground vegetation was much higher. The aboveground respiration was dominated by tree foliage which accounted for one third of the ecosystem respiration. Rate of wood respiration was in the order of 10% of total ecosystem respiration. CO2 efflux from the soil dominated the ecosystem respiratory fluxes in all phases of stand development. Instantaneous and delayed responses to the environmental driving factors could predict well within-year variability in photosynthetic production: In the short term and during the growing season photosynthesis follows primarily light while the seasonal variation is more strongly connected to temperature. The temperature relationship of the annual cycle of photosynthesis was found to be almost equal in the southern boreal zone and at the timberline in the northern boreal zone. The respiratory fluxes showed instantaneous and seasonal temperature relationships but they could also be connected to photosynthesis at an annual timescale.
  • Kemppinen, Jasmin (Helsingin yliopisto, 2020)
    Reactive oxygen species (ROS) are one of the prominent groups of signal compounds that are produced in stress conditions such as excess light. Nuclear protein RADICAL-INDUCED CELL DEAT (RCD1) is sensitive to ROS and controls the expression of organelle components, e.g. mitochondrial alternative oxidases (AOX), thus balancing the redox-status of a plant cell. Plants have fast responses to fluctuating light conditions that happen even before gene expression: i.e. readjusting the capability to receive light energy between the two photosystems by state transitions and increasing the capacity to remove excess energy by non-photochemical quenching (NPQ). Various small auxiliary proteins function in these fast acclimation events. However, many of them are identified on gene level only. The goal of this master’s thesis is to describe the role of a hypothetical protein, PPD8 in Arabidopsis thaliana. We evaluate how PPD8 is associated with RCD1 and a chloroplast thiol-regulator enzyme NTRC. We created double (rcd1 ppd8) and triple mutant plant lines (rcd1 ppd8 ntrc) by crossing single knockout lines ppd8, rcd1 and ntrc. Photosynthetic performance, NPQ and sensitivity to ROS were observed in each line by using two different chlorophyll fluorescence measurement methods: pulse-amplitude-modulation (PAM) and novel OJIP imaging fluorometry. The leaves were exposed to methyl viologen (MV), which accelerates the chloroplastic ROS production in light, and also to hypoxic conditions in order to study how the effect of MV is altered in low concentrations of oxygen. Additionally, we examined the amount of photosynthetic proteins and stoichiometry of photosystems in ppd8, rcd1 and rcd1 ppd8 by immunological methods. Finally, PPD8 gene with attached hemagglutinin encoding tags was generated by cloning and reintroduced back to the ppd8 knockout lines. Plants lacking RCD1 are very tolerant against MV and ROS, but when rcd1 was crossed with ppd8 the resistance was suppressed. Both rcd1 ppd8 and ppd8 exhibited elevated chlorophyll fluorescence and NPQ values. The removal of PPD8 gene had an impact on the abundance and the stoichiometry of photosynthetic proteins reducing the plants’ performance. When RCD1, PPD8 and NTRC were simultaneously absent the plants had major defects: their NPQ and fluorescence values were drastically increased. Furthermore, several results hinted towards possible issues in the function of ATP synthase in ppd8 background plants. It is also known that NTRC regulates ATP synthase: taken together, the results suggest that PPD8 is necessary for a fully operative ATP synthase and photosynthetic machinery. By reintroducing PPD8 to knockout line ppd8, the phenotype could be reverted back to wild type -like, thus confirming the significance of the PPD8 gene product in plant.
  • Lehtonen, Valtteri (Helsingin yliopisto, 2020)
    Fluctuating light conditions can cause light stress for plants. The photosynthetic apparatus can be damaged by the excess light. Light stress causes formation of reactive oxygen species in chloroplasts. Arabidopsis thaliana’s mutant radical induced cell death1 (rcd1) is tolerant to this stress. In my thesis I used a compound called methyl viologen which causes the formation of reactive oxygen species in chloroplasts. It has been used as a herbicide. By using this compound, we can make the light stress worse and see bigger differences between the rcd1 mutant and the wild type. We identified the causative gene of rcd1’s chloroplastic stress tolerance, clarified the dependence of growth light intensity for chloroplastic stress tolerance and explored possible structural differences at the cellular level between the wild type and rcd1. Finding the genes that prevent light stress would allow a light stress tolerant crop production which could make food production easier in hot and dry areas of the world. My thesis is a part of a screening study where rcd1 mutants were screened for lowered tolerance to light stress. The amount of stress of the leaves was defined by measuring the chlorophyll fluorescence. Two most promising lines which got damaged by methyl viologen were called #20 and #54. For these a backcrossing was made with the rcd1. Clear correlation was found from their offspring between the phenotype and the methyl viologen tolerance. The correlation was strongest in the line #20 so we focused on it. Small and yellowish pale individuals which resembled their parents were the most sensitive to methyl viologen. These individuals were selected for the sequencing. Candidate genes were in the chromosome 3. The most promising one was called AT3G29185 or BIOGENESIS FACTOR REQUIRED FOR ATP SYNTHASE1 (BFA1). We ordered bfa1 mutant’s seeds. We found that bfa1 mutant was itself sensitive to methyl viologen proving our observation. We discovered that methyl viologen tolerance is growth light dependent. The individuals that grew under higher intensity of light were more tolerant to methyl viologen in both the wild type and rcd1 mutant. We didn’t find structural differences at the cellular level by confocal microscopy. Thus, they can’t explain the differences in the methyl viologen tolerance.
  • Alanko, Teija (Helsingin yliopisto, 2017)
    Archaeobotany combines botany, archaeology and history, and studies useful plants and interactions between humans and plants in the past, including horticulture. Garden history has been studied in Finland mainly through historical sources, but not much with archaeological or archaeobotanical methods, although the importance of multidisciplinary work has been noted, since written sources available are often not sufficient. Archaeobotany in Finland has revealed garden plant remains, but garden soils have not been investigated much. Archaeobotanical material, obtained from soil samples, i.e. macrosubfossil plant remains, is interpreted in archaeological and historical contexts. Excavations are, however, often restricted for practical reasons, determining also sites for macrofossil analyses. An alternative sampling method may be one solution to carry out macrofossil studies in sites unlikely to be excavated, such as historical gardens. The aims of this study were to elucidate a part of Finnish and Swedish garden history by means of archaeobotany, and to test archaeobotanical sampling in gardens in the absence of excavations with a sampler and applying AMS-radiocarbon dating. The research comprises four case studies and a review from five sites; Naantali Cloister, Kumpula Manor, and academic gardens in Uppsala, Turku and Helsinki. The sites are partly linked historically to each other, and they reach from the 15th century to the 21st century. Soil samples were collected at four sites with a sampler from different levels from narrow pits, one by one in vertical series. At one site, samples came from excavations. The samples were floated and sieved in a laboratory, and macrofossil remains were identified and counted. Altogether 8,404 macrofossil plant remains belonging to 154 plant taxa were obtained. In total 30 AMS-radiocarbon dates were measured from seeds, charred grains, and pieces of charred wood. The oldest dated seeds and grains were medieval, the youngest were modern. Macrofossil plant remains included cereals, berries, ornamental, medicinal and garden plants, and cultural or garden weeds, indicating both consumption and garden cultivation at the sites. Other soil contents, such as fish scales and chips of wood and charcoal, referred to fertilization and thus also gardening. The sampling method worked reasonably well. Sampling was independent of excavations, and relatively quick. Still, the maximum size of a sample was limited, although larger samples could have yielded more macrofossils and species. Written sources were necessary for the background, but in the cases of historical gardens, the literature gave historical contexts well enough. Garden history can and should be studied with both written sources and archaeobotanical methods. Informative macrofossil sampling can be carried out both from excavations and straight from garden soil. Plant lists, when existing, give information of cultivated species, but not of plants consumed or having grown as garden weeds at the sites. Still, quite few species that were mentioned in the plant lists were obtained as macrofossils in this study, perhaps due to the relatively poor state of preservation of the seeds in garden soil, and the probable scarce accumulation of seeds of cultivated species into the garden soil. Nevertheless, in sites with no comprehensive plant lists, archaeobotany revealed valuable information of plants that could not be gained otherwise. The Naantali Cloister case showed the importance of searching remains of garden plants also from structures outside of gardens.
  • Hällfors, Maria (Helsingin yliopisto, 2016)
    Global climate change will make the current habitat of many species unfavourable. It can also cause species suitable areas to shift or disappear. Under rapid climate change many species will not be able to adapt or disperse fast enough. Therefore, human-mediated dispersal of species has been proposed as a conservation method for mitigating the negative effects of climate change on biodiversity. In scientific discussions on the method, several different terms and definitions have been used. Such inconsistent use of terminology can lead to misunderstandings and to conflicting studies and evaluations of the method. In this thesis, assisted migration (AM) is suggested as the preferred term for the idea of translocating species threatened by climate change, and a concise definition that distinguishes it from other translocation practices is proposed. Should AM be accepted as a conservation tool, there is a demand for a readily applicable, rapid, and effective way of evaluating the species-specific benefit of AM. This thesis presents a method for estimating the need and potential of AM from predictions of changes in the range of species. The method is applied to several plant species and this thesis thus provides on of the first data-based estimations of the need to apply AM as a conservation strategy under different scenarios of climate change. The results indicate that the need and potential of AM for these species increases substantially with the strength of climate change and the temporal extent of climate change projections. Furthermore, this thesis suggests ways to deal with uncertainties in the process of obtaining range change predictions through species distribution models. Conventional assumptions concerning local adaptation within species, according to which species are treated as a single entity, may lead to erroneous predictions when applying species distribution models. Here, the magnitude of error in conservation guidance that can be introduced through opposing assumptions concerning local adaptation is explored. It is found that the assumption of local adaptation and, therefore, separate modelling of populations can provide different and more precautionary outcomes compared to the assumption of no local adaptation and, hence, modelling the species as a whole. To obtain insight into the presence of intraspecific local adaptation to climatic conditions, a translocation trial of two geographically separated populations of the same plant species was initiated. The preliminary results presented here indicate that one of the studied populations is less adapted to conditions in its home environment while the other population exhibits stronger local adaptation. Knowledge of this kind provided by experimental studies should be reflected in studies using species distribution modelling to reduce uncertainty in predictions and threat estimates based on the models. This thesis concludes that predictive tools such as species distribution models hold great potential in providing rough estimates of future trajectories for conservation of biodiversity and could provide a useful scientific basis for policy decisions. However, more in-depth knowledge, which can be gained through experimental approaches, is needed to detail how individual species and populations may respond to altered conditions in their environment and which conservation method is the most relevant.
  • Holopainen-Mantila, Ulla (Helsingin yliopisto, 2015)
    Barley (Hordeum vulgare L.) is a globally important grain crop. The composition and structure of barley grain is under genotypic and environmental control during grain development, when storage compounds (mainly starch and protein), are accumulated. Grain structure plays a significant role in malting and feed- and food-processing quality of barley. Hordeins, the major storage proteins in barley grains, are centrally located in the endosperm forming a matrix surrounding starch granules, but their role in the structural properties of barley grain is not completely understood. Thus, the main aim of the current study was to demonstrate the role of hordeins in barley grain structure. The dependence of the grain structure on the growth environment, in particular with respect to day-length and sulphur application relevant to northern growing conditions, was studied. The effects of the grain structure on end use properties in milling as well as in hydration and modification during malting were characterized. The longer photoperiod typical to latitudes in Southern Finland resulted in a C hordein fraction, entrapped by aggregated B and D hordeins, being more deeply located in the endosperm of barley cultivar Barke. Thus the impact of the growing environment on hordein deposition during grain filling was observed both at the tissue and subcellular level. However, the mechanism behind the differential accumulation of C hordein remains unclear. The deeper localization of entrapped C hordein was linked to improved hydration of grains during malting in three barley cultivars. Thus, the role of the subaleurone region in barley grain was found to be significant with respect to end use quality. Moreover, the results suggest that the growing environment affects the end-use properties of barley and that especially the northern growing conditions have a positive impact on barley processing quality. The influence of sulphur application on hordein composition in the Northern European growing conditions was demonstrated for the first time. Asparagine and C hordein served as nitrogen storage pools when the S application rate was lower than 20 mg S / kg soil, whereas total hordein and B hordein contents increased with higher S application rates. The current study also showed that even when sulphur is sufficiently available in field conditions, the hordein composition may react to sulphur application. The observed sulphur responses were in accordance with those reported earlier for hordein composition. This indicates that the more intensive growth rhythm induced in northern growing conditions does not alter greatly the effect of sulphur on grain composition. The current study confirmed that the main grain components: starch, protein and β-glucan, influence grain processing properties including milling, hydration and endosperm modification. However, their influence on endosperm texture (hardness or steeliness), which also affects the performance of barley grains in these processes, cannot be directly derived or estimated on the basis of the grain composition. The results obtained suggest that hordeins should also be taken into account in the evaluation of the processing behaviour of barley grains.
  • Niskanen, Tuula (Helsingin yliopisto, 2008)
    Cortinarius is the largest genus of Agaricales with a worldwide distribution. So far, over 4000 Cortinarius names and combinations have been published. Cortinarius spp. form ectomycorrhizae with different trees and shrubs. A majority of the Cortinarius species have narrow ecological preferences and many form ectomycorrhiza with only one or few host species. The subgenus Telamonia sensu lato (s. lat.), comprising the greatest number of species, is the most poorly known of the subgenera of Cortinarius. The centre of diversity is in the northern hemisphere, although some species of the group are also recognized in the southern hemisphere. The aim of this thesis was to study the taxonomy of Cortinarius subgenus Telamonia p.p. species based on morphological and molecular data, as well as to study the ecology and distribution of the species in North Europe. The taxonomical problems encountered and the difficulty in finding and studying all the relevant names and types slowed down the study. The diversity of the subgenus Telamonia s. lat. in North Europe (excluding sect. Hydrocybe, Icrustati and Anomali) was found to be far greater than previously thought. Even many of the common species have not yet been described. So far, ca. 200 species have been recognised from the Nordic countries, but the sampling in most groups does not cover the whole diversity and especially the southern deciduous forest species are underrepresented in our study. In most cases phylogenetic (only based on ITS data) and morphological species recognition were in concordance, but in a few cases morphologically delimited species had almost identical ITS sequences, raising the question as to whether ITS is always variable enough for species recognition. The opposite situation, in which a morphologically uniform species included two phylogenetically distinct lineages, however, was also encountered, suggesting the possibility of cryptic species in Cortinarius. In our studies no taxa below species level were recognised and the aforementioned results indicate that presumably they can only be recognised genetically. Based on our preliminary results a revision of the infrageneric classification in Cortinarius subgenus Telamonia s. lat. is needed, and more sections should be established for a meaningful and functional classification. Many groups have turned out to be artificial, and it seems evident that many characteristics have been over- or underemphasised. Many morphological characteristics, however, are useful in the identification of telamonioid species and e.g. some spore characteristics have often been overlooked. Our studies have concentrated on North Europe, but we have found some similarities with North European and North American taxa.
  • Kaasalainen, Ulla (Helsingin yliopisto, 2012)
    Lichens are symbiotic associations between a fungus (mycobiont) and a photosynthetic partner (photobiont) which may be a green alga or cyanobacterium (cyanobiont). In lichen symbiosis the mycobiont lives on sugars photosynthesized by the photobiont and, in cyanobacterial symbiosis, also nitrogen compounds are provided to the fungal host. Several cyanobacterial genera are known to associate with lichen forming fungi but by far the most common cyanobacterial genus in lichen symbioses is Nostoc. Lichen-symbiotic Nostoc is a diverse group including at least two distinct phylogenetic lineages which tend to associate with different groups of lichen mycobionts. Microcystins and nodularins are small, cyclic, hepatotoxic peptides responsible for poisonings of humans and animals. They are produced by aquatic, bloom forming cyanobacteria of several different genera and found in fresh and brackish waters around the world. The previously known microcystin producers of the genus Nostoc include the lichen associated cyanobacterium Nostoc sp. IO-102-I isolated from Finland, and some aquatic strains from Brazil, Finland, and India. While all producers of nodularin were previously thought to belong to the genus Nodularia, it has recently been shown that also some Nostoc strains isolated from cycad roots can produce nodularin. The aim of this study was to find out which cyanobacterial toxins are produced in lichen symbiosis and how widespread this production is, both from the geographical and lichen-symbiotic perspective. In addition I wanted to broaden the knowledge on lichen-symbiotic cyanobacteria and symbiont selectivity in lichen symbiosis. The study was based on the analysis of over 800 cyanolichen specimens collected from different parts of the world, mainly analysed with molecular biological methods and liquid chromatography-mass spectrometry. The results show that hepatotoxic microcystins are produced in situ in lichen symbioses by symbiotic cyanobacteria, and that these compounds are produced quite commonly in many different lichen genera all around the world. Also nodularin is produced in some lichens. The cyanobacterial toxins may act as grazing deterrents and provide some protection to the thallus. However the actual consequences to grazers and the faith of the toxins in the food chain remain unknown. The chemical and genetic diversity of microcystin production in lichens was remarkable. The evolution of this diversity may be related to genetic bottlenecks that commonly occur during the lifecycle of symbiotically dispersing cyanobacteria and the concurrent close association with the fungal hosts. The presently known distribution of toxin-producing cyanobacteria in lichens was found to concentrate into certain taxonomic groups within the Lobariaceae, Nephromataceae, and Peltigeraceae (Peltigerales, Ascomycota). The diversity of microcystin structures correlated with the genetic identity of Nostoc symbionts in different lichens, but also geographical patterns seemed to exist. Symbiont selection in the lichen genus Nephroma was found to be more specific locally than globally, and the identity of the cyanobiont to differ between bi- and tripartite members of the genus.
  • Nieminen, Kaisa (Helsingin yliopisto, 2009)
    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.
  • Pakarinen, Aku (Helsingin yliopisto, 2019)
    Modern agriculture uses great amounts of fertilizers. A large portion of these fertilizers leaches from the fields to the surrounding environment and causes eutrophication of water ecosystems. Fertilizers are an expense for the farmer. Sustainable agriculture aims to minimize the use of fertilizers by using natural processes and nutrient circulation. Crop rotation is an important tool in sustainable agriculture. In crop rotation different crop species are cultivated alternately in the same field. Arbuscular mycorrhizal (AM) symbiosis is one of the world’s most important symbioses — 80 % of land plants form it. AM symbiosis enhances host plant’s nutrient uptake and provides nutrients from low concentrations in the soil. The important role of AM symbiosis in agriculture is widely recognized. However, the effect of different crop sequences on soil AM fungi is poorly studied, especially in boreal climate. In this thesis, I study the effect of four different preceding green manure crops (white lupin Lupinus albus, french marigold Tagetes patula, crimson clover Trifolium incarnatum and common vetch/hairy vetch Vicia sativa/V. villosa) on the AM colonization rate and diversity in onion (Allium cepa) roots and rhizosphere. White lupin does not form a mycorrhiza, unlike the other three preceding crops in the experiment. Onion is one of the most cultivated vegetable crops in Finland and is particularly dependent on its AM symbiont. My thesis is based on a field experiment executed in Natural Resources Institute Finland’s study field, in Mikkeli, eastern Finland, from 2017 to 2018. One of the four preceding crops was sowed in each cultivated row for 2017 growing season. Preceding crops were ploughed into the soil in autumn 2017. Onion was cultivated in all rows in 2018 growing season. I studied the effect of different preceding crops on the AM colonization rate in onion roots with microscopic methods. I studied the effect of preceding crops on the AM diversity in onion roots and rhizosphere with molecular methods. The preceding crop did not have an effect on the AM colonization rate, nor did it affect the AM diversity in onion roots or rhizosphere. Unlike in previous studies in warmer climates, the non-mycorrhizal preceding crop white lupin did not have a negative impact on the soil AM community. My study suggests that non-mycorrhizal preceding crops can be used in crop rotations, in the climate conditions of eastern Finland, especially in combination with mycorrhizal plants. Future studies should investigate the effect of longer crop rotations on the soil AM fungal communities.
  • Donner, Jalmar (Helsingin yliopisto, 2020)
    Climate warming is expected to cause changes in winter conditions in northern regions. These changes include reduced depth and duration of the snow cover, and strong fluctuations in winter temperatures. A mesocosm experiment was planned to study the short term effects of contrasting winter conditions, and an introduced species (garden lupin; Lupinus polyphyllus), on chlorophyll fluorescence and pigment concentrations of native meadow species in southern Finland. Twelve different meadow species, representing different overwintering strategies were planted in each mesocosm at the beginning of summer in 2016 in Viikki, Helsinki. One year later, a lupin was planted in half of the mesocosms. Over the winter 2017-18, one half of the mesocosms was moved to Nåtö on the Åland islands, and the other half was moved to Lammi, Hämeenlinna. To each site, both lupin-containing mesocosms and lupin free controls were moved. In the inland site in Lammi, the mesocosms spent the winter covered by a thick snow cover that isolated them from harsh air temperatures from beginning of December to end of March. In coastal Nåtö, a thin snow cover formed in January and melted by mid-March. In the experiment, the maritime winter climate on Nåtö represented such winter conditions that are expected to be common on the mainland in the future, when climate warming progresses. Leaf chlorophyll fluorescence as well as concentrations of leaf chlorophyll and flavonoids were repeatedly measured nondestructively for all species using optical apparatus. Growth and flowering of the lupin was monitored during spring and summer 2018. No marked differences were observed in the meadow species chlorophyll fluorescence and content between sites, indicating that these are well adapted to variable winter conditions. The flavonoid composition of the meadow species seemed to be regulated by seasonal changes in light intensity and temperature. Small reductions in chlorophyll content for some species indicated that these were disadvantaged by the lupins presence. This was attributed to the lupins shadowing effect. In contrast, two evergreen species seemed to take advantage of the nitrogen input from the lupin in terms of higher chlorophyll content in summer 2018. The lupin overwintered successfully in mainland Lammi, but seemed to suffer from the maritime and snow poor winter conditions in Nåtö, which led to reduced production of leaves and inflorescences during the growing season 2018. The results indicate that native meadow species in Finland are relatively tolerant of the expected changes in mainland winter conditions, whereas these changes will be disadvantageous for the lupin.
  • Fontell-Seppelin, Laura (Helsingin yliopisto, 2020)
    According to The Finnish Act on Water Resource Management, the ecological status of Finnish streams and lakes have to be monitored and assessed based on the severity of human impact on biota. The ecological assessment of freshwaters is based on comparing the impacted ecosystems with those freshwater ecosystems of a nearly intact state. The Finnish Act on Water Resource Management is based on the European Union Water Framework Directive, or WFD. Macrophytes (aquatic bryophytes, macroalgae, and vascular plants) are used as an element in freshwater assessment. In Finland, the used of macrophytes have been long established along with other organism groups in ecological assessment of lakes, but macrophytes have not yet been used extensively in ecological assessment of rivers. A rough method has been developed, but further study and improvement needs to be made before reliable ecological assessments using river macrophytes can be done. Currently, there is a great need for a uniform method for river assessment using macrophytes. In Finland, the ecological state of freshwaters is classified by using biological metrics based on the abundance and variety of different organism groups. The biological metrics are converted to a scale of 0-1 into a so-called Ecological Quality Ratio (EQR) in order to be able to compare their results. Suitable biological metrics have been studied in Finland, and so far, the Percent Model Affinity (PMA) and Observed-to-Expected-taxa index (O/E-taxa index) have proven to be promising. Both metrics have been observed to explain human impact in the catchment and changes in water quality. These metrics are hence used in this thesis. The variety and abundance of freshwater macrophytes was studied according to the rough method developed at the Finnish Environment Institute (SYKE) in 2008. In this thesis, the objective was to study how the results of the biological metrics varied between different river parts of Mätäjoki. The EQR and biological metrics results obtained earlier from diatoms and benthic invertebrates were also compared with the results obtained with macrophytes in the same river parts. A possible link to the results of the River Habitat Survey (RHS) and riverbank vegetation was also studied. The biological metrics used in this thesis are based on using reference sites (sites in natural condition) to assess the ecological condition of the studied sites. Data collected for the MaaMet-survey by the Finnish Environment Institute formed the reference conditions. The reference sites included were as pristine as possible. The field method consisted of gathering macrophyte data from two 50-metre-long adjacent river parts: a riffle and a pool. A total of 18 rivers and pools were included, forming 9 river-pool pairs. The riverbank vegetation was studied on the banks of the pools. In this thesis, we observed significant variation in both the biological metrics results and EQR results. The results of the biological metrics were surprisingly low, indicating a possibly bad ecological condition. The mean of EQR results using combined data, bryophyte data and vascular plant data were found to be very similar. The EQR results using macrophyte data were considerably lower than the EQR results of the diatom and benthic invertebrate data. Macrophytes thus indicated a possibly inferior ecological state than diatoms and benthic invertebrates. The species richness of Mätäjoki was found to be considerably lower than that of the reference sites. The surprising results may indicate shortcomings in the rough river macrophyte method. The small size of the reference condition data and issues in the national Finnish river classification system may also be responsible for some of the results. Low EQR results, indicating low ecological state, may be a result from the impaired ecological state of Mätäjoki due to human impact. Moreover, the ecological assessment of urban rivers based on biota has in some studies produced unreliable results on other organism groups. The results show that biological metric values show a large variation between river parts. This must be taken into consideration in the development of the river macrophyte method and in choosing the sampling sites of studied rivers.
  • Hyrkäs, Noora (Helsingin yliopisto, 2018)
    Limasienet (Myxomycota) ovat aitoameeboihin (Amoebozoa) kuuluvia, aitotumaisia eliöitä, joiden elinkierrossa vuorottelevat yksisoluinen, yleensä haploidi ameeba- ja kenosyyttinen, diploidi limakkovaihe. Limasieniä tunnetaan noin 1000 lajia, joista Suomessa on tavattu reilut 200. Lajimonimuotoisuus on suurinta metsissä mm. karikkeessa, lahopuussa ja elävien puiden kaarnalla. Suurimman osan elämästään ne viettävät joko lepovaiheina (esim. itiöinä tai sklerootioina) tai ameeboina. Limakko kehittyy tavallisesti ameebojen pariutuessa, ja se kykenee liikkumaan hitaasti elinalustallaan etsien ravinnokseen mm. bakteereja ja sieni-itiöitä. Sopivissa olosuhteissa limakko muuttuu kokonaisuudessaan itiöpesäkkeiksi, joissa syntyvät meioottiset itiöt. Kaarnalimasienet ovat sopeutuneet viemään koko elinkiertonsa läpi elävien puiden kaarnalla. Niiden lepoasteet kestävät kasvualustalleen tyypillisiä ääreviä ja nopeasti vaihtuvia kosteus- ja lämpöoloja. Elinkierto ja limakkovaihe ovat yleensä nopeita ja limakot sekä itiöpesäkkeet pienikokoisia, tuskin silmin havaittavia. Ehdottomien kaarnalajien lisäksi kaarnalla elää myös joukko laaja-alaisempia ja opportunistisia lajeja. Tässä tutkimuksessa kartoitettiin kaarnalimasienten lajistoa 15 yleisellä, Suomessa luonnonvaraisena esiintyvällä puulajilla ja neljällä eri kasvillisuusvyöhykkeellä (boreaalisen vyöhykkeen alavyöhykkeellä). Tavoitteena oli selvittää lajiston lisäksi, onko eri isäntäpuulajien tai vyöhykkeiden välillä eroja limasienilajistossa. Kaarnanäytteitä kerättiin yhteensä 196 puuyksilöstä (yksi näyte/yksilö) hemi-, etelä- ja pohjoisboreaaliselta sekä orohemiarktiselta vyöhykkeeltä. Näytteistä kasvatettiin limasieniä kosteakammioviljelmissä, ja itiöpesäkkeitä tuottaneet lajit tunnistettiin ja valokuvattiin. Puulajien ja vyöhykkeiden eroja tutkittiin tilastollisin menetelmin. Lisäksi mitattiin ja tutkittiin kaarnan happamuuden ja vedenpidätyskyvyn vaikutusta limasienilajistoon. Kaarnanäytteistä 65 % tuotti limasienten itiöpesäkkeitä. Tutkituilta 15 puulajilta löytyi yhteensä 23 tunnistettua limasienilajia, joista kaksi hapsista (suku Echinostelium) havaittiin nyt Suomessa ensi kertaa. Yhden puulajin limasienilajien lukumäärä vaihteli välillä 1-9 ja vyöhykkeittäin 1-19. Sekä puulajien että vyöhykkeiden välillä havaittiin merkitseviä eroja, eli ainakin osa limasienilajeista vaikuttaa suosivan tiettyjä isäntäpuulajeja tai lajiryhmiä (esim. havu- tai lehtipuita) ja painottuvan levinneisyydeltään maan etelä- tai pohjoisosiin. Toisaalta muutamaa limasienilajia esiintyi hyvin laajalti eri puilla ja alueilla. Kasvualustan happamuuden ja vedenpidätyskyvyn vaikutukset lajistoon eivät olleet yksiselitteisiä. Tutkimustulosten perusteella limasienet ovat sienten ja jäkälien tavoin hyvin yleinen osa kaarnan mikrobistoa, eikä niiden esiintyminen eri puulajeilla tai kasvillisuusvyöhykkeillä ole täysin satunnaista. Tulokset tukivat useiden aiempien tutkimusten tuloksia kaarnalimasienten puulaji- ja aluespesifisyydestä. Edellä kuvattu tutkimus oli puulajien osalta laajin tähän mennessä tehty selvitys Suomen kaarnalimasienistä.
  • Koutaniemi, Sanna (Helsingin yliopisto, 2007)
    Lignin is a hydrophobic polymer that is synthesised in the secondary cell walls of all vascular plants. It enables water conduction through the stem, supports the upright growth habit and protects against invading pathogens. In addition, lignin hinders the utilisation of the cellulosic cell walls of plants in pulp and paper industry and as forage. Lignin precursors are synthesised in the cytoplasm through the phenylpropanoid pathway, transported into the cell wall and oxidised by peroxidases or laccases to phenoxy radicals that couple to form the lignin polymer. This study was conducted to characterise the lignin biosynthetic pathway in Norway spruce (Picea abies (L.) Karst.). We focused on the less well-known polymerisation stage, to identify the enzymes and the regulatory mechanisms that are involved. Available data for lignin biosynthesis in gymnosperms is scarce and, for example, the latest improvements in precursor biosynthesis have only been verified in herbaceous plants. Therefore, we also wanted to study in detail the roles of individual gene family members during developmental and stress-induced lignification, using EST sequencing and real-time RT-PCR. We used, as a model, a Norway spruce tissue culture line that produces extracellular lignin into the culture medium, and showed that lignin polymerisation in the tissue culture depends on peroxidase activity. We identified in the culture medium a significant NADH oxidase activity that could generate H2O2 for peroxidases. Two basic culture medium peroxidases were shown to have high affinity to coniferyl alcohol. Conservation of the putative substrate-binding amino acids was observed when the spruce peroxidase sequences were compared with other peroxidases with high affinity to coniferyl alcohol. We also used different peroxidase fractions to produce synthetic in vitro lignins from coniferyl alcohol; however, the linkage pattern of the suspension culture lignin could not be reproduced in vitro with the purified peroxidases, nor with the full complement of culture medium proteins. This emphasised the importance of the precursor radical concentration in the reaction zone, which is controlled by the cells through the secretion of both the lignin precursors and the oxidative enzymes to the apoplast. In addition, we identified basic peroxidases that were reversibly bound to the lignin precipitate. They could be involved, for example, in the oxidation of polymeric lignin, which is required for polymer growth. The dibenzodioxocin substructure was used as a marker for polymer oxidation in the in vitro polymerisation studies, as it is a typical substructure in wood lignin and in the suspension culture lignin. Using immunolocalisation, we found the structure mainly in the S2+S3 layers of the secondary cell walls of Norway spruce tracheids. The structure was primarily formed during the late phases of lignification. Contrary to the earlier assumptions, it appears to be a terminal structure in the lignin macromolecule. Most lignin biosynthetic enzymes are encoded for by several genes, all of which may not participate in lignin biosynthesis. In order to identify the gene family members that are responsible for developmental lignification, ESTs were sequenced from the lignin-forming tissue culture and developing xylem of spruce. Expression of the identified lignin biosynthetic genes was studied using real-time RT-PCR. Candidate genes for developmental lignification were identified by a coordinated, high expression of certain genes within the gene families in all lignin-forming tissues. However, such coordinated expression was not found for peroxidase genes. We also studied stress-induced lignification either during compression wood formation by bending the stems or after Heterobasidion annosum infection. Based on gene expression profiles, stress-induced monolignol biosynthesis appeared similar to the developmental process, and only single PAL and C3H genes were specifically up-regulated by stress. On the contrary, the up-regulated peroxidase genes differed between developmental and stress-induced lignification, indicating specific responses.
  • Rapeli, Hanne (Helsingin yliopisto, 2020)
    Kaupunkien rakennetut puistot voivat olla lajirikkaita paikkoja ja jopa monimuotoisuuden keskittymiä kaupunkimaisemassa. Tutkin lopputyössäni Helsingin rakennettujen puistojen putkilokasvien, lintujen ja jäkälien lajistolliseen monimuotoisuuteen vaikuttavia tekijöitä. Lisäksi tarkastelen ilmanlaadusta kertovien indikaattorijäkälien esiintyvyyttä tutkimuspuistoissa. Aiempien tutkimusten perusteella tärkeimpiä puistojen lajistolliseen monimuotoisuuteen vaikuttavia tekijöitä ovat esimerkiksi puiston koko, puiston sisäinen habitaattien monimuotoisuus ja puiston kytkeytyneisyys muihin viheralueisiin. Puistojen monimuotoisuustutkimuksissa paljon käytettyjä teorioita ovat mm. gradienttiparadigma ja saarieliömaantieteellinen teoria. Tutkimukseen valittiin 12 puistoa kolmelta kaupunkivyöhykkeeltä: kantakaupungista, välikaupungista ja esikaupungista. Vyöhykejaon taustalla on ajatus kaupungistumisen voimistumisesta ja viheralueiden kytkeytyneisyyden heikkenemisestä kohti kaupungin keskusta siirryttäessä. Puistojen valintaan ja aineiston keruun menetelmiin vaikutti EU-rahoitteinen, puistojen biokulttuurista monimuotoisuutta tutkiva GREEN SURGE -hanke. Tutkimuskysymykseni ovat: Kasvaako putkilokasvien, lintujen ja jäkälien lajimäärä puiston koon kasvaessa? Vaikuttaako habitaattien monimuotoisuus putkilokasvien lajirikkauteen, Shannonin diversiteetti-indeksin avulla laskettuun putkilokasvien lajistolliseen monimuotoisuuteen tai alkuperäislajien osuuteen putkilokasvien kokonaislajimäärästä? Vaikuttaako putkilokasvien lajirikkaus tai puuvartisten kasvien lajimäärä lintujen lajirikkauteen? Esiintyykö tutkimuspuistoissa ilman laadusta kertovia indikaattorijäkäliä? Onko kaupunkivyöhykkeiden välillä eroa putkilokasvien, lintujen tai jäkälien lajimäärissä? Entä alkuperäisten kasvilajien osuuksissa tai yksi- kaksi- ja monivuotisten putkilokasvien esiintyvyydessä? Onko kaupunkivyöhykkeiden välillä eroa herkkien ja erittäin herkkien indikaattorijäkälien esiintyvyydessä? Tutkin näitä kysymyksiä kvantitatiivisesti korrelaatioanalyysin ja yksisuuntaisen varianssianalyysin avulla. Tutkimuspuistoista löytyi 171 putkilokasvilajia, mikä on noin 16 % kaikista Helsingin putkilokasvilajeista. Näiden joukossa oli mm. kuusi saraa (Carex), joita pidetään kaupunkipakoisina lajeina. Habitaattien monimuotoisuus nosti putkilokasvien lajimäärää ja vaikutti positiivisesti myös Shannonin indeksin avulla laskettuun putkilokasvien lajirikkauteen sekä alkuperäislajien osuuteen putkilokasvien kokonaislajimäärästä. Nämä tulokset olivat tilastollisesti merkittäviä. Alkuperäislajien, tulokaslajien ja viljelykarkulaisten osuudessa ei ollut eroja kaupunkivyöhykkeiden välillä, mikä kertoo siitä, että Helsingissä kasvaa alkuperäisiä kasvilajeja hyvinkin lähellä kaupungin keskustaa. Suuremmissa puistoissa on yleensä enemmän lajeja kuin pienemmissä puistoissa. Tässä tutkielmassa se piti paikkansa erityisesti lintujen kohdalla. Lintujen lajimäärän ja puiston pinta-alan välille löytyi tilastollisesti merkittävä yhteys. Toinen lintujen lajirikkauteen vaikuttava tekijä oli puuvartisten kasvien lajimäärä. Tutkimuspuistojen puista ja pensaista hyvin pieni osuus on alkuperäislajeja, joten myös koristelajit saattavat vaikuttaa lintujen monimuotoisuuteen positiivisesti. Lintujen lajimäärä oli korkein kantakaupungissa, kun taas putkilokasvien ja jäkälien lajirikkaus oli korkein esikaupungissa. Kaupunkivyöhykkeiden väliset erot eivät kuitenkaan olleet tilastollisesti merkittäviä. Ilmanlaadusta kertovia herkkiä ja erittäin herkkiä indikaattorilajeja esiintyi eniten esikaupungin ja vähiten kantakaupungin puistoissa. Puistojen välinen vaihtelu indikaattorijäkälien esiintyvyydessä oli kuitenkin suurempaa kuin kaupunkivyöhykkeiden välistä vaihtelua suurempaa.
  • Martikainen, Tuomo (Helsingin yliopisto, 2019)
    Niittyliekosammal (Rhytidiadelphus squarrosus) esiintyy poh-joisen pallonpuoliskon lauhkealla ja viileällä vyöhykkeellä. Suomessa se esiintyy yleisenä Etelä- ja Keskiosissa sekä har-vinaisena tai puuttuvana Lapissa. Laji on heikko kilpailija ja menestyy parhaiten kulttuurivaikutteisilla kasvupaikoilla. Sen arvellaan myös suosivan mereistä ilmastoa. Niittyliekosammal on kaksikotinen, joten siittiö- ja munape-säkkeet ovat eri kasveissa. Kaksikotisilla sammalilla, joiden primaarinen sukupuolijakauma on teoriassa 1:1, on usein vinou-tunut jakauma populaatiotasolla. Pääsyynä vinoutumaan pidetään sukupuolten erilaisia resurssivaatimuksia. Ympäristötekijöiden lisäksi myös perimä säätelee sukupuolijakaumaa. Kaksikotisuus ja vinoutunut sukupuolijakauma alentavat hedelmöittymistoden-näköisyyttä ja niittyliekosammal lisääntyykin pääasiassa kas-vullisesti. Erikoistuneita leviäimiä lajilla ei tunneta, joten tämä tapahtuu irronneiden versojen tai näiden osien avulla. Tämän opinnäytetyön päätarkoitus oli selvittää niittyliekosam-malen sukupuolijakaumaa sekä mahdollisia eroja siinä eri si-jaintipaikoilla kasvavien populaatioiden välillä. Aineisto ke-rättiin Mäntyharjulta sekä Helsingistä ja tutkittujen näyttei-den kokonaismäärä oli 675 kpl. Sukupuolen määritin sukusolu-pesäkkeiden perusteella ja jakaumien vertailuun käytin riippu-mattomuustestiä. Lajin sukupuolijakaumaa ei ole aikaisemmin tutkittu Suomen oloissa, joten tämän tutkimuksen myötä syntyi myös aineistoa eri maiden väliseen vertailuun. Kasvatuskokeen avulla tutkin myös millä verson osilla lajin suvuton lisäänty-minen tehokkaimmin tapahtuu. Kasvimuseon herbaarionäytteiden pohjalta tarkastelin lisäksi niittyliekosammalen ajallista ja paikallista esiintymistä Suomessa. Tutkimukseen kerätyn aineiston perusteella niittyliekosammalen sukupuolijakauma oli naaraspainotteinen. Jakaumat kuitenkin erosivat toisistaan sekä paikkakuntien että saman paikkakunnan populaatioiden välillä. Sukupuolijakaumat erosivat toisistaan myös maiden välisessä vertailussa. Eri ilmastovyöhykkeet voi-vat osaltaan selittää jakaumien eroja paikkakuntien ja maiden välillä. Lisääntymistä selvittävässä kasvatuskokeessa versojen kasvu painottui ainakin alkuvaiheessa sivuhaaroihin. Alkuperäisten sivuhaarojen kasvu oli tehokkainta verson nuoremmissa osissa. Uusien sivuhaarojen tuotto oli yleisempää versoissa, joissa oli mukana verson alempien osien vanhempaa solukkoa. Verson runsas sivuhaarojen määrä korreloi negatiivisesti irtoamisen jälkeiseen kasvuun. Juurtumahapsiston kasvu oli hyvin vähäistä ja irronneiden lehtien avulla tapahtuvaa kasvua ei ilmennyt. Herbaarionäytteitä oli kerätty aikavälillä 1812–2010. Eliömaa-kunnittaisessa vertailussa näytemäärä heijasti pääpiirteissään lajin kirjallisuudessa mainittua esiintymisrunsautta sekä väestöjakaumaa Suomessa. Itiöpesäkkeitä sisältävät herbaario-näytteet oli kerätty Maamme eteläosissa ja niiden suhteellinen osuus oli suurin Karjalan kannaksella ja Ahvenanmaalla. Kym-menvuotiskausilla 1860–1909 itiöpesäkkeitä sisältävien näyt-teiden osuus oli selkeästi suurempi kuin muina ajanjaksoina.
  • Lundell, Robin (Helsingin yliopisto, 2011)
    Winter is a significant period for the seasonality of northern plants, but is often overlooked when studying the interactions of plants and their environment. This study focuses on the effects of overwintering conditions, including warm winter periods, snow, and snowmelt on boreal and sub-Arctic field layer plants. Wintertime photosynthesis and related physiological factors of evergreen dwarf shrubs, particularly of Vaccinium vitis-idaea, are emphasised. The work combines experiments both in the field and in growth chambers with measurements in natural field conditions. Evergreen dwarf shrubs are predominantly covered by snow in the winter. The protective snow cover provides favourable conditions for photosynthesis, especially during the spring before snowmelt. The results of this study indicate that photosynthesis occurs under the snow in V. vitis-idaea. The light response of photosynthesis determined in field conditions during the period of snow cover shows that positive net CO2 exchange is possible under the snow in the prevailing light and temperature. Photosynthetic capacity increases readily during warm periods in winter and the plants are thus able to replenish carbohydrate reserves lost through respiration. Exposure to low temperatures in combination with high light following early snowmelt can set back photosynthesis as sustained photoprotective measures are activated and photodamage begins to build up. Freezing may further decrease the photosynthetic capacity. The small-scale distribution of many field layer plants, including V. vitis-idaea and other dwarf shrubs, correlates with the snow distribution in a forest. The results of this study indicate that there are species-specific differences in the snow depth affinity of the field and ground layer species. Events and processes taking place in winter can have a profound effect on the overall performance of plants and on the interactions between plants and their environment. Understanding the processes involved in the overwintering of plants is increasingly important as the wintertime climate in the north is predicted to change in the future.